Variant Of Plasminogen Activator Inhibitor-1 Research Articles

Abstract 14009: Plasminogen Activator Inhibitor-1 (PAI-1) is an Essential Driver of Cardiovascular Aging in Mice

Introduction: PAI-1 is the protein product of the gene Serpine1 . PAI-1 is a key contributor to cellular senescence in humans and mice, and elevated PAI-1 predicts the development of aging-related disorders including Type 2 diabetes and hypertension. GrimAge, a composite measure of epigenetic age, includes a DNA methylation estimator of plasma PAI-1 levels that independently predicts the development of cardiovascular (CV) morbidity including hypertension and time to heart failure. While many mechanistic contributions of PAI-1 to senescence and aging are well documented, its fundamental role in CV aging has not been fully investigated. Hypothesis: PAI-1 overexpression in mice promotes CV aging, while PAI-1 deficiency attenuates this phenotype in the presence of a stressor. Methods: To assess the effect of PAI-1 overexpression on CV aging, mice transgenic for a stable variant of human PAI-1 (n=14 transgenics, n=8 wild-type littermates) were characterized at 2 months and 7 months. To assess the effect of PAI-1 deficiency, mice heterozygous for a Serpine1 frame-shifting loss-of-function mutation (n=9) and wild-type littermates (n=10) were assessed; these mice underwent cardiovascular stress using N(ω)-nitro-L-arginine methyl ester (L-NAME) (1mg/L) for 8 weeks. Cardiovascular phenotyping included treadmill, pulse-wave velocity (PWV), echocardiography, and blood pressure (BP) measurement at the beginning and end of study. Histology was performed on aortas using Masson’s Trichome and analyzed for fibrosis quantification. Results: PAI-1 transgenic mice exhibited worse diastolic (E/e’) and vascular function (PWV, systolic and diastolic BP) compared to their wild-type counterparts. Histology showed more extensive peri-aortic fibrosis. In contrast, PAI-1 loss-of-function heterozygotes were broadly resistant to the vascular aging effects of L-NAME compared to wild-type mice. Molecular profiling of vascular tissues collected from animals is underway and includes bulk aorta RNAseq and measures of epigenetic age. Conclusion: PAI-1 is necessary and sufficient for the development of a CV aging phenotype in mice while PAI-1 deficiency attenuates stress-induced CV aging. Inhibition of PAI-1 will likely be tested for preventing CV aging in humans.

Association of plasminogen-activator inhibitor 1 (PAI-1) 4G/5G gene polymorphism with survival and chemotherapy-related vascular toxicity in non-seminomatous testicular cancer (TC)

5083 Background: High PAI-1 expression by tumor has been associated with poor prognosis in different cancer types, while high systemic PAI-1 levels may increase the risk of vascular thrombosis. We investigated whether the 4G/5G del/ins polymorphism in the PAI-1 promoter (rs1799889; 4G might lead to higher transcription), is associated with differences in survival and prevalence of cardiovascular events in TC. METHODS: Data were collected on survival and cardiovascular events (venous thromboembolism [VTE] and coronary heart disease [CHD]) of TC patients treated with standard platinum based chemotherapy from 1977-2004. PAI-1 genotype was determined from non-tumor genomic DNA by a Taqman SNP assay. Genotypes were compared for survival (Kaplan-Meier curves + log-rank and Cox-regression analysis), disease outcome (logistic regression) and prevalence of VTE and CHD (χ(2)-test). RESULTS: Data are available for 324 patients with median follow-up of 10 yrs (range 0-28). The 3 genotypes 4G/4G (n = 84), 4G/5G (n = 164), and 5G/5G (n = 76) do not differ in age and initial chemotherapy regime. However, the 4G/4G variant shows a higher prevalence of International Germ Cell Cancer Classification (IGCCC) poor prognosis compared to 4G/5G + 5G/5G (24% vs 10%; p = 0.003), as well as a decreased TC related survival compared to 4G/5G + 5G/5G (83% vs 94%; p = 0.001) with a hazard ratio of 2.68 for TC related death (95%CI 1.26-5.72; adjusted for IGCCC p = 0.011). In addition, the 4G/4G variant shows an odds ratio of 3.35 for refractory TC and early relapses (<2 yrs) (95% CI 1.48-7.58; p = 0.004). The 3 genotypes do not differ significantly in prevalence of VTE (4G/4G 11.9%, 4G/5G 8.5%, 5G/5G 7.9%; p = 0.616) and CHD during/after chemotherapy (4G/4G 6.0%; 4G/5G 4.9%; 5G/5G 2.6%; p = 0.594). CONCLUSIONS: The 4G/4G variant of the PAI-1 4G/5G gene polymorphism is associated with IGCCC poor prognosis, reduced survival and higher prevalence of refractory disease and early relapses. No effect on vascular toxicity was found. The 4G/4G variant of the PAI-1 gene may be an unfavorable prognostic factor as well as an unfavorable predictive factor for response to chemotherapy in patients with TC. No significant financial relationships to disclose.

