Plasminogen Activator Inhibitor-1 Activity Research Articles

Effect of ACE Inhibition on the Fibrinolytic System in Patients Requiring Coronary Artery Bypass Grafting

Regulation of the fibrinolytic balance between plasminogen activators and inhibitors is modulated by the renin-angiotensin system. Thus, alterations in the renin-angiotensin system by ACE inhibitors probably result in modification of the fibrinolytic system. We examined the effect of a short-term treatment with the ACE inhibitor enalapril in 47 patients with severe coronary artery disease requiring coronary artery bypass grafting (CABG). Patients received either 20 mg/d enalapril or placebo for 6 days. Tissue-type plasminogen activator (TPA), plasminogen activator inhibitor-1 (PAI-1), plasmin-a2-antiplasmin-complex (PAP) and D-dimers were measured initially and after treatment. In the enalapril group PAI-1 levels were significantly reduced after treatment (11.9 +/- 2.3 U/ml vs. 17.1 +/- 3.0 U/l; P < 0.05). In the placebo group PAP levels were significantly higher ( P < 0.05) after treatment compared to initial values. No differences could be detected between the study groups with regard to TPA and D-dimers. Although PAI-1 activity levels are reduced after short-term treatment with ACE inhibitors in patients with stable angina pectoris while TPA antigen is unaffected, treatment with ACE inhibitors does not lead to a marked change in plasmin activation.

Anomalies of lipoprotein pattern and fibrinolysis in acromegalic patients: relation to growth hormone levels and insulin-like growth factor I.

The influence of hGH and IGF-I levels on lipid-, lipoprotein metabolism and fibrinolysis were studied in 23 patients with active acromegaly (14 women and 9 men, mean age 49.8 +/- 2.1 years) compared to a sex, BMI and age-matched control group. Mean Lp(a) levels were significantly higher in acromegalics than in controls (469.8 +/- 140.1; n = 23 vs. 162.7 +/- 64.9 mg/l; n = 111; p < 0.01). We found elevated apolipoprotein A-I and Apo E-concentrations in acromegalic patients compared to controls (apo A-I: 1.79 +/- 0.06 vs. 1.46 +/- 0.04 g/l; p < 0.01; apo E: 98.35 +/- 6.4 vs. 72.53 +/- 3.38 mg/l; p < 0.05). 30% of the acromegalics showed increased plasminogen activator inhibitor activity (PAI) while 66% had increased tissue-type plasminogen activator (t-PA) concentrations. There was a correlation between hGH and Lp(a) (r = 0.414; p = 0.05), between hGH and PAI (r = -0.59; p < 0.005) and IGF-I and t-PA activity (r = -0.44; p < 0.05). In a subgroup of nine acromegalics Lp(a) was reduced by 32.2 +/- 6.7% (p < 0.05) after a six-month octreotide therapy and HDL2-cholesterol-concentration increased from 0.17 +/- 0.04 to 0.24 +/- 0.04 mmol/l (p < 0.05). In conclusion, our results demonstrate that elevated Lp(a)-concentrations and changes in fibrinolysis contribute to the cardiovascular complications and should therefore be controlled in acromegalic patients.

Role for nuclear factor-κB in augmented lung injury because of interaction between hyperoxia and high stretch ventilation

High-tidal-volume mechanical ventilation and hyperoxia used in patients with acute lung injury (ALI) can induce alveolar coagulopathy and fibrin depositions within the airways. Hyperoxia has been shown to increase ventilator-induced lung injury (VILI), but the mechanisms that regulate interaction between high-tidal-volume mechanical ventilation and hyperoxia are unclear. We hypothesized that mechanical stretch with hyperoxia synergistically augmented neutrophil infiltration and production of plasminogen activator inhibitor-1 (PAI-1) via the nuclear factor-kappaB (NF-kappaB) pathway. C57BL/6 mice (n=5 per group) were exposed to high-tidal-volume (30 mL/kg) or low-tidal-volume (6 mL/kg) mechanical ventilation with room air or hyperoxia for 1 to 5h after 2-microg/g NF-kappaB inhibitor (SN-50) administration. Nonventilated mice with room air or hyperoxia served as control groups. Evans blue dye, myeloperoxidase, electrophoretic mobility shifting of nuclear protein, and inflammatory cytokine were measured. The expression of tumor necrosis factor-alpha (TNF-alpha) and PAI-1 were studied by immunohistochemistry. The addition of hyperoxia to high-tidal-volume ventilation-augmented lung injury, as demonstrated by increased microvascular leak, neutrophil migration into the lung, TNF-alpha and active PAI-1 production, DNA binding activity of NF-kappaB, and NF-kappaB activation. No statistically significant increase of neutrophil infiltration and inflammatory cytokine production was found in the mice ventilated at 6 mL/kg using hyperoxia. Hyperoxia-induced augmentation of VILI was attenuated in mice with pharmacologic inhibition of NF-kappaB activity by SN-50. We conclude that hyperoxia increased high-tidal-volume-induced cytokine production and neutrophil influx through activation of the NF-kappaB pathway.

