Enhancement by interleukin-1 (IL-1) of plasminogen activator inhibitor (PA-I) activity in cultured human endothelial cells

Integrated analysis of gene expression changes associated with coronary artery disease

BACKGROUND

This study investigated the pathways and genes involved in coronary artery disease (CAD) and the associated mechanisms.

METHODS

Two array data sets of GSE19339 and GSE56885 were downloaded. The limma package was used to analyze the differentially expressed genes (DEGs) in normal and CAD specimens. Examination of DEGs through Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment and Gene Ontology annotation was achieved by Database for Annotation, Visualization and Integrated Discovery (DAVID). The Cytoscape software facilitated the establishment of the protein-protein interaction (PPI) network and Molecular Complex Detection (MCODE) was performed for the significant modules.

RESULTS

We identified 413 DEGs (291 up-regulated and 122 down-regulated). Approximately 256 biological processes, only 1 cellular component, and 21 molecular functions were identified by GO analysis and 10 pathways were enriched by KEGG. Moreover, 264 protein pairs and 64 nodes were visualized by the PPI network. After the MCODE analysis, the top 4 high degree genes, including interleukin 1 beta (IL1B, degree = 29), intercellular adhesion molecule 1 (ICAM1, degree = 25), Jun proto-oncogene (JUN, degree = 23) and C-C motif chemokine ligand 2 (CCL2, degree = 20) had been identified to validate in RT-PCR and Cox proportional hazards regression between CAD and normals.

CONCLUSIONS

The relative expression of IL1B, ICAM1 and CCL2 was higher in CAD than in normal controls (P < 0.05-0.001), but only IL1B and CCL2 genes were confirmed after testing the gene expression in blood and/or analyzing in Cox proportional hazards regression (P < 0.05-0.001), and the proper mechanism may involve in the AGE-RAGE signaling pathway, fluid shear stress, the tumor necrosis factor (TNF) and cytokine-cytokine receptor interaction.

A Review of Interleukin-1 in Heart Disease: Where Do We Stand Today?

Cardiovascular diseases are the leading cause of death worldwide. Research in the last two decades has emphasized the inflammatory process as a key component in the pathogenesis of many of them. The Interleukin-1 family is a pivotal element of inflammation and has been well studied as a therapeutic target in various inflammatory states. Recent trials have explored the effect of Interleukin-1 blockade in cardiovascular diseases and initial evidence of the relevance of such treatment in this field of medicine accumulate. This review will describe the role of Interleukin-1 in heart diseases and the potential therapeutic effect of its blockade in such diseases.

Interleukin-1 Gene Cluster Polymorphisms and Their Association with Coronary Artery Disease: Separate Evidences from the Largest Case-Control Study amongst North Indians and an Updated Meta-Analysis

