Plasminogen Activator Inhibitor Type 1 mRNA Research Articles

MiR-30c may serve a role in endometriosis by targeting plasminogen activator inhibitor-1.

The present study aimed to investigate the role of miR-30c in endometriosis (EMs) and the underlying mechanism. The expression of miR-30c and plasminogen activator inhibitor type 1 (PAI-1) mRNA in EMs tissues was detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and the expression of PAI-1 protein was detected by western blot analysis. The proliferation, migration, invasion and adhesion of endometrial stromal cells (ESCs) in different groups transfected with miR-30c mimic or inhibitor were compared. It was demonstrated that miR-30c expression in ectopic and eutopic endometriosis tissues were significantly lower than in normal endometrial tissue. However, PAI-1 mRNA expression in ectopic and eutopic endometrial tissues was higher than in normal endometrial tissues. Furthermore, the expression of PAI-1 protein was higher in ectopic and eutopic endometrosis tissues than in normal tissues. RT-qPCR results indicated that miR-30c expression was significantly increased or decreased in ESCs following transfection of mimic or inhibitor of miR-30c, respectively. Overexpression of miR-30c repressed the expression of PAI-1 mRNA and protein, while inhibition of miR-30c upregulated the expression of PAI-1 in ESCs. In addition, the invasion, migration, proliferation and adhesion of ESCs was repressed following the overexpression of miR-30c, whereas they were promoted when miR-30c expression was downregulated. The results of the present study indicated that miR-30c serves an important role in the development and progression of EMs by regulating the expression of PAI-1.

Plasminogen activator inhibitor type 1 expression induced by lipopolysaccharide of Porphyromonas gingivalis in human gingival fibroblast

In the gingival tissues of patients with periodontitis, inflammatory responses are mediated by a wide variety of genes. In our previous screening study, plasminogen activator inhibitor type 1 (PAI-1) mRNA binding protein expression was increased in gingiva from periodontitis patients. In this study, we further investigated the signaling pathway involved in PAI-1 expression induced by Porphyromonas gingivalis LPS (Pg LPS) in human gingival fibroblasts (HGF). When HGFs were treated with Pg LPS, both PAI-1 mRNA expression and PAI-1 protein were induced in a dose-dependent manner. Pg LPS induced NF-κB activation and the expressions of PAI-1 mRNA and protein were suppressed by pretreating with a NF-κB inhibitor. Pg LPS also induced ERK, p38, and JNK activation, and Pg LPS-induced PAI-1 expression was inhibited by ERK/p38/JNK inhibitor pretreatment. In conclusion, Pg LPS induced PAI-1 expression through NF-κB and MAP kinases activation in HGF.

Carbamylated LDL induces a pro-thrombotic state via the LOX-1 receptor and arterial thrombus formation: a novel mechanism of cardiovascular events in end-stage renal disease

Background: Carbamylation of low-density lipoproteins (cLDL) alters protein structure and is thought to promote vascular inflammation and dysfunction during end-stage renal disease (ESRD). However, it remains unknown whether cLDL exerts prothrombotic effects in vascular cells and platelets and whether cLDL affects arterial thrombus formation in vivo. Methods: LDL was isolated from healthy subjects or patients with ESRD by sequential ultra-centrifugation. Ex vivo carbamylation of LDL (cLDL) from healthy subjects was induced with potassium cyanate. Arterial thrombus formation was analysed in a murine carotid artery photochemical injury model. Analysis of tissue factor (TF) and plasminogen activator inhibitor type-1 (PAI-1) expression was performed by Western blot and real-time PCR analysis. Platelet aggregation was analysed by impedance aggregometry. Results: Intravenous administration of cLDL (2mg/kg body weight) accelerated arterial thrombus formation in a murine photochemical carotid artery injury model as compared to treatment with native LDL (2mg/kg body weight) or vehicle (PBS) (n=8; p<0.05 versus nLDL and control). Analyses of tissue lysates demonstrated that cLDL induced the expression of TF and PAI-1 mRNA levels in carotid arteries (n=5, p<0.01). In human aortic smooth muscle cells (AoSMC) cLDL (10-300 μg/ml) induced TF and PAI-1 expression by 3.5- and 3-fold, as compared with nLDL (n=4; p<0.01). cLDL also enhanced basal and TNF-α induced expression of TF and PAI-1 in human aortic endothelial cells (n=4; p<0.02). In contrast, native LDL (nLDL) had no effect on endothelial expression or activity of TF and PAI-1. In both cell types, cLDL activated the mitogen-activated protein kinases p38 and ERK (n=3; p<0.05) as well as the transcription factor NFkB (n=4, p<0.05). Silencing of lectin-like oxidized LDL receptor-1 (LOX-1) using specific siRNA prevented the induction of TF and PAI-1 expression in vascular cells. In platelets cLDL activated the p38 MAP kinase and induced platelet aggregation. Finally, LDL isolated from patients with ESRD mimicked the prothrombotic effects of cLDL on vascular cells and platelets. Conclusions: These data demonstrate that cLDL at physiologically relevant concentrations,via activation of the LOX-1 receptor induces potent pro-thrombotic effects in vascular cells and platelets leading to enhanced thrombus formation in vivo. This observation may explain the markedly increased incidence of fatal acute thrombotic events in patients with end-stage renal disease and lead to the development of novel LDL targeting strategies in this population.