Gabexate Mesilate Inhibits the Expression of HMGB1 in Lipopolysaccharide-Induced Acute Lung Injury

High mobility group box 1 (HMGB1) is an important late mediator of acute lung injury. Gabexate mesilate (GM) is a synthetic protease inhibitor with some anti-inflammatory action. We aimed to evaluate the effect of GM on HMGB1 in lipopolysaccharide (LPS)-induced lung injury in rats. Prior to the injection of LPS to induce lung injury, rats were administered saline or GM. Injury to the lung and expression of HMGB1, plasminogen activator inhibitor-1 (PAI-1), and protease-activated receptor-2 (PAR-2) were examined. In an accompanying in vitro study, we performed LPS stimulation under GM administration in a mouse macrophage cell line and measured the quantity of HMGB1 and cytokines in the supernatant, and cell signal in the cells. Histologic examination revealed that interstitial edema, leukocytic infiltration, and HMGB1 protein expression were markedly reduced in the GM+LPS group compared wih the LPS group. Furthermore, LPS-induced increases in PAI-1 and PAR-2 activity and in plasma HMGB1 concentrations were lower in the rats given both GM and LPS than in the rats given LPS alone. Release of HMGB1 and cytokines from the cell after the administration of LPS were decreased by GM. Phosphorylation of IκB was inhibited by GM. GM may have inhibited PAI-1 and PAR-2, thereby indirectly inhibiting HMGB1 and reducing tissue damage in the lung. This indicates that GM can inhibit lung injury induced by LPS in rats. GM is a candidate for use in novel strategies to prevent or minimize lung injury in sepsis.

Nox4 mediates the expression of plasminogen activator inhibitor-1 via p38 MAPK pathway in cultured human endothelial cells

Introduction Plasminogen Activator Inhibitor-1 (PAI-1) is the most potent endogenous inhibitor of fibrinolysis which is implicated in the pathogenesis of myocardial infarction and metabolic syndrome. The formation of reactive oxygen species (ROS) plays an important role in the pathology of vascular disorders and has been shown to increase PAI-1 expression by endothelial cells. Growing evidence indicates that NADPH oxidase and in particular the constitutively active Nox4-p22 phox complexes are major sources of ROS in endothelial cells. The aim of the present study was to characterize the role of NADPH oxidase and in particular Nox4 in the regulation of PAI-1 expression in cultured Human Umbilical Venous Endothelial Cells (HUVECs). Methods and Results N-acetylcysteine (NAC, scavenger of ROS), diphenylene iodonium chloride (DPI, inhibitor of flavoproteins), M40403 (superoxyde dismutase mimic) and S17834 (inhibitor of NADPH oxidase) inhibited PAI-1 release and promoter activity in HUVECs. Specific knock down of Nox4 mRNA by siRNA caused a decrease in ROS production and NADPH oxidase activity. Moreover, Nox4 silencing decreased PAI-1 expression, release and activity as well as p38 MAPK pathways and NFκB activation. These signalling pathways are also involved in PAI-1 release. Conclusions The NADPH oxidase inhibitors DPI and S 17834 as well as Nox4 silencing decreased PAI-1 synthesis in human cultured endothelial cells demonstrating the involvement of the constitutively active Nox4-containing NADPH oxidase in ROS-mediated PAI-1 transcription via p38 MAPK pathways. NADPH oxidase targeting with inhibitors such as S17834 could be an interesting strategy to decrease both oxidative stress and PAI-1 synthesis.