Several researchers have reported significant association of numerous single nucleotide polymorphisms (SNPs) residing in the interleukin-1 (IL-1) gene cluster with coronary artery disease (CAD). However, their association status amongst North Indian ancestry (NIA) have never been systematically assessed. Despite a published meta-analysis on this subject, their association status worldwide as well as amongst different major ancestral subgroups still remains unclear. We therefore decided to prospectively test the association of 11 IL-1 gene cluster SNPs with CAD, vide a case-control study amongst a cohort of NIA and attempted to validate our results with the help of an updated meta-analysis of all relevant published association studies. Included studies were segregated into ancestral subgroups and association statuses for each subgroup were determined. A total of 323 cases and 400 healthy, age and sex matched controls belonging to NIA were prospectively enrolled and subsequently genotyped for 11 selected IL-1 gene cluster SNPs. Although results for none of the evaluated IL-1 gene cluster SNPs reached the adjusted level of significance (p<0.0045), clear trends of association were seen for IL1B -511 C>T and IL1RN 86bp VNTR in several of the constructed genetic models (p range = 0.01–0.044 and 0.005–0.034 respectively). The presence of >1, ‘T’ (minor) allele of IL1B -511 C>T in a genotype seemed to provide protection against CAD (OR = 0.62, p = 0.044), while the presence of >1, ‘C’ (major) allele seemed to increase the risk of CAD (OR = 1.36, p = 0.041). The minor allele (allele 2) of IL1RN 86bp VNTR and its homozygous genotype (2/2 genotype) also seemed to carry an increased risk for CAD (OR = 1.62, p = 0.005 and OR = 2.25, p = 0.031 respectively). On the other hand, several haplotype combinations constructed out of IL1B and IL1RN gene variants clearly showed statistically significant associations with CAD (p<0.0045). Our meta-analysis was conducted for 8 previously assessed IL-1 SNPs. We included 53 different studies which involved a total sample of 26,210 (13,982 cases and 12,228 controls). Our pooled results concurred with the findings of our case-control study and was not able to deduce any statistically significant associations for any of the 8 studied SNPs (p>0.05). Subgroup analysis, however, yielded interesting results, where significant differences in association statuses were seen for IL1A +4845 G>T, IL1B -511 C>T, IL1RN 86bp VNTR and IL1RN +8006 T>C for select ancestral subgroups. The hints of associations deduced for subjects belonging to NIA in our case-control study for both IL1B -511 C>T and IL1RN 86bp VNTR were duly validated vide significant p values seen for NIA in all three genetic models (OR range = 0.62–0.76, p range = 0.01–0.04 and OR range = 1.51–2.25, p range = 0.004–0.04 respectively). On the other hand, Mixed Ancestry (MA) subgroup carrying IL1B -511 C>T, IL1RN 86bp VNTR or IL1RN +8006 T>C polymorphisms seemed to enjoy significant protection against CAD. A few other ancestral subgroups also demonstrated significant associations for a few of the studied SNPs vide one of the three genetic models. Clinical interpretation of derived results is however recommended.

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.

Evaluation of low PAI-1 activity as a risk factor for hemorrhagic diathesis

BACKGROUND

Prospective studies of the epidemiology and clinical significance of low plasminogen activator inhibitor type 1 (PAI-1) activity are lacking.

OBJECTIVE

To evaluate the prevalence of low PAI-1 activity in patients with a bleeding tendency in comparison with a normal population.

METHODS

In 586 consecutive patients, referred because of bleeding symptoms, we added analyses of PAI-1 activity and tissue plasminogen activator complex with PAI-1 (t-PA-PAI-1) to the routine investigation, consisting of platelet count, bleeding time, prothrombin time, activated partial thromboplastin time, fibrinogen, factor VIII, von Willebrand factor activity, and antigen. Controls were 100 blood donors and 100 age- and sex-matched healthy individuals. The latter were also evaluated regarding the previous bleeding episodes. The bleeding history was classified as clinically significant or not, and the criteria were fulfilled in 75% of the patients and 18% of the healthy controls.

RESULTS

The routine laboratory investigation of the patients was negative in 57%. Low PAI-1 activity, defined as <1.0 U mL(-1), was found in 23% of the patients and in 13% and 10% of the blood donors and healthy controls, respectively (odds ratio and 95% CI, 2.04; 1.11-3.77 and 2.75; 1.39-5.42, respectively). The difference remained statistically significant after the adjustment for body mass index, use of estrogens, sex and age (odds ratio for patients vs. healthy controls 3.23; 95% CI, 1.22-8.56, P = 0.019). The distribution of the 4G/5G genotypes in the patients was not different from that of two control populations. No specific symptom predicted for low PAI-1, which did not aggravate the clinical picture in association with the other hemostatic defects. Low tPA-PAI-1 was not associated with the increased bleeding tendency.

CONCLUSION

Low PAI-1 activity is common in patients with a bleeding diathesis, but it is a risk factor of minor clinical importance and not associated with specific bleeding manifestations.

Fibroblast growth factor and heparin protect endothelial cells from the effects of interleukin 1

