Cytokine activation of vascular endothelium. Effects on tissue-type plasminogen activator and type 1 plasminogen activator inhibitor

Matrix metalloproteinase inhibition therapy for vascular diseases

The matrix metalloproteinases (MMPs) are 23 secreted or cell surface proteases that act together and with other protease classes to turn over the extracellular matrix, cleave cell surface proteins and alter the function of many secreted bioactive molecules. In the vasculature MMPs influence the migration proliferation and apoptosis of vascular smooth muscle, endothelial cells and inflammatory cells, thereby affecting intima formation, atherosclerosis and aneurysms, as substantiated in clinical and mouse knockout and transgenic studies. Prominent counterbalancing roles for MMPs in tissue destruction and repair emerge from these experiments. Naturally occurring tissue inhibitors of MMPs (TIMPs), pleiotropic mediators such as tetracyclines, chemically-synthesised small molecular weight MMP inhibitors (MMPis) and inhibitory antibodies have all shown effects in animal models of vascular disease but only doxycycline has been evaluated extensively in patients. A limitation of broad specificity MMPis is that they prevent both matrix degradation and tissue repair functions of different MMPs. Hence MMPis with more restricted specificity have been developed and recent studies in models of atherosclerosis accurately replicate the phenotypes of the corresponding gene knockouts. This review documents the established actions of MMPs and their inhibitors in vascular pathologies and considers the prospects for translating these findings into new treatments.

Targeted long-term venous occlusion using pulsed high-intensity focused ultrasound combined with a pro-inflammatory agent

Esophageal and gastric varices are associated with significant morbidity and mortality for cirrhotic patients. The current modalities available for treating bleeding esophageal and gastric varices, namely endoscopic band ligation and sclerotherapy, require frequent sessions to obtain effective thrombosis and are associated with significant adverse effects. A more effective therapy that results in long-term vascular occlusion has the potential to improve patient outcomes. In this study, we investigated a new potential method for inducing long-term vascular occlusion by targeting segments of a rabbit's auricular vein in vivo with low-duty-cycle, high-peak-rarefaction pressure (9 MPa), pulsed high-intensity focused ultrasound in the presence of intravenously administered ultrasound microbubbles followed by local injection of fibrinogen and a pro-inflammatory agent (ethanol, cyanoacrylate or morrhuate sodium). The novel method introduced in this study resulted in acute and long-term complete vascular occlusions when injecting a pro-inflammatory agent with fibrinogen. Future investigation and translational studies are needed to assess its clinical applicability.

Antithrombotic and profibrinolytic activities of phloroglucinol

Phloroglucinol is the monomeric units of phlorotannins abundant in brown algae. Several biological effects of phloroglucinol have been reported, however, antithrombotic and profibrinolytic activities of phloroglucinol have not been studied yet. In this study, the anticoagulant properties of phloroglucinol were determined by assays of activated partial thromboplastin time (aPTT), prothrombin time (PT) and cell based thrombin and activated factor X (FXa) generation activities. And the effects of phloroglucinol on the expression of plasminogen activator inhibitor type 1 (PAI-1) and tissue-type plasminogen activator (t-PA) were tested in tumor necrosis factor-α (TNF-α) activated human endothelial cells (HUVECs). I found that phloroglucinol prolonged aPTT and PT significantly and inhibited thrombin and FXa generation in HUVECs. Furthermore, phloroglucinol inhibited TNF-α induced PAI-1 production. I then used pathway inhibitors to investigate which step of the TNF-α induced signaling pathway was targeted by phloroglucinol. I observed that the c-Jun N-terminal kinase (JNK) inhibitor increased the inhibitory effects of phloroglucinol, whereas the nuclear factor factor-κB (NF-κB) and the extracellular signal-regulated kinase (ERK) inhibitor did not. Therefore these results suggest that phloroglucinol possess antithrombotic and profibrinolytic activities and that NF-κB and ERK pathways are possible targets of phloroglucinol in the regulation of TNF-α stimulated PAI-1 production in HUVECs.

Differential gene expression of serine protease inhibitors in bovine ovarian follicle: possible involvement in follicular growth and atresia

BACKGROUND

SERPINs (serine protease inhibitors) regulate proteases involving fibrinolysis, coagulation, inflammation, cell mobility, cellular differentiation and apoptosis. This study aimed to investigate differentially expressed genes of members of the SERPIN superfamily between healthy and atretic follicles using a combination of microarray and quantitative real-time PCR (QPCR) analysis. In addition, we further determined mRNA and protein localization of identified SERPINs in estradiol (E2)-active and E2-inactive follicles by in situ hybridization and immunohistochemistry.

METHODS

We performed microarray analysis of healthy (10.7 +/- 0.7 mm) and atretic (7.8 +/- 0.2 mm) follicles using a custom-made bovine oligonucleotide microarray to screen differentially expressed genes encoding SERPIN superfamily members between groups. The expression profiles of six identified SERPIN genes were further confirmed by QPCR analysis. In addition, mRNA and protein localization of four SERPINs was investigated in E2-active and E2-inactive follicles using in situ hybridization and immunohistochemistry.

RESULTS

We have identified 11 SERPIN genes expressed in healthy and atretic follicles by microarray analysis. QPCR analysis confirmed that mRNA expression of four SERPINs (SERPINA5, SERPINB6, SERPINE2 and SERPINF2) was greater in healthy than in atretic follicles, while two SERPINs (SERPINE1 and SERPING1) had greater expression in atretic than in healthy follicles. In situ hybridization showed that SERPINA5, SERPINB6 and SERPINF2 mRNA were localized in GCs of E2-active follicles and weakly expressed in GCs of E2-inactive follicles. SERPING1 mRNA was localized in both GCs and the theca layer (TL) of E2-inactive follicles and a weak hybridization signal was also detected in both GCs and TL of E2-active follicles. Immunohistochemistry showed that SERPINA5, SERPINB6 and SERPINF2 were detected in GCs of E2-active and E2-inactive follicles. SERPING1 protein was localized in both GCs and the TL of E2-active and E2-inactive follicles.

CONCLUSIONS

Our results demonstrate a characteristic expression of SERPIN superfamily member genes in bovine healthy and atretic follicles. The cell-type-and stage-specific expression of SERPINs may be associated with bovine follicular growth and atresia.

Effect of preoperative biliary drainage on coagulation and fibrinolysis in severe obstructive cholestasis

GOALS

To evaluate the function of coagulation and fibrinolysis in cholestatic patients before and after preoperative biliary drainage (PBD).

BACKGROUND

Cholestasis owing to an obstructive biliary malignancy is associated with postoperative complications related to a proinflammatory state, an impaired hepatic synthesis function, and a potential derangement of hemostasis. Hence, PBD is advocated for cholestatic patients undergoing major surgery.

STUDY

Plasma coagulation and fibrinolytic parameters were assessed in 24 cholestatic patients and 10 controls. In 9 cholestatic patients, the parameters were reassessed at least 4 weeks after PBD.

RESULTS

Compared with controls, cholestatic patients showed lower concentrations (P<0.001) of plasma vitamin K-dependent factors II and VII, whereas prothrombin time, activated partial thromboplastin time, and factor V were unaltered. Thrombin generation was increased in cholestatic patients, as reflected by higher plasma concentrations of thrombin-antithrombin complexes and D-dimers. Fibrinolysis was significantly impaired as evidenced by low plasminogen activator activity (PAA) owing to an increase in plasminogen activator inhibitor -1). Elevated markers for thrombin generation thrombin-antithrombin decreased after PBD from 10.7±1.2 to 5.7±0.7 ng/mL (P<0.05). Additionally, impairment of fibrinolysis in cholestatic patients resolved after PBD (plasminogen activator inhibitor-1 levels decreased from 19±1 to 10±1 IU/mL and plasminogen activator activity increased from 82±3 to 110±4%, respectively). D-dimers remained unaltered after PBD, likely because of normalization of coagulation and fibrinolytic activity.

