Increased intramural expression of plasminogen activator inhibitor type 1 after balloon injury: a potential progenitor of restenosis

Plasminogen activator inhibitor-1 regulates the vascular expression of vitronectin

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

SUMMARY

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

The role of fibrinolytic genes and proteins in the development of allograft vascular disease

BACKGROUND

We have previously shown that lack of plasminogen activator inhibitor-1 (PAI-1) expression in donor tissue greatly increases intimal proliferation (IP) after allogeneic transplantation. We sought to determine the relative role of PAI-1 and other fibrinolytic proteins in the development of IP.

METHODS

We used an abdominal aortic transplant model in mice to investigate IP in 3 groups of 6 recipients. In the isograft group, CBA/J strain mice were donors and recipients, donors for allograft group were C57BL/6J mice, and for the allograft/knockout group, C57BL/6J PAI-1 knockout mice. All groups received weekly injections of anti-CD8/CD4 monoclonal antibodies. IP was calculated at 50 days, and sections were analyzed for fibrinolytic proteins, messenger RNA (mRNA) and PAI-1 activity using immunohistochemistry (IHC), in situ hybridization (ISH), reverse transcription-polymerase chain reaction (RT-PCR), and Western blot analysis.

RESULTS

Significantly more IP developed in the allograft/knockout group vs the isograft (p < 0.001) and the allograft groups (p = 0.003). There was marked intimal expression of tissue plasminogen activator (tPA), urokinase PA (uPA), and uPA receptor (uPAR) proteins and mRNA in the allograft and allograft/knockout groups vs the isograft group. Allografts also showed significant intimal staining for PAI-1 protein and mRNA. RT-PCR demonstrated a stepwise increase in profibrinolytic protein mRNA from isograft to allograft to allograft/knockout groups, particularly uPA (p = 0.02) and uPAR (p = 0.016). Western blot data showed complementary findings. PAI-1 activity was persistently present in isograft and allograft animals, only. Intimas in allograft and allograft/knockout groups were primarily smooth muscle cells.

CONCLUSIONS

PAI-1 reduces IP by limiting smooth muscle cell activity, with little change in matrix composition likely by modulating profibrinolytic protein expression.

Inhibition of plasminogen activator inhibitor-1 expression in vascular smooth muscle cells by protoporphyrins through a heme oxygenase-independent mechanism

Heme oxygenase-1 (HO-1), a rate-limiting enzyme in heme catabolism, has been shown to play a regulatory role in the expression of plasminogen activator inhibitor-1 (PAI-1), a risk factor for vascular disease. Accordingly, we examined the effect of protoporphyrins, both HO inhibitors and activators, on PAI-1 expression in human vascular smooth muscle cells (VSMCs). Tin-protoporphyrin (SnPP) markedly inhibited the transforming growth factor beta1 (TGFbeta1)-induced expression of PAI-1 protein. Protoporphyrins, whether they are inhibitors or activators of HO, produced a similar inhibitory effect. However, SnPP had no effect on the level of PAI-1 mRNA transcripts. Knockdown of human HO-1 with a specific siRNA did not reduce the PAI-1 protein level in TGFbeta1-treated cells. In addition, the proteasome inhibitor lactacystin reversed the inhibitory effect of SnPP on PAI-1 protein expression. Both cobalt-protoporphyrin (CoPP) and CoCl2 markedly induced HO-1 expression. However, CoPP did not affect PAI-1 gene expression, whereas CoCl2 upregulated PAI-1 mRNA in a dose-dependent manner. Our results demonstrate that protoporphyrins can block the TGFbeta1-mediated induction of PAI-1 protein in VSMCs and that this inhibitory effect is independent of HO activity.

Genes overexpressed in cerebral arteries following salt-induced hypertensive disease are regulated by angiotensin II, JunB, and CREB

Although changes in gene expression are necessary for arterial remodeling during hypertension, the genes altered and their mechanisms of regulation remain uncertain. The goal of this study was to identify cerebral artery genes altered by hypertension and define signaling pathways important in their regulation. Intact cerebral arteries from Dahl salt-sensitive normotensive and hypertensive high-salt (HS) rats were examined by immunostaining, revealing an increased phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) and expression of the proliferative marker Ki-67 in arteries from hypertensive animals. Arterial RNA analyzed by microarray and validated with RT-quantitative PCR revealed that jun family member junB and matricellular genes plasminogen activator inhibitor-1 (PAI-1) and osteopontin (OPN) were significantly overexpressed in HS arteries. Fisher exact test and annotation-based gene subsets showed that genes upregulated by Jun and Ca2+/cAMP-response element-binding protein (CREB) were overrepresented. A model of cultured rat cerebrovascular smooth muscle cells was used to test the hypothesis that angiotensin II (ANG II), JunB, and CREB are important in the regulation of genes identified in the rat hypertension model. ANG II induced a transient induction of junB and a delayed induction of PAI-1 and OPN mRNA levels, which were reduced by ERK inhibition with U-0126. Silencing junB using small-interfering RNA reduced mRNA levels of OPN but not PAI-1. The silencing of CREB reduced PAI-1 induction by ANG II but enhanced the transcription of OPN. Together, these results suggest that salt-induced hypertensive disease promotes changes in matricellular genes that are stimulated by ANG II, regulated by ERK, and selectively regulated by JunB and CREB.

Screening the Single Nucleotide Polymorphisms in Patients with Internal Carotid Artery Stenosis by Oligonucleotide-Based Custom DNA Array

Early screening of individuals considered to be at risk for severe internal carotid artery (ICA) stenosis is an important strategy for preventing ischemic cerebral stroke. The purpose of this study is to screening candidate single nucleotide polymorphisms (SNPs) associated with severe ICA stenosis using a newly developed oligonucleotide-based custom DNA array. The subjects consisted of 47 controls and 46 patients with severe ICA stenosis (≥70%) who underwent carotid endarterectomy (CEA). Subjects gave informed consent and we obtained samples of blood and genomic DNA. We studied 8 candidate genes: renin-angiotensin system [angiotensinogen (AGT), angiotensin II receptor type 1 (AGTR1), nitric oxide synthase 3 (NOS3)]; growth factor [hepatocyte growth factor (HGF)]; transgelin (SM22); cytokine [chemokine receptor 2 (CCR2)]; coagulation-fibrinolysis system [5,10-methylenetetrahydrofolate reductase (MTHFR)]; and plasminogen activator inhibitor 1 (PAI-1). Genotyping of candidate SNPs was done with a line probe assay (LiPA) based on an oligonucleotide-based DNA array. Results: The allele frequency of PAI-1 -1965 delG (odds ratio (OR), 0.3; 95% confidence interval (CI), 0.2–0.6) and MTHFR (OR 1.3, 95% CI, 1.0–1.5) were significantly different between controls and cases with ICA stenosis by Fisher's exact test. Multiple logistic analysis revealed that diabetes mellitus (DM), SNPs in PAI-1 -1965 delG and MTHFR were an independent risk for ICA stenosis. In conclusion, genetic factors of coagulation-fibrinolysis as well as diabetes mellitus (DM) were relevant in ICA stenosis.

