Increased monocyte tissue factor expression in coronary disease

Association of platelet-derived microparticles with C-C chemokines on vascular complication in patients with acute myocardial infarction

The levels of platelet-derived microparticles (PDMPs), platelet activation markers (P-selectin, CD63, and PAC-1 on activated platelets), and C-C chemokines (monocyte chemotactic peptide [MCP]-1 and regulated on activation normally T-cell expressed and secreted [RANTES] were measured and compared in patients with acute myocardial infarction (AMI) or stable pectoris angina. These substances are thought to paricipate in the development of complications in patients with AMI. The percentage binding of anti-P-selectin, CD63, and PAC-1 antibody to platelets, and the levels of PDMPs (per 10(4) platelets) were higher in the patients with AMI than in those with stable pectoris angina (P-selectin, 23.1% +/- 2.1% vs. 10.3% +/- 1.2%, p < 0.001; CD63, 24.6% +/- 3.3% vs. 11.2% +/- 3.1%, p < 0.01; PAC-1, 14.1% +/- 1.7% vs. 9.3% +/- 2.1%, p < 0.05; PDMPs, 613 +/- 71 vs. 413 +/- 55, p < 0.01). There were no differences in platelet levels of GPIIb/IIIa and GPIb between groups. Levels of MCP-1 and RANTES were higher in the patients with AMI than in patients with stable pectoris angina (MCP-1, 430 +/- 35 vs. 265 +/- 23, p<0.01; RANTES, 175 +/- 32 vs. 88 +/- 29, p<0.001). The effects of percutaneous transluminal coronary angioplasty (PTCA) on the levels of these agents in patients with AMI were studied. Platelet activation markers were significantly decreased in patients with AMI after PTCA. RANTES level was also significantly decreased after treatment, but MCP-1 level was not changed. In addition, this tendency was clearer in STENT patients. These findings suggest that in patients with AMI PTCA, particularly STENT, may prevent the development of complications in which activated platelet and RANTES participate.

Rho/Rho-kinase is involved in the synthesis of tissue factor in human monocytes

Monocytes and macrophages synthesize tissue factor (TF) which plays a role in thrombogenicity in coronary artery disease. This study was conducted to investigate the effect of Rho/Rho-kinase inhibition on the synthesis of TF in cultured human monocytes. 3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins), C3 exoenzyme and Rho-kinase inhibitors were added to isolated peripheral blood monocytes and the synthesis of TF was assessed by reverse transcriptase polymerase chain reaction (RT-PCR), Western blotting and immunohistochemistry. Rho activity was determined by measuring the GTP-bound form of Rho A. Cerivastatin and pravastatin reduced the levels of TF antigen and mRNA. The suppressive effect of statins on TF synthesis was reversed by geranylgeranylpyrophosphate (GGPP) and the restoring effect of GGPP was eliminated by C3 exoenzyme and Y-27632. Pravastatin decreased the activity of Rho A, suggesting that the suppression of TF synthesis by statins is mediated via inhibition of the geranylgeranylation of Rho. Moreover, inhibition of Rho and Rho-kinase downregulated the synthesis of TF. Our results suggest that Rho/Rho-kinase signaling is involved in the synthesis of TF in human monocytes and that inhibition of Rho/Rho-kinase may be useful for treating thrombogenicity in coronary artery disease.

Evolving role of tissue factor and its pathway inhibitor

OBJECTIVE

To review the experimental and clinical evidence of the emerging role of tissue factor in intravascular thrombosis and to examine evidence supporting the potential use of tissue factor pathway inhibitor as an antithrombotic therapeutic agent.

DATA SOURCES AND STUDY SELECTION

A PubMed search was conducted encompassing articles in the English language relating to tissue factor and tissue factor pathway inhibitor in intravascular coagulation.

CONCLUSIONS

Tissue factor, a membrane-bound procoagulant glycoprotein, is the initiator of the extrinsic clotting cascade, which is the predominant coagulation pathway in vivo. The traditional view localizes tissue factor to extravascular sites, where it remains sequestered from circulating factor VII until vascular integrity is disrupted or until tissue factor expression is induced in endothelial cells or monocytes. This perspective has been challenged since the discovery of tissue factor antigen in plasma, on circulating microparticles, and on leukocytes in whole blood. Recently, the apparent role of tissue factor has expanded with the demonstration that this molecule also functions as a signaling receptor. Recombinant tissue factor pathway inhibitor, an analogue of the physiologic inhibitor of tissue factor, is a potent inhibitor of thrombus formation in experimental models. In summary, the tissue factor pathway initiates thrombosis in vivo. In addition to its classic tissue-bound distribution, recently discovered blood-borne tissue factor may have an important procoagulant function. Despite showing promise in early human studies, a recently completed phase 3 trial of recombinant tissue factor pathway inhibitor in severe sepsis failed to show a reduction in the primary end point of 28-day all-cause mortality. Tissue factor pathway inhibitor, however, remains a plausible therapeutic agent in other conditions of increased thrombogenicity, such as acute coronary syndromes, and further studies to examine this potential are warranted.