Posttranscriptional regulation of expression of plasminogen activator inhibitor type-1 by sphingosine 1-phosphate in HepG2 liver cells

Altered expression of plasminogen activator inhibitor type-1 (PAI-1), a major physiologic inhibitor of fibrinolysis, is implicated in the progression of atherosclerosis. Sphingosine 1-phosphate (S1P) regulates expression of diverse genes and alters expression of PAI-1 in several types of cells. However, the nature of posttranscriptional regulation of expression of PAI-1 by S1P has not yet been thoroughly elucidated. The present study was undertaken to determine whether S1P has important effects on the posttranscriptional regulation of PAI-1 expression. To evaluate this possibility, we determined promoter activity, mRNA levels, 3′-untranslated region (UTR) activity, and protein levels of PAI-1 in HepG2 cells. S1P increased PAI-1 promoter activity and the expression of PAI-1 mRNA within 4h of exposure. It decreased the expression of PAI-1 mRNA and the accumulation of PAI-1 protein into the media in 24h. Human PAI-1 mRNA exists in two subspecies (3.2 and 2.2kb). S1P decreased the baseline luciferase activity of the 1kb fragment of the 3′ terminus (+2177 to 3176nt) of the 3′-UTR of the 3.2kb PAI-1 mRNA [3′-UTR (+2177–3176)]. S1P decreased expression of PAI-1 protein, presumably by regulating PAI-1 expression at the posttranscriptional level thereby affecting mRNA stability. SERPINE1 mRNA binding protein (SERBP1) and ARE3 in the 3′-UTR were involved in the posttranscriptional regulation by S1P. Our data suggest that S1P can destabilize 3.2kb PAI-1 mRNA through specific effects on the 3′-UTR. These effects appear to involve SERBP1 leading to decreased expression of PAI-1 protein.

Modulators of induction of plasminogen activator inhibitor type-1 in HepG2 cells by transforming growth factor-β

An increased expression of plasminogen activator inhibitor type-1 (PAI-1) has been implicated in accelerating atherogenesis and coronary artery disease in patients with type 2 diabetes. Transforming growth factor (TGF)-β increases its expression. An increased PAI-1 appears to predispose also to augmented fibrosis potentially contributing to negative left ventricular remodeling and heart failure after myocardial infarction. Diabetes is well known to induce oxidative stress. To elucidate molecular mechanisms underlying an increased PAI-1 production, the effects of TGF-β and oxidative stress implicated as agonists of PAI-1 synthesis were characterized with the use of human liver-derived HepG2 cells. PAI-1 mRNA was assayed by real-time PCR, and PAI-1 protein was assayed by western blotting. PAI-1 promoter (-825 -+42 bp) activity was assessed with the luciferase assay. The role of the 3'-untranslated region was delineated with the use of luciferase constructs containing the 3'-untranslated region. Oxidative stress was measured after loading carboxy-2,7-dichlorodihydrofluorescein into cells. TGF-β increased oxidative stress, which was accompanied by increases in NADPH oxidase 3 mRNA and membrane translocation of Rac proteins. TGF-β-inducible increases in the PAI-1 promoter activity involved Smad-binding elements and a nuclear factor-κB-binding site. TGF-β did not increase the activity of the PAI-1 mRNA 3'-untranslated region. TGF-β-inducible PAI-1 expression was attenuated by simvastatin and curcumin, a natural polyphenol. TGF-β can increase the expression of PAI-1 through multiple mechanisms involving Smad and nuclear factor-κB pathways and oxidative stress. As both oxidative stress and PAI-1 production were reduced by simvastatin and curcumin, modulation of oxidative stress and PAI-1 production are attractive targets for pharmacotherapy of cardiovascular disorders associated with an increased PAI-1 including type 2 diabetes and its associated consequences including accelerated coronary artery disease and an increased fibrosis that may exacerbate adverse left ventricular remodeling after myocardial infarction.