Association of a PAI-1 Gene Polymorphism and Early Life Infections with Asthma Risk, Exacerbations, and Reduced Lung Function.

BackgroundPlasminogen activator inhibitor-1 (PAI-1) is induced in airways by virus and may mediate asthmatic airway remodeling. We sought to evaluate if genetic variants and early life lower respiratory infections jointly affect asthma risk.MethodsWe included Latino children, adolescents, and young adults aged 8–21 years (1736 subjects with physician-diagnosed asthma and 1747 healthy controls) from five U.S. centers and Puerto Rico after excluding subjects with incomplete clinical or genetic data. We evaluated the independent and joint effects of a PAI-1 gain of function polymorphism and bronchiolitis / Respiratory Syncytial Virus (RSV) or other lower respiratory infections (LRI) within the first 2 years of life on asthma risk, asthma exacerbations and lung function.ResultsRSV infection (OR 9.9, 95%CI 4.9–20.2) and other LRI (OR 9.1, 95%CI 7.2–11.5) were independently associated with asthma, but PAI-1 genotype was not. There were joint effects on asthma risk for both genotype-RSV (OR 17.7, 95% CI 6.3–50.2) and genotype-LRI (OR 11.7, 95% CI 8.8–16.4). A joint effect of genotype-RSV resulted in a 3.1-fold increased risk for recurrent asthma hospitalizations. In genotype-respiratory infection joint effect analysis, FEV1% predicted and FEV1/FVC % predicted were further reduced in the genotype-LRI group (β -2.1, 95% CI -4.0 to -0.2; β -2.0, 95% CI -3.1 to -0.8 respectively). Similarly, lower FEV1% predicted was noted in genotype-RSV group (β -3.1, 95% CI -6.1 to -0.2) with a trend for lower FEV1/FVC % predicted.ConclusionsA genetic variant of PAI-1 together with early life LRI such as RSV bronchiolitis is associated with an increased risk of asthma, morbidity, and reduced lung function in this Latino population.

Right atrial thrombus: A rare presentation of plasminogen activator inhibitor deficiency

Free-floating right atrial thrombi are rare but associated with high mortality. Although advances in echocardiography have improved diagnosis, their management is still the subject of debate. A 24-year-old woman with a history of smoking, obesity and oral contraceptive use presented to the emergency department with dyspnea, cough and hemoptysis. Transthoracic echocardiography revealed a large free-floating cardiac mass occupying the right atrial chamber and restricting tricuspid valve opening. In view of recurrent pulmonary embolism, she was referred for cardiac surgery and the cardiac mass was excised. Anatomopathological analysis revealed an organized and calcified thrombus. Genetic study showed her to be homozygous for the 4G/4G allelic variant of plasminogen activator inhibitor-1 and heterozygous for the allelic variant A1298C of 5,10-methylenetetrahydrofolate reductase.

Trombo na aurícula direita: apresentação rara da deficiência do inibidor do ativador do plaminogénio

Free-floating right atrial thrombi are rare but associated with high mortality. Although advances in echocardiography have improved diagnosis, their management is still the subject of debate. A 24-year-old woman with a history of smoking, obesity and oral contraceptive use presented to the emergency department with dyspnea, cough and hemoptysis. Transthoracic echocardiography revealed a large free-floating cardiac mass occupying the right atrial chamber and restricting tricuspid valve opening. In view of recurrent pulmonary embolism, she was referred for cardiac surgery and the cardiac mass was excised. Anatomopathological analysis revealed an organized and calcified thrombus. Genetic study showed her to be homozygous for the 4G/4G allelic variant of plasminogen activator inhibitor-1 and heterozygous for the allelic variant A1298C of 5,10-methylenetetrahydrofolate reductase.