Tissue factor - a therapeutic target for thrombotic disorders

Exposure of blood to tissue factor (TF) sets off the coagulation cascade. TF is a transmembrane protein that serves as an essential cofactor for activated coagulation factor VII (FVIIa). TF may be exposed locally by vascular injury (such as balloon angioplasty) or by spontaneous rupture of an atherosclerotic plaque. Expression of TF may also be induced on monocytes and endothelial cells in conditions like sepsis and cancer, causing a more generalised activation of clotting. TF may thus play a central role in thrombosis in a number of settings, and attention has turned to blocking TF as a means to prevent thrombosis. Inhibiting the inducible expression of TF by monocytes can be achieved by 'deactivating' cytokines, such as interleukin (IL)-4, -10 and -13, or by certain prostanoids; by drugs that modify signal transduction, such as pentoxifylline, retinoic acid or vitamin D(3), or by antisense oligonucleotides. Such approaches are for the most part at a preclinical stage. The function of TF can be blocked by antibodies that prevent the binding of FVIIa to TF; by active site-inhibited FVIIa, which competes with native FVIIa for binding; by antibodies or small molecules that block the function of the TF/FVIIa complex; and by molecules, such as TF pathway inhibitor or nematode anticoagulant peptide C2, which inhibit the active site of FVIIa in the TF/FVIIa complex after first binding to activated factor X. The latter two agents have entered Phase II clinical trials. Perhaps most intriguing is the use of anti-TF agents locally, which holds the promise of stopping thrombosis at a specific site of injury without the bleeding risk associated with systemic anticoagulation.

Relationships between brachial artery flow mediated dilation and carotid artery intima-media thickness in patients with suspected coronary artery disease

The correlation of peripheral endothelial dysfunction and intima-media thickness (IMT) in patients with suspected coronary artery disease (CAD) has been unclear. Inflammation and thrombosis may play a role at early stages of atherosclerosis. Thus, early atherosclerosis was noninvasively examined morphologically by IMT of carotid arteries, and functionally by flow mediated dilation (FMD) of brachial arteries in patients who were suspected of CAD and had undergone coronary angiography. Plasma antigen levels of tumor necrosis factor (TNF)-alpha and interleukin (IL)-6, representative atherogenic cytokines, tissue factor (TF) and tissue factor pathway inhibitor (TFPI), markers of coagulation, and plasma activity level of plasminogen activator inhibitor type-1 (PAI-1), a marker of defective fibrinolysis, were measured. Patients with coronary atherosclerosis in one or more vessels with lesion > or = 50% had significantly reduced FMD compared with those with angiographically normal coronary arteries. Carotid artery IMT increased significantly only in patients with advanced coronary atherosclerosis in one or more vessels with lesion > or = 90%. Plasma antigen levels of IL-6 were significantly increased in patients with reduced FMD (< 5%) compared to those in patients with FMD between 10 and 15%. Plasma antigen levels of TF, total and free TFPI, and PAI-1 activity tended to increase with a reduction in FMD. Thus, (1) FMD was reduced at early stages of CAD while IMT was increased in advanced CAD, and (2) inflammation and thrombosis may play a role in the early stages of the atherosclerotic process.

Monocyte function and plasma levels of interleukin-8 in acute ischemic stroke

Activated monocytes may contribute to the pathogenesis of ischemic stroke. We tested the hypothesis that release products and procoagulant activity of monocytes are increased in acute ischemic stroke. In patients on days 1, 3 and 7 after ischemic stroke and in age- and sex-matched healthy control subjects, we assessed plasma levels of interleukin 8 (IL-8) and neopterin (enzyme linked immunosorbent assay, ELISA) and investigated superoxidanion release (ferricytochrome C reduction), procoagulant activity (one-stage clotting assay) and tissue factor (TF) gene transcription (reverse transcriptase polymerase chain reaction) by monocytes. As compared to control subjects (n=23), IL-8 levels were increased on day 1 after stroke (n=22; p=0.005) and remained elevated on days 3 and 7. Neopterin levels were elevated on days 3 and 7 (p<0.05, respectively) but not on day 1. Neopterin and IL-8 were not correlated with monocyte counts. Superoxid anion production by stimulated and unstimulated monocytes was not different between groups. TF mRNA could neither be detected in monocytes from patients investigated within 12 h after ischemia (n=12) nor in control subjects (n=10) and procoagulant activity of cells was similar in both groups. Our results indicate increased monocyte activation after ischemic stroke although not all activation parameters were elevated. We found no support for the hypothesis that circulating monocytes express TF and possess increased procoagulant activity. Elevated IL-8 may contribute to stroke pathophysiology by activating polymorphonuclear leukocyte (PMNL) activation early after ischemia.

Activation of CD14 on circulating monocytes in patients with acute coronary syndrome

BACKGROUND

Increasing evidence supports the involvement of inflammation in acute phase of coronary artery diseases.

METHODS

We analyzed the status of activation of inflammatory cells in 38 patients with acute coronary syndrome, 14 stable angina patients, and 19 control subjects by flow-cytometry. Expression levels of CD14 and the percentage of HLA-DR(+) T-lymphocytes were used as markers of monocyte and T-lymphocytes activation, respectively.