Vascular endothelium is involved in both active and passive processes in haemostasis, but inflammatory cytokines such as interleukin 1 (IL-1) and tumour necrosis factor (TNF) have been reported to convert the comparatively inert endothelial cell to an inflammatory state. Acidic fibroblast growth factor (aFGF) in the presence of heparin has effects opposite to IL-1 on cultured human umbilical vein endothelial cells (HUVEC); therefore, we have investigated the modulation of IL-1-induced effects by the c combination of aFGF and heparin (aFGF/heparin). First passage HUVEC were cultured for 6 days in the presence of 20% human serum with and without the addition of 625 pM human recombinant aFGF (hr aFGF) and 7 microM heparin. On day 5, recombinant IL-1 beta was included for 24 h. The following day the cells were washed and measurements made of the release of prostacyclin, von Willebrand factor, plasminogen activator inhibitor type 1, and thrombospondin, both in the resting state and following stimulation for 60 min with 1 U/ml thrombin. Tissue-type plasminogen activator was assayed in HUVEC lysates. Similar experiments were performed to assess effects on the expression of vascular adhesion molecule, intracellular adhesion molecule, and E-selectin using an ELISA on cells in situ. This study indicates that aFGF/heparin in the culture medium of HUVEC abrogates the measured responses to IL-1. These data imply that routine endothelial cell culture with aFGF/heparin may cause artefacts, the effects of FGF and Il-1 may involve common pathways, and FGF/heparin may offer an approach to design therapeutics to counter the adverse effects of IL-1.

Increased synthesis of plasminogen activator inhibitor-1 by cultured human endothelial cells exposed to native and modified LDLs. An LDL receptor-independent phenomenon

The effects of native and acetylated low density lipoproteins (LDLs and acetyl-LDLs, respectively) on the release of plasminogen activator inhibitor type 1 (PAI-1) by cultured human umbilical vein endothelial cells (ECs) were evaluated. LDL and acetyl-LDL incubated with ECs for 16-18 hours increased the PAI-1 antigen levels in conditioned medium. At a concentration of 100 micrograms/mL, LDL and acetyl-LDL increased PAI-1 by 10.8 and 12.0 ng/mL, respectively (p < 0.05 and p < 0.01 versus control). The increases in PAI-1 antigen levels exerted by the lipoproteins paralleled the changes in PAI-1 activity. The effect of LDL and acetyl-LDL was concentration dependent and specific for PAI-1 because tissue-type plasminogen activator and expression of procoagulant activity were not affected by either lipoprotein. In addition, total protein synthesis evaluated in [35S] methionine-labeled ECs was not affected, and studies with cycloheximide showed that the effect of LDL and acetyl-LDL on PAI-1 release was due to de novo protein synthesis. Experiments using the C7 monoclonal antibody against the LDL receptor and binding-defective LDL indicated that the effect of LDL on the synthesis of PAI-1 was not dependent on the interaction of the LDLs with their specific receptors. Finally, extensive oxidation of LDL prevented and even reversed the effect of LDL on PAI-1 release by ECs. It is concluded that LDL specifically increases the synthesis of PAI-1 by ECs with mechanisms that are not receptor mediated.

Effect of aspirin on the fibrinolytic response in perfused rat hindquarters

The role of aspirin on tissue plasminogen activator (t-PA) release was studied in rats after experimental venous occlusion. For this purpose, we developed a new experimental model which combines a vascular perfusion system (isolated rat hindquarters) with vascular stimulation, namely the application of venous stasis. Application of venous stasis for 30 min induced the release of t-PA from the vascular endothelium into the perfusate (from 0.19 +/- 0.05 to 0.39 +/- 0.05 UI/ml), reaching a peak 90 s after reperfusion. Aspirin administered to rats 60 min before the experiments (100 mg/kg i.v.), or dissolved in Tyrode solution (100 microM), suppressed 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) synthesis (0.38 +/- 0.09 in control and < 0.01 and 0.15 +/- 0.09 ng/ml, respectively, in aspirin-treated groups) but did not prevent the increase in fibrinolytic activity after venous occlusion (from 0.20 +/- 0.04 to 0.38 +/- 0.06 and from 0.07 +/- 0.03 to 0.27 +/- 0.03 IU/ml, respectively, in the aspirin-treated group). Our results suggest that the increase in fibrinolytic activity after experimental venous occlusion in isolated rat hindlegs is modulated by mechanism(s) other than the cyclooxygenase pathway in the vascular wall.