Association of PAI‐1 gene polymorphism with survival and chemotherapy‐related vascular toxicity in testicular cancer

High Plasminogen-Activator Inhibitor 1 (PAI-1) expression by tumors has been associated with poor prognosis in several cancer types, and high systemic PAI-1 levels with increased thrombosis risk. The authors investigated whether the germline 4G/5G deletion/insertion polymorphism in the PAI-1 promoter (rs1799889), which may influence PAI-1 expression, is associated with survival and chemotherapy-related vascular toxicity in testicular cancer (TC). Data were collected on PAI-1 4G/5G polymorphism, survival, venous thromboembolism (VTE), and coronary heart disease (CHD) for 324 non-seminomatous TC patients treated with platinum-based chemotherapy. Genotypes were compared regarding survival and disease outcome. VTE and CHD incidence were compared with adjustment for cardiovascular risk factors and prothrombotic gene polymorphisms of coagulation factors II/prothrombin (G20210A) and V (G1691A). The 4G/4G variant of PAI-1 4G/5G polymorphism shows a higher prevalence of International Germ Cell Cancer Classification (IGCCC) poor prognosis compared with 4G/5G and 5G/5G (24% vs 8% and 15%; chi-square P = .003). In addition, the 4G/4G variant shows reduced TC-related survival with a hazard ratio of 2.69 (95% CI, 1.26-5.73; P = .010) for TC-related death (adjusted for IGCCC). This is related to an increased risk for refractory disease and early relapses (odds ratio, 3.35; 95% CI, 1.48-7.59; P = .004). PAI-1 4G/5G polymorphism is not associated with VTE and CHD risk. The 4G/4G variant of PAI-1 4G/5G polymorphism may be an unfavorable prognostic as well as predictive factor for response to chemotherapy in TC patients. If confirmed, it may contribute to the identification of patients with increased risk for refractory disease.

Transgenic overexpression of a stable Plasminogen Activator Inhibitor-1 variant

Introduction Plasminogen Activator Inhibitor-1 (PAI-1) is a member of the Serine Protease Inhibitor (SERPIN) gene family and a key regulator of fibrinolysis. PAI-1 is unique among SERPINs in its spontaneous transition to a latent, inactive state, with a half-life of approximately 2 hours under physiologic conditions. The biologic importance of the PAI-1 transition to latency is unknown. This study aimed to engineer transgenic overexpression of a stable murine PAI-1 variant to examine the physiologic effects in vivo from delayed transition of PAI-1 to latency. Materials and Methods Ten independent transgenic lines were generated with expression of a stable PAI-1 variant driven by the hybrid CMV/chicken β-actin promoter. Results Plasma PAI-1 levels in the transgenic founders ranged from 3.1 ± 0.1 ng/mL to 1268.8 ± 717.0 ng/mL. Quantitative PCR analysis in 3 transgenic lines demonstrated elevated PAI-1 mRNA in multiple tissues, with the highest increases observed in liver, brain, heart, and kidney. The fold-increase in PAI-1 mRNA over wild-type ranged from 2-fold to > 2000-fold. Immunohistochemistry showed increased PAI-1 in liver, kidney, heart, spleen, and lung. Histologic examination of transgenic mice showed no evidence of thrombosis. The two founders with the highest plasma PAI-1 levels failed to produce any transgenic offspring that survived to weaning, although genotyping of expired pups revealed successful transmission of the transgene. Conclusion These results suggest that high expression of a stable variant of PAI-1 may be lethal in mice, while more moderate expression is generally well tolerated and produces no apparent thrombosis.