RESULTS

The expression of CD14 on monocytes in acute coronary syndrome patients (mean fluorescence intensity+/-S.D.=158.1+/-77.1) was increased significantly in comparison to control subjects (57.1+/-8.0) and the stable angina group (63.6+/-22.0) (P<0.0001 for both). A significantly higher percentage of HLA-DR positive T-lymphocytes (20.4+/-9.0 vs. 12.7+/-3.7%, P<0.01) was observed in acute coronary syndrome patients in comparison to control subjects. Incubation of whole blood cells with bacterial lipopolysaccharide resulted in a 2.4-fold higher secretion of tumor necrosis factor-alpha in acute coronary syndrome patients than in control subjects (P<0.05). When these markers of activation were measured in acute coronary syndrome patients 6 weeks after medical treatment, a significant reduction both in monocytic CD14 expression and percentage of HLA-DR positive T-lymphocytes (P<0.05 for both) was observed.

DISCUSSION

We observed markedly increased levels of monocytic CD14 expression in ACS patients, which appear to indicate the activated status of monocytes and hyper-responsiveness to external stimuli. The CD14 expression levels decreased as the patients were treated, indicating that the expression of CD14 accurately represents the activation status of monocytes during the acute phase of coronary artery diseases.

Blood cell activation, coagulation, and inflammation in men and women with coronary artery disease

We investigated in some detail the immunologic and procoagulant activation patterns in men and women with unstable (UA, n=26) versus stable (SA, n=40) coronary artery disease (CAD). Leukocyte activation and platelet-leukocyte complex formation were assessed by flow cytometry. Plasma markers of coagulation and inflammation were analyzed. Unstable patients displayed higher levels of platelet-leukocyte complexes (P<.001), of leukocyte CD11b (P<.01), and of T cell HLA-DR (P<.05) than healthy controls did. Female UA patients presented the highest degree of complexes. SA patients only differed significantly from controls with respect to HLA-DR (P=.02). UA patients had higher levels of C-reactive protein (P<.01), IL-6 (P<.001), IL-10 (P<.01), and soluble fibrin (P<.001) than did stable ones. Regarding P-selectin levels, 25% of SA and 50% of UA patients were above normal range. Again, UA women presented the highest marker amounts. As for soluble tissue factor, women had higher levels than men regardless of the severity of disease (P<.001 in SA). We conclude that in unstable coronary syndromes, there is an activation of both coagulation and inflammation that coincides with an increased activation of platelets and leukocytes. Cellular interactions may contribute to the systemic responses observed. Women have different patterns of cellular activation than men, indicating differences in pathogenetic mechanisms.

Emerging concepts in disease management: a role for antimicrobial therapy in coronary artery disease

Coronary artery disease, the leading cause of morbidity and mortality in developed countries, is a chronic inflammatory process that develops in response to a variety of injuries. A number of microbial organisms have been implicated in its pathogenesis. The strongest evidence to date for an association between an infectious agent and coronary heart disease is that for Chlamydia pneumoniae. Evidence implicating other microbial organisms is much less compelling. Sero-epidemiological and pathological data have linked infection with C. pneumoniae to atherosclerotic coronary artery disease. A possible mechanism by which C. pneumoniae may participate in the pathogenesis of atherosclerosis is through immune activation and the initiation of a chronic inflammatory state in the infected arterial wall. Locally secreted inflammatory cytokines trigger a cascade of secondary cellular processes that lead to characteristic structural changes. C. pneumoniae has been detected in atherosclerotic plaques and in the serum of patients with coronary artery disease. It induces foam cells (the hallmark of early atherosclerosis) and it markedly accelerates this disease process in animal models. C. pneumoniae has been associated with elevated levels of inflammatory cytokines and acute phase reactants. Data from three interventional studies in humans have suggested that treatment with antibiotics decreases inflammatory markers and perhaps influences the anti-C. pneumoniae antibody titers; however, adverse clinical events were not uniformly reduced in all trials. Two large prospective clinical trials, the WIZARD trial and ACES, are underway to confirm these preliminary findings and test the hypothesis that antibiotics may be beneficial in preventing or modifying the course of coronary artery disease. At present, antimicrobial therapy for atherosclerosis is not advocated outside of well-controlled research settings.

Tissue factor/tissue factor pathway inhibitor system and long-term prognosis after acute myocardial infarction

The tissue factor and tissue factor pathway inhibitor (TFPI) system has been studied in the acute phase of coronary disease but its prognostic importance has been less well assessed. We evaluated its association with recurrent coronary events during long-term follow-up after a myocardial infarction.

METHODS

We studied 55 consecutive patients with the following criteria for inclusion: (1) first myocardial infarct; (2) aged < 70 years; (3) non-complicated infarct; (4) low risk effort-test. Blood samples were taken 60-80 days after infarction. Tissue factor, total and free-TFPI were measured. A 4-year follow-up was carried out. Death, unstable angina and new myocardial infarction were considered as poor prognosis.

RESULTS

There were no statistical differences in tissue factor/TFPI levels between patients and controls. Total-TFPI showed statistical correlation with total cholesterol (r = 0.59), triglycerides (r = 0.34), LDL-cholesterol (r = 40) and Lipoprotein(a) (r = 0.48). Patients with high levels of cholesterol, LDL-cholesterol and triglycerides showed elevated levels of total-TFPI with no differences in free-TFPI. During follow-up, 8 patients showed poor prognosis. There were no statistical associations between tissue factor/TFPI levels and prognosis.