CONCLUSIONS

Obstructive cholestasis is associated with a procoagulant state, despite an impaired vitamin K-dependent coagulation factor synthesis. Virtually all alterations in coagulation and fibrinolysis were reversed by biliary drainage.

Plasminogen activator inhibitor-1 (PAI-1): a key factor linking fibrinolysis and age-related subclinical and clinical conditions

INTRODUCTION

The close relationship existing between aging and thrombosis has growingly been studied in this last decade. The age-related development of a prothrombotic imbalance in the fibrinolysis homeostasis has been hypothesized as the basis of this increased cardiovascular and cerebrovascular risk. Fibrinolysis is the result of the interactions among multiple plasminogen activators and inhibitors constituting the enzymatic cascade, and ultimately leading to the degradation of fibrin. The plasminogen activator system plays a key role in a wide range of physiological and pathological processes.

METHODS

Narrative review.

RESULTS

Plasminogen activator inhibitor-1 (PAI-1) is a member of the superfamily of serine-protease inhibitors (or serpins), and the principal inhibitor of both the tissue-type and the urokinase-type plasminogen activator, the two plasminogen activators able to activate plasminogen. Current evidence describing the central role played by PAI-1 in a number of age-related subclinical (i.e., inflammation, atherosclerosis, insulin resistance) and clinical (i.e., obesity, comorbidities, Werner syndrome) conditions is presented.

CONCLUSIONS

Despite some controversial and unclear issues, PAI-1 represents an extremely promising marker that may become a biological parameter to be progressively considered in the prognostic evaluation, in the disease monitoring, and as treatment target of age-related conditions in the future.

Inflammatory stress and idiosyncratic hepatotoxicity: hints from animal models

Adverse drug reactions (ADRs) present a serious human health problem. They are major contributors to hospitalization and mortality throughout the world (Lazarou et al., 1998; Pirmohamed et al., 2004). A small fraction (less than 5%) of ADRs can be classified as "idiosyncratic." Idiosyncratic ADRs (IADRs) are caused by drugs with diverse pharmacological effects and occur at various times during drug therapy. Although IADRs affect a number of organs, liver toxicity occurs frequently and is the primary focus of this review. Because of the inconsistency of clinical data and the lack of experimental animal models, how IADRs arise is largely undefined. Generation of toxic drug metabolites and induction of specific immunity are frequently cited as causes of IADRs, but definitive evidence supporting either mechanism is lacking for most drugs. Among the more recent hypotheses for causation of IADRs is that inflammatory stress induced by exogenous or endogenous inflammagens is a susceptibility factor. In this review, we give a brief overview of idiosyncratic hepatotoxicity and the inflammatory response induced by bacterial lipopolysaccharide. We discuss the inflammatory stress hypothesis and use as examples two drugs that have caused IADRs in human patients: ranitidine and diclofenac. The review focuses on experimental animal models that support the inflammatory stress hypothesis and on the mechanisms of hepatotoxic response in these models. The need for design of epidemiological studies and the potential for implementation of inflammation interaction studies in preclinical toxicity screening are also discussed briefly.

Hepatotoxic interaction of sulindac with lipopolysaccharide: role of the hemostatic system

Sulindac (SLD) is a nonsteroidal anti-inflammatory drug (NSAID) that has been associated with a greater incidence of idiosyncratic hepatotoxicity in human patients than other NSAIDs. One hypothesis regarding idiosyncratic adverse drug reactions is that interaction of a drug with a modest inflammatory episode precipitates liver injury. In this study, we tested the hypothesis that lipopolysaccharide (LPS) interacts with SLD to cause liver injury in rats. SLD (50 mg/kg) or its vehicle was administered to rats by gavage 15.5 h before LPS (8.3 x 10(5) endotoxin unit/kg) or its saline vehicle (i.v.). Thirty minutes after LPS treatment, SLD or vehicle administration was repeated. Rats were killed at various times after treatment, and serum, plasma, and liver samples were taken. Neither SLD nor LPS alone caused liver injury. Cotreatment with SLD/LPS led to increases in serum biomarkers of both hepatocellular injury and cholestasis. Histological evidence of liver damage was found only after SLD/LPS cotreatment. As a result of activation of hemostasis induced by SLD/LPS cotreatment, fibrin and hypoxia were present in liver tissue before the onset of hepatotoxicity. Heparin treatment reduced hepatic fibrin deposition and hypoxia and protected against liver injury induced by SLD/LPS cotreatment. These results indicate that cotreatment with nontoxic doses of LPS and SLD causes liver injury in rats, and this could serve as a model of human idiosyncratic liver injury. The hemostatic system is activated by SLD/LPS cotreatment and plays an important role in the development of SLD/LPS-induced liver injury.

Effects of IL-1beta and IL-6 on tissue-type plasminogen activator expression in vascular endothelial cells

INTRODUCTION

The increased risk of thrombus formation in inflammatory conditions is generally considered to be due to the pro-coagulant effect of inflammatory cytokines. However, cytokines may also decrease the expression of the key fibrinolytic enzyme tissue-type plasminogen activator (t-PA) causing a reduced clearance of emerging intravascular thrombi. This study investigated the effects of the inflammatory cytokines interleukin (IL)-1beta and IL-6 on t-PA gene and protein expression, and elucidated by which signaling mechanisms the effects are mediated.

MATERIALS AND METHODS

Cultured human umbilical vein endothelial cells (HUVEC) were exposed to recombinant IL-1beta or IL-6. t-PA mRNA was quantified by real-time RT-PCR and t-PA antigen by ELISA. To clarify signaling mechanisms, selective inhibitors of major cytokine-activated signaling pathways were used. Interactions of nuclear proteins with potential t-PA gene regulatory elements were studied by gel shift assays.

RESULTS

Already at low concentrations, IL-1beta caused a distinct suppression of t-PA transcript and protein levels, mediated primarily by NF-kappaB signaling. This cytokine also increased binding of NF-kappaB subunits to a t-PA specific kappaB element. IL-6 stimulation per se did not affect t-PA mRNA or protein levels whereas soluble IL-6 receptor, in the presence of endogenous IL-6, suppressed t-PA expression.

CONCLUSIONS

We conclude that the proinflammatory cytokine IL-1beta impairs fibrinolytic capacity in vascular endothelial cells by an NF-kappaB dependent suppression of t-PA expression. In contrast, an effect of IL-6 on t-PA expression could not be detected, probably due to lack of IL-6 receptor expression on HUVEC.

WRN polymorphisms affect expression levels of plasminogen activator inhibitor type 1 in cultured fibroblasts

BACKGROUND

Recessive mutations in WRN gene eliminate WRN protein function (helicase) and cause Werner syndrome. One of the most important clinical features of Werner syndrome patients are the premature onset and accelerated atherosclerosis process. Studies carried out on polymorphic WRN locus have shown that the alleles 1367R and 1074L confer protection for cardiovascular disease. Given that the levels of plasminogen activator inhibitor type 1 (PAI-1) were found to be significantly increased in Werner syndrome patients, is quiet possible that PAI-1 expression could be under regulation of WRN helicase. Therefore the purpose of this work was to evaluate the role of WRN polymorphism in modulating the expression of PAI-1.

METHODS

In order to accomplish our aim, an array of primary cultured fibroblasts from normal adult donors was genotyped for polymorphisms of both the WRN and PAI-1 loci. In addition, steady state levels of WRN and PAI-1 were measured by semi-quantitative RT-PCR assays in such cultures. To search for the potential relationship between the lack of WRN protein and PAI-1 expression, heterozygous cultures of fibroblasts (1367RC/1074LF; WRN genotype) were treated with a molecule of interference RNA against WRN messenger RNA (mRNA).