Ascochlorin suppresses TGF-β1-induced PAI-1 expression through the inhibition of phospho-EGFR in rat kidney fibroblast cells

Fibrosis is induced by the excessive and abnormal deposition of extracellular matrix (ECM) with various growth factors in tissues. Transforming growth factor-β1 (TGF-β1), the growth factor involved in fibrosis, modulates ECM synthesis and accumulation. TGF-β1 enhances the production of stimulators of ECM synthesis such as plasminogen activator inhibitor type 1 (PAI-1). As such, PAI-1 expression directly influences the proteolysis, invasion, and accumulation of ECM. It was shown in this study that ascochlorin, a prenylpenl antiobiotic, prevents the expression of profibrotic factors, such as PAI-1 and collagen type I, and that the TGF-β1-induced PAI-1 promoter activity is inhibited by ascochlorin. Ascochlorin abolishes the phosphorylation of the EGFR-MEK-ERK signaling pathway to regulate the TGF-β1-induced expression of PAI-1 without the inhibition of TβRII phosphorylation. Furthermore, the MEK inhibitor and EGFR siRNA block PAI-1 expression, and the Raf-1, MEK, and ERK signaling pathways for the regulation of PAI-1 expression. Ascochlorin suppresses the matrix metalloproteinases (MMPs) activity to activate the heparin-binding EGF-like growth factor (HB-EGF), to induce the phosphorylation of EGFR, and the MMPs inhibitor suppresses EGFR phosphorylation and the PAI-1 mRNA levels. These results suggest that ascochlorin prevents the expression of PAI-1 via the inhibition of an EGFR-dependent signal transduction pathway activated by MMPs.

Posttranscriptional regulation of expression of plasminogen activator inhibitor type-1 by cAMP in HepG2 liver cells

Altered expression of plasminogen activator inhibitor type-1 (PAI-1), a physiologic fibrinolysis inhibitor, is implicated in atherosclerosis. Cyclic adenosine monophosphate (cAMP) alters PAI-1 expression in several cells. Nevertheless, posttranscriptional regulation of PAI-1 has not been elucidated. To determine whether cAMP affects PAI-1 expression at posttranscriptional level, we determined promoter activity, mRNA levels, 3'-untranslated region (UTR) activity and protein levels of PAI-1 using HepG2 cells. cAMP decreased PAI-1 promoter activity at 24 h and mRNA expression at 4 h while it increased mRNA expression and accumulation of PAI-1 protein into media at 24 h. Human PAI-1 mRNA exists in two subspecies (3.2 and 2.2 kb), and cAMP increased baseline luciferase activity of 3'-UTR of the 3.2 kb PAI-1 mRNA [3'-UTR (+1358-3176)] and 1 kb fragment of 3'-terminus of 3'-UTR of 3.2 kb mRNA [3'-UTR (+2177-3176)]. cAMP increased PAI-1 protein expression despite decrease in promoter activity, presumably by regulating PAI-1 expression at the posttranscriptional level and thereby affecting mRNA stability. The 53-nt fragment in 3'-UTR (+2591 to +2643 nt) was involved in posttranscriptional regulation by cAMP. Thus, cAMP can stabilize 3.2 kb PAI-1 mRNA mediated by specific effects on 3'-UTR, and these effects are associated with increased expression of PAI-1 protein.

Dual diverse dynamic reversible actions of Ankaferd on EPCR and PAI-1 inside vascular endothelial cells with and without LPS

Objective: Ankaferd blood stopper (ABS) is comprised of a mixture of the plants Thymus vulgaris, Glycyrrhiza glabra, Vitis vinifera, Alpinia officinarum, and Urtica dioica. ABS is used as a topical hemostatic agent due to its antihemorrhagic effect, yet its hemostatic mechanism of action remains to be investigated. ABS does not affect the levels of coagulation factors II, V, VII, VIII, IX, X, XI and XII. The aim of this study was to investigate the effects of ABS on endothelium and immune response. As such, we evaluated changes in endothelial cell protein C receptor (EPCR) and plasminogen activator inhibitor type-1 (PAI-1) expression inside human umbilical vein endothelial cells (HUVECs) in the presence and absence of lipopolysaccharides (LPSs). Material and Methods: We exposed HUVECs to 10 μL and 100 μL of ABS for 5 min, 25 min, 50 min, 6 h, and 24 h. Additionally, 10 μg mL–1 of LPS was administered for 1 h to observe the effects of LPS challenge on HUVECs, and then the cells were treated with ABS for 5 min, 25 min, 50 min, and 6 h to observe the effects of ABS on HUVECs. Total RNA was isolated from HUVECs and then the level of expression of EPCR and PAI-1 mRNA was measured. Results: Cells were microscopically observed to arise from the surface and adhere to each other following the administration of ABS to HUVECs. Additionally, after 24 h the cells had normal growth and physiology, which suggests that the adhesive cellular effects of ABS might be reversible. ABS had a negative effect on EPCR and PAI-1 expression; the effect in response to 100 µL was greater than that to 10 µL. EPCR and PAI-1 expression increased over time in response to LPS and 10 µL of ABS. EPCR and PAI-1 expression was very low during the first hour of exposure to LPS and 100 µL of ABS, but after 6 h increased to levels similar to those observed in response to LPS and 10 µL of ABS. Conclusion: It was observed that ABS had dual diverse dynamic reversible effects on EPCR and PAI-1 expression in HUVECs, which were dependent on dose and concentration. ABS might play a role in numerous cellular mechanisms, in addition to having hemostatic effects.Conflict of interest:None declared.