The role of fibrinolytic system in no-reflow after stenting with and without predilation in patients with acute coronary syndromes

BACKGROUND

No-reflow developed after coronary revascularization is an independent predictor of in-hospital mortality and poor clinical outcome. In this study, we investigated the difference between direct stenting and stenting with predilation, regarding to development of no-reflow in patients with acute coronary syndromes (ACS) and the role of fibrinolytic system in that phenomenon.

METHODS

Fifty eight patients with the diagnosis of ACS in whom percutaneous coronary intervention (PCI) was applied were included in study. Patients were divided into two groups according to stent application with and without predilation. Pre- and post-intervention corrected TIMI frame counts (cTFC) were calculated. Post-PCI plasminogen activator inhibitor-1 (PAI-1), tissue plasminogen activator (tPA), plasminogen and D-Dimer levels were measured.

RESULTS

Pre-intervention cTFC values were similar between stenting with and without predilation groups (P > 0.05). There was a significant decrease in post-intervention cTFC values in both groups (P < 0.002 and P < 0.05, respectively). But, there was no significant difference between post-intervention cTFC values of the groups, regardless to stent implantation techniques. (P > 0.05). In patients having high cTFC values compared with having low cTFC values; PAI-1 (P = 0.002), tPA (P = 0.015), plasminogen (P = 0.040) and D-dimer (P = 0.049) levels were significantly higher. Also, significant relationship was determined between cTFC and PAI-1, tPA, plasminogen, D-dimer levels (P values 0.003, <0.05, <0.05, and <0.002, respectively).

CONCLUSIONS

Results of this study indicated an important role of increased fibrinolytic activity in development of no-reflow phenomenon after PCI. We didn't observe any differences between direct stenting and stenting with predilation according to the occurrence of no-reflow.

Notoginsenoside R1 from Panax notoginseng inhibits TNF-alpha-induced PAI-1 production in human aortic smooth muscle cells

Notoginsenoside R1 is the main ingredient with cardiovascular activity in Panax notoginseng. We reported that notoginsenoside R1 significantly decreased tumor necrosis factor-alpha (TNF-alpha)-induced plasminogen activator inhibitor-1 (PAI-1) mRNA, protein level and secretion in human aortic smooth muscle cells (HASMCs) in a dose-dependent manner. TNF-alpha significantly increased extracellular signal-related kinases (ERK) and protein kinase B (PKB) activation and, which was blocked by notoginsenoside R1, PD098059, U0126 or wortmannin. Our data demonstrates that TNF-alpha-induced up-regulation of PAI-1 mRNA and protein levels and secretion occur via activation of ERK and PKB, which was prevented by treatment of notoginsenoside R1, PD098059, U0126 or wortmannin. These results suggest that notoginsenoside R1 inhibits TNF-alpha-induced PAI-1 overexpression in HASMCs by suppressing ERK and PKB signaling pathways.

The status of plasminogen activator inhibitor-1 as a therapeutic target

Plasminogen activator inhibitor-1 (PAI-1) is the major physiological inhibitor of tissue-type plasminogen activator (tPA). An increase in the plasma concentration of PAI-1 has been proposed as a risk factor in thrombotic disease and elevated PAI-1 is associated with a poor prognosis in a variety of cancers. These observations have led to numerous studies addressing the physiological and pathophysiological role of PAI-1 and to the proposal that manipulation of PAI-1 activity presents a new therapeutic target. Recent experimental studies with anti-PAI-1 antibodies and low molecular weight inhibitors have demonstrated efficacy in both arterial and venous thrombosis models. These studies have confirmed the potential clinical benefit of reducing PAI-1 activity. As it is now possible to manipulate PAI-1 activity in vivo, future studies should be aimed at confirming the importance of PAI-1 as a major therapeutic target.

Effect of rosiglitazone on restenosis after coronary stenting in patients with type 2 diabetes

BACKGROUND

Thiazolidinediones have been shown to have an antiproliferative vascular effect in experimental models. We sought to study the effect of rosiglitazone on in-stent restenosis in patients with established type 2 diabetes.

METHODS

Patients with treated type 2 diabetes (mean duration 5.5 +/- 7.5 years) referred for coronary stenting were randomized in a double-blind fashion to receive oral rosiglitazone or placebo for 6 months. Quantitative coronary angiography and intravascular ultrasound data were obtained at baseline and follow-up. Plasma plasminogen activator inhibitor-1 levels were prospectively measured.

RESULTS

Sixteen patients were enrolled. There were no significant differences in follow-up in-stent luminal diameter stenosis measured by quantitative coronary angiography or in-stent luminal area stenosis and neointimal volume index obtained by intravascular ultrasound, nor were there any differences in plasma plasminogen activator inhibitor-1 levels after long-term use despite improvement in diabetes control and insulin sensitivity.

CONCLUSIONS

Rosiglitazone, given at the time of stent implantation in treated diabetics, did not reduce in-stent restenosis in this small series. The vascular biological effects of this agent await further clarification in humans and evaluation in larger clinical trials.

Association between plasmin activation system and intravascular ultrasound signs of plaque instability in patients with unstable angina and non-st-segment elevation myocardial infarction

BACKGROUND

The association between intravascular ultrasound (IVUS) signs of plaque instability and plasma levels of biomarkers was determined in patients with unstable angina and non-ST-segment elevation myocardial infarction (UA/NSTEMI).

METHODS

Fifty-two patients underwent coronary angiography and IVUS 8 +/- 5 hours after the onset of chest pain. IVUS analysis included plaque morphology, disruption, thrombi and eccentricity, lumen, external elastic membrane, and plaque plus media areas of culprit lesion and reference segments and arterial remodeling. Plasma levels of the thrombin activation system (thrombin-antithrombin complex [TAT], tissue factor pathway inhibitor [TFPI], and prothrombin fragments 1+2 [F1+2]) and plasmin activation system (tissue and urokinase-type plasminogen activator [t-PA and u-PA], plasminogen activator inhibitor-1 [PAI-1], and D-dimer) were measured with enzyme-linked immunosorbent assay kits before angiography.