RESULTS

We found that, carriers of 1367R and 1074L alleles of WRN shown to have low amounts of PAI-1 in plasma (7.56 +/- 5.02), as compared with carriers of 1367C and 1074F alleles (16.09 +/- 6.03). Moreover, fibroblasts from carriers with these alleles had low expression levels of PAI-1 mRNA. The treatment of heterozygous primary fibroblast cultures (1367RC/1074LF; WRN genotype) with iRNA against WRN mRNA caused PAI-1 overexpression. Treatment with normal PAI-1 inducers (TGFbeta, TNFalpha, or insulin) in these cultures and from those with genotypes 1367CC/1074FF and 1367RR/1074FL resulted in a genotype-dependent PAI-1 expression level.

CONCLUSION

Our results suggest that polymorphisms in the WRN gene might have a significant role regulating PAI-1 levels in healthy individuals and "normal states" as well as acute or chronic stress, obesity, aging, acute inflammation, among others, where characteristic high levels of insulin, TNF alpha and TGFbeta, could favor PAI-1 high levels in carriers with polymorphic variants (C and F alleles), beyond the levels reached by carriers with other alleles (R and L alleles).

Salvianolic acid B attenuates plasminogen activator inhibitor type 1 production in TNF-alpha treated human umbilical vein endothelial cells

Plasminogen activator inhibitor type 1 (PAI-1), which plays a role in the development of atherosclerosis, is produced by endothelial cells following stimulation with various inflammatory cytokines such as tumor necrosis factor (TNF-alpha). In the present study, we investigated the effects of a potent water-soluble antioxidant, salvianolic acid B (SalB; derived from the Chinese herb, Salvia miltiorrhiza), on the expression of PAI-1 in TNF-alpha-treated human umbilical vein endothelial cells (HUVECs). We found that SalB inhibited TNF-alpha-induced PAI-1 mRNA production and protein secretion in HUVECs. Treatment with SalB (0.05 and 0.15 microM) notably attenuated TNF-alpha induced expression of PAI-1 to 90.5% and 74.6%, respectively, after 12 h, and to 75.1% and 64.2%, respectively, after 18 h. We also observed a dose-dependent decrease in PAI-1 protein production in the presence of SalB. We then used pathway inhibitors to investigate which step of the TNF-alpha induced signaling pathway was targeted by SalB. We found that the c-Jun N-terminal kinase (JNK) inhibitor, SP600125, increased the inhibitory effects of SalB on TNF-alpha-induced PAI-1 secretion, whereas the nuclear factor-kappaB (NF-kappaB) inhibitor, emodin, and the extracellular signal-regulated kinase (ERK) inhibitor, PD98059, did not. A gel shift assay further showed that SalB inhibited the TNF-alpha-activated NF-kappaB and AP-1 DNA binding activities in a dose-dependent manner. Collectively, these results indicate that the NF-kappaB and ERK-AP-1 pathways are possible targets of SalB in the regulation of TNF-alpha-stimulated PAI-1 production in HUVECs.

IL-8 induces imbalances between nitric oxide and endothelin-1, and also between plasminogen activator inhibitor-1 and tissue-type plasminogen activator in cultured endothelial cells

Interleukin-8 (IL-8), a member of the CXC chemokine family, plays an important role in the modulation of multiple biological functions in endothelial cells containing the receptors CXCR1 and CXCR2. It has previously been shown that IL-8 directly enhances endothelial cell survival, and stimulates the production of matrix metalloproteinases, which in turn regulates angiogenesis. However, its role in the regulation of the production of vasoactive substances in endothelial cells is less well defined. In this study, we investigate the effects of IL-8 on the proliferation of human umbilical vein endothelial cells (HUVECs). In addition, we also study the effects of IL-8 on the production of vasodilator, vasoconstrictor and fibrinolytic factors in these cells. The results show that recombinant IL-8 (50-200ng/ml) induces neither HUVEC proliferation nor nitric oxide (NO) release. However, it significantly increases the production of endothelin-1 (ET-1) in a concentration-dependent manner. Furthermore, incubation of endothelial cells with IL-8 (200ng/ml) up-regulates the plasminogen activator inhibitor-1 (PAI-1) in HUVECs, while it down-regulates the tissue plasminogen activator (t-PA). These findings suggest that IL-8 offsets the balance between endothelial vasoconstrictors and vasodilators. Furthermore, IL-8 also leads to an imbalance between PAI-1 and t-PA, which causes the ECs to become procoagulative and hypofibrinolytic.

The Role of Tumor Necrosis Factor Alpha in Lipopolysaccharide/Ranitidine-Induced Inflammatory Liver Injury

Exposure to a nontoxic dose of bacterial lipopolysaccharide (LPS) increases the hepatotoxicity of the histamine-2 (H2) receptor antagonist, ranitidine (RAN). Because some of the pathophysiologic effects associated with LPS are mediated through the expression and release of inflammatory mediators such as tumor necrosis factor alpha (TNF), this study was designed to gain insights into the role of TNF in LPS/RAN hepatotoxicity. To determine whether RAN affects LPS-induced TNF release at a time near the onset of liver injury, male Sprague-Dawley rats were treated with 2.5 x 10(6) endotoxin units (EU)/kg LPS or its saline vehicle (iv) and 2 h later with either 30 mg/kg RAN or sterile phosphate-buffered saline vehicle (iv). LPS administration caused an increase in circulating TNF concentration. RAN cotreatment enhanced the LPS-induced TNF increase before the onset of hepatocellular injury, an effect that was not produced by famotidine, a H2-receptor antagonist without idiosyncrasy liability. Similar effects were observed for serum interleukin (IL)-1beta, IL-6, and IL-10. To determine if TNF plays a causal role in LPS/RAN-induced hepatotoxicity, rats were given either pentoxifylline (PTX; 100 mg/kg, iv) to inhibit the synthesis of TNF or etanercept (Etan; 8 mg/kg, sc) to impede the ability of TNF to reach cellular receptors, and then they were treated with LPS and RAN. Hepatocellular injury, the release of inflammatory mediators, hepatic neutrophil (PMN) accumulation, and biomarkers of coagulation and fibrinolysis were assessed. Pretreatment with either PTX or Etan resulted in the attenuation of liver injury and diminished circulating concentrations of TNF, IL-1beta, IL-6, macrophage inflammatory protein-2, and coagulation/fibrinolysis biomarkers in LPS/RAN-cotreated animals. Neither PTX nor Etan pretreatments altered hepatic PMN accumulation. These results suggest that TNF contributes to LPS/RAN-induced liver injury by enhancing inflammatory cytokine production and hemostasis.

Fibrinolysis, inflammation, and regulation of the plasminogen activating system

The maintenance of a given physiological process demands a coordinated and spatially regulated pattern of gene regulation. This applies to genes encoding components of enzyme cascades, including those of the plasminogen activating system. This family of proteases is vital to fibrinolysis and dysregulation of the expression pattern of one or more of these proteins in response to inflammatory events can impact on hemostasis. Gene regulation occurs on many levels, and it is apparent that the genes encoding the plasminogen activator (fibrinolytic) proteins are subject to both direct transcriptional control and significant post-transcriptional mechanisms. It is now clear that perturbation of these genes at either of these levels can dramatically alter expression levels and have a direct impact on the host's response to a variety of physiological and pharmacological challenges. Inflammatory processes are well known to impact on the fibrinolytic system and to promote thrombosis, cancer and diabetes. This review discusses how inflammatory and other signals affect the transcriptional and post-transcriptional expression patterns of this system, and how this modulates fibrinolysis in vivo.

Plasminogen activator inhibitor-1 plasma concentration in allergic asthma patients during allergen challenge

BACKGROUND

The -675 4G/5G plasminogen activator inhibitor-1 (PAI-1) polymorphism is linked with asthma and bronchial hyperreactivity. The aim of this study was to evaluate the effect of allergen challenge on plasma PAI-1 concentration in relation to the -675 4G/5G PAI-1 gene polymorphism in house dust mite-allergic asthma patients (HDM-AAs).