Apelin protects against angiotensin II-induced cardiovascular fibrosis and decreases plasminogen activator inhibitor type-1 production

To test the hypothesis that apelin protects against angiotensin II (Ang II)-induced cardiovascular fibrosis and vascular remodeling. Wild-type mice administered apelin or apelin along with Ang II exhibited less cardiovascular fibrosis and decreased plasminogen activator inhibitor type-1 (PAI-1) gene expression than mice receiving Ang II, N-nitro-L-arginine methyl ester (L-NAME), apelin plus L-NAME or apelin plus Ang II plus L-NAME. In-vitro analysis using a luciferase construct driven by 3.1 kb of the human PAI-1 promoter revealed that apelin blocked Ang II-mediated PAI-1 gene expression. Immunoblotting for phosphorylated myosin phosphatase subunit and myosin light chain revealed that apelin blocked Ang II activation of the Rho kinase pathway, which is associated with induction of PAI-1 gene expression by Ang II. In addition, treatment of human aortic smooth muscle cells with apelin reduced PAI-1 mRNA and protein production in the presence and absence of Ang II. Conversely, L-NAME treatment attenuated the downregulation of PAI-1 by apelin in cells. Apelin protects against cardiac fibrosis and vascular remodeling through direct regulation of PAI-1 gene expression. This protective effect is mediated through the synergistic inhibition of Ang II signaling and increased production of nitric oxide by apelin. Our data extend previous findings and provide new insight into the molecular mechanisms by which apelin elicits a cardioprotective effect.

Curcumin Down-Regulates Cytokine-Mediated Tissue Factor and Plasminogen Activator Type 1 Expression In Human Endothelial Cells

AbstractAbstract 3333Curcumin (diferuloyl methane), an active component of the spice turmeric, has been shown to exhibit anti-inflammatory and antioxidant activities in addition to an anticartinogenic activity in vitro and in vivo. Recent studies reported that curcumin acts as a non-stressful and non-cytotoxic inducer of the cytoprotective heme oxigenase-1 (HO-1). HO-1 is an inducible enzyme which degrades oxidative heme into biliverdin, free iron, and carbon monoxide. The first human case of HO-1 deficiency was described from Japan by Yachie, et al (J Clin Invest 1999; 103:129). This HO-1 deficient child exhibited severe persistent endothelial damage and extremely hyper-coagulable state. These findings prompted us to study roles of HO-1 in the regulation of coagulability. Epstein-Barr virus-transformed lymphoblastoid cell line (LCL) derived from the HO-1 deficient patient was not able to produce HO-1 production at all. In comparison to control LCLs, the HO-1 deficient LCLs expressed markedly higher levels of tissue factor (TF) mRNA and protein (2-fold, p<0.05) as well as of plasminogen activator inhibitor type 1 (PAI-1) (2-fold, p<0.05), upon exposure to oxidative stress such as hemin, suggested important roles of HO-1 or HO-1 products in the regulating of coagulation and fibrinolytic system. We then hypothesized that endothelial HO-1 induced by curcumin may ameliorate hyper-coagulable state associated with inflammation or oxidative stress. The exposure of human umbilical vein endothelial cells (HUVECs) to curcumin (15 mM) for 6 hr resulted in a significant increase in the level of both HO-1 mRNA (15-fold) and protein. The treatment of HUVECs with 15 mM curcumin for 3hr before stimulation with tumor necrosis factor-α (TNF-α, 10 ng/ml) for additional 5hr markedly inhibited TNF-a-induced expression of TF (approximately 90 % suppression) and PAI-1 (approximately 70 % suppression) (Figure1). The inhibitory effect of curcumin on the TF expression was partially abrogated by tin protoporphyrin IX (SnPP) (20 mM), an inhibitor of heme oxigenase activity, indicating that the curcumin-induced suppression of TF is partly mediated by HO-1 (Figure 1). Moreover, curcumin inhibited TNF-a-induced phosphorylation of p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase 1and 2 (ERK1/2), and c-Jun N-terminal kinase (JNK), indicating the inhibition of these signal pathways may also be responsible for the suppression of TF/PAI-1 expressions in HUVECs by curcumin. In conclusion, these results indicate that curcumin exerts anti-thrombotic effects directly and indirectly through the induction of HO-1. Curcumin may serve as a novel anti-thrombotic agent for the treatment of hyper-coagulable state or thrombus formation associated with inflammation.Figure 1. Effects of curcumin on TNF-α-induced TF and PAI-1 protein (A) and mRNA (B) expression in HUVECs. The columns represent the mean ± SD (n=3) percentages of the control culture. *p<0.05 versus TNF-α alone. [Display omitted] Disclosures:No relevant conflicts of interest to declare.