TGF-&amp;beta;1 -Induced Expression of the Anti-Apoptotic PAI-1 Protein Requires EGFR Signaling

TGF-β1 and its target gene encoding plasminogen activator inhibitor-1 (PAI-1) are major regulators of capillary outgrowth, vessel maturation and angiogenic network stability. The increasing realization of the complexity of PAI-1 action in the vascular system requires analysis of specific signaling events that impact its expression in a physiologically-relevant cell system. PAI-1 was required for tubular differentiation and maintenance of cellular survival in complex gels since targeted disruption of PAI-1 synthesis or activity with antisense constructs or function-blocking antibodies resulted in network regression. Indeed, serum-deprivation-induced apoptosis of tubulogenic T2 cells was concentration-dependently inhibited by addition of a stable PAI-1 mutant protein consistent with the established pro-survival role of PAI-1 in vascular endothelial cells. PAI-1 induction and ERK pathway activation in response to TGF-β1 was attenuated by EGFR signaling blockade (with AG1478) or preincubation with the MMP/ADAM inhibitor GM6001. The combination of AG1478 + GM6001 completely ablated both responses suggesting that EGFR transactivation is important in PAI-1 gene control and may, at least partially, involve ligand shedding. TGF-β1-stimulated PAI-1 induction was preceded, in fact, by EGFR phosphorylation on Y845 (a src kinase target residue). EGFR1 knockdown with lentiviral shRNA constructs, moreover, effectively decreased (by >75%) TGF-β1-stimulated PAI-1 expression whereas infection with control (i.e. GFP) viruses had no effect. TGF-β1 failed to induce PAI-1 synthesis in EGFR-deficient fibroblasts while introduction of a wild-type EGFR1 construct in EGFR(-/-) cells rescued the PAI-1 response to TGF-β1 confirming, at a genetic level, the targeted knockdown data. The continued clarification of novel cooperative signaling cascades that impact expression of important angiogenic genes (e.g. PAI-1) may provide therapeutically useful targets to manage the pathophysiology of human neoplastic and vascular diseases.

Antimetastatic Potential of PAI-1–Specific RNA Aptamers

The serine protease inhibitor plasminogen activator inhibitor-1 (PAI-1) is increased in several cancers, including breast, where it is associated with a poor outcome. Metastatic breast cancer has a dismal prognosis, as evidenced by treatment goals that are no longer curative but are largely palliative in nature. PAI-1 competes with integrins and the urokinase plasminogen activator receptor on the surface of breast cancer cells for binding to vitronectin. This results in the detachment of tumor cells from the extracellular matrix, which is critical to the metastatic process. For this reason, we sought to isolate RNA aptamers that disrupt the interaction between PAI-1 and vitronectin. Through utilization of combinatorial chemistry techniques, aptamers have been selected that bind to PAI-1 with high affinity and specificity. We identified two aptamers, WT-15 and SM-20, that disrupt the interactions between PAI-1 and heparin, as well as PAI-1 and vitronectin, without affecting the antiprotease activity of PAI-1. Furthermore, SM-20 prevented the detachment of breast cancer cells (MDA-MB-231) from vitronectin in the presence of PAI-1, resulting in an increase in cellular adhesion. Therefore, the PAI-1 aptamer SM-20 demonstrates therapeutic potential as an antimetastatic agent and could possibly be used as an adjuvant to traditional chemotherapy for breast cancer.

Metformin decreases angiogenesis via NF-κB and Erk1/2/Erk5 pathways by increasing the antiangiogenic thrombospondin-1