CONCLUSIONS

After acute myocardial infarction, we did not find any differences in the tissue factor/TFPI system between controls and patients. The tissue factor/TFPI system showed little value as a prognostic factor.

Pathogenesis of Hyperhomocysteinemia-New Insights

Mild to moderately elevated levels of homocysteine (Hey) in plasma, denoted as hyperhomocysteinemia, is emerging as a prevalent and strong risk factor for atherosclerotic vascular disease in coronary, cerebral and peripheral vessels, as well as for arterial and venous thromboembolism. Despite its clinical significance, the molecular mechanism of homocysteine's effects is not yet clearly defined. Most of the effects of homocysteine that have been demonstrated in vitro, affecting endothelial function have been attributed to the oxidant reactivity of this molecule, which is shown to affect the vasoregulatory and thrombotic/fibrinolytic function of endothelium. However, the relevance of these observations to the clinical situations is questionable, since excessively high concentrations of homocysteine are used in most of the experiments. We have observed that homocysteine, at physiologically relevant concentrations, specifically induces the expression of tissue factor by monocytes, and a non-specific redox effect is not involved. Tissue factor expression by monocytes is mediated by increased intracellular concentrations of the metabolic intermediate, S-adenosylhomocysteine, which is a potent inhibitor of methyl transferases. These studies suggest that tissue factor expression by circulating monocytes by intracellular perturbations may be a plausible mechanism by which homocysteine may induce thrombosis.

The effect of heparin on tissue factor and tissue factor pathway inhibitor in patients with acute myocardial infarction

We examined plasma TF and free TFPI levels in 26 consecutive patients with AMI, 26 patients with stable exertional angina, and 25 patients with chest pain syndrome. In patients with AMI, blood samples were obtained immediately after admission and at 4, 8, 16, 24, and 48 h, and the third, fifth, seventh, and fourteenth day after initiation of reperfusion therapy. Plasma TF levels in patients with AMI on admission were significantly higher than in the chest pain syndrome and stable exertional angina groups (248.0+/-117. 4 vs. 179.5+/-29.2 vs. 189.5+/-29.6 pg/ml, P<0.01). In patients with AMI, the level subsequently decreased after heparin administration and was maintained at significantly lower levels compared to those on admission. Plasma free TFPI levels in patients with AMI on admission were significantly higher than in the chest pain syndrome and stable exertional angina groups [33.5+/-12.4 vs. 26.0+/-7.6 ng/ml (P<0.01) vs. 27.5+/-6.3 ng/ml, P<0.05]. In patients with AMI, it reached the maximum level at 4 h after the administration of heparin, and gradually decreased over the time course. These data indicated that continuous administration of a low dose of heparin was effective in decreasing TF levels without affecting TFPI levels. Our results elucidate one of the mechanisms by which the administration of heparin is beneficial in AMI patients undergoing percutaneous revascularization.

The in vivo kinetics of tissue factor messenger RNA expression during human endotoxemia: relationship with activation of coagulation

Triggering of the tissue factor (TF)-dependent coagulation pathway is considered to underlie the generation of a procoagulant state during endotoxemia. To determine the in vivo pattern of monocytic TF messenger RNA (mRNA) expression during endotoxemia, 10 healthy volunteers were injected with lipopolysaccharide (LPS, 4 ng/kg) and blood was collected before and 0.5, 1, 2, 3, 4, 6, 8, and 24 hours after LPS administration. Total blood RNA was isolated and amplified by NASBA (nucleic acid sequence-based amplification), followed by quantitation of TF mRNA by an electrochemiluminescence (ECL) assay. To compare the pattern of coagulation activation with the kinetics of monocytic TF mRNA expression, we measured plasma levels of markers of thrombin generation, thrombin-antithrombin (TAT) complexes, and prothrombin fragment 1 + 2 (F1 + 2). Baseline value (mean ± SEM) of the number of TF mRNA molecules per monocytic cell was 0.08 ± 0.02. A progressive and significant (P < .0001) increase in TF expression was observed after LPS injection (+0.5 hour: 0.3 ± 0.1, +1 hour: 1.3 ± 0.9, +2 hours: 4.1 ± 0.9), peaking at +3 hours (10 ± 1.9 TF mRNA molecules per monocyte). As TF mRNA levels increased, thrombin generation was augmented. Peak levels of TAT and F1 + 2 were reached later (at t +4 hours) than those of TF mRNA. TF mRNA, TAT, and F1 + 2 levels returned to baseline after 24 hours. In conclusion, we used a NASBA/ECL-based technique to quantify TF mRNA in whole blood during human endotoxemia and observed a 125-fold increase in TF mRNA levels. Our data demonstrate a pivotal role for enhanced TF gene activity in the activation of coagulation after LPS challenge.