Carbon Monoxide-Releasing Molecule-Derived CO Regulates Tissue Factor, Plasminogen Activator Inhibitor Type 1, and Thrombomodulin Production by Human Endothelial Cells.

AbstractAbstract 1146 Background and purpose:Heme oxygenase-1 (HO-1) is a cytoprotective and anti-inflammatory protein that catalyzes the conversion of heme into biliverdin, free iron, and carbon monoxide (CO). HO-1 is rapidly induced by various oxidative stresses and inflammation, thereby playing an important role in the self defence system. Recently, Yachie, et al. reported the first human case of HO-1 deficiency. This patient showed prominent signs of intravascular hemolysis, endothelial cell injury, and abnormalities in the coagulation / fibrinolysis system, suggesting the involvement of HO-1 or HO-1 products, such as CO, regulation of coagulation / fibrinolysis system. The current study examined whether tricarbonyldichlororuthenium (II) dimer (CORM-2), which liberated CO in the presence of dimethyl sulfoxide (DMSO), modulates the expression of tissue factor (TF), plasminogen activator inhibitor type 1 (PAI-1) and thrombomodulin (TM) in human umbilical vein endothelial cells (HUVECs). Methods:HUVECs were pretreated with CORM-2 at the concentration of 50 μM for 3h, washed and stimulated with tumor necrosis factor-α(TNF-α, 10 ng/ml) for additional 2 or 5h. The mRNA and protein levels of TF, PAI-1 and TM in the cultured HUVECs were determined by real-time reverse transcriptase polymerase chain reaction and Western blotting. To determine whether CORM-2 affects the MAPK signaling pathways, the phosphorylation of p38 mitogen-activated protein kinase (p38MAPK) and extracellular signal-regulated kinase1/2 (ERK1/2) in the HUVECs were analyzed with Western blotting. Results:After TNF-α stimulation, TF mRNA levels were approximately 6-fold and PAI-1 mRNA levels were approximately 8-fold increased, and TM mRNA levels were decreased by 20% compared to the control. Similarly to the mRNA expression, TF and PAI-1 protein levels were increased while the TM protein level was decreased. On the other hand, pretreatment of HUVECs with CORM-2 significantly decreased TF mRNA levels (approximately 80% suppression), and PAI-1 mRNA levels (approximately 90% suppression) while increased TM mRNA levels by 3-fold as compared to the TNF-α-stimulated group (p<0.05; Figure 1). Similarly, the pretreatment with CORM-2 inhibited TNF-α-induced TF and PAI-1 protein up-regulation and TM protein down-regulation. CORM-2 inhibited TNF-α-induced activation of p38MAPK and ERK1/2 by 50% compared to the control. Conclusions:These results indicate that CO liberated by CORM-2 suppresses the TNF-α-induced TF and PAI-1 up-regulation and prevents the TNF-α-induced TM down-regulation in HUVECs via MAPK signaling pathways. Thus, the modulation of endothelial function by CO may offer a novel antithrombotic option for treatment of the hypercoagulable state associated with inflammation. [Display omitted] Disclosures:No relevant conflicts of interest to declare.

Increased expression of plasminogen activator inhibitor type-1 (PAI-1) in HEPG2 cells induced by insulin mediated by the 3′-untranslated region of the PAI-1 gene and its pharmacologic implications