Modulation of Serpin Reaction through Stabilization of Transient Intermediate by Ligands Bound to α-Helix F

Mechanism-based inhibition of proteinases by serpins involves enzyme acylation and fast insertion of the reactive center loop (RCL) into the central beta-sheet of the serpin, resulting in mechanical inactivation of the proteinase. We examined the effects of ligands specific to alpha-helix F (alphaHF) of plasminogen activator inhibitor-1 (PAI-1) on the stoichiometry of inhibition (SI) and limiting rate constant (k(lim)) of RCL insertion for reactions with beta-trypsin, tissue-type plasminogen activator (tPA), and urokinase. The somatomedin B domain of vitronectin (SMBD) did not affect SI for any proteinase or k(lim) for tPA but decreased the k(lim) for beta-trypsin. In contrast to SMBD, monoclonal antibodies MA-55F4C12 and MA-33H1F7, the epitopes of which are located at the opposite side of alphaHF, decreased k(lim) and increased SI for every enzyme. These effects were enhanced in the presence of SMBD. RCL insertion for beta-trypsin and tPA is limited by different subsequent steps of PAI-1 mechanism as follows: enzyme acylation and formation of a loop-displaced acyl complex (LDA), respectively. Stabilization of LDA through the disruption of the exosite interactions between PAI-1 and tPA induced an increase in the k(lim) but did not affect the SI. Thus it is unlikely that LDA contributes significantly to the outcome of the serpin reaction. These results demonstrate that the rate of RCL insertion is not necessarily correlated with SI and indicate that an intermediate, different from LDA, which forms during the late steps of PAI-1 mechanism, and could be stabilized by ligands specific to alphaHF, controls bifurcation between the inhibitory and the substrate pathways.

Transgenic over-expression of plasminogen activator inhibitor-1 results in age-dependent and gender-specific increases in bone strength and mineralization

The plasminogen activation system (PAS) and its principal inhibitor, plasminogen activator inhibitor-1 (PAI-1), are recognized modulators of matrix. In addition, the PAS has previously been implicated in the regulation of bone homeostasis. Our objective was to study the influence of active PAI-1 on geometric, biomechanical, and mineral characteristics of bone using transgenic mice that over-express a variant of human PAI-1 that exhibits enhanced functional stability. Femora were isolated from male and female, wildtype (WT) and transgenic (PAI-1.stab) mice at 16 and 32 weeks of age ( n = 10). Femora were imaged via DEXA for BMD and μCT for cortical mid-slice geometry. Torsional testing was employed for biomechanical properties. Mineral composition was analyzed via instrumental neutron activation analysis. Female femora were further analyzed for trabecular bone histomorphometry ( n = 11). Whole animal DEXA scans were performed on PAI-1.stab females and additional transgenic lines in which the functional domains of the PAI-1 protein were specifically disrupted. Thirty-two week female PAI-1.stab femora exhibited decreased mid-slice diameters and reduced polar moment of area compared to WT, while maintaining similar cortical bone width. Greater biomechanical strength and stiffness were demonstrated by 32 week PAI-1.stab female femora in addition to a 52% increase in BMD. PAI-1.stab trabecular bone architecture was comparable to WT. Osteoid area was decreased in PAI-1.stab mice while mineral apposition rate increased by 78% over WT. Transgenic mice expressing a reactive-site mutant form of PAI-1 showed an increase in BMD similar to PAI-1.stab, whereas transgenic mice expressing a PAI-1 with reduced affinity for vitronectin were comparable to WT. Over-expression of PAI-1 resulted in increased mineralization and biomechanical properties of mouse femora in an age-dependent and gender-specific manner. Changes in mineral preceded increases in strength/stiffness and deterred normal cross-sectional expansion of cortical bone in females. Trabecular bone was not altered in PAI-1.stab mice whereas MAR increased significantly, further supporting mineral changes as the underlying factor in strength differences. The primary influence of PAI-1 occurred during a period of basal bone remodeling, attributing a role for this system in remodeling as opposed to development. Comparison of transgenic lines indicates that PAI-1's influence on bone is dependent on its ability to bind vitronectin, and not on its proteolytic activity. The impact of PAI-1 on mouse femora supports a regulatory role of the plasminogen activation system in bone homeostasis, potentially elucidating novel targets for the treatment of bone disease.