The in vivo kinetics of tissue factor messenger RNA expression during human endotoxemia: relationship with activation of coagulation

Triggering of the tissue factor (TF)-dependent coagulation pathway is considered to underlie the generation of a procoagulant state during endotoxemia. To determine the in vivo pattern of monocytic TF messenger RNA (mRNA) expression during endotoxemia, 10 healthy volunteers were injected with lipopolysaccharide (LPS, 4 ng/kg) and blood was collected before and 0.5, 1, 2, 3, 4, 6, 8, and 24 hours after LPS administration. Total blood RNA was isolated and amplified by NASBA (nucleic acid sequence-based amplification), followed by quantitation of TF mRNA by an electrochemiluminescence (ECL) assay. To compare the pattern of coagulation activation with the kinetics of monocytic TF mRNA expression, we measured plasma levels of markers of thrombin generation, thrombin-antithrombin (TAT) complexes, and prothrombin fragment 1 + 2 (F1 + 2). Baseline value (mean ± SEM) of the number of TF mRNA molecules per monocytic cell was 0.08 ± 0.02. A progressive and significant (P &lt; .0001) increase in TF expression was observed after LPS injection (+0.5 hour: 0.3 ± 0.1, +1 hour: 1.3 ± 0.9, +2 hours: 4.1 ± 0.9), peaking at +3 hours (10 ± 1.9 TF mRNA molecules per monocyte). As TF mRNA levels increased, thrombin generation was augmented. Peak levels of TAT and F1 + 2 were reached later (at t +4 hours) than those of TF mRNA. TF mRNA, TAT, and F1 + 2 levels returned to baseline after 24 hours. In conclusion, we used a NASBA/ECL-based technique to quantify TF mRNA in whole blood during human endotoxemia and observed a 125-fold increase in TF mRNA levels. Our data demonstrate a pivotal role for enhanced TF gene activity in the activation of coagulation after LPS challenge.

Mouse embryogenesis requires the tissue factor extracellular domain but not the cytoplasmic domain

Recent studies indicate that tissue factor (TF) acts in embryogenesis, metastasis, and angiogenesis. Three independent groups showed that targeted disruption of the murine TF (mTF) gene results in 90% lethality of mTF null embryos at embryonic days 9. 5-10.5. We have demonstrated that expression of wild-type human TF (hTF) from a minigene rescues the embryonic lethality of mTF null embryos. To investigate the role of TF in embryogenesis, we made mutant hTF minigenes whose products either bound FVII/VIIa at a reduced level or lacked the cytoplasmic domain. Two independent transgenic lines expressing the hTF extracellular domain mutant failed to rescue the embryonic lethality of mTF null embryos, suggesting that FVII/VIIa binding by TF, proteolytic activity by the TF/FVIIa complex, or both were required for embryogenesis. In contrast, two transgenic lines expressing the hTF cytoplasmic domain mutant rescued the embryonic lethality of mTF null embryos, indicating that the cytoplasmic domain of TF was not required for embryogenesis. We propose that TF/FVIIa-dependent extracellular protease activity is required for embryogenesis.

Cytokine and intracellular signaling regulation of tissue factor expression in astrocytes

There is evidence that inflammatory cytokines such as IL-1beta, TNFalpha, and IL-6 are involved in the pathogenesis of cerebrovascular disorders including stroke. One action of cytokines that contributes to diseases in peripheral tissues is upregulation of the procoagulant receptor tissue factor (TF). In the CNS, astrocytes are the primary cells that express TF; although little is known about how TF is regulated in these cells. Experiments were performed to evaluate the effect of cytokine treatment on TF activity in primary cultures of murine cortical astrocytes and in the human astrocytoma cell line (CCF). IL-1beta treatment induced a 2.5-fold increase in TF activity in the primary astrocytes and a 3-fold induction in the astrocytoma cells. TNFalpha treatment induced a 2.5-fold increase in TF activity in both the primary astrocytes and astrocytoma cells. IL-6 upregulated TF activity 2-fold in primary astrocytes, however, it had no effect on TF activity in the astrocytoma cells. The signaling pathways regulating TF expression in these cells were examined by using staurosporine, a broad spectrum inhibitor of serine-threonine protein kinases, and by examining the effects of intermediates in the sphingomyelin signaling pathway. Staurosporine inhibited IL-1beta-induced TF activity in the primary astrocytes but did not effect IL-1beta- or TNFalpha-induced TF activity in the astrocytoma cells. TF activity in the astrocytoma cells was upregulated 1.5-fold over constitutive levels by a ceramide analogue or the enzyme sphingomyelinase, however the ceramide analogue had no effect on TF activity in the primary astrocytes. These results suggest inflammatory cytokines can upregulate TF activity in astrocytes and the astrocytoma CCF cell line although the two cell types appear to utilize different signaling pathways to mediate TF expression. Further studies will be important to more completely define the signaling regulation of TF in astrocytes since alterations in brain TF levels may play a key role in CNS pathophysiology.

Angiotensin-converting enzyme inhibition reduces monocyte chemoattractant protein-1 and tissue factor levels in patients with myocardial infarction

OBJECTIVES

We investigated the effects of enalapril therapy on plasma tissue factor (TF), tissue factor pathway inhibitor (TFPI) and monocyte chemoattractant protein-1 (MCP-1) levels in patients with acute myocardial infarction.