Insulin increases, through several molecular mechanisms, expression of plasminogen activator inhibitor-1 (PAI-1), the major physiologic inhibitor of fibrinolysis. This phenomenon has been implicated as a cause of accelerated coronary artery disease and the increased incidence of acute coronary syndromes associated with type 2 diabetes. We have previously reported that physiologic and pharmacologic concentrations of insulin induce PAI-1 synthesis in human HepG2 cells and that simvastatin can attenuate its effects. This study was performed to further elucidate mechanisms responsible for the insulin-induced PAI-1 production. Concentrations of PAI-1 mRNA were determined by real-time PCR, and PAI-1 protein was assayed by western blotting. PAI-1 promoter (-829 to +36 bp) activity was assayed with the use of luciferase reporter assays. The potential role of the 3'-untranslated region (UTR) in the PAI-1 gene was assayed with the use of luciferase constructs containing the 3'-UTR. Oxidative stress was measured by loading cells with carboxy-2,7 dichlorodihydrofluorescein. Insulin increased PAI-1 promoter activity, PAI-1 mRNA, and accumulation of PAI-1 protein in the conditioned media. Insulin-inducible PAI-1 promoter activity was attenuated by simvastatin. Experiments performed with luciferase reporters containing the 3'-UTR showed that insulin increased luciferase activity through this region. Insulin also increased oxidative stress. Both insulin-inducible luciferase activity through the 3'-UTR and oxidative stress were attenuated by simvastatin. Insulin can increase PAI-1 expression through multiple mechanisms including induction mediated by the 3'-UTR of the PAI-1 gene. Accordingly, beneficial pleiotropic effects of statins on coronary artery disease may be attributable, in part, to attenuation of overexpression of PAI-1 mediated by the 3'-UTR in syndromes of insulin resistance (such as the metabolic syndrome) and type 2 diabetes.

Contribution of Genetic and Metabolic Syndrome to Omental Adipose Tissue PAI-1 Gene mRNA and Plasma Levels in Obesity

Plasminogen activator inhibitor type-1 (PAI-1) has already been associated with atherosclerosis; myocardial infarction; and cardiovascular disease risk factors such as obesity, insulin resistance, and dyslipidemia. However, factors regulating PAI-1 adipose tissue (AT) gene expression and plasma levels are not yet well defined. This study aims to assess the contribution of PAI-1 omental AT mRNA levels and genetic and metabolic factors to variation in plasma PAI-1 concentrations. Ninety-one non-diabetic premenopausal severely obese women (body mass index, BMI >35 kg/m(2)) undergoing bariatric surgery were phenotyped (fasting plasma glucose, lipid-lipoprotein, and PAI-1 levels) and genotyped for four PAI-1 polymorphisms. Omental AT PAI-1 mRNA levels were determined using real-time polymerase chain reaction. Stepwise regression analysis was used to identify independent PAI-1 AT mRNA and plasma level predictors. Among the variables included to the stepwise regression analysis, plasma high-density lipoprotein (HDL)-cholesterol (r = 0.38; p = 0.0004) and total cholesterol (r = 0.16; p = 0.0541) levels were the only two (out of 12) independent variables retained as predictive of PAI-1 omental AT mRNA levels, whereas BMI (r = 0.35; p = 0.0039), plasma HDL-cholesterol concentrations (r = -0.31; p = 0.0375), PAI-1 omental AT mRNA levels (r = 0.19; p = 0.0532) and PAI-1-844G/A (p = 0.0023), and rs6092 (p.A15T; p = 0.0358) polymorphisms contributed independently to plasma PAI-1 concentrations. Taken together, these variables explained 17.8% and 31.0% of the variability in PAI-1 AT mRNA and plasma levels, respectively. These results suggest that PAI-1 polymorphisms contribute significantly to PAI-1 plasma levels but do not support the notion that omental AT is one of its major source.

Potentiating effect of endothelial cells on astrocytic plasminogen activator inhibitor type-1 gene expression in an in vitro model of the blood–brain barrier

There is accumulating evidence of the importance of cellular communication between the cells that compose the blood-brain barrier (BBB). Astrocytes are known to affect the expression of tissue-type plasminogen activator (t-PA) and its inhibitor plasminogen activator inhibitor type-1 (PAI-1) in endothelial cells. We investigated the influence of endothelial cells on astrocytic gene expression of PAI-1, protease nexin-1 (PN-1) and t-PA using an in vitro model of the BBB. Primary rat astrocyte-enriched cultures were cocultured with primary adult rat brain microvascular endothelial cells on opposite sides of a transwell membrane. After coculturing for 9–11 days, the cultures were treated with lipopolysaccharide (LPS) for 8 h or 24 h. The levels of PAI-1, PN-1 and t-PA mRNA in untreated and treated monocultures and cocultures were analyzed by Real-Time RT-PCR. Cocultivation of astrocytes and endothelial cells increased astrocytic PAI-1 mRNA expression, and this response was further amplified by LPS treatment. The levels of PN-1 and t-PA mRNA expression in astrocytes were unaffected by cocultivation and/or LPS treatment. Analysis of endothelial PAI-1 and t-PA gene expression revealed increased PAI-1 mRNA levels in cocultured cells, whereas t-PA mRNA levels remained unchanged. These results demonstrate that the cocultivation of astrocytes and endothelial cells induces a pronounced increase in astrocytic PAI-1 gene expression, and that this effect is amplified by LPS treatment. These findings imply an important role for intercellular crosstalk in modulating PAI-1 gene expression within the BBB, under both physiologic and pathophysiologic conditions.