MATERIALS AND METHODS

The study was performed in 54 HDM-AAs and 54 healthy nonatopic controls (HCs). Plasma samples were collected in HDM-AAs before, as well as 30 min, 6 h and 24 h after allergen challenge and at corresponding time points in sham-challenged HCs.

RESULTS

In subjects carrying the individual PAI-1 genotype, the mean baseline plasma PAI-1 concentration was greater in HDM-AAs than in HCs. At 30 min the mean increase in plasma PAI-1 concentration was significantly greater in HDM-AAs (14.4 +/- 12.9 ng/ml) than in HCs (3.4 +/- 3.2 ng/ml; p < 0.001). At 6 h, plasma PAI-1 concentration greater than before challenge was found in only 4 HCs (7.4%) but in 48 HDM-AAs (88.9%; p < 0.0001). An increase in plasma PAI-1 concentration at 6 h was found in all HDM-AAs carrying the 4G allele but only in 33.3% of the 5G homozygotes (p < 0.0001). The strongest correlation was found between log PC20 and PAI-1 plasma concentration over the period of 24 h (r = -0.507; p = 0.0001).

CONCLUSION

Changes in plasma PAI-1 concentration associated with allergen-induced bronchoconstriction are modulated by the -675 4G/5G polymorphism of the PAI-1 gene. Allergen-induced upregulation of PAI-1 synthesis may participate in the development of bronchial hyperreactivity in HDM-AAs.

Kruppel-like Factor 4 Regulates Endothelial Inflammation

The vascular endothelium plays a critical role in vascular homeostasis. Inflammatory cytokines and non-laminar blood flow induce endothelial dysfunction and confer a pro-adhesive and pro-thrombotic phenotype. Therefore, identification of factors that mediate the effects of these stimuli on endothelial function is of considerable interest. Kruppel-like factor 4 expression has been documented in endothelial cells, but a function has not been described. In this communication we describe the expression in vitro and in vivo of Kruppel-like factor 4 in human and mouse endothelial cells. Furthermore, we demonstrate that endothelial Kruppel-like factor 4 is induced by pro-inflammatory stimuli and shear stress. Overexpression of Kruppel-like factor 4 induces expression of multiple anti-inflammatory and anti-thrombotic factors including endothelial nitric-oxide synthase and thrombomodulin, whereas knockdown of Kruppellike factor 4 leads to enhancement of tumor necrosis factor alpha-induced vascular cell adhesion molecule-1 and tissue factor expression. The functional importance of Kruppel-like factor 4 is verified by demonstrating that Kruppel-like factor 4 expression markedly decreases inflammatory cell adhesion to the endothelial surface and prolongs clotting time under inflammatory states. Kruppel-like factor 4 differentially regulates the promoter activity of pro- and anti-inflammatory genes in a manner consistent with its anti-inflammatory function. These data implicate Kruppel-like factor 4 as a novel regulator of endothelial activation in response to pro-inflammatory stimuli.

The influence of biomaterials on endothelial cell thrombogenicity

Driven by tissue engineering and regenerative medicine, endothelial cells are being used in combination with biomaterials in a number of applications for the purpose of improving blood compatibility and host integration. Endothelialized vascular grafts are beginning to be used clinically with some success in some centers, while endothelial seeding is being explored as a means of creating a vasculature within engineered tissues. The underlying assumption of this strategy is that when cultured on artificial biomaterials, a confluent layer of endothelial cells maintain their non-thrombogenic phenotype. In this review the existing knowledge base of endothelial cell thrombogenicity cultured on a number of different biomaterials is summarized. The importance of selecting appropriate endpoint measures that are most reflective of overall surface thrombogenicity is the focus of this review. Endothelial cells inhibit thrombosis through three interconnected regulatory systems (1) the coagulation cascade, (2) the cellular components of the blood such as leukocytes and platelets and (3) the complement cascade, and also through effects on fibrinolysis and vascular tone, the latter which influences blood flow. Thus, in order to demonstrate the thrombogenic benefit of seeding a biomaterial with EC, the conditions under which EC surfaces are more likely to exhibit lower thrombogenicity than unseeded biomaterial surfaces need to be consistent with the experimental context. The endpoints selected should be appropriate for the dominant thrombotic process that occurs under the given experimental conditions.

Tumor necrosis factor-alpha-induced production of plasminogen activator inhibitor 1 and its regulation by pioglitazone and cerivastatin in a nonmalignant human hepatocyte cell line

Plasminogen activator inhibitor 1 (PAI-1) is an important mediator of atherosclerosis and liver fibrosis in insulin resistance. Circulating levels of PAI-1 are elevated in obese individuals, and PAI-1 messenger RNA is significantly higher in the livers of obese type 2 diabetic individuals than in nonobese type 2 diabetic individuals. To address the mechanism underlying the up-regulation of hepatic PAI-1 in obesity, we tested the effects of tumor necrosis factor alpha (TNF-alpha), an important link between obesity and insulin resistance, on PAI-1 production in the nonmalignant human hepatocyte cell line, THLE-5b. Incubation of THLE-5b cells with TNF-alpha stimulated PAI-1 production via protein kinase C-, mitogen-activated protein kinase-, protein tyrosine kinase-, and nuclear factor-kappaB-dependent pathways. A thiazolidinedione, pioglitazone, reduced TNF-alpha-induced PAI-1 production by 32%, via protein kinase C- and nuclear factor-kappaB-dependent pathways. The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor cerivastatin inhibited TNF-alpha-induced PAI-1 production by 59%, which was reversed by coincubation with mevalonic acid. In conclusion, obesity and TNF-alpha up-regulation of PAI-1 expression in human hepatocytes may contribute to the impairment of the fibrinolytic system, leading to the development of atherosclerosis and liver fibrosis in insulin-resistant individuals. A thiazolidinedione and a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor may thus be candidate drugs to inhibit obesity-associated hepatic PAI-1 production.

TNF-alpha mediated suppression of tissue type plasminogen activator expression in vascular endothelial cells is NF-kappaB- and p38 MAPK-dependent

BACKGROUND

Several proatherothrombotic conditions are associated with enhanced levels of circulating proinflammatory cytokines, which are believed to impair endothelial fibrinolytic capacity.

OBJECTIVE

This study aims at investigating how tumor necrosis factor (TNF)-alpha regulates endothelial gene expression of the key fibrinolytic enzyme tissue-type plasminogen activator (t-PA).

METHODS

Cultured human umbilical vein endothelial cells were pretreated with selective inhibitors of the three major inflammatory signaling pathways activated by TNF-alpha; the nuclear factor kappa-B (NF-kappaB), the p38 mitogen-activated protein kinase (p38 MAPK), and the c-jun N-terminal kinase (JNK) pathways. Following TNF-alpha stimulation, effects on t-PA gene expression were evaluated with real-time reverse transcriptase polymerase chain reaction and interactions of nuclear proteins with potential gene regulatory elements were studied with electrophoretic mobility shift assays.

RESULTS

Approximately 50% suppression of t-PA gene expression was observed after prolonged stimulation with TNF-alpha (> or =24 h). The repression was shown to be preferentially dependent on NF-kappaB activation, but also on p38 MAPK signaling. Further, we provide evidence for a TNF-alpha induced binding of NF-kappaB to the recently described kappaB site in the t-PA gene and of cyclic adenosine monophosphate response element binding protein (CREB) to the t-PA CRE-like site.

CONCLUSIONS

We conclude that TNF-alpha impairs fibrinolytic capacity in vascular endothelial cells by a NF-kappaB and p38 MAPK-dependent suppression of t-PA. This mechanism sheds a light on how inflammation contributes to the pathogenesis of cardiovascular diseases.