BACKGROUND

Macrophages express TF in human coronary atherosclerotic plaques. Both TF and TFPI are major regulators of coagulation and thrombosis. Monocyte chemoattractant protein-1 is a monocyte and macrophage chemotactic and activating factor.

METHODS

In a randomized, double-blind, placebo-controlled study beginning about two weeks after myocardial infarction, 16 patients received four weeks of placebo (placebo group) and another 16 patients received four weeks of enalapril 5 mg daily therapy (enalapril group). We performed blood sampling after administration of the doses.

RESULTS

There were no significant differences in the serum angiotensin-converting enzyme (ACE) activity, plasma TF, free TFPI or MCP-1 levels before administration between the enalapril and placebo groups. In the enalapril group, ACE activity (IU/liter) (14.0 before, 5.2 on day 3, 5.8 on day 7, 6.3 on day 28), TF levels (pg/ml) (223, 203, 182, 178) and MCP-1 levels (pg/ml) (919, 789, 790, 803) significantly decreased by day 28. However, the free TFPI levels (ng/ml) (28.2, 26.5, 26.8, 28.4) did not change. These four variables were unchanged during the study period in the placebo group.

CONCLUSIONS

This study demonstrated that administration of enalapril reduces the increased procoagulant activity in patients with myocardial infarction associated with inhibition of the activation and accumulation of macrophages and monocytes.

Predictors of stent thrombosis after primary stenting for acute myocardial infarction

The aim of the study was to determine if a hypercoagulable state that may persist for several months after an acute myocardial infarction may contribute to an increased incidence of stent thrombosis. Primary stenting was performed in 104 consecutive patients with acute myocardial infarction using 147 coronary stents. Twenty-eight patients (27%) were diabetic and 55 patients (53%) were smokers. A single stent was placed in 63%, two stents in 33%, and more than two stents in 4% of the patients. Procedural success was obtained in 97% of the patients. All stents were deployed using high-pressure balloon inflation. The reference vessel diameter and minimal lumen diameter after stent deployment were 3.30 +/- 0.42 and 3.23 +/- 0.42 mm, respectively. Six patients (5.7%) developed stent thrombosis within 1 month after the procedure complicated by reinfarction in five of the six patients. At 1-month follow-up, all patients remained alive. On multivariate analysis, independent predictors of stent thrombosis were diabetes mellitus (relative risk [RR] 5.2; 95% confidence interval [CI] 1.8, 25.1), tobacco use (RR 4.5; 95% CI 1.3, 24.5), number of stents: 1 vs. > 1 (RR 3.7; 95% CI 1.1, 15.9), minimal lumen diameter poststent placement (RR 0.03; 95% CI 0.0002, 0.74), and duration of chest pain before intervention (RR 1.1; 95% CI 1.01, 1.25). Stent thrombosis had not been associated with diabetes mellitus and tobacco use previously but is in agreement with the enhanced platelet aggregability, coagulation factor abnormalities, and impaired fibrinolysis characteristic of these patients.

Tissue factor in atherosclerosis

Thrombosis is a key feature of the initiation and progression of atherosclerosis and its clinical sequelae. Acute thrombosis can lead to arterial occlusion and consequently provoke myocardial infarction, unstable angina, stroke and sudden death. Acute thrombosis can also be a complication of arterial bypass surgery, balloon angioplasty, atherectomy, or coronary artery stenting. The thrombotic response is influenced by several factors, among them the thrombogenicity of the vessel wall and of certain blood components as well as their interaction with the lipid pool. Tissue factor (TF) is considered to be the primary cofactor of cellular origin that is involved in activation of the coagulation pathway. The active form of TF has been shown to be present in specimens of human coronary artery in association both with acellular lipid areas and with macrophages and smooth muscle cells, which suggests that TF plays a major role in determining plaque thrombogenicity. We discuss here what is currently known about the role of tissue factor in atherogenesis, and focus attention on pharmacological approaches in this area.

Chronic infection in the aetiology of atherosclerosis--focus on Chlamydia pneumoniae

An inflammatory basis to atherosclerosis is now accepted. It remains plausible (but unproven) that common infectious agents may contribute to the inflammatory signal, and hence the development (and/or progression of atherosclerosis and its clinical sequelae. Of the candidate microorganisms implicated, Chlamydia pneumoniae has emerged as the most likely pathogen to have a casual role. Evidence for this is based on sero-epidemiological, pathological and laboratory-based evidence, in addition to early animal models and small-scale antibiotic studies. A past decade of research has now culminated in prospective antibiotic intervention trials in coronary heart disease to be conducted. The results of these studies should help to finally determine whether infection with C. pneumoniae is a pathogenetic factor in atherosclerosis, and whether antibiotic therapy has a role in the secondary prevention of coronary heart disease.

Monocyte expression of tissue factor and adhesion molecules: the link with accelerated coronary artery disease in patients with chronic renal failure

OBJECTIVE

To investigate the expression of monocyte tissue factor (MTF) and adhesion molecules in patients with chronic renal failure (CRF) and to look for any correlation with thrombin generation and Lp(a) lipoprotein.

DESIGN

A study of MTF expression and adhesion molecules, prothrombin fragments 1+2 (PTf1+2), an index of thrombin generation, and lipoproteins in patients with CRF and in normal control subjects.