Post-Transcriptional Regulation of Plasminogen Activator Inhibitor Type–1 Expression in Human Pleural Mesothelial Cells

The plasminogen activator inhibitor type-1 (PAI-1) effectively blocks the activities of free and receptor-bound urokinase-type plasminogen activator. Incubation of cultured human pleural mesothelial (Met5A) cells with TGF-beta increased PAI-1 protein. TGF-beta, phorbol myristate acetate, and the translation inhibitor cycloheximide induced PAI-1 mRNA and slowed its degradation, suggesting that PAI-1 mRNA could be regulated by interaction of a PAI-1 binding protein (PAI-1 mRNABp) with PAI-1 mRNA. We found that an approximately 60 kD cytoplasmic PAI-1 mRNABp is detectable in cytoplasmic extracts of MeT5A human pleural mesothelial and malignant mesothelioma cells. The PAI-1 mRNABp specifically binds to a 33-nt sequence in the 3' untranslated region of PAI-1 mRNA. Insertion of this 33-nt sequence destabilizes otherwise stable beta-globin mRNA, indicating that the binding sequence accelerates decay of endogenous PAI-1 mRNA. Competitive inhibition by overexpression of the 33-nt binding sequence in MeT5A cells reduced PAI-1 mRNA decay and increased PAI-1 protein and mRNA expression, indicating that the PAI-1 mRNABp destabilizes PAI-1 mRNA by its interaction with the endogenous 33-nt binding sequence. Incubation of Met5A cells with TGF-beta attenuated the interaction of the PAI-1 mRNABp with the 33-nt sequence. By conventional and affinity purification, we isolated the PAI-1 mRNABp and confirmed its identity as 6-phospho-d-gluconate-NADP oxidoreductase, which specifically interacts with the full-length and the 33-nt sequence of the PAI-1 mRNA 3' untranslated region. This newly recognized pathway could influence expression of PAI-1 by mesothelial or mesothelioma cells at the level of mRNA stability in the context of pleural inflammation or malignancy.

Plasminogen Activator Inhibitor Type 1 Up-Regulation Is Associated with Skeletal Muscle Atrophy and Associated Fibrosis

Muscle wasting remains a feature of many diseases and is counteracted by anabolic supplementation or exercise. Persisting atrophy-inducing conditions can be complicated by skeletal muscle fibrosis, which leads to functional impairment. Identification of early mechanisms that initiate atrophy-induced fibrosis may reveal novel targets for therapy or diagnosis. Therefore, we investigated changes in the expression of genes involved in extracellular matrix homeostasis during glucocorticoid-induced atrophy of myotubes and compared them with insulin-like growth factor-1-induced hypertrophy. Obtained results were verified in rat gastrocnemius muscle that was exposed to microgravity by space flight for 2 weeks. Myostatin and atrogin-1 mRNA levels reflected the magnitude of atrophy. Despite differential induction of these negative muscle mass regulators, no major changes in matrix metalloproteinases-2, -9, and -14 mRNAs or their physiological inhibitors could be detected in either atrophy model. In contrast, transcript levels of plasminogen activator inhibitor type 1 (PAI-1) was dramatically increased in atrophic myotubes and microgravity-exposed rat gastrocnemius muscle, while plasminogen activators remained unaltered. In contrast to atrophy, no increase in PAI-1 mRNA levels could be detected in rat hindlimb that was electrically stimulated for 21 days. Furthermore, a strong increase in PAI-1 mRNA levels was identified in skeletal muscle of patients with neurogenic muscle atrophy. Our study suggests that increased PAI-1 expression in atrophic skeletal muscle may lead to muscle fibrosis by reducing plasmin generation.

Effect of oxidative stress on the expression of t-PA, u-PA, u-PAR, and PAI-1 in endothelial cells

In this study we examined the effects of exogenous nitric oxide (sodium nitroprusside, SNP) and hydrogen peroxide (H2O2) on the expression level of tissue-type plasminogen activator (t-PA), urokinase-type plasminogen activator (u-PA), urokinase-type plasminogen activator receptor (u-PAR), and plasminogen activator inhibitor type 1 (PAI-1) in human umbilical vein endothelial cells (HUVEC). The expression of selected genes involved in fibrynolysis under the influence of oxidative stress was analyzed at the levels of mRNA, protein, and promoter activity. The results of the conducted studies revealed that oxidative stress in endothelial cells causes a significant increase in PAI-1 and u-PAR expression and a moderate increase in t-PA and u-PA expression at all of the investigated levels. We attempted to elucidate the molecular signaling mechanisms by which SNP and H2O2 regulate expression of the respective fibrinolytic factors. Therefore, we tested the protein levels of AP-1, NF-kappaB, and HIF-1 and their DNA-binding activity in endothelial cells subjected to oxidative stress. We found strong correlation between AP-1, NF-kappaB, and HIF-1 in the contribution of regulation of selected genes. In addition, we also found that the inhibition of PAI-1 synthesis by antisense oligonucleotide to PAI-1 mRNA results in markedly increased u-PAR expression and that NF-kappaB and AP-1 are involved in this regulation.