Plasma and plasma components in the management of disseminated intravascular coagulation

A variety of clinical conditions can cause systemic activation of coagulation that ranges from insignificant laboratory changes to severe disseminated intravascular coagulation (DIC). DIC consists of a widespread systemic activation of coagulation, resulting in diffuse fibrin deposition in small and midsize vessels. There is compelling evidence from clinical and experimental studies that DIC is involved in the pathogenesis of microvascular dysfunction and contributes to organ failure. In addition, the massive and ongoing activation of coagulation can result in depletion of platelets and coagulation factors, which might cause bleeding. Recent insight into important pathogenetic mechanisms that might lead to DIC has resulted in novel preventive and therapeutic approaches to patients with sepsis and derangement of coagulation. Supportive strategies aimed at inhibition of coagulation activation might theoretically be justified and have been found beneficial in experimental and initial clinical studies. These strategies comprise inhibition of tissue factor-mediated activation of coagulation or restoration of physiological anticoagulant pathways.

Thiazolidinediones inhibit TNFalpha induction of PAI-1 independent of PPARgamma activation

Increased plasminogen activator inhibitor type 1 (PAI-1) levels are observed in endothelial cells stimulated by tumour necrosis factor alpha (TNFalpha). Thiazolidinediones (TZDs) may inhibit elevated endothelial cell PAI-1 accounting, in part, for the putative atheroprotective effects of TZDs. In an endothelial cell line, Rosiglitazone (RG) and Pioglitazone (PG) inhibited induction of PAI-1 by TNFalpha. The specific peroxisome proliferator-activated receptor gamma (PPARgamma) inhibitor, SR-202, failed to modulate this effect. RG also inhibited the effect of TNFalpha on a reporter gene construct harbouring the proximal PAI-1 promoter and PAI-1 mRNA in cells co-transfected with a dominant-negative PPARgamma construct. RG and PG attenuated TNFalpha-mediated induction of trans-acting factor(s) Nur77/Nurr1 and binding of nuclear proteins (NP) to the cis-acting element (NBRE). SR-202 failed to modulate these effects. The observations suggest TZDs inhibit TNFalpha-mediated PAI-1 induction independent of inducible PPARgamma activation and this may involve in the modulation of Nur77/Nurr1 expression and NP binding to the PAI-1 NBRE.

C-reactive protein decreases tissue plasminogen activator activity in human aortic endothelial cells: evidence that C-reactive protein is a procoagulant

OBJECTIVE

C-reactive protein (CRP) can promote atherothrombosis by decreasing endothelial nitric oxide synthase and prostacyclin, and by stimulating both plasminogen activator inhibitor-1 in endothelial cells and tissue factor in mononuclear cells. Plasminogen activator-1, a marker of fibrinolysis, is the primary inhibitor of tissue plasminogen activator (tPA). Thus, we tested the effect of CRP on tPA in human aortic endothelial cells.

METHODS AND RESULTS

Incubation of human aortic endothelial cells with CRP (> or =12.5 microg/mL) significantly decreased tPA antigen and activity. Adenyl cyclase inhibitors, an endothelin receptor antagonist, superoxide dismutase, and a nitric oxide donor failed to reverse the effect of CRP on tPA. CRP increased interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha. Neutralization of both IL-1beta and TNFalpha reversed the inhibition of tPA by CRP. Furthermore, in volunteers that have high CRP levels, euglobulin clot lysis time was significantly increased compared with those that have low CRP levels, providing further evidence that high CRP levels are associated with a procoagulant state.

CONCLUSIONS

CRP inhibits tPA activity via generation of proinflammatory cytokines (IL-1beta and TNFalpha). This study provides additional novel data that CRP is a procoagulant and has implications for atherothrombosis.

Endothelial cell activation by IL-1beta in the presence of fibrinogen requires alphavbeta3

OBJECTIVE

The purpose of this study was to investigate the receptor requirements for enhanced IL-1beta-induced secretion of nitric oxide (NO) by endothelial cells (ECs) in the presence of fibrinogen.

METHODS AND RESULTS

ECs were exposed to IL-1beta with or without fibrinogen and NO was measured as nitrite. NO production by EC exposed to fibrinogen (0.3+/-0.1 micromol/L) was comparable concentration to control (0.2+/-0.1 micromol/L), but IL-1beta significantly increased NO production (0.8+/-0.1 micromol/L), and the combination of both fibrinogen and IL-1beta resulted in a further increase to 2.2+/-0.2 micromol/L (P<0.002). 7E3 or LM609, antibodies to alphavbeta3, inhibited NO production stimulated by fibrinogen-bound IL-1beta to 0.2+/-0.1 micromol/L (P<0.001) or 0.2+/-0.03 micromol/L (P<0.0001), respectively. These levels were comparable to control and significantly less than with IL-1beta (P<0.002). EC or fibroblasts exposed to both fibrinogen and IL-1beta, but not vitronectin and IL-1beta, demonstrated positive Western blotting for alphavbeta3 after immunopurification with anti- IL-1R, indicating specific association between alphavbeta3 and IL-1R. Dual immunofluorescence also revealed colocalization of alphavbeta3 and IL-1R only when the cells were exposed to both fibrinogen and IL-1beta.

CONCLUSIONS

The enhanced NO production by ECs in the presence of fibrinogen-bound IL-1beta requires the coordinated effects of colocalized alphavbeta3 and IL-1R.

In vivo and in vitro analysis of the human tissue-type plasminogen activator gene promoter in neuroblastomal cell lines: evidence for a functional upstream kappaB element

Besides its well-established role in wound healing and fibrinolysis, tissue-type plasminogen activator (t-PA) has been shown to contribute to cognitive processes and memory formation within the central nervous system, and to promote glutamate receptor-mediated excitotoxicity. The t-PA gene is expressed and regulated in neuronal cells but the regulatory transcriptional processes directing this expression are still poorly characterized. We have used DNase I-hypersensitivity mapping and in vivo foot printing to identify putative regulatory elements and transcription factor binding sites in two human neuroblastomal (KELLY and SK-N-SH) and one human glioblastomal (SNB-19) cell lines. Hypersensitive sites were found in the proximal promoter region of all cell lines, and within the first exon for KELLY and SNB-19 cells. Mapping of methylation-protected residues in vivo detected a cluster of protected residues corresponding to a cAMP response element (CRE) and Sp1 sites in the proximal promoter previously shown to be essential for basal expression in other cell types. Protected residues were also found at other sites, notably a kappaB element at position bp -3081 to -3072 that was partly protected in KELLY and SNB-19 cells. Analysis of transfected reporter constructs in KELLY and SNB-19 cells confirmed that this particular element is functionally significant in the transactivation of the t-PA promoter in both cell types. This study defines, by in vivo and in vitro methods, a previously undescribed kappaB site in the t-PA gene promoter that influences t-PA expression in neuronal cells.

Free cholesterol-loaded macrophages are an abundant source of tumor necrosis factor-alpha and interleukin-6: model of NF-kappaB- and map kinase-dependent inflammation in advanced atherosclerosis

Two key features of atherosclerotic plaques that precipitate acute atherothrombotic vascular occlusion ("vulnerable plaques") are abundant inflammatory mediators and macrophages with excess unesterified, or "free," cholesterol (FC). Herein we show that FC accumulation in macrophages leads to the induction and secretion of two inflammatory cytokines, tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6). The increases in TNF-alpha and IL-6 mRNA and protein were mediated by FC-induced activation of the IkappaB kinase/NF-kappaB pathway as well as activation of MKK3/p38, Erk1/2, and JNK1/2 mitogen-activated protein kinases (MAPK). Activation of IkappaB kinase and JNK1/2 was needed for the induction of both cytokines. However, MKK3/p38 signaling was specifically involved in TNF-alpha induction, and Erk1/2 signaling was required for IL-6. Most interestingly, activation of all of the signaling pathways and induction of both cytokines required cholesterol trafficking to the endoplasmic reticulum (ER). The CHOP branch of the unfolded protein response, an ER stress pathway, was required for Erk1/2 activation and IL-6 induction. In contrast, one or more other ER-related pathways were responsible for activation of p38, JNK1/2, and IkappaB kinase/NF-kappaB and for the induction of TNF-alpha. These data suggest a novel scenario in which cytokines are induced in macrophages by endogenous cellular events triggered by excess ER cholesterol rather than by exogenous immune cell mediators. Moreover, this model may help explain the relationship between FC accumulation and inflammation in vulnerable plaques.