Polycystic ovary syndrome (PCOS) is associated with insulin resistance (IR), obesity, and cardiovascular complications. Thrombospondin-1 (TSP-1) is a novel antiangiogenic adipokine highly expressed in obese insulin-resistant subjects. We sought to assess TSP-1 levels in adipose tissue (AT) from PCOS women and matched controls. The effects of metformin treatment on circulating TSP-1 levels in PCOS subjects, the effects of serum from normal and PCOS women on in vitro migration and angiogenesis before and after metformin treatment, and ex vivo regulation of AT TSP-1 by D-glucose were also studied. Serum TSP-1 (ELISA), subcutaneous and omental AT TSP-1 mRNA (reverse transcriptase-polymerase chain reaction), and protein (western blotting) were significantly lower in PCOS women (P < 0.05). Corresponding plasminogen activator inhibitor-1 (PAI-1) and PAI-1 activity were significantly higher (P < 0.01). After 6 months of metformin treatment, there was a significant increase in serum TSP-1 (P < 0.05) and a corresponding decrease in PAI-1 and PAI-1 activity (P < 0.01). In vitro migration and angiogenesis were significantly increased in serum from PCOS women (P < 0.01); these effects were significantly attenuated by metformin treatment (P < 0.01) through the regulation of TSP-1 levels via nuclear factor-kappaB (NF-kappaB), extracellular regulated-signal kinase 1/2 (Erk1/2) and Erk5 pathways. Importantly, changes in the intima media thickness were predictive of changes in serum TSP-1 (P = 0.049). In AT explants, glucose significantly decreased TSP-1 protein production and secretion into conditioned media (ELISA) (P < 0.05, P < 0.001). TSP-1 levels are lower in PCOS women. Metformin treatment increases serum TSP-1 in these women. Our findings provide novel insights into the relationship between obesity, IR, and angiogenesis.

The role of plasminogen activator inhibitor 1 in renal and cardiovascular diseases

The 50 kDa glycoprotein plasminogen activator inhibitor 1 (PAI-1) is the major physiological inhibitor of tissue-type and urokinase-type plasminogen activator. These two molecules convert inactive plasminogen into its fibrin-degrading form, plasmin. Plasma and tissue concentrations of PAI-1 are extremely low under normal circumstances but increase under pathologic conditions. This increase is mediated by many factors, including reactive oxygen species. Increased PAI-1 activity is associated with an increased risk of ischemic cardiovascular events and tissue fibrosis. Whereas the antifibrinolytic property of PAI-1 derives mainly from its inhibition of serine proteases, its profibrotic actions seem to derive from a capacity to stimulate interstitial macrophage recruitment and increase transcription of profibrotic genes, as well as from inhibition of serine proteases. Despite studies in mice that lack or overexpress PAI-1, the biological effects of this molecule in humans remain incompletely understood because of the complexity of the PAI-1-plasminogen-activator-plasmin system. The cardioprotective and renoprotective properties of some currently available drugs might be attributable in part to inhibition of PAI-1. The development of an orally active, high-affinity PAI-1 inhibitor will provide a potentially important pharmacological tool for further investigation of the role of PAI-1 and might offer a novel therapeutic strategy in renal and cardiovascular diseases.

Plasminogen activator inhibitor‐1 can regulate myoendothelial junction formation

Myoendothelial junctions are cellular projections that form between the vascular smooth muscle cell and endothelial cell layers of the resistance vasculature by disruption of the internal elastic lamina. How and why these structures form is unknown, but given the location of the MEJ, it is likely that degradation of the internal elastic lamina is required. We have recently identified plasminogen activator inhibitor ‐1 (PAI‐1), a mediator of the fibrinolytic system, as being preferentially localized at the MEJ both in vivo and in vitro (see abstract by Heberlein, et al.). Using Metamorph software analysis on a vascular cell co‐culture model (Isakson et al., 2005), we show that inhibition of PAI‐1 activity using a monoclonal antibody (1000 ng/mL) has an approximate 20% increase in the number of MEJs formed, as identified by phalloidin labeling of actin. Conversely the addition of PAI‐1 (100 ng/mL) results in an approximate 20% decrease in number of MEJs formed. The formation of MEJs in response to PAI‐1 and PAI‐1 monoclonal antibodies appears to be dose‐dependent. These results were compared to MEJ formation in PAI‐1‐/‐ mice. Based on these data we conclude that PAI‐1 may regulate the formation of MEJs in the vasculature. Supported by NIH RO1 088554 and an AHA SDG.