RESULTS

Elevated levels of TAT (7.2 +/- 6.0 microg/L), F1+2 (1.8 +/- 1.0 nmol/L), TFPI (179.1 +/- 131.0 ng/mL), PAI-1 (95.4 +/- 54.6 ng/mL), t-PA (10.6 +/- 8.8 ng/mL), and u-PA (2.6 +/- 0.9 ng/mL) were found in patients with UA/NSTEMI. The serum levels of D-dimer (40.0 +/- 39.5 ng/mL) remained in reference range. Expansive and constrictive remodeling were found in 18 (35%) and 12 (23%) patients, respectively. Expansive remodeling of the culprit lesion was associated with significantly higher plasma levels of PAI-1 (121.6 +/- 55.0 vs 87.7 +/- 61.5 and 77.4 +/- 42.8 ng/ml, P =.039), and u-PA (3.0 +/- 1.2 vs 2.2 +/- 0.5 and 2.5 +/- 0.7 ng/mL, P =.026) as compared with constrictive and neutral remodeling. Increased plasma levels of u-PA were associated with plaque rupture (3.0 +/- 0.7 vs 2.5 +/- 0.9 ng/mL, P =.062). Plasma levels of PAI-1 and u-PA correlated positively with plaque plus media (P =.0297 and P =.0093) and external elastic membrane areas (P =.010 and P =.0002).

CONCLUSIONS

Elevated levels of biomarkers of plasmin activation system are associated with signs of plaque instability of culprit lesion in UA/NSTEMI and might therefore serve as non-invasive determinants of the population that is at high risk for subsequent adverse events.

MEK1,2 response element mediates angiotensin II-stimulated plasminogen activator inhibitor-1 promoter activation

The MEK1,2 (MAPK/ERK kinase 1 and 2) pathway mediates the up-regulation of plasminogen activator inhibitor-1 (PAI-1) expression in vascular smooth muscle cells by a variety of hormones, including angiotensin II. Transfection of constitutively active MEKK-1, an upstream activator of the mitogen-activated protein (MAP) kinase pathways, was used to isolate an enhancer element located between -89 and -50 bp in PAI-1 promoter that was activated by MEKK-1 and selectively blocked by the MEK1,2 inhibitor PD98059. Mutational analysis revealed that the MEKK-1 response element (MRE) contained 2 cis-acting Sp1- and AP-1-like sequences, located between -75 to -70 and -63 to -52 bp, respectively. Overexpression of Sp1 enhanced MEKK-1-induced MRE promoter activity and a dominant-negative c-Fos blocked this Sp1 response. The combination of Sp1 and c-Jun or c-Fos was required to activate this MRE. Angiotensin II (Ang II) stimulation increased c-Fos, c-Jun, and Sp1 binding to the MRE by 100-, 4.9-, and 1.9-fold, respectively, and these responses were inhibited by PD98059 and AT1 receptor antagonist candesartan. Intravenous Ang II infusion in rats increased aortic c-Fos binding to the MRE. This MRE sequence mediated a 4-fold increase of MEK1,2-dependent PAI-1/luciferase mRNA expression by angiotensin II stimulation. This report identifies the MEK1,2 response element that mediates angiotensin II-stimulated PAI-1 promoter activation and shows that activation of this element requires Sp1 and AP-1 co-activation.

Donor PAI-1 expression inhibits the intimal response of early allograft vascular disease

BACKGROUND

The development of allograft vascular disease (AVD) may be related to altered expression of the fibrinolytic system. We determined the extent to which plasminogen activator inhibitor type 1 (PAI-1) expression in donor tissue influences intimal proliferation (IP) in a mouse model of AVD.

METHODS

We utilized an end-to-end abdominal aortic transplant model in mice to investigate the development of IP in 3 groups of 6 recipients. Group A (negative control) utilized C57BL/6J strain mice as both donors and recipients. In Groups B (positive control) and C, C57BL/6J mice were vessel donors and CBA/J mice were recipients. Both groups received intraperitoneal anti-CD4 and anti-CD8 monoclonal antibodies (250 microg/week for 5 weeks). Group C recipients, however, were transplanted with vessels from C57BL/6J PAI-1 knockout mice. Animals were killed at 50 days. Transplanted aortas were removed and intimal areas calculated using morphometric analysis.

RESULTS

Group A (mean intimal area 6421 +/- 8507 microm(2)) demonstrated very little IP in comparison to the other groups. IP was significantly higher in Group B (mean intimal area 56357 +/- 35629 microm(2)) than Group A (p = 0.008). Group C (mean intimal area 288195 +/- 123279 microm(2)) demonstrated significantly more intimal proliferation than either Groups A or B (vs B, p = 0.003; vs A, p < 0.001). The significance of these results is maintained if intimal thickness is measured as a stand-alone reference for the intimal response.

CONCLUSIONS

Lack of PAI-1 expression in donor tissue greatly exaggerates the extent of IP after allogeneic transplantation and suggests that PAI-1 is important in limiting the early phase of AVD.

Plasminogen activator inhibitor contributes to the coronary wall thickening in patients with angiographically normal coronary

INTRODUCTION

Angiographically normal coronary arteries have concealed intimal thickening that importantly contribute to coronary arterial disease activity. Increased plasma levels of plasminogen activator inhibitor (PAI) are associated with myocardial infarction and atherosclerosis. However, it remains unclear whether the PAI contributes to vascular wall thickening detected by intravascular ultrasound (IVUS) in normal coronary angiogram. The aim of this study was to evaluate if the PAI activity contributes to the extent of atherosclerotic changes in angiographically normal coronary arteries using IVUS technique.

MATERIALS AND METHODS

We studied 33 consecutive patients with normal coronary angiograms. These patients were divided into a high level of plasma PAI activity group (H-PAI; n=12) and a normal range of PAI activity group (N-PAI; n=21), according to the plasma PAI activity levels.

RESULTS

The average of "percent intima+media area (%I+M area)" and "maximal intima+media (I+M) thickness" were significantly greater in the H-PAI group as compared with those in the N-PAI group (p<0.05). Minimal lumen diameter and lumen area were comparable between these groups. The plasma PAI activity level was the independent predictor of increase in maximal I+M thickness, in multiple regression analysis with the traditional risk factors as covariates.

CONCLUSIONS

Thickened intima+media of angiographically normal coronary arteries were associated with high plasma level of PAI activity, independently of other traditional risk factors. PAI may contribute to the pathogenesis of coronary intimal thickening that might increase coronary arterial tone.