BACKGROUND

Patients with end stage renal failure have an increased risk of coronary artery disease despite advances in therapy. Stimulated monocytes are potent activators of blood coagulation through the generation of MTF, which was recently implicated in the aetiology of acute coronary ischaemic syndromes.

METHODS

MTF expression and adhesion molecules were measured in whole blood using immunofluorescence of monocytes labelled with anti-tissue factor antibody and CD11b and c by flow cytometry. PTf1+2 and Lp(a) lipoprotein in plasma were measured by enzyme linked immunosorbent assay (ELISA).

PATIENTS

70 patients with CRF without documented coronary artery disease (30 patients with CRF undialysed, 20 patients undergoing chronic ambulatory peritoneal dialysis (CAPD), and 20 undergoing haemodialysis (HD)), together with 20 normal controls, were studied.

RESULTS

The (mean (SD)) increased MTF of CRF (48.0 (29) v 33.3 (7.2) mesf unit/100 monocytes in controls, p = 0.04) was more pronounced in patients undergoing dialysis (HD 73.1 (32.8) (p < 0.003) and CAPD 62.8 (28.9) mesf unit/100 monocytes, p < 0.04). MTF activity showed a positive correlation with both PTf1+2 and serum creatinine (p < 0.003) but not with Lp(a) lipoprotein. Lp(a) lipoprotein was significantly increased in both dialysis groups compared with controls (p < 0.005) and non-dialysis CRF groups (p < 0.02). Monocyte adhesion molecule (CD11b) was significantly higher in all three CRF groups than in the controls (p = 0.006).

CONCLUSION

This study has demonstrated a hypercoagulable state in patients with CRF. This was especially pronounced in the dialysis patients. These findings provide a possible explanation for the increased cardiovascular and cerebrovascular morbidity and mortality in these patients.

Plasma tissue factor pathway inhibitor and tissue factor antigen levels after administration of heparin in patients with angina pectoris

The hypercoagulability is associated with expression of tissue factor in patients with angina. Tissue factor pathway inhibitor regulates the extrinsic coagulation pathway mediated by tissue factor. Plasma samples were obtained from 14 patients with angina pectoris and 9 with chest pain syndrome before and 5, 30, 60, and 120 minutes after administration of heparin (50 IU/kg). The tissue factor and prothrombin fragment 1+2 levels before administration were elevated in patients with angina pectoris and were reduced to the levels of chest pain syndrome after the administration. The free tissue factor pathway inhibitor levels after the administration were higher in patients with angina pectoris than in patients with chest pain syndrome. Plasma tissue factor pathway inhibitor levels correlated positively with plasma tissue factor and prothrombin fragment 1+2 levels. We showed that plasma-free TFPI levels after administration of heparin, which may indicate endothelial cell associated TFPI levels, increased in patients with angina pectoris compared with patients with chest pain syndrome. Increased endothelial cell associated TFPI was associated with hypercoagulability in patients with angina pectoris. These may help to explain the reduction in thrombotic risk associated with the use of heparin.

Lipoprotein(a) and inflammation in human coronary atheroma: association with the severity of clinical presentation

OBJECTIVES

The purpose of this study was the investigation of the in vivo role of lipoprotein(a) [Lp(a)] and inflammatory infiltrates in the human coronary atherosclerotic plaque and their correlation with the clinical syndrome of presentation.

BACKGROUND

Lipoprotein(a) is an atherogenic and thrombogenic lipoprotein, and has been implicated in the pathogenesis of acute coronary syndromes. Lipoprotein(a) induces monocyte chemoattraction and smooth muscle cell activation in vitro. Macrophage infiltration is considered one of the mechanisms of plaque rupture.

METHODS

This study of atherectomy specimens investigated the in vivo role of Lp(a) at different stages of the atherogenic process, and its relationship with macrophage infiltration. We examined coronary atheroma removed from 72 patients with stable or unstable angina. Specimens were stained with antibodies specific for Lp(a), macrophages (KP-1), and smooth muscle cells (alpha-actin). Morphometric analysis was used to quantify the plaque areas occupied by each of the three antigens, and their colocalization.

RESULTS

All specimens had localized Lp(a) staining; the mean fractional area was 58.2%. Ninety percent of the macrophage areas colocalized with Lp(a) positive areas, whereas 31.3% of the smooth muscle cell areas colocalized with Lp(a) positive areas. Patients with unstable angina (n = 46) had specimens with larger mean plaque Lp(a) areas than specimens from stable angina patients (n = 26): 64.4% versus 47.7% (p = 0.004). Unstable angina patients with rest pain (n = 28) had greater mean plaque Lp(a) area than unstable angina patients with crescendo exertional pain (n = 18): 71.1% versus 52.4% (p < 0.001). Mean KP-1 area was 31.2% in unstable rest angina versus 18.3% in stable angina (p = 0.05); alpha-actin area was greater in stable (48.5%) and crescendo exertional angina (48.8%) than in rest angina (30.4%). The strongest correlation between plaque KP-1 and Lp(a) area was in unstable rest angina (r = 0.88, p < 0.001), and between alpha-actin and Lp(a) areas in the crescendo exertional angina (r = 0.62, p < 0.01).