Prediction of chronic allograft damage index of renal allografts using serum level of plasminogen activator inhibitor‐1

Plasminogen activator inhibitor-1 (PAI-1) plays an important role in renal fibrosis. We conducted this study to examine whether serum PAI-1 has a role in predicting chronic allograft nephropathy (CAN). Fifty kidney transplant recipients receiving graft biopsies were enrolled. The pathologic diagnoses were acute tubular necrosis (ATN; n = 12), borderline rejection (BR; n = 7), acute rejection (ACR; n = 12), CAN (n = 11), polyomavirus nephropathy (PVN; n = 3) and others (n = 5; glomerulopathy, n = 4; calcineurin inhibitor nephropathy, n = 1). The serum level of PAI-1 and chronic allograft damage index (CADI) score of each patient were determined. The CADI score of all patients was 4 (0-10) (median and range) and in each group was ATN 0.5 (0-4), BR 2.0 (1-4), ACR 4.0 (2-8), CAN 5.0 (4-10), PVN 7 (4-8) and others 2 (0-8). The serum PAI-1 level of each group was ATN 9.38 (2.35-14.52) ng/mL, BR 10.09 (0.61-18.06) ng/mL, ACR 11.08 (2.32-20.68) ng/mL, CAN 14.51 (3.66-21.12), PVN 14.79 (13.94-21.94) and others 16.35 (4.05-21.01) ng/mL. CADI score is associated with serum PAI-1 activity (r = 0.405, p = 0.003) and is inversely associated with serum creatinine (r = -0.348, p = 0.011), but not with estimated glomerular filtration rate (p = 0.124). Serum PAI-1 level has the potential to be a marker to predict CADI score, the quantitative score of CAN.

Unfractionated heparin and enoxaparin reduce high-stretch ventilation augmented lung injury: a prospective, controlled animal experiment

IntroductionDysregulation of coagulation and local fibrinolysis found in patients with acute lung injury often results in the need for the support of mechanical ventilation. High-tidal-volume mechanical ventilation can increase lung damage and suppression of fibrinolytic activity, but the mechanisms are unclear. We hypothesized that subcutaneous injections of unfractionated heparin and enoxaparin would decrease neutrophil infiltration, lung edema, and plasminogen-activator inhibitor-1 (PAI-1) production in mice exposed to high-tidal-volume ventilation.MethodsMale C57BL/6 mice, weighing 20 to 25 g, were exposed to either high-tidal-volume (30 ml/kg) or low-tidal-volume (6 ml/kg) mechanical ventilation with room air for 1 to 5 hours after 200 IU/kg or 400 IU/kg unfractionated heparin and 4 mg/kg or 8 mg/kg enoxaparin administration. Nonventilated mice served as a control group. Evan blue dye, lung wet- to dry-weight ratio, histopathologic grading of epithelium, myeloperoxidase, and gene expression of PAI-1 were measured. The expression of PAI-1 was studied by immunohistochemistry.ResultsHigh-tidal-volume ventilation induced increased microvascular permeability, neutrophil influx, PAI-1 mRNA expression, production of PAI-1 protein, and positive staining of PAI-1 in epithelium in a dose-dependent manner. Lung injury induced by high-tidal-volume ventilation was attenuated with PAI-1-deficient mice and pharmacologic inhibition of PAI-1 activity by low-dose unfractionated heparin and enoxaparin.ConclusionsWe conclude that high-tidal-volume mechanical ventilation increased microvascular permeability, neutrophil influx, lung PAI-1 mRNA expression, production of active PAI-1. The deleterious effects were attenuated by low-dose unfractionated heparin or enoxaparin treatment. Understanding the protective mechanism of unfractionated heparin and enoxaparin related to the reduction of PAI-1 may afford further knowledge of the effects of mechanical forces in the lung and development of possible therapeutic strategies involved in acute lung injury.

Function of dynamically stimulated endothelium and renin–angiotensin–aldosterone system in normotensive subjects with a family history of hypertension