Fibrillar collagen regulation of plasminogen activator inhibitor-1 is involved in altered smooth muscle cell migration

OBJECTIVE

Vascular smooth muscle cells (SMCs) cultured on polymerized type I collagen fibrils are arrested in the G1 phase of the cell cycle, and their phenotypic markers and pattern of expressed genes are markedly altered. In this study, we examined polymerized collagen regulation of plasminogen activator inhibitor (PAI)-1 and its involvement in SMC migration.

METHODS AND RESULTS

We demonstrate that secretion and cell surface accumulation of PAI-1 are suppressed in SMCs cultured on polymerized collagen compared with SMCs cultured on monomer collagen. SMCs replated on vitronectin after culture on monomer collagen result in PAI-1 accumulation at focal adhesions and colocalization with alpha(v)beta3 integrins. In contrast, polymerized collagen inhibits PAI-1 accumulation at focal adhesions when the SMCs are replated on vitronectin. Furthermore, for SMCs cultured on polymerized collagen, platelet-derived growth factor-stimulated migration on vitronectin is enhanced by PAI-1, with its function counteracted by urinary plasminogen activator. Finally, exogenous addition of PAI-1 appears to partly restore platelet-derived growth factor-stimulated alpha(v)beta3-dependent SMC migration that is specifically suppressed by polymerized collagen.

CONCLUSIONS

Polymerized type I collagen fibrils dynamically regulate PAI-1, which may be involved in altered alpha(v)beta3 integrin-dependent SMC migration.

Plasminogen activator inhibitor type-1 in cardiovascular disease. Status report 2001

Plasminogen activator inhibitor type-1 (PAI-1) is known to contribute to thrombus formation and to the development and the clinical course of acute and chronic cardiovascular disease, as well as of other arterial and venous thromboembolic diseases. Recently, an important role of elevated pretreatment levels of PAI-1 for failure of thrombolytic therapy of acute myocardial infarction has been discussed. PAI-1 plasma levels depend on the one hand on gene regulation but are related on the other hand to known risk factors of atherosclerosis like insulin resistance, diabetes or hypertriglyceridemia, respectively. Furthermore, an activated renin-angiotensin-aldosterone system (RAAS) significantly contributes to the upregulation of PAI-1 concentration via a receptor-mediated mechanism. In accordance to the known mechanisms of regulation of PAI-1 plasma levels, the use of specific agents like antidiabetic drugs, fibrates, statins, ACE inhibitors and angiotensin II type-1 receptor-blockers may contribute to the downregulation of circulating PAI-1 and, therefore, increase the fibrinolytic capacity and consecutively counteract the thrombotic tendency. To further improve the efficacy of thrombolytic therapy, a PAI-1 resistant variant of t-PA, TNK-t-PA, has been developed and is now available for acute myocardial infarction.

The 4G/5G promotor polymorphism of the plasminogen activator inhibitor-1 gene and late lumen loss after coronary stent placement in smoking and nonsmoking patients

BACKGROUND

Instent restenosis remains a significant clinical problem. Identification of patients at risk for instent restenosis may allow selection of individualized appropriate therapeutic approaches. Genetic polymorphisms have been suggested to be associated with the risk of instent restenosis. Smoking is known to influence hemostatic parameters.

HYPOTHESIS

This study investigated the influence of the 4G/5G promotor polymorphism of the plasminogen activator inhibitor type I (PAI-1) gene on instent restenosis in smoking and nonsmoking patients.

METHODS

In all, 300 consecutive patients (133 nonsmoking; 167 smoking) with elective coronary stent placement and 6-month angiographic follow-up were studied. Quantitative coronary angiography and genotyping with polymerase chain reaction analysis were performed in all patients.

RESULTS

Nonsmoking PAI-1 4G/4G carriers showed a significantly greater late lumen loss (n = 38; 0.54 +/- 0.53 mm) compared with nonsmoking PAI-1 4G/5G (n = 68; 0.38 +/- 0.45 mm) or 5G/5G (n = 27; 0.19 +/- 0.23 mm) carriers, analysis of variance (ANOVA) p < 0.001. Smoking patients with the genotypes 4G/4G (n = 46; 0.53 +/- 0.54 mm) and 4G/5G (n = 79; 0.37 +/- 0.41 mm) had a late loss similar to that of nonsmoking patients. Smoking 5G/5G carriers had the highest late loss of all smoking patients (n = 42; 0.63 +/- 0.50); ANOVA p < 0.05; nonsmoking 5G/5G vs. smoking 5G/5G p < 0.001.

CONCLUSION

The promotor polymorphism of the PAI-1 gene has a significant influence on instent restenosis after coronary stent implantation. The 5G/5G genotype predisposes nonsmoking gene carriers to less late lumen loss, whereas in smoking gene carriers this genotype is associated with the greatest late lumen loss. This might be explained by an altered expression pattern of hemostatic parameters.

Critical role of Rho-kinase and MEK/ERK pathways for angiotensin II-induced plasminogen activator inhibitor type-1 gene expression

Plasminogen activator inhibitor type-1 (PAI-1) plays an integral role not only in the regulation of fibrinolytic activity but also in the pathogenesis of atherosclerosis and hypertension. We investigated the signaling pathways of angiotensin II (Ang II) leading to PAI-1 gene expression. Ang II increased the PAI-1 mRNA and protein levels in a time- and dose-dependent manner through the Ang II type 1 receptor in vascular smooth muscle cells. PAI-1 gene promoter activity measured by luciferase assay was significantly increased by Ang II. PAI-1 mRNA stability was also increased by Ang II. Ang II-induced PAI-1 mRNA upregulation was inhibited by BAPTA-AM, genistein, and AG1478, suggesting that intracellular calcium, tyrosine kinase, and epidermal growth factor receptor transactivation are involved. Furthermore, PD98059, an inhibitor of extracellular signal-regulated kinase (ERK) kinase (MEK), almost completely suppressed Ang II-induced PAI-1 upregulation. Adenovirus-mediated overexpression of the dominant-negative form of Rho-kinase or Y27632, a Rho-kinase inhibitor, also completely prevented PAI-1 induction by Ang II without affecting Ang II-induced ERK activation. These data suggest that activation of MEK/ERK and Rho-kinase pathways plays a pivotal role in PAI-1 gene upregulation by Ang II. The Rho-kinase pathway may be a novel target to inhibit Ang II signaling, and its inhibition may be useful in the treatment of hypertension as well as atherosclerosis.