Additivity in Effects of Vitronectin and Monoclonal Antibodies against α-Helix F of Plasminogen Activator Inhibitor-1 on Its Reactions with Target Proteinases

The serpin plasminogen activator inhibitor-1 (PAI-1) is a potential therapeutic target in cardiovascular and cancerous diseases. PAI-1 circulates in blood as a complex with vitronectin. A PAI-1 variant (N-((2-(iodoacetoxy)ethyl)-N-methyl)amino-7-nitrobenz-2-oxa-3-diazole (NBD) P9 PAI-1) with a fluorescent tag at the reactive center loop (RCL) was used to study the effects of vitronectin and monoclonal antibodies (mAbs) directed against alpha-helix F (Mab-2 and MA-55F4C12) on the reactions of PAI-1 with tissue-type and urokinase-type plasminogen activators. Both mAbs delay the RCL insertion and induce an increase in the stoichiometry of inhibition (SI) to 1.4-9.5. Binding of vitronectin to NBD P9 PAI-1 does not affect SI but results in a 2.0-6.5-fold decrease in the limiting rate constant (klim) of RCL insertion for urokinase-type plasminogen activator at pH 6.2-8.0 and for tissue-type plasminogen activator at pH 6.2. Binding of vitronectin to the complexes of NBD P9 PAI-1 with mAbs results in a decrease in klim and in a 1.5-22-fold increase in SI. Thus, vitronectin and mAbs demonstrated additivity in the effects on the reaction with target proteinases. The same step in the reaction mechanism remains limiting for the rate of RCL insertion in the absence and presence of Vn and mAbs. We hypothesize that vitronectin, bound to alpha-helix F on the side opposite to the epitopes of the mAbs, potentiates the mAb-induced delay in RCL insertion and the associated substrate behavior by selectively decreasing the rate constant for the inhibitory branch of PAI-1 reaction (ki). These results demonstrate that mAbs represent a valid approach for inactivation of vitronectin-bound PAI-1 in vivo.

Age-Dependent Spontaneous Coronary Arterial Thrombosis in Transgenic Mice That Express a Stable Form of Human Plasminogen Activator Inhibitor-1

Plasminogen activator inhibitor-1 (PAI-1) regulates fibrinolysis and has been reported to be an independent risk factor for ischemic cardiovascular events. This study describes the age-dependent development of spontaneous coronary arterial thrombi that are associated with evidence of subendocardial myocardial infarction in mice transgenic for human PAI-1. We generated two independent transgenic mice founder lines that express a stable variant of active human PAI-1 under control of the murine preproendothelin-1 (mPPET-1) promoter. Backcrossed homozygous transgenic animals from founder line I had plasma PAI-1 levels of 23+/-12 ng/mL. PAI-1 transgenic animals younger than 4 months do not exhibit any evidence of arterial or venous thrombosis. Ninety percent of transgenic animals (n=10) older than 6 months developed spontaneous occlusions of typically multiple, penetrating coronary arteries, with histological evidence of subendocardial infarction identified in 50% of animals. This study shows that chronically elevated levels of PAI-1 are associated with age-dependent coronary arterial thrombosis in mice transgenic for human PAI-1. This is the first study of a murine model of coronary thrombosis that occurs in the absence of severe hypercholesterolemia or multiple genetic manipulations. These findings provide new evidence to support the hypothesis that PAI-1 excess contributes to the development of coronary arterial thrombosis.

Inactivation of Plasminogen Activator Inhibitor-1 by Specific Proteolysis with Stromelysin-1 (MMP-3)