Genetic influences on the acute stimulation of the renin-angiotensin-aldosterone system (RAAS) and on endothelial activation were studied by examining healthy blood donors with and without hypertensive parents. Healthy blood donors were assigned to two groups, according to the presence or absence of a parental history of hypertension. Plasma levels of renin, nitric oxide (NO) and plasminogen activator inhibitor 1 (PAI-1) were studied before and after acute alterations in renal perfusion induced by phlebotomy, and the two groups compared. During phlebotomy, 400-500 mL of blood was extracted from each subject, with that volume varying relative to each subject's body surface area (m(2)). No statistically significant inter-group differences were observed between the baseline mean levels of plasma renin, NO or PAI-1. After phlebotomy, significant increases were detected in mean plasma renin activity (PRA) and NO levels and in PAI-1 activity (P < 0.001). However, the increases in mean PRA (P < 0.05) level and PAI-1 activity (P < 0.05) were more pronounced in those with hypertensive parents than those without; conversely, the increase in NO levels was more pronounced in the latter group. No statistically or clinically significant difference was found between the mean body mass indices of these two groups. Only two subjects were overweight, and none were obese; the remainder had weights that were normal. We found no significant correlation between body mass index and either NO or PAI-1 level. Post-phlebotomy, PRA and PAI-1 responses were more dramatic, but the NO response less in normotensive subjects having a parental history of hypertension, suggesting that these changes may represent familial, possibly genetic influences before overt hypertension occurs.

Autonomic Function and Prothrombotic Activity in Women after an Acute Coronary Event

The link between decreased heart rate variability (HRV) and atherosclerosis progression is elusive. We hypothesized that reduced HRV relates to increased levels of prothrombotic factors previously shown to predict coronary risk. We studied 257 women (aged 56 +/- 7 years) between 3 and 6 months after an acute coronary event and obtained very low frequency (VLF), low frequency (LF), and high frequency (HF) power, and LF/HF ratio from 24-hour ambulatory ECG recordings. Plasma levels of activated clotting factor VII (FVIIa), fibrinogen, von Willebrand factor antigen (VWF:Ag), and plasminogen activator inhibitor-1 (PAI-1) activity were determined, and their levels were aggregated into a standardized composite index of prothrombotic activity. In bivariate analyses, all HRV indices were inversely correlated with the prothrombotic index explaining between 6% and 14% of the variance (p < 0.001). After controlling for sociodemographic factors, index event, menopausal status, cardiac medication, lifestyle factors, self-rated health, metabolic variables, and heart rate, VLF power, LF power, and HF power explained 2%, 5%, and 3%, respectively, of the variance in the prothrombotic index (p < 0.012). There were also independent relationships between VLF power and PAI-1 activity, between LF power and fibrinogen, VWF:Ag, and PAI-1 activity, between HF power and FVIIa and fibrinogen, and between the LF/HF power ratio and PAI-1 activity, explaining between 2% and 3% of the respective variances (p < 0.05). Decreased HRV was associated with prothrombotic changes partially independent of covariates. Alteration in autonomic function might contribute to prothrombotic activity in women with coronary artery disease (CAD).

Characterization of a Site on PAI-1 That Binds to Vitronectin Outside of the Somatomedin B Domain

Vitronectin and plasminogen activator inhibitor-1 (PAI-1) are proteins that interact in the circulatory system and pericellular region to regulate fibrinolysis, cell adhesion, and migration. The interactions between the two proteins have been attributed primarily to binding of the somatomedin B (SMB) domain, which comprises the N-terminal 44 residues of vitronectin, to the flexible joint region of PAI-1, including residues Arg-103, Met-112, and Gln-125 of PAI-1. A strategy for deletion mutagenesis that removes the SMB domain demonstrates that this mutant form of vitronectin retains PAI-1 binding (Schar, C. R., Blouse, G. E., Minor, K. M., and Peterson, C. B. (2008) J. Biol. Chem. 283, 10297-10309). In the current study, the complementary binding site on PAI-1 was mapped by testing for the ability of a battery of PAI-1 mutants to bind to the engineered vitronectin lacking the SMB domain. This approach identified a second, separate site for interaction between vitronectin and PAI-1. The binding of PAI-1 to this site was defined by a set of mutations in PAI-1 distinct from the mutations that disrupt binding to the SMB domain. Using the mutations in PAI-1 to map the second site suggested interactions between alpha-helices D and E in PAI-1 and a site in vitronectin outside of the SMB domain. The affinity of this second interaction exhibited a K(D) value approximately 100-fold higher than that of the PAI-1-somatomedin B interaction. In contrast to the PAI-1-somatomedin B binding, the second interaction had almost the same affinity for active and latent PAI-1. We hypothesize that, together, the two sites form an extended binding area that may promote assembly of higher order vitronectin-PAI-1 complexes.