Plasminogen activator inhibitor type-1 (part one): basic mechanisms, regulation, and role for thromboembolic disease

Plasminogen activator inhibitor type-1 (PAI-1) is a rapid inhibitor of tissue plasminogen activator (tPA) in circulation. Evidence suggests that the PAI-1 concentration is responsible for the regulation of the endogenous fibrinolytic system through its tPA/PAI-1 interactions. Accordingly, increased levels of PAI-1 have emerged as a masker for an increased thrombolic risk. This article represents a status report of mechanism of action, regulation of plasma levels, as well as the role of PAI-1 in arterial and venous thromboembolic disease.

Plasminogen activator inhibitor-1 and its cofactor vitronectin stabilize arterial thrombi after vascular injury in mice

BACKGROUND

The origin and contribution of plasminogen activator inhibitor-1 (PAI-1) and its cofactor vitronectin (VN) to arterial thrombosis/thrombolysis in vivo is controversial.

METHODS AND RESULTS

Ferric chloride was used to induce carotid artery injury in 97 wild-type (WT), 84 PAI-1-/-, and 84 VN-/- mice. Complete thrombotic occlusion was observed in 70% of PAI-1-/- mice versus 92% of WT (P:<0.001) and 87% of VN-/- (P:=0.015) mice. In vessels that occluded, mean times to occlusion were significantly longer in PAI-1-/- than in WT or VN-/- mice. The initial thrombotic response of VN-/- mice was similar to that of WT mice, but their thrombi were unstable and frequently embolized. As a result, the patency rate of carotid vessels 30 minutes after injury was as high in VN-/- mice (36%) as in PAI-1-/- mice (which demonstrate progressive thrombolysis) and significantly higher than that of WT mice (12%; P:=0.013). Histochemical and reverse transcription-polymerase chain reaction studies revealed an early upregulation of PAI-1 mRNA and protein expression in the thrombus and the vessel wall, which persisted for >/=1 week. VN protein also accumulated after injury, but VN mRNA levels remained low at all times.

CONCLUSIONS

PAI-1 and VN participate in the thrombotic response to arterial injury by preventing premature thrombus dissolution and embolization. The accumulation of PAI-1 in the thrombus/vessel wall after injury may result, at least in part, from local synthesis, whereas the VN protein appears to be derived from plasma.

Oxidized LDL and lysophosphatidylcholine stimulate plasminogen activator inhibitor-1 expression in vascular smooth muscle cells

Plasminogen activator inhibitor-1 (PAI-1) functions as an important regulator of fibrinolysis by inhibiting both tissue-type and urokinase-type plasminogen activator. PAI-1 is produced by smooth muscle cells (SMCs) in atherosclerotic arteries, but the mechanisms responsible for induction of PAI-1 in SMCs are less well understood. In cultured human aortic SMCs, PAI-1 mRNA expression and protein secretion were increased after incubation with oxidized low-density lipoprotein (LDL) and the lipid peroxidation product lysophosphatidylcholine, whereas the effects of native LDL on PAI-1 production and release were more variable and did not reach statistical significance. The effect of LDL on arterial expression of PAI-1 in vivo was also studied in an animal model. Intravenous injection of human LDL in Sprague-Dawley rats resulted in accumulation of apolipoprotein B in the aorta within 12 hours as assessed by immunohistochemical testing. Epitopes specific for oxidized LDL began to develop in the aorta 12 hours after injection of LDL and peaked at 24 hours; this peak was accompanied by intense expression of PAI-1 immunoreactivity in the media. Also, increased aortic expression of PAI-1 mRNA after LDL injection was detected by using in situ hybridization. The transcription factor activator protein-1, which is known to bind to the promoter of the PAI-1 gene, was activated in the aortic wall 24 hours after LDL injection as assessed by electrophoretic mobility shift assay. Pretreatment of LDL with the antioxidant probucol decreased expression of oxidized LDL and PAI-1 immunoreactivity and activator protein-1 induction in the aorta but did not affect expression of apolipoprotein B immunoreactivity. These findings demonstrate that LDL oxidation enhances secretion of PAI-1 from cultured SMCs and that a similar mechanism may be involved in vascular expression of PAI-1.

Plasmin activation system in restenosis: role in pathogenesis and clinical prediction?

During recent years it has become increasingly recognized that the plasmin activation system is involved in the development of atherosclerosis and restenosis. Responsible pathophysiologic mechanisms, however, remain elusive. This review focuses primarily on the clinicians, point of view, suggesting that increases in plasminogen activator inhibitor type-1 (PAI-1) plasma levels after balloon angioplasty or permanently elevated lipoprotein (a) (Lp(a)) plasma levels might be helpful in the prediction of restenosis after coronary angioplasty. In contrast, tissue-type plasminogen activator (tPA) plasma levels appear unrelated to restenosis, and data regarding a possible role of urokinase-type plasminogen activator (uPA) in circulation are not available at present. Furthermore, a new hypothesis on the pathophysiological role of local PAI-1 overexpression as a beneficial negative feedback mechanism to limit excess cellular proliferation in atherogenesis and restenosis is presented.

Pertussis Toxin-Sensitive Signal Controls the Trafficking of Thymocytes Across the Corticomedullary Junction in the Thymus

We investigated a role of chemokines in thymocyte trafficking. Genes encoding stromal cell-derived factor-1 and its receptor CXCR4 were detected in the cortex by in situ hybridization. Early immigrant cells did not express CXCR4, whereas their descendant CD44+CD25+CD4−CD8− cells did. CXCR4 expression was down-modulated when CD4+CD8+ double-positive cells became CD4+CD8− or CD4−CD8+ single-positive (SP) cells. Positively selected CD69+CD3intermediate cells gained CCR4, of which ligand, thymus activation-regulated chemokine, was expressed in the medulla. At the next developmental stage, CD69−CD3high cells lost CCR4 but gained CCR7. These results suggest that thymocytes use different chemokines along with their development. Blockade of chemokine receptor-mediated signaling by pertussis toxin perturbed the normal distribution of SP cells and resulted in the accumulation of SP cells in the cortex. Thus, a pertussis toxin-sensitive event controls the trafficking of SP cells across the corticomedullary junction.