Ghrelin attenuates plasminogen activator inhibitor‐1 production induced by tumor necrosis factor‐α in HepG2 cells via NF‐κB pathway

Plasminogen activator inhibitor type 1 (PAI-1), produced partly from liver is a risk factor for macrovascular and microvascular complications of diabetes. Ghrelin, a recently described orexigenic peptide hormone, attenuates PAI-1 induced by TNF-alpha in the human hepatoma cell line (HepG2). Exposure to TNF-alpha (1 ng/ml) for 24h caused a significant increase in PAI-1 mRNA expression and protein secretion, as evaluated by RT-PCR and ELISA, but pretreatment with ghrelin (1-100 ng/ml) inhibited both basal and TNF-alpha-induced PAI-1 release in a dose and time-dependent manner in HepG2. PDTC, selective NF-kappaB inhibitor, had no additive inhibitory effects with ghrelin. The results indicate that ghrelin inhibits both basal and TNF-alpha-induced PAI-1 production via NF-kappaB pathway in HepG2 cells, and suggest that the peptide plays a therapeutic role in atherosclerosis, especially in obese patients with insulin resistance, in whom ghrelin levels were reduced.

Impact of statins on modulation by insulin of expression of plasminogen activator inhibitor type-1

Plasminogen activator inhibitor type-1 (PAI-1) is a physiologic inhibitor of fibrinolysis and a known determinant of cardiovascular risk. That its expression is stimulated by insulin in HepG2 human hepatoma cells has been shown earlier. Others have found that increased expression of PAI-1 is a risk factor for acute myocardial infarction. Pleiotropic (noncholesterol lowering) effects of statins seem to reduce cardiovascular risk. This study was designed to determine whether insulin stimulation of PAI-1 expression is attenuated by statins, and if so to explore mechanisms that are responsible for the attenuation. PAI-1 protein in the conditioned media was assayed by western blotting, and PAI-1 mRNA expression was measured by real-time reverse transcriptase polymerase chain reactions. Insulin (0.001-10 micromol/l) increased accumulation of PAI-1 protein in the conditioned media and PAI-1 mRNA expression in HepG2 cells. A transient transfection assay of the human PAI-1 promoter-luciferase construct demonstrated that insulin increased PAI-1 promoter activity. Increased PAI-1 mRNA was attenuated significantly by U0126 and PD98059, specific inhibitors of mitogen-activated protein kinase. In contrast, GF109203X, an inhibitor of the protein kinase C pathway, and LY294002, an inhibitor of phosphatidylinositol 3-kinase, exerted no effects. Simvastatin (10 micromol/l), known to translocate membrane-bound sterol regulatory element-binding protein to nuclei, attenuated PAI-1 mRNA expression induced by insulin. It did not affect baseline PAI-1 mRNA expression. Intraperitoneal injection of insulin (0.1 IU/kg) increased concentrations of PAI-1 antigen in plasma in mice within 3 h, correlating with hepatic PAI-1 mRNA expression. Insulin-mediated augmented expression of PAI-1 may be amenable to suppression attributable to pleiotropic effects of statins, potentially diminishing cardiovascular risk in patients with insulin resistance.

Unequal tissue expression of proteins from the PA/PAI system, myoma necrosis, and uterus survival after uterine artery occlusion

Objective To further the understanding of the mechanism behind myoma necrosis and uterus survival after uterine artery occlusion. Method Myomal and myometrial gene transcription and protein expression of tissue plasminogen activator (tPA), urokinase plasminogen activator (uPA), and plasminogen activator inhibitor type 1 (PAI-1) were investigated in 30 uteri. Results Compared with myometrial expression, myomal expression was less for uPA mRNA (1.34% ± 2.18% vs 2.84% ± 2.97%; P < 0.05) and greater for PAI-1 mRNA (2.67% ± 1.82% vs 1.27% ± 1.99%; P < 0.05), but the difference in tPA mRNA expression was not significant. Accordingly, compared with myometrial expression, myomal expression was less for the uPA protein ( P < 0.05) and greater for the PAI-1 protein ( P < 0.05), but the difference in tPA protein was not significant. Conclusion The PA/PAI system was found to be expressed differently in myomas and the myometrium, which may play a role in uterus survival and myoma necrosis after uterine artery occlusion.