Plasminogen Activator Inhibitor-1 Protects Endothelial Cells from FasL-Mediated Apoptosis

Plasminogen activator inhibitor-1 (PAI-1) paradoxically enhances tumor progression and angiogenesis; however, the mechanism supporting this role is not known. Here we provide evidence that PAI-1 is essential to protect endothelial cells (ECs) from FasL-mediated apoptosis. In the absence of host-derived PAI-1, human neuroblastoma cells implanted in PAI-1-deficient mice form smaller and poorly vascularized tumors containing an increased number of apoptotic ECs. We observed that knockdown of PAI-1 in ECs enhances cell-associated plasmin activity and increases spontaneous apoptosis in vitro. We further demonstrate that plasmin cleaves FasL at Arg144-Lys145, releasing a soluble proapoptotic FasL fragment from the surface of ECs. The data provide a mechanism explaining the proangiogenic activity of PAI-1.

Sex-related differences in the associations between hyperleptinemia, insulin resistance and dysfibrinolysis

The adipocyte-derived hormone leptin is associated with insulin resistance and reduced fibrinolytic status--or dysfibrinolysis--in humans. As leptin associates differentially to the development of cardiovascular disease and diabetes in men and women, we hypothesized that leptin and insulin sensitivity are related to dysfibrinolysis in a sex-dependent manner. Thirty-two men and 40 women were recruited from the Monitoring of trends and determinants in Cardiovascular disease (MONICA) population sample, representing the highest and lowest quartiles of fasting insulin levels. Lipids, fibrinolytic status [plasminogen activator inhibitor 1 (PAI-1) activity, tissue plasminogen activator (tPA) mass and activity, and tPA-PAI complex], leptin, testosterone and sex-hormone-binding globulin were measured. Insulin sensitivity was estimated using the euglycaemic clamp technique. Body composition was determined by bioimpedance. Determinants for circulating levels of fibrinolytic factors were explored in a multivariate linear regression analysis. Levels of fibrinolytic variables and estimated insulin sensitivity did not differ between men and women. Leptin was independently associated with reduced fibrinolytic status (high PAI-1 activity, low tPA activity, high tPA mass, and high tPA-PAI complex) in men (P < 0.001-0.002). In women, fat mass and/or insulin sensitivity were related to these factors (P < 0.001-0.03), and leptin only to reduced tPA activity (P = 0.002). Hyperleptinemia, dysfibrinolysis, insulin sensitivity and androgenicity associate differentially in men and women.

Administration of pigment epithelium-derived factor prolongs bleeding time by suppressing plasminogen activator inhibitor-1 activity and platelet aggregation in rats

We have recently found that pigment epithelium-derived factor (PEDF), a glycoprotein with potent neuronal differentiating activity, not only inhibits endothelial cell damage, smooth muscle cell proliferation and platelet aggregation in vitro, but also suppresses occlusive thrombus formation in rats. These observations suggest PEDF may play a protective role against atherothrombosis. However, effects of PEDF on hemostasis, fibrinolysis and platelet function in vivo are not fully understood. In this study, we examined the effects of PEDF on tail vein bleeding time, plasminogen activator inhibitor-1 (PAI-1) activity and ex vivo-platelet aggregation in rats. Intravenous injection of 30 microg PEDF significantly prolonged the tail vein bleeding time by about 25%. Administration of 30 microg PEDF was also found to reduce the PAI-1 activity in rats. Further, ADP-induced platelet aggregation was suppressed in PEDF-treated rats. The present study demonstrated first that PEDF exerted anti-hemostatic effects in rats, at least in part by suppressing PAI-1 activity and platelet aggregation. PEDF may be a novel therapeutic target for the treatment of patients with thrombogenic tendency and hypercoagulability.