Changes in the fibrinolytic system in patients with peripheral arterial occlusive disease undergoing percutaneous transluminal angioplasty

We have investigated fibrinolytic parameters in 33 patients with peripheral arterial occlusive disease (PAOD) before and 6, 24, and 48 hours after percutaneous transluminal angioplasty (PTA) as well as in 35 gender-matched healthy controls, whose mean age was not significantly different from the mean age of the patients. PAOD patients had significantly higher plasma levels of t-PA antigen (12.0+/-4.9 vs. 9.2+/-5.5 ng/ml), PAI-1 antigen (34.8+/-22.1 vs. 27.2+/-23.6 ng/ml), PAI-1 activity (10.0+/-6.5 vs. 8.0+/-8.0 U/ml), PCI (188.2+/-55.6 vs. 134.1+/-75.5% as compared with normal human plasma), and fibrinogen (420.2+/-92.6 vs. 261.9+/-32.7 mg/dl) as compared with controls. After angioplasty, fibrinolytic parameters and fibrinogen levels increased, reaching higher than preintervention levels 24 and 48 hours after the intervention. Six months after initially successful PTA, restenosis was demonstrated in 14 out of 33 patients (42%). Patients with late restenosis had significantly higher levels of PAI-1 activity 24 and 48 hours after PTA, as compared with patients with late patency (24 hours: 16.1+/-8.0 vs. 10.0+/-7.4; 48 hours: 16.5+/-7.9 vs. 12.0+/-7.0; p<0.05 for both time points). The results suggest that impaired fibrinolysis early after PTA might be a cause or marker of a disturbed repair process of vascular injury, leading to restenosis.

Adventitial delivery minimizes the proinflammatory effects of adenoviral vectors

PURPOSE

Adenovirus-mediated arterial gene transfer is a promising tool in the study of vascular biology and the development of vascular gene therapy. However, intraluminal delivery of adenoviral vectors causes vascular inflammation and neointimal formation. Whether these complications could be avoided and gene transfer efficiency maintained by means of delivering adenoviral vectors via the adventitia was studied.

METHODS

Replication-defective adenoviral vectors encoding a beta-galactosidase (beta-gal) gene (AdRSVnLacZ) or without a recombinant gene (AdNull) were infused into the lumen or the adventitia of rabbit carotid arteries. Two days after infusion of either AdRSVnLacZ (n = 8 adventitial, n = 8 luminal) or AdNull (n = 4 luminal), recombinant gene expression was quantitated by histochemistry (performed on tissue sections) and with a beta-gal activity assay (performed on vessel extracts). Inflammation caused by adenovirus infusion was assessed 14 days after infusion of either AdNull (n = 6) or vehicle (n = 6) into the carotid adventitia. Inflammation was assessed by means of examination of histologic sections for the presence of neointimal formation and infiltrating T cells and for the expression of markers of vascular cell activation (ICAM-1 and VCAM-1). To measure the systemic immune response to adventitial infusion of adenovirus, plasma samples (n = 3) were drawn 14 days after infusion of AdNull and assayed for neutralizing antibodies.

RESULTS

Two days after luminal infusion of AdRSVnLacZ, approximately 30% of luminal endothelial cells expressed beta-gal. Similarly, 2 days after infusion of AdRSVnLacZ to the adventitia, approximately 30% of adventitial cells expressed beta-gal. beta-gal expression was present in the carotid adventitia, the internal jugular vein adventitia, and the vagus nerve perineurium. Elevated beta-gal activity (50- to 80-fold more than background; P <.05) was detected in extracts made from all AdRSVnLacZ-transduced arteries. The amount of recombinant protein expression per vessel did not differ significantly between vessels transduced via the adventitia (17.1 mU/mg total protein [range, 8.1 to 71.5]) and those transduced via a luminal approach (10.0 mU/mg total protein [range, 3.9 to 42.6]). Notably, adventitial delivery of AdNull did not cause neointimal formation. In addition, vascular inflammation in arteries transduced via the adventitia (ie, T-cell infiltrates and ICAM-1 expression) was confined to the adventitia, sparing both the intima and media. Antiadenoviral neutralizing antibodies were present in all rabbits after adventitial delivery of AdNull.

CONCLUSION

Infusion of adenoviral vectors into the carotid artery adventitia achieves recombinant gene expression at a level equivalent to that achieved by means of intraluminal vector infusion. Because adventitial gene transfer can be performed by means of direct application during open surgical procedures, this technically simple procedure may be more clinically applicable than intraluminal delivery. Moreover, despite the generation of a systemic immune response, adventitial infusion had no detectable pathologic effects on the vascular intima or media. For these reasons, adventitial gene delivery may be a particularly useful experimental and clinical tool.

Natriuretic factors and nitric oxide suppress plasminogen activator inhibitor-1 expression in vascular smooth muscle cells. Role of cGMP in the regulation of the plasminogen system

Increased expression of plasminogen activator inhibitor-1 (PAI-1) has been reported in atherosclerotic and balloon-injured vessels. Little is known regarding the factors and mechanisms that may negatively regulate PAI-1 expression. In this report, the effect of cGMP-coupled vasoactive hormones, including natriuretic factors and nitric oxide, on the regulation of PAI-1 expression in vascular smooth muscle cells was examined. Atrial natriuretic factor 1-28 (ANF) and C-type natriuretic factor-22 (CNP) reduced angiotensin II (Ang II)- and platelet-derived growth factor-stimulated PAI-1 mRNA expression in rat aortic smooth muscle cells by 50% to 70%, with corresponding reductions in PAI-1 protein release. Treatment of human aortic smooth muscle cells with CNP similarly inhibited both platelet-derived growth factor-induced PAI-1 mRNA expression and PAI-1 protein release by 50%. Dose-response studies revealed that the inhibitory effects of CNP and ANF on PAI-1 expression were concentration dependent, with IC50s of approximately 1 nmol/L for both natriuretic peptides. Ang II-stimulated PAI-1 expression was also inhibited by the nitric oxide donor S-nitroso-N-acetylpenicillamine. The membrane-permeant cGMP analogue 8-Br-cGMP reduced Ang II-stimulated PAI-1 expression by 60%, and an inhibitor of soluble guanylyl cyclase (1H-[1,2,4]oxadiazolo[4, 3-a]quinoxalin-1-one) significantly impaired the inhibitory effects of S-nitroso-N-acetylpenicillamine on Ang II-stimulated PAI-1 expression. Studies of PAI-1 mRNA stability in cells treated with actinomycin D showed that ANF did not alter PAI-1 mRNA half-life, suggesting that natriuretic factors reduce PAI-1 transcription. These data show that natriuretic factors and nitric oxide, via a cGMP-dependent mechanism, inhibit PAI-1 synthesis in vascular smooth muscle cells. Thus, cGMP-coupled vasoactive hormones may play an important role in suppressing vascular PAI-1 expression.