Kruppel-like factor 2 (KLF2) regulates endothelial thrombotic function

The vascular endothelium maintains blood fluidity by inhibiting blood coagulation, inhibiting platelet aggregation, and promoting fibrinolysis. Endothelial cells lose these nonthrombogenic properties on exposure to proinflammatory stimuli. We recently identified the Kruppel-like factor KLF2 as a novel regulator of endothelial proinflammatory activation. Here it is found that KLF2 differentially regulates key factors involved in maintaining an antithrombotic endothelial surface. Overexpression of KLF2 strongly induced thrombomodulin (TM) and endothelial nitric oxide synthase (eNOS) expression and reduced plasminogen activator inhibitor-1 (PAI-1) expression. Furthermore, overexpression of KLF2 inhibited the cytokine-mediated induction of tissue factor (TF). In contrast, siRNA mediated knockdown of KLF2 reduced antithrombotic gene expression while inducing the expression of pro-coagulant factors. The functional importance of KLF2 was verified by in vitro clotting assays. By comparison to control infected cells, KLF2 overexpression increased blood clotting time as well as flow rates under basal and inflammatory conditions. In contrast, siRNA-mediated knockdown of KLF2 reduced blood clotting time and flow rates. These observations identify KLF2 as a novel transcriptional regulator of endothelial thrombotic function. The full text of this article is available online at http://circres.ahajournals.org.

The role of microvascular thrombosis in sepsis

The acute inflammatory response to sepsis gives rise to significant morbidity and mortality. The mechanisms underlying this form of tissue injury are poorly understood. This review examines the evidence that tissue ischaemia due, to generalized microvascular thrombosis may play an important role. Microvascular thrombosis is probably an adaptive response that prevents bacteria in the tissues reaching the systemic circulation via the capillaries. In time, a definitive response by leucocytes removes the bacteria and repairs the damaged tissues. There is however evidence that if microvascular thrombosis becomes generalized, then extensive tissue ischaemia may precipitate organ failure and death. Post-mortem studies of patients with sepsis demonstrate microvascular thrombi in many organs including the kidney, liver, lung, gut, adrenals and brain, and the degree of organ injury is related to the quantity of thrombi. Furthermore studies in human and animal models of sepsis demonstrate therapies that inhibit coagulation or promote fibrinolysis reduce organ failure and mortality. In view of the personal and economic burdens that tissue injury associated with the acute inflammatory response places on the community, further studies to establish the role of microvascular thrombosis are clearly required. Such studies may lead to new therapies to limit or prevent this form of injury.

Effects of TNF-α and curcumin on the expression of thrombomodulin and endothelial protein C receptor in human endothelial cells

The objective of this study was to elucidate the effects of tumor necrosis factor-alpha (TNF-alpha) on the expression of thrombomodulin (TM) and endothelial protein C receptor (EPCR) in human endothelial cells as well as the effect of curcumin, a spice and coloring food compound, as a potential therapeutic agent. Human umbilical vein endothelial cells (HUVECs) treated with TNF-alpha (2.0 ng/ml) showed reduced TM mRNA levels by 80%, 97%, 94%, and 97% at 3, 6, 12, and 24 h, respectively (P<0.05), by real-time PCR analysis. Dose-dependent study showed that TM mRNA levels of HUVECs were decreased by 86%, 89%, 91%, and 94% after treatment of TNF-alpha (0, 0.25, 0.5, 1, and 2 ng/ml) for 6 h, respectively (P<0.05). TM protein levels in HUVECs were significantly reduced by 69% in TNF-alpha-treated cells as compared to controls (P<0.05) by Western blot analysis. Secreted protein and activity of TM of HUVEC cultures were also significantly reduced in TNF-alpha-treated cells. In addition, EPCR mRNA levels of HUVECs were significantly reduced in TNF-alpha-treated group as compared to controls (P<0.05). Furthermore, these effects were observed in other types of endothelial cells from human coronary arteries, lung, and skin. Curcumin effectively blocked these effects of TNF-alpha on downregulation of TM and EPCR. These data demonstrate that TNF-alpha significantly decreases expression of TM and EPCR at both mRNA and protein levels in several human endothelial cells. Curcumin can effectively block TNF-alpha-induced endothelial dysfunction. This study suggests a new molecular mechanism of inflammation-induced thrombosis and a new therapeutic strategy to prevent this clinical problem.

An increase of C-reactive protein is associated with enhanced activation of endogenous fibrinolysis at baseline but an impaired endothelial fibrinolytic response after venous occlusion

OBJECTIVES

The goal of this study was to determine whether chronic inflammation of the vascular wall may be associated with an impaired activation of the fibrinolytic system.

BACKGROUND

Inflammation plays an important role in the initiation and progression of atherosclerosis, and the fibrinolytic system may prevent local thrombus formation.

METHODS

We included 50 patients six months after their first myocardial infarction. Plasma levels of the inflammatory marker C-reactive protein (CRP) were determined at basal conditions, and the fibrinolytic parameters tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor type-1 (PAI-1) were measured at basal conditions and after a standardized venous occlusion (VO) of the forearm.

RESULTS

Patients with high CRP levels (> or =3 mg/l) showed a significantly higher t-PA activity at baseline compared with patients with medium (1 to 2.9 mg/l) and low (<1 mg/l) CRP levels (p <0.005). In contrast, patients with low CRP levels showed a higher increase of t-PA activity (p <0.05) and a higher reduction of PAI-1 activity during VO (p <0.05) compared with patients with medium and high CRP levels. A multivariate analysis that included cardiovascular risk factors and medical treatment showed that CRP is an independent predictor of the t-PA response after a standardized VO.

CONCLUSIONS

Chronic low-grade inflammation is associated with enhanced activation of endogenous fibrinolysis at baseline but a reduced fibrinolytic response to VO. This impaired endogenous fibrinolytic capacity might be an important contributor to the increased coronary event rate associated with elevated CRP levels.

Inhibition of tumor necrosis factor-alpha reduces atherosclerosis in apolipoprotein E knockout mice

OBJECTIVE

Inflammation plays an important role in atherosclerosis. One of the most potent pro-inflammatory cytokines is tumor necrosis factor-alpha (TNF-alpha), a cytokine identified to have a pathogenic role in chronic inflammatory diseases such as rheumatoid arthritis (RA). The aim of the study was to evaluate the importance of TNF-alpha in atherogenesis.

METHODS AND RESULTS

Mice deficient in both apolipoprotein E (apoE) and TNF-alpha were compared regarding their atherosclerotic burden. Mice were fed a Western-style diet (WD) or normal chow. Mice deficient in both apoE and TNF-alpha exhibited a 50% (P=0.035) reduction of relative lesion size after 10 weeks of WD. Bone marrow transplantation of apoE(o) mice with apoE(o)tnf-alpha(o) bone marrow resulted in a 83% (P=0.021) reduction after 25 weeks on WD. In apoE knockout mice treated with recombinant soluble TNF receptor I releasing pellets, there was a reduction in relative lesion size after 25 weeks of 75% (P=0.018).

CONCLUSIONS

These findings demonstrate that TNF-alpha is actively involved in the progression of atherosclerosis. Accordingly, TNF-alpha represents a possible target for prevention of atherosclerosis. This may be of particular importance in rheumatoid arthritis because these patients have an increased risk for cardiovascular disease.