Interleukin-2 induces activation of coagulation and fibrinolysis: resemblance to the changes seen during experimental endotoxaemia

The administration of Interleukin-2 (IL-2) causes the release or generation of other cytokines such as tumour necrosis factor (TNF) which, by disturbing the anticoagulant properties of the endothelium, may induce a procoagulant state in patients receiving this drug. We therefore evaluated the effects of IL-2 on coagulation and fibrinolysis in 14 patients receiving 12 or 18 x 10(6) IU/m2/d of IL-2 given as a 15 min infusion for 5 d. Blood samples were drawn at short intervals after the first IL-2 infusion. The parameters were analysed by way of analysis for repeated measures (F tests rather than t tests). During the first day, thrombin-antithrombin (TAT) complexes started to increase 2 h after the IL-2 infusion, reaching peak levels at 4 h (n = 14; 11.2 +/- 6.4 micrograms/l v 49.8 +/- 49.2 micrograms/l, P < 0.01). Plasma alpha 2 antiplasmin (PAP) complexes showed a similar pattern rising from a mean baseline value of 17.5 +/- 7.6 nmol/l to 66.8 +/- 47.7 nmol at 4 h (P < 0.01). In four patients the peak of PAP preceeded that of TAT. Tissue plasminogen activator (tPA) rose from a mean baseline value of 4.9 +/- 3.7 micrograms/l to 26.3 +/- 13.5 micrograms/l at 4 h (P < 0.01). Plasminogen-activator-inhibitor-1 (PAI-1) levels increased from 59 +/- 35 micrograms/l to 113 +/- 39 micrograms/l at 6 h (P < 0.01). tPA PAI-1 complexes increased from 0.15 +/- 0.07 to 0.69 +/- 0.21 nmol/l at 6 h (P < 0.01). Our study indicates that IL-2 activates the coagulation and fibrinolytic systems in vivo. The changes resemble the perturbations observed after endotoxin/TNF administration. These abnormalities may play a role in the side-effects induced by IL-2 therapy.

The Potential Role of Cytokines in the Pathogenesis of Systemic Sclerosis (Scleroderma)

Systemic sclerosis (scleroderma) is characterized by excessive fibroblastic activity taking place through mechanisms largely unknown. It has been speculated that soluble factors, collectively categorized as lymphokines or monokines, and released by inflammatory or other differentiated cells, may modulate fibroblast multiple functions including migration, chemotaxis and protein synthesis. Vascular endothelium itself, which is deeply injured in systemic sclerosis, is acting as a target for the action of cytokines and is an important producer of polypeptide mediators that contribute to the inflammatory reaction and to the establishment of fibrosis. Thus, interactions through soluble mediators between fibroblasts, endothelial cells and immunocompetent cells appear crucial for the development of systemic sclerosis lesions. The aim of the present study is to evaluate the available information on the role of cytokines and to discuss their potential influence in the pathogenesis of systemic sclerosis.

Use of fibrinogen to enhance the antitumor effect of OK-432. A new approach to immunotherapy for colorectal carcinoma

OK-432 (5 KE), an immunomodulatory agent prepared from an attenuated strain of Streptococcus pyogenes, was dissolved in 1 ml of aprotinin (1000 KIE) and mixed with 80 mg of fibrinogen containing Factor XIII. A single intratumoral injection of the mixture was performed preoperatively under endoscopy in 20 patients with colorectal carcinoma. Postoperative histopathologic examinations revealed the formation of fibrin fibers at the site of injection and marked infiltration of inflammatory cells into the tumor stroma on the day after injection; the formation of granulomas containing many giant cells after 4 to 7 days; and extensive regression of tumor tissue after 14 days. This study suggests that the high concentration of exogenous fibrinogen gelatinized enough to trap OK-432 in tumor stroma and that OK-432 induced granulomatous hypersensitivity to degenerate tumor stroma, thereby causing regression of the tumors.

Decreased fibrinolytic activity in juvenile chronic arthritis

The basal fibrinolytic activity in 17 children with active juvenile chronic arthritis (JCA) was investigated. It was found that patients with JCA, and particularly those with the systemic form, show decreased plasma fibrinolytic activity and a marked increase in plasminogen activator inhibitor. Additionally, it was found that patients with systemic JCA, but not those with the polyarticular or pauciarticular form, have increased circulating levels of tissue-type plasminogen activator, and endothelial cell protein, suggesting possible endothelial cell participation in systemic JCA.