Elevated expression of urokinase-like plasminogen activator and plasminogen activator inhibitor type 1 during the vascular remodeling associated with pulmonary thromboembolism

Information is lacking on the mechanisms involved in the organization, resolution, and repair of the vascular lumen after acute pulmonary thromboembolism. Because recent data suggest that the balance between plasminogen activators (PAs) and type 1 plasminogen activator inhibitor (PAI-1) plays a role in regulating cell migration within the extracellular matrix, we investigated the expression of these molecules by immunohistochemical and in situ hybridization analysis of pulmonary artery specimens from patients suffering fatal pulmonary embolism. The data were compared with the expression of these molecules in both patients' noninvolved pulmonary arteries and organ donor pulmonary arteries. Regions of initial organization and vascular remodeling were identified by a modified trichrome stain and by the presence of proliferating cell nuclear antigen (PCNA), a cell marker of proliferation. Staining for tissue-type PA antigen was low to undetectable in endothelial cells directly in contact with the fibrin-platelet thromboembolus and in areas in which the endothelial cell lining was replaced by cell growth into the thrombus. Urokinase-like PA (u-PA) expression was detected in mononuclear cells within the thrombus in the initial phase of thromboembolism and within cells migrating into the thrombus during the later stages of organization. PAI-1 expression was elevated in the monolayer of endothelial cells underlying the fresh platelet-fibrin thromboembolus and in a PCNA-positive cell population present between the pulmonary arterial intima and the thromboembolus that represents early organization. Increased expression of PAI-1 may play a role in inhibiting proteolysis and fostering the localization of the acute fibrin-platelet thrombus to the vascular wall, which is followed by the upregulation of u-PA in migrating cells during the reorganization process.

Immunoelectron microscopic localization of plasminogen activator inhibitor type 1 (PAI-1) in smooth muscle cells from morphologically normal and atherosclerotic human arteries

Vascular wall fibrinolytic system proteins are believed to play a pivotal role in atherogenesis. Tissue-type plasminogen activator (t-PA) and urokinase plasminogen activator (u-PA) influence persistence of luminal thrombi and proteolysis of extracellular matrix, respectively. The major physiologic inhibitor of t-PA and u-PA is plasminogen activator inhibitor type 1 (PAI-1). All three of these fibrinolytic system proteins have been detected in vascular endothelial cells, smooth muscle cells, and macrophages by light microscopic immunohistochemistry. This study was undertaken to delineate, by immunoelectron microscopy, the loci of PAI-1 in smooth muscle cells from intact morphologically normal and atherosclerotic human arteries as well as in isolated and cultured smooth muscle cells from arteries. In intact vessels, PAI-1 immunoreactivity was associated with contractile filaments in cells in both normal and atherosclerotic tissues. Lipid-laden smooth muscle cells in atherosclerotic vessels were mainly of the synthetic phenotype and displayed lesser amounts of PAI-1 associated with rough endoplasmic reticulum and contractile filaments. Isolated smooth muscle cells exhibited either a contractile or synthetic phenotype. In the cells with a contractile phenotype, PAI-1 was associated with the contractile elements, whereas in the cells with a synthetic phenotype, the PAI-1 was associated predominantly with elements of the endoplasmic reticulum. Because PAI-1 is associated predominantly with contractile filaments in smooth muscle cells, the net amount of immunodetectable PAI-1 appears to be greater in contractile compared with synthetic phenotype cells.

Changes in arterial expression of fibrinolytic system proteins in atherogenesis

Plasminogen activators (PAs) and their inhibitor, plasminogen activator inhibitor type-1 (PAI-1), have been implicated in modulation of luminal fibrinolysis and mural proteolysis contributing to atherogenesis. Expression of PAs/PAI-1 (normalized to extracted tissue protein) was delineated by assays of conditioned media and of extracts from walls of human arterial segments in culture. Arterial specimens (n = 39 from 26 subjects) were divided into four groups: normal (n = 14), fatty streak (n = 6), moderate atherosclerosis (mural thickening with < 70% lumen obstruction, n = 5), and severe atherosclerosis (mural thickening with > 70% lumen obstruction, n = 14). Paired samples from the same individual comprising a normal arterial segment and an atherosclerotic segment were evaluated also. A fourfold molar excess in PAI-1:t-PA was seen in conditioned media from samples with any evidence of atherosclerosis compared with normal specimens (normal 21 +/- 4, diseased 82 +/- 21, P < or = .05). Compared with normal pairs, the tissue content of PAI-1 (ng) was increased in fatty streak lesions (n = 3, normal 35 +/- 12, fatty streak 50 +/- 8, P < or = .05); stable to decreased in moderate atherosclerosis (n = 3, normal 34 +/- 3, moderate 22 +/- 7, P = .16); and increased in severe atherosclerosis (n = 6, normal 48 +/- 9, severe 85 +/- 19, P < or = .05). The tissue content of PAs (ng), though not increased in fatty streak lesions, was elevated in moderately and severely atherosclerotic segments (normal 0.7 +/- 0.2, moderate 1.6 +/- 0.1; normal 0.8 +/- 0.3, severe 2.1 +/- 0.3, P < or = .05 for each comparison). Atherogenesis is associated with decreased luminal fibrinolytic capacity that may exacerbate thrombosis. Decreased mural proteolysis in early atherogenesis may exacerbate matrix accumulation. Increased mural proteolysis later is associated with, and may potentiate, smooth muscle cell migration and proliferation.

Antifibrinolytic properties of the vascular wall. Dependence on the history of smooth muscle cell doublings in vitro and in vivo