The impact of the PAI-1 4G/5G polymorphism on the outcome of patients with ALI/ARDS

Intoduction Increased levels of plasminogen activator inhibitor-1 (PAI-1) have been associated with worse outcome in ALI/ARDS. A single guanosine insertion/deletion (4G/5G) polymorphism in the promoter region of the PAI-1 gene, may play an important role in the regulation of PAI-1 expression. The objective of the study was to evaluate the effect of this polymorphism on the outcome of critically ill patients with ALI/ARDS. Materials and Methods 52 consecutive ventilated patients with ALI/ARDS were studied. Bronchoalveolar lavage was performed within 48 hours from diagnosis. Measurement of plasma and BALF PAI-1 activity and D-dimers levels, and 4G/5G genotyping of PAI-1 were carried out. The primary outcome was 28-day mortality, and secondary outcomes included organ dysfunction and ventilator-free days. Results 17 patients were homozygotes for the 4G allele. Severity scores were not different between subgroups upon study enrollment. 28-day mortality was 70.6% and 42.9% for the 4G-4G and the non-4G-4G patients, respectively (p = 0.06). PAI-1 activity levels and D-dimer in plasma and BALF were not significantly different between the 4G-4G and the non-4G-4G subgroups. In the multivariate analysis, genotype 4G/4G was the only variable independently associated with 28-day mortality (Odds Ratio = 9.95, 95% CI: 1.79-55.28, p = 0.009). Furthermore, genotype 4G/4G and plasma PAI-1 activity levels were independently negatively associated with ventilator free days (p = 0.033 and p = 0.008, respectively). Conclusions ALI/ARDS patients, homozygous for the 4G allele of the PAI-1 gene, experienced higher 28-day mortality. This genotype was associated with a reduction in the number of days of unassisted ventilation and was inversely associated with the number of days without organ failure.

Correlationship of plasminogen activator inhibitor-1 (PAI-1) and mullerian inhibiting substance (MIS) in follicular fluid with endometrial receptivity and pregnancy outcome in ART cycles

OBJECTIVE: Plasminogen activator inhibitor -1 (PAI-1)and Mullerian inhibiting substance (MIS) also known as antimullerian hormone (AMH) in follicular fluid were estimated to evaluate their relationships with endometrial receptivity and pregnancy outcome in ART cycles. DESIGN: Prospective study of 124 IVF cycles. MATERIALS AND METHODS: Controlled ovarian hyperstimulation in all women (Mean age: 30.8 ± 0.4 yrs, BMI: 24.66 ± 0.4) was done with gonadotropin (225 IU / day). Oocyte retrieval was done 34 hours after hCG administration. PAI-1 and MIS concentrations per mg of protein by ELISA and serum E2 and P by RIA method in FF were estimated. Conventional luteal phase support was given in all cycles. Seven days after embryo transfer (ET), serum P, 17OHP and E2 along with transvaginal sonography for endometrial response were measured. Measurement of β hCG on day 14 of ET indicated pregnancy outcome. By the end of sixth week, presence of gestational sac with cardiac activity confirmed clinical pregnancy. Statistical analysis, viz.t test, correlation coefficient and receiver operator characteristics ROC AUC of PAI-1 to determine the cutoff value for achieving pregnancy, was done using Graph pad Prism version 5.0. RESULTS: Out of 124 IVF cycles, six cycles were abandoned due to no response and in eight cycles no ETs were done. A mean of 2.5 ± 0.1 embryos was transferred in 110 IVF cycles. Out of 46 pregnancies (PR: 41.8 %) that resulted, 6 turned out as biochemical pregnancies. The cycles were divided into pregnant and non-pregnant groups. Both FF PAI-1 and FF MIS levels in pregnant group were significantly low (P value: <0.0001) as compared to non-pregnant group. FF MIS strongly correlated with FF PAI-1 and D7 OHP in pregnant group (Pearson r: 0.4515 and 0.3321 respectively). Serum17- OHP levels and endometrial thickness on D7 in non-pregnant group showed inverse correlation with FF PAI-1 (Pearson r = - o.3324). Though sr. P in both groups remained almost unchanged, 17- OHP and E2 levels were found to be significantly high (0.05 and 0.005 respectively) in pregnant group as compared to non-pregnant group on D7 of ET. CONCLUSIONS: MIS seemed to regulate the activity of PAI-1 in ART cycles. Lower PAI-1 activity in follicular fluid seemed to denote the promotion or triggering factor for increased proteolytic activity at the endometrial level to prepare a favorable bed for invasion of trophoblasts of the embryo, which facilitated its implantation.