Biochemical and biological aspects of the plasminogen activation system

Plasminogen activators (PAs) are specific proteolytic enzymes which convert the inactive proenzyme plasminogen to plasmin. The plasmin formed is a potent and nonspecific protease which cleaves blood fibrin clots and several other extracellular proteins. In addition to their primary role in the initiation of fibrinolysis, PAs are implicated in a variety of basic biological processes, such as, degradation of the extracellular matrix, tumor invasiveness, tissue remodelling, and cellular differentiation. This review describes recent observations on the biochemical and biophysical characteristics of the different components of the plasminogen activation system. This complex system includes: the proenzymes of tissue type PA (tPA) and urokinase type PA (uPA); the active enzymes tPA, uPA and plasmin; the substrate plasminogen; several natural inhibitors of PA and plasmin activity; and the cellular receptors that bind the proenzymes, enzymes, and inhibitor-enzyme complexes. Through the coordinated interactions of these components, the location, timing, and extent of potent proteolytic activity is controlled. Recent findings on the structure, properties, biological functions, and regulation of the different components of the plasminogen activation cascade are reviewed. Current methods for assay of the amount and activity of the enzymes, inhibitors, and receptors are described. Observations implying specific functions of the system in health and disease, and its potential utilization for diagnosis are examined. Specifically, the potential application of PAs as laboratory markers of neoplasia, as diagnostic tools in diseases of the blood clotting system, their use for monitoring of thrombolytic therapy, and their possible relevance in certain disease states are described.

Modulation of plasminogen activator production by interleukin 1: differential responses of fibroblasts derived from human skin and rheumatoid and non-rheumatoid synovium

Rheumatoid synovial fibroblasts were treated with purified porcine interleukin 1 alpha and recombinant human interleukin 1B, and the production of secreted and cell-associated plasminogen activator activity was measured. No stimulation of plasminogen activator activity was seen in response to either preparation of interleukin 1, and in more than half of the cell cultures interleukin 1 caused a significant decrease in the secreted levels of PA activity. Increased levels of prostaglandin E were produced in the same experiments, indicating that the cells were responsive to the interleukin 1 preparations. Both retinoic acid and unfractionated monocyte conditioned medium were able to stimulate the production of PA activity by the rheumatoid synovial fibroblast cultures. The rheumatoid synovial fibroblasts produced two species of plasminogen activator as indicated by SDS polyacrylamide gel electrophoresis, with apparent Mr of approx. 50,000 and 100,000. The Mr = 50,000 species co-migrates with urokinase-type plasminogen activator. No species is produced which co-migrates with tissue type plasminogen activator. Studies with antibodies also indicate that the activity produced is urokinase-type plasminogen activator. The Mr = 100,000 species may be an enzyme-inhibitor complex. Two non-rheumatoid synovial fibroblast cultures and two out of six human skin fibroblast cultures did produce elevated levels of plasminogen activator activity in response to recombinant human interleukin 1B. The results suggest that fibroblast populations may differ in their response to interleukin 1, in terms of production of plasminogen activator activity.

Enhanced release of plasminogen activator inhibitor(s) but not of plasminogen activators by cultured rat glial cells treated with interleukin-1

Astroglial cells are known to proliferate during development of the nervous system, as well as during post-traumatic gliosis. We have previously shown that the proliferation of cultured astrocytes can be stimulated by the urokinase-type (uPA) of plasminogen activator (PA) and that astrocytes are able to release such uPA upon stimulation with basic fibroblast growth factor, which is known to act as a mitogen for these cells. Here we report studies on the effects of human interleukin-1 (IL-1) on the release of PA activity by cultured newborn rat astroglial cells. Whereas there is controversy in the literature as to whether IL-1 stimulates multiplication of astroglial cells, we failed to observe such an effect in our system. We did observe, however, a dose-dependent decrease in PA activity in the supernatant of the IL-1 treated cultures. Further analysis revealed that this apparent decrease in PA release was in fact due to an increased release of plasminogen activator inhibitor (PAI). A similar IL-1 induced increase in PAI release was also found to occur in cultures of transformed astrocytes (human glioma LN18) and in cultured Schwann cells, but not in cultures of neurons or neuronal tumour cells. Since protease inhibitors are known to possess neuritogenic properties, our results suggest that IL-1, by its capacity to induce PAI, may promote neuritogenesis.