Increased expression of plasminogen activator inhibitor-1 (PAI-1) mRNA in atherosclerotic human arteries suggests a linkage between PAI-1 gene expression and cellular proliferation, the fundamental feature of atherosclerosis. To investigate whether smooth muscle cell (SMC) proliferation influences overall fibrinolytic properties of the vascular wall, we examined the effect of serial in vitro passaging of human SMCs on tissue plasminogen activator (TPA) and PAI-1 synthesis levels as well as the ability to modulate TPA and PAI-1 synthesis of human umbilical vein endothelial cells (HUVECs). As in vivo correlates for such late-passage cells in culture, SMCs derived from human atherosclerotic plaques were used, because they are thought to have already undergone numerous cell doublings. We observed an increase of PAI-1 secretion (from 591 +/- 106 to 2952 +/- 290 ng PAI-1.10(5) cells-1.24 h-1) with a concomitant fourfold to fivefold increase of PAI-1 mRNA levels, as well as a decrease of TPA secretion (from 118 +/- 34 to 8 +/- 1.3 ng TPA.10(5) cells-1.24 h-1) and a twofold to threefold decrease of TPA mRNA levels with increasing in vitro passage number (from passage 3 to 11) of normal pulmonary artery smooth muscle cells (PASMCs) (P < .05). SMCs derived from atherosclerotic plaques of coronary arteries (CASMCs) displayed higher levels of PAI-1 antigen synthesis (3093 +/- 507 ng PAI-1.10(5) cells-1.24 h-1) with an approximately twofold increase of PAI-1 mRNA levels, as well as decreased levels of TPA antigen synthesis (10 +/- 1.6 ng TPA.10(5) cells-1.24 h-1) with an approximately 1.5- to 2-fold decrease of TPA mRNA levels in passage 1, compared with their counterparts derived from normal-appearing arterial tissue of the same vessel (1794 +/- 525 ng PAI-1.10(5) cells-1.24 h-1; 17 +/- 5 ng TPA.10(5) cells-1.24 h-1) (P < .001; P < .01). Incubation of HUVEC cultures with the 24-hour conditioned media (CM) of early-passage PASMCs decreased endothelial PAI-1 antigen synthesis by approximately 42% (P < .001) and endothelial PAI-1 mRNA levels about twofold to threefold (P < .001), whereas by incubation with the 24-hour CM of late-passage PASMCs, endothelial PAI-1 antigen synthesis was upregulated by 68% (P = .001), with a concomitant twofold increase of endothelial PAI-1 mRNA levels (P < .001). The apparent MW of this heat- and acid-stable PAI-1 upregulating factor appears to be between 50 and 100 kD, as judged by ultrafiltration. Incubation of HUVEC cultures with the 24-hour CM of early-passage CASMCs derived from normal-appearing arterial tissue showed no significant influence on endothelial PAI-1 synthesis, whereas incubation with late-passage normal CASMCs, as well as early-passage atherosclerotic CASMCs from the same vessel, increased endothelial PAI-1 antigen secretion by 45% and 48% (P < .001), with a concomitant 1.5 fold to 2-fold increase of endothelial PAI-1 mRNA levels (P < .05). No significant change in endothelial TPA synthesis was observed by incubation with CM of either PASMCs (early or late passage) or CASMCs (atherosclerotic or normal). These data suggest that SMC proliferation is associated with (1) increased SMC PAI-1 synthesis as well as decreased TPA synthesis and (2) upregulation of endothelial PAI-1 synthesis by SMC CM. This phenomenon is observed with either late passages of normal PASMCs and CASMCs or early passages of atherosclerotic plaque CASMCs. This suggests that proliferating SMCs are a major regulator of the fibrinolytic potential within the vessel wall, thereby contributing to the thrombotic risk associated with the development of atherosclerosis.

[Blood coagulation, genetics and post-angioplasty restenosis]

Throughout the last few decades, different factors have been related to coronary stenosis which is clinically evidenced by coronary heart disease, the leading cause of death in developed countries. Different experimental models have contributed towards defining some of these factors, and to an understanding of the physiopathology of the atherosclerotic lesion. The genetic basis related to individual responses to the same event is currently being established. As endothelial injury reparative mechanisms are fundamental in atherosclerosis pathogeny, patients who experiment restenosis after undergoing revascularization procedures are useful human models in the study of these processes. We review from the literature the genetic factors related to thrombus formation, which may be associated with restenosis after percutaneous transluminal coronary angioplasty, in order to define the most suitable anticoagulant therapy for each patient. We refer to the recently characterized gene for the platelet receptors and its relationship with fibrinogenous, factor Xa, PAI-I, and the involvement of apolipoprotein (a) in the coagulation process.

Endothelial cells modulate smooth muscle cell morphology by inhibition of transforming growth factor-beta 1 activation

BACKGROUND

We have previously demonstrated in a coculture model that endothelial cells (ECs) exert regulatory control over smooth muscle cell (SMC) morphology. This study was performed to test the hypothesis that ECs inhibit transforming growth factor-beta 2 (TGF-beta 1) activation through the release of plasminogen activator inhibitor (PAI-1).

METHODS

Bovine SMCs were cultured on a thin, semipermeable membrane, either alone or opposite ECs in coculture (SMC/EC). Conditioned media and cell lysates at 1, 5, and 21 days were assayed for TGF-beta 1 and PAI-1 by enzyme-linked immunoabsorbent assay. Cell proliferation rates, protein, and DNA content were measured and compared with SMC morphology.

RESULTS

Activation of TGF-beta 1 was significantly decreased (1.2% versus 18.9% active TGF-beta 1 p < 0.05) and PAI-1 was increased (659 pg/ml versus 343 pg/ml p < 0.05) in SMC/EC medium on day 1, compared with the medium of SMC alone. Significantly higher levels of PAI-1 were measured in cell lysates of cocultured ECs (128 pg/micrograms DNA) than in cocultured SMCs (5.8 pg/micrograms DNA, p < 0.05). SMC/EC coculture prevented the SMC hill-and-valley growth morphology seen in SMCs cultured alone.

CONCLUSIONS

In a model designed to study SMC/EC interactions, it was seen that ECs can alter growth characteristics of SMCs by producing PAI-1, which interferes with the plasminogen pathway of TGF-beta 1 activation. This suggests that reduced EC PAI-1 production could play a role in alteration of SMC phenotype in vivo.

Angiotensin-converting enzyme inhibition suppresses plasminogen activator inhibitor-1 expression in the neointima of balloon-injured rat aorta

BACKGROUND

Plasminogen activator inhibitor-1 (PAI-1), an important regulator of fibrinolysis and extracellular matrix turnover, has been implicated in a number of vascular diseases. Studies demonstrating angiotensin II (Ang II) to be a potent stimulator of PAI-1 expression in cultured vascular cells suggests that the renin-angiotensin system may modulate vascular PAI-1 expression.

METHODS AND RESULTS

We examined the effects of the ACE inhibitor captopril on PAI-1 expression in control and balloon-injured rat aorta. Northern blot analysis demonstrated that aortic PAI-1 mRNA expression was 7.6-fold elevated 3 hours (P<.05) after balloon injury, back to baseline at 2 days, increased again at 4 days, and by 7 days after balloon injury was 3.2-fold elevated (P<.05) when compared with control. In captopril-treated rats, the induction of PAI-1 expression by balloon injury was significantly suppressed by 44% (P<.05) in the 7 day group but was not altered in the 3-hour group. Captopril also reduced baseline aortic PAI-1 mRNA. In situ hybridization and immunohistochemistry revealed dense PAI-1 staining of 7-day neointima in untreated rats and a dramatic decrease in PAI-1 in neointima of captopril-treated rats.

CONCLUSIONS

This report demonstrates that balloon injury results in both a rapid ACE inhibitor-independent induction of aortic PAI-1 expression and a later increase in PAI-1 in the neointima that is significantly suppressed by captopril. This provides the first evidence that the renin-angiotensin system regulates neointimal PAI-1 expression and that ACE inhibitors can reduce PAI-1 in the vessel wall in vivo.