Matrix metalloproteinase-3 (MMP-3 or stromelysin-1) specifically hydrolyzes the Ser(337)-Ser(338) (P10-P9) and Val(341)-Ile(342) (P6-P5) peptide bonds in human plasminogen activator inhibitor-1 (PAI-1). Cleavage is completely abolished in the presence of the metal chelators EDTA or 1,10-phenanthroline. A stabilized active PAI-1 variant was also cleaved by MMP-3. At an enzyme/substrate ratio of 1/10 at 37 degrees C, PAI-1 protein cleavage occurred with half-lives of 27 or 14 min for active or stable PAI-1 and was associated with rapid loss of inhibitory activity toward tissue-type plasminogen activator with half-lives of 15 or 13 min, respectively. A substrate-like variant of PAI-1, lacking inhibitory activity but with exposed reactive site loop, was cleaved with a half-life of 23 min, whereas latent PAI-1 in which a major part of the reactive site loop is inserted into the molecule, was resistant to cleavage. Biospecific interaction analysis indicated comparable binding of active, stable, and substrate PAI-1 to both proMMP-3 and MMP-3 (K(A) of 12-22 x 10(6) m(-1)), whereas binding of latent PAI-1 occurred with lower affinity (1.7-2.3 x 10(6) m(-1)). Stable PAI-1 bound to vitronectin was cleaved and inactivated by MMP-3 in a manner comparable with that of free PAI-1; however, the cleaved protein did not bind to vitronectin. Cleavage and inactivation of PAI-1 by MMP-3 may thus constitute a mechanism decreasing the antiproteolytic activity of PAI-1 and impairing the potential inhibitory effect of vitronectin-bound PAI-1 on cell adhesion and/or migration.

Plasminogen activator inhibitor 1 may promote tumour growth through inhibition of apoptosis.

Plasminogen activator inhibitor 1 (PAI-1) has been found to be a bad prognostic factor in a number of tumours but the reason has not been fully explained. The human prostate cancer cell line PC-3 and the human promyelocytic leukaemia cell line HL-60 were used in this study to determine the effect of PAI-1 on spontaneous and induced apoptosis in culture. Apoptosis was induced with camptothecin or etoposide. Addition of a stable variant of PAI-1 or wild-type PAI-1 to these cells resulted in a significant inhibition of apoptosis. In contrast, both the latent form of PAI-1 and the stable variant of PAI-1 inactivated by a specific neutralizing monoclonal antibody, or the stable variant of PAI-1 in a complex with recombinant urokinase did not inhibit apoptosis. This indicated that the inhibitory activity of PAI-1 was required for its anti-apoptotic effect but the urokinase-type plasminogen activator receptor was not involved. These findings provide an explanation for the bad prognostic correlation of high PAI-1 levels in tumours. The anti-apoptotic effect was also found in non-tumoural cells including human umbilical vein endothelial cells and the benign human breast epithelial cell line MCF-10A, suggesting that this is a novel physiologic function of PAI-1. © 2000 Cancer Research Campaign

Plasminogen activator inhibitor 1 (PAI-1) in its active conformation: crystallization and preliminary X-ray diffraction data.

Because of its intrinsic lability, wild-type plasminogen activator inhibitor 1 (PAI-1) cannot be crystallized in its active conformation. Therefore, a stable variant of PAI-1 was used to retain the active conformation during crystallization. Four different crystallization conditions were evaluated in detail and two major types of crystals were detected. Whereas solutions consisting of either (i) cacodylate and sodium acetate, (ii) lithium sulfate and polyethylene glycol 4K, or (iii) imidazole, sodium chloride and sodium potassium phosphate buffer revealed thin platelet crystals, a solution (iv) containing ammonium acetate, citrate and polyethylene glycol 4K appeared to enhance the formation of clustered brush-like crystals. Crystals grown under condition (iii) were found to be suitable for X-ray data collection and consequent structural investigation. Data collection was 79.8% complete with a maximum resolution of 2.92 A. Importantly, PAI-1 retained its functional properties under all conditions.

Mechanisms contributing to the conformational and functional flexibility of plasminogen activator inhibitor-1

Plasminogen activator inhibitor-1 (PAI-1) is unique among the serine proteinase inhibitors (serpins) in that it can adopt at least three different conformations (active, substrate and latent). We report the X-ray structure of a cleaved substrate variant of human PAI-1, which has a new beta-strand s4A formed by insertion of the amino-terminal portion of the reactive-site loop into beta-sheet A subsequent to cleavage. This is in contrast to the previous suggestion that the non-inhibitory function of substrate-type serpins is mainly due to an inability of the reactive-site loop to adopt this conformation. Comparison with the structure of latent PAI-1 provides insights into the molecular determinants responsible for the transition of the stressed active conformation to the thermostable latent conformation.