Cytokines as communication signals between leukocytes and endothelial cells

Hemostasis, inflammatory reactions and immunity involve close interactions between immunocompetent cells and the vascular endothelium. Cytokines, produced by and acting on endothelial cells, are mediators of the complex bidirectional interactions between leukocytes and vascular cells. Cytokines affect endothelial cell function in inflammation, thrombosis and angiogenesis, in addition to their role as accessory cells. As well as acting as targets for the action of cytokines, endothelial cells are important producers of polypeptide mediators that regulate hematopoiesis, the differentiation and proliferation of T and B cells and the extravasation of leukocytes. In this review, Alberto Mantovani and Elisabetta Dejana discuss endothelial cells as important participants in the induction and regulation of coagulation, inflammation and immunity and cytokines as crucial mediators of the symbiotic interactions between vascular cells and leukocytes.

Interleukin-1, endotoxin or tumor necrosis factor/cachectin enhance the level of plasminogen activator inhibitor messenger RNA in bovine aortic endothelial cells

It is known that either endotoxin (LPS) or interleukin-1 (IL-1) increase the activity of plasminogen activator inhibitor (PAI) in the culture media of human and bovine endothelial cells. We have confirmed these results in bovine aortic endothelial cells (BAEC). To determine if this effect was mediated by increases in the level of PAI messenger RNA (mRNA) we examined the effects of these cytokines on PAI mRNA levels in BAEC, using RNA blot analyses. Treatment of BAEC with either IL-1, LPS, or human recombinant tumor necrosis factor/cachectin (TNF) dramatically increased the level of PAI mRNA. Since elevated levels of PAI will decrease fibrinolytic potential, this mechanism is in concert with the known increase in in vivo procoagulant potential induced by these agents and could contribute to thromboembolic phenomena.

Interleukin 1 regulation of interleukin 2 and interferon-gamma gene activation in a human leukemic HSB.2 subclone

The role of interleukin 1 (IL1) in causing IL2 and interferon-gamma (IFN-gamma) production and their associated gene activation has been studied in a human leukemic HSB.2 subclone. One of the subclones, HSB.2-C5B2 clone #28, which produced only low levels of IL2 and IFN-gamma when stimulated with phytohemagglutinin (PHA) or with a combination of phorbol-myristate-acetate (PMA) and Ca2+ ionophore, ionomycin, showed marked IL2 and IFN-gamma production in the presence of IL1. The augmentation by IL1 was observed in both dot and Northern blot analysis, indicating that IL1 regulates lymphokine genes at the pretranslational level. The kinetics of IL2 and IFN-gamma production were essentially similar for both lymphokines except that there was a faster accumulation of IFN-gamma mRNA than IL2 mRNA. In contrast to the IL2 and IFN-gamma gene activation, IL2 receptor (Tac/p55 antigen) expression was induced directly by IL1 itself as with PMA in this subclone. In these studies, IL1 action was not replaced by the drugs raising intracellular cyclic AMP (cAMP). Taken collectively, these experiments support the notion that IL1 does not trigger IL2 gene activation per se, but amplifies the preactivated lymphokine genes initiated by PMA and ionomycin, whereas IL1 can activate the IL2 receptor gene without any other known signal requirements.

Tumor necrosis factor-alpha regulates mRNA for urokinase-type plasminogen activator and type-1 plasminogen activator inhibitor in human neoplastic cell lines

Tumor necrosis factor-alpha (TNF-alpha) was found to induce type-1 plasminogen activator inhibitor (PAI-1) antigen in the human fibrosarcoma cell line HT-1080, and PAI-1 and urokinase-type plasminogen activator (u-PA) antigens in the human carcinoma cell line T-CAR1; tissue-type plasminogen activator (t-PA) antigen was not affected or slightly decreased. The effects in HT-1080 and T-CAR1 cells were preceded by increases in the cellular levels of the corresponding mRNAs. Cycloheximide caused an increase of PAI-1 mRNA in T-CAR1 cells, but not in HT-1080 cells; during this increase the relative abundance of the two PAI-1 mRNA species, of 2.3 kb and 3.4 kb, respectively, changed strongly in favor of the longer transcript. We conclude that TNF-alpha may affect proteolytic activity in the microenvironment of cells in malignant tumors by affecting gene expression of u-PA and PAI-1.