Impaired Endothelial Release of Tissue-Type Plasminogen Activator in Patients With Chronic Kidney Disease and Hypertension

We have shown that the capacity for local release of tissue-type plasminogen activator (tPA) from the vascular endothelium is impaired in patients with primary hypertension. Because this response is an important protective mechanism against intravascular clotting, we investigated whether this system is also defective in patients with advanced chronic kidney disease and hypertension. Nine nondiabetic nonsmoking men with chronic kidney disease (glomerular filtration rate 11 to 28 mL/min x 1.73 m2; aged 33 to 75 years) were compared with age-matched healthy controls. Intraarterial infusions of desmopressin, methacholine, and sodium nitroprusside were given locally in the brachial artery. Forearm blood flow was measured by venous occlusion plethysmography and blood collected repeatedly during the desmopressin infusion for determination of stimulated net and total cumulated release of tPA. The maximal release rate of active tPA (P<0.05) and the capacity for acute tPA release were markedly impaired in the renal patients as compared with healthy subjects (ANOVA, P=0.013). Accordingly, the accumulated release of tPA was 1905 (SEM 366) and 3387 (718) ng/L tissue, respectively (P<0.05). However, there were no significant differences in vasodilator responses between the groups. Thus, patients with advanced chronic kidney disease and hypertension have a markedly impaired capacity for acute release of tissue plasminogen activator, despite preserved endothelium-dependent vasodilation. This defect may contribute to a defective local defense against arterial thrombosis.

Differential regulation of biglycan and decorin synthesis by connective tissue growth factor in cultured vascular endothelial cells

It is possible that connective tissue growth factor (CTGF) serves as either an independent regulator or a downstream effector of transforming growth factor-beta (TGF-beta) on the proteoglycan synthesis in vascular endothelial cells. Since TGF-beta regulates endothelial proteoglycan synthesis in a cell density-dependent manner, dense and sparse cultures of bovine aortic endothelial cells were metabolically labeled with [(35)S]sulfate or (35)S-labeled amino acids in the presence of CTGF, and the labeled proteoglycans were characterized by biochemical techniques. The results indicate that CTGF suppresses the synthesis of biglycan but newly induced that of decorin in the cells when the cell density is low; in addition, no change was observed in the hydrodynamic size and the glycosaminoglycan chain length of these two small chondroitin/dermatan sulfate proteoglycans. The regulation of endothelial proteoglycan synthesis by CTGF is completely different from that by TGF-beta, suggesting that CTGF is not a downstream effector of TGF-beta but an independent regulator in vascular endothelial cells with respect to the proteoglycan synthesis.

Oxidative stress and hypoxia: implications for plasminogen activator inhibitor-1 expression

Plasminogen activator inhibitor-1 (PAI-1) is the major physiological inhibitor of urokinase-type and tissue-type plasminogen activators. It has gained special interest among clinicians because a number of pathological conditions, such as myocardial infarction, atherosclerosis, thrombosis, several types of cancer, and the metabolic syndrome, as well as type 2 diabetes mellitus, are associated with increased PAI-1 levels. Interestingly, a number of these diseases are also accompanied by oxidative stress and the enhanced production of reactive oxygen species or tissue hypoxia. This article tries to summarize some aspects leading to enhanced PAI-1 production under oxidative stress or hypoxia.

A neurokinin 1 receptor antagonist decreases postoperative peritoneal adhesion formation and increases peritoneal fibrinolytic activity

Fibrous adhesions remain a major sequela of abdominal surgery. The proinflammatory peptide substance P (SP), known to participate in inflammatory events, may play a key role in adhesion formation. This hypothesis was tested by using an antagonist, CJ-12,255 (Pfizer), that blocks the binding of SP to the neurokinin 1 receptor (NK-1R). Adhesion formation was surgically induced in the peritoneum of rats receiving daily doses of the NK-1R antagonist (NK-1RA; 5.0 or 10.0 mg/kg per day) or saline. On postoperative day 7, both the low and high doses of NK-1RA significantly (P < 0.05) reduced adhesion formation by 45% and 53%, respectively, compared with controls. Subsequently, the effect of NK-1RA administration on peritoneal fibrinolytic activity was investigated to determine a potential mechanism for SP action in the peritoneum. Samples were collected from nonoperated controls and from animals 24 h postsurgery that were administered either NK-1RA or saline. Fibrinolytic activity in peritoneal fluid was assayed by zymography, and expression of tissue plasminogen activator (tPA) and plasminogen activator inhibitor 1, both regulators of fibrinolytic activity, was assessed in peritoneal tissue and fluid by RT-PCR and bioassay, respectively. NK-1RA administration led to a marked (P < 0.05) increase in tPA mRNA levels in peritoneal tissue compared with nonoperated and saline-administered animals. Likewise, NK-1RA administration significantly (P < 0.05) increased tPA in the peritoneal fluid. These data suggest that activation of the NK-1R promotes peritoneal adhesion formation by limiting fibrinolytic activity in the postoperative peritoneum, thus enabling fibrinous adhesions to persist.

Interleukin-1beta but not IL-1alpha binds to fibrinogen and fibrin and has enhanced activity in the bound form

Fibrin is formed at sites of injury or inflammation and provides the temporary matrix to support vascular cell responses that are also mediated by cytokines including interleukin-1 (IL-1). We have shown previously that fibroblast growth factor 2 (FGF-2) binds with high affinity to fibrin(ogen). Because IL-1 has a structure similar to FGF-2, we have investigated the possible binding of IL-1 to fibrin(ogen). Experiments using IL-1 immobilized on Sepharose beads and soluble iodine 125 ((125)I)-labeled fibrinogen demonstrated no specific interaction of IL-1alpha with fibrinogen, but IL-1beta showed saturable and specific binding. Scatchard analysis indicated a single binding site with an apparent K(d) = 1.5 nM and a maximum molar binding ratio of IL-1beta to fibrinogen of 1.8:1. Binding of (125)I-IL-1beta to Sepharose-immobilized fibrinogen also demonstrated a single binding site with an apparent K(d) of 3.5 nM. IL-1beta also bound specifically to fibrin monomer and polymerized fibrin with apparent K(d)s of 3.4 nM and 2.3 nM, respectively. IL-1beta displaced FGF-2 for binding to fibrin, indicating an interaction with the same or a closely related site. Compared with free form, fibrinogen-bound IL-1beta stimulated increased activation of endothelial cell nuclear factor kappaB (NF-kappaB), monocyte chemoattractant protein-1 (MCP-1) secretion, and nitric oxide (NO) synthesis. We conclude that IL-1beta binds with high affinity to fibrin(ogen) and demonstrates increased activity in the bound form.

Plasminogen activator inhibitor-1 in the pathogenesis of asthma

Plasminogen activator inhibitor (PAI)-1 is the main inhibitor of the fibrinolytic system and is known to play an essential role in tissue remodeling. Recent evidence indicates that chronic asthma may lead to tissue remodeling such as subepithelial fibrosis and extracellular matrix (ECM) deposition in the airways. However, the role of PAI-1 in asthma is unknown. Recently the mast cell (MC), which plays a major role in asthma, was found as a novel source of PAI-1, and a large number of MCs expressing PAI-1 are infiltrated in the airways of patients with severe asthma. Furthermore, PAI-1-deficient mice show reduced ECM deposition in the airways of a murine model of chronic asthma by inhibiting MMP-9 activity and fibrinolysis. In a human study, the 4G allele frequency was significantly higher in the asthmatic patients than in the control group. In view of the findings that the 4G allele is associated with elevated plasma PAI-1 level, elevated PAI-1 level in the lung may contribute to the development of asthma. In summary, PAI-1 may play an important role in the pathogenesis of asthma and further studies evaluating the mechanisms of PAI-1 action may lead to the development of a novel therapeutic target for the treatment and prevention of asthma.

Pro- and antifibrinolytic properties of human pulmonary microvascular versus artery endothelial cells: impact of endotoxin and tumor necrosis factor-alpha

OBJECTIVE

Microvascular thrombosis is a common feature of acute inflammatory lung injury, as occurs in sepsis and acute respiratory distress syndrome, but the underlying pathomechanisms are presently not fully understood.

DESIGN

Experimental.

SETTING

University laboratory.

SUBJECTS

Lung endothelial cells.