Plasminogen activator inhibitor type 1: cell-specific and differentiation-induced expression and regulation in human cell lines, as determined by enzyme-linked immunosorbent assay

We have performed a comparative study of the regulation by glucocorticoids and phorbol 12-myristate 13-acetate (PMA) of the production of type 1 plasminogen activator inhibitor (PAI-1) by 12 human cell lines. A sandwich-type enzyme-linked immunosorbent assay (ELISA) for PAI-1 that measures free PAI-1 as well as complexes between PAI-1 and both types of plasminogen activators has been used. Basal PAI-1 accumulation varied more than 5000-fold between the cell lines. No correlation was found between the PAI-1 level and other characteristics of the cell lines, except that three lines of SV40-transformed fibroblasts produced more PAI-1 than two non-transformed fibroblast cell lines. Three out of the 12 cell lines responded to glucocorticoids by an increased PAI-1 production. Four cell lines responded to PMA by an increased PAI-1 production. In addition, PMA-induced differentiation of the monocyte cell line U937 and the promyelocytic cell line HL-60 into macrophage-like cells was found to be correlated with an up to 100-fold increase in PAI-1 accumulation. The PMA-dependent differentiation of HL-60 cells led to acquisition of glucocorticoid inducibility of PAI-1. These findings provide information for future studies of the molecular mechanism of cell-specific expression and regulation of PAI-1.

Interleukin-1 induces c-fos protooncogene expression in cultured human endothelial cells

In the present study we have evaluated the expression of c-fos protooncogene in normal human endothelial cells (HEC) by Northern blot analysis. HEC do not show neither constitutive nor cycloheximide-induced expression of c-fos protooncogene. When HEC were treated with cytokines known to modulate a number of specialized functions of these cells, we observed that, unlike interferon-gamma, interleukin-1 (IL-1) and tumor necrosis factor (TNF) were able to induce appreciable levels of c-fos in HEC. Both IL-1 alpha and IL-1 beta induced c-fos transcripts in HEC. Maximal levels of c-fos mRNA induced by IL-1 were found after 1 hour of treatment, with undetectable levels at 4 and 7 hours. c-fos induction in HEC by IL-1 and TNF may play a role in the acquisition of functional properties induced in HEC by these cytokines.

The regulatory region of the human plasminogen activator inhibitor type-1 (PAI-1) gene

The human gene for plasminogen activator inhibitor type-1 (PAI-1) has been isolated and its promoter region characterized. PAI-1 regulation by glucocorticoids, transforming growth factor-beta (TGF-beta) and the phorbol ester PMA is shown to be exerted at the promoter level. A fragment spanning 805 nucleotides of the 5' flanking and 72 of the 5' untranslated region contain information enough to promote transcription and to respond to glucocorticoids when fused to a reporter gene and transfected into human fibrosarcoma cells. A moderately repetitive DNA sequence, containing a TATA box, a GRE consensus, a Z-DNA forming sequence and two imperfect direct repeats at the extremities, is present a few nucleotides 5' of the human PAI-1 gene transcription start site, raising the possibility that this gene could have been activated by DNA insertion during evolution.

The recruitment of leukocytes and their interaction with the vessel wall: the role of interleukin-1 and tumor necrosis factor

The vascular endothelium has long been considered to have very little or no active function in inflammatory reactions and hemostasis. However, it has been recently discovered that endothelial cells can dramatically change their functional competence in response to the mononuclear phagocyte products interleukin-1 (IL-1) and tumor necrosis factor (TNF). IL-1 induces synthesis of prostacyclin, platelet activating factor, thromboplastin and plasminogen activator inhibitor. Both IL-1 and TNF cause leukocyte adhesion to the endothelium. On the other hand endothelial cells can themselves initiate the immune response through synthesis and release of IL-1. TNF, released in tissues may act as a chemoattractant and further promote interaction of leukocytes with the vascular lining. IL-1 and TNF can therefore act as a communications signal between circulating cells and the vessel wall and play an important role in the inflammatory and coagulation disorders.