INTERVENTIONS

We characterized the expression of tissue-type and urokinase-type plasminogen activator (t-PA and u-PA) as well as plasminogen activator inhibitor (PAI)-1 and PAI-2 in human endothelial cells (EC) from the microvascular pulmonary circulation (HMVEC-L) and compared it with that of EC from pulmonary artery (HPAEC) and umbilical vein (HUVEC) under baseline conditions and upon stimulation with either tumor necrosis factor-alpha or lipopolysaccharide.

MEASUREMENTS AND MAIN RESULTS

Real-time reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay were employed for quantification of messenger RNA and protein concentrations. Under baseline conditions, comparable PAI-1 expression was noted in all EC. HPAEC were characterized by significantly higher baseline expression of t-PA and PAI-2 compared with HUVEC and HMVEC-L. In contrast, u-PA messenger RNA concentrations were found to be significantly higher in nonstimulated HMVEC-L compared with HUVEC and HPAEC. In all EC, stimulation with tumor necrosis factor-alpha and lipopolysaccharide increased the expression of PAI-1, PAI-2, and u-PA and decreased t-PA expression. The changes in messenger RNA content were reflected by corresponding changes in the protein concentrations.

CONCLUSIONS

High baseline u-PA expression is a prominent feature of human lung microvascular EC, whereas pulmonary artery EC are characterized by high t-PA concentrations. Microbial and inflammatory challenge provokes up-regulation of PAI-1 and PAI-2 and down-regulation of t-PA in both macro- and microvascular pulmonary EC, which may favor local fibrin deposition.

Activation systems for latent matrix metalloproteinase-2 are upregulated immediately after focal cerebral ischemia

During focal cerebral ischemia, matrix metalloproteinase-2 (MMP-2) can contribute to the loss of microvessel integrity within ischemic regions by degrading the basal lamina. MMP-2 is secreted in latent form (pro-MMP-2), but the activation of pro-MMP-2 in the ischemic territory has not been shown. Immunohistochemical and in situ hybridization studies of the expression of the direct activators of MMP-2, MT1-MMP and MT3-MMP, and the indirect activation system tissue plasminogen activator, urokinase (u-PA), its receptor (u-PAR), and its inhibitor PAI-1 after middle cerebral artery occlusion/reperfusion were undertaken in basal ganglia samples from 26 adolescent male baboons. The expressions of all three MMPs, u-PA, u-PAR, and PA1-1, but not tissue plasminogen activator, were increased from 1 hour after middle cerebral artery occlusion in the ischemic core. mRNA transcripts confirmed the increases in latent MMP-2, u-PA, u-PAR, and PAI-1 antigen very early after middle cerebral artery occlusion. The expression patterns are consistent with secretion of pro-MMP-2 and its activators in the ischemic core, perhaps from separate cell compartments. The rapid and coordinate appearance of pro-MMP-2 and its activation apparatus suggest that in the primate striatum this protease may participate in matrix injury during focal cerebral ischemia.

Increased levels of hemostatic proteins are independent of inflammation in glycogen storage disease type Ia

OBJECTIVES

Glycogen storage disease type Ia (GSD-Ia), a congenital deficiency of hepatic glucose-6-phosphatase activity, is often associated with hyperproteinemia. To document the mechanism of hyperproteinemia, the proteins of the hemostatic system were analyzed according to their site of synthesis: hepatocyte, endothelial cell, or both. The role of inflammation was investigated by the measurement of tumor necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6) levels in plasma.

METHODS

Twenty-seven patients with GSD-Ia were evaluated, as were 14 patients with other types of GSD and 30 healthy control subjects. Of the 41 patients with GSD, 15 also had hepatic adenoma (14 patients with GSD-Ia and 1 with GSD type III).

RESULTS

In patients with GSD-Ia, there was a two-fold increase in all hepatocyte-synthesized proteins (i.e., factor VII, protein C, C4b binding protein) compared with control subjects and patients with other types of GSD. The proteins with mixed endothelial and hepatocyte origin (i.e., antithrombin and protein S) also were significantly increased but to a lesser extent. In contrast, the mean concentration of von Willebrand factor, which is exclusively synthesized in endothelial cells, was normal, as was the concentration of TNF-alpha and IL-6.

CONCLUSIONS

These results suggest that the hyperproteinemia of GSD-Ia (including hemostatic proteins) is attributable to hepatocyte dysfunction and not related to an inflammatory process.

Tumor necrosis factor-alpha and troglitazone regulate plasminogen activator inhibitor type 1 production through extracellular signal-regulated kinase- and nuclear factor-kappaB-dependent pathways in cultured human umbilical vein endothelial cells

Plasminogen activator inhibitor type 1 (PAI-1) plays a role in the development of atherosclerosis in diabetic patients. PAI-1 is produced by endothelial cells stimulated with various inflammatory cytokines, such as tumor necrosis factor (TNF)-alpha, which induces insulin resistance. In diabetic patients, troglitazone, a thiazolidinedione, can lower the concentration of PAI-1. We investigated the TNF-alpha-induced signaling pathway that leads to PAI-1 synthesis and the target step of troglitazone in this pathway. TNF-alpha induced PAI-1 mRNA expression and protein production in human umbilical vein endothelial cells (HUVECs). A specific inhibitor for p38 mitogen-activated protein kinase, 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole (SB 203580), and a protein kinase C inhibitor, calphostin C, had no inhibitory effects on TNF-alpha-induced PAI-1 secretion. A protein tyrosine kinase inhibitor, genistein, completely inhibited TNF-alpha-induced PAI-1 secretion, whereas an inhibitor of extracellular signal-regulated kinase (ERK) kinase, 2'-amino-3'-methoxyflavone (PD98059), and a nuclear factor-kappaB (NF-kappaB) inhibitor, emodin, partly inhibited TNF-alpha-induced PAI-1 secretion. Together, PD98059 and emodin completely inhibited TNF-alpha-induced PAI-1 secretion, suggesting that both NF-kappaB-dependent and NF-kappaB-independent pathways are involved in TNF-alpha-induced signal pathway to PAI-1 production and that the latter pathway is mediated by activation of ERK. Furthermore, we have shown that troglitazone inhibited both TNF-alpha-induced PAI-1 protein secretion and mRNA in HUVECs. Genistein, but neither PD98059 nor emodin, was additive to the inhibitory effect of troglitazone on TNF-alpha-induced PAI-1 secretion. These results indicate That ERK and NF-kappaB are possible targets of TNF-alpha and troglitazone in the regulation of PAI-1 production.

Plasminogen activator inhibitor-1 supports IL-8-mediated neutrophil transendothelial migration by inhibition of the constitutive shedding of endothelial IL-8/heparan sulfate/syndecan-1 complexes

The endothelium is the primary barrier to leukocyte recruitment at sites of inflammation. Neutrophil recruitment is directed by transendothelial gradients of IL-8 that, in vivo, are bound to the endothelial cell surface. We have investigated the identity and function of the binding site(s) in an in vitro model of neutrophil transendothelial migration. In endothelial culture supernatants, IL-8 was detected in a trimolecular complex with heparan sulfate and syndecan-1. Constitutive shedding of IL-8 in this form was increased in the presence of a neutralizing Ab to plasminogen activator inhibitor-1 (PAI-1), indicating a role for endothelial plasminogen activator in the shedding of IL-8. Increased shedding of IL-8/heparan sulfate/syndecan-1 complexes was accompanied by inhibition of neutrophil transendothelial migration, and aprotinin, a potent plasmin inhibitor, reversed this inhibition. Platelets, added as an exogenous source of PAI-1, had no effect on shedding of the complexes or neutrophil migration. Our results indicate that IL-8 is immobilized on the endothelial cell surface through binding to syndecan-1 ectodomains, and that plasmin, generated by endothelial plasminogen activator, induces the shedding of this form of IL-8. PAI-1 appears to stabilize the chemoattractant form of IL-8 at the cell surface and may represent a therapeutic target for novel anti-inflammatory strategies.