CONCLUSIONS

Lipoprotein(a) is ubiquitous in human coronary atheroma. It is detected in larger amounts in tissue from culprit lesions in patients with unstable compared to stable syndromes, and has significant colocalization with plaque macrophages. A correlation of plaque alpha-actin and Lp(a) area suggests a role of Lp(a) in plaque growth.

Procoagulant inflammatory responses of monocytes after direct balloon angioplasty in acute myocardial infarction

This study sought to investigate monocyte procoagulant activity and Mac-1 expression after successful percutaneous transluminal coronary angioplasty (PTCA) in acute myocardial infarction (AMI). An increased leukocyte count is an important risk factor for subsequent adverse cardiac events in AMI. Cellular procoagulant responses may contribute to the risk of thrombotic events after AMI. In 20 patients with AMI serial venous blood samples were obtained before, 4, 8 hours, and daily after direct PTCA. Twenty patients with elective PTCA served as a control group. We measured leukocyte procoagulant activity with a 1-stage clotting assay, Mac-1 expression of monocytes by flow cytometry, concentrations of tumor necrosis factor-alpha, interleukin (IL)-1beta, IL-6, and IL-8 using immunoassays. Forty-eight hours after PTCA in patients with AMI, an increase in systemic IL-6 and C-reactive concentrations was found (p = 0.001, p = 0.008) associated with an increase in monocyte Mac-1 expression by 49 +/- 18% (p = 0.04) and followed by an increase in monocyte procoagulant activity by 140 +/- 63% 72 hours after PTCA (p = 0.01). None of these changes were detectable in the control group. No changes in the concentrations of the cytokines IL-1beta, tumor necrosis factor-alpha, or IL-8 were found. The present study demonstrates an increase in procoagulant activity along with an increase in Mac-1 expression on circulating monocytes after successful PTCA in AMI associated with an increase in systemic IL-6. These cellular procoagulant responses may limit the clinical benefit from timely reperfusion.

IL-10 inhibits LPS-induced human monocyte tissue factor expression in whole blood

Interleukin 4 (IL-4), IL-10 and IL-13 are all known to modulate several proinflammatory functions in human monocytes. They have also previously been shown to down-regulate lipopolysaccharide (LPS)-induced tissue factor (TF) expression in isolated cultured monocytes. In this study we investigated the effect of these three cytokines on the induction of monocytic TF in a whole blood environment at three levels: mRNA quantitation, surface antigen expression and procoagulant activity. We showed that IL-10 attenuated LPS-induced monocyte TF expression and activity in whole blood in a concentration-dependent manner, both when added to the blood prior to LPS and, although to a lesser extent, when added up to 1 h subsequent to LPS challenge. Maximum inhibition occurred at 5 ng/ml of IL-10 when the cytokine was added before LPS. IL-4 and IL-13, however, did not exhibit any inhibitory effect in the whole blood environment, contrary to the reported findings in cell culture experiments. Our results confirm the potential of IL-10 as an anti-inflammatory, TF-preventing drug, whereas the effects of IL-4 and IL-13 on monocytes in whole blood seem more complex, and require further investigation.

Monocyte tissue factor-like activity in post myocardial infarction patients

It is widely recognized that thrombosis is the major event in the evolution of stable vascular disease to unstable ischaemic syndromes including myocardial infarction and stroke. The purpose of this case-control study was to establish clinical and laboratory data on the possible relationship between specific components of the haemostatic system and coronary heart disease. The procoagulant activity (PCA) of peripheral monocytes and polymorphonuclear neutrophils was assessed in 21 males who had suffered a myocardial infarction (MI) and in age-matched controls. In addition, total factor VII activity, fibrinogen, tissue factor pathway inhibitor (TFPI). D-dimers, tissue plasminogen activator (t-PA), plasminogen activator inhibitor (PAI-1), tumour necrosis factor-alpha (TNF-alpha) and full blood counts were measured. Post MI patients had significantly higher monocyte PCA, higher plasma concentrations of TFPI, fibrinogen, t-PA, T/P100 and also higher total white blood cell and neutrophil counts compared to age-matched controls. This elevated procoagulant state in post MI patients could further exacerbate the disease process and increase the risk of subsequent acute ischaemic events.

Is there an infective aetiology to atherosclerosis?

Conventional cardiovascular risk factors fail to completely explain the observed variations in the prevalence and severity of coronary heart disease (CHD). Common chronic infections may have an aetiological role in the development of atherosclerosis and CHD, either independently or by interacting with traditional atherogenic risk factors. The evidence for Chlamydia pneumoniae as a potential causative agent is strongest, and is based on findings of numerous sero-epidemiological studies, examination of atheromatous plaque specimens, in vitro animal models and, recently, pilot antichlamydial antibiotic intervention trials. However, the complete natural history of C. pneumoniae, its mechanisms of damage in atherosclerotic disease, and the temporal sequence of infection and CHD remain unclear. Confirmation of true causality for the link between C. pneumoniae and CHD could come after the results of large-scale prospective antibiotic trials, which are to be conducted over the next few years. A proven association could have important implications for public health worldwide, potentially leading to novel and relatively inexpensive therapeutic measures in the secondary prevention of CHD--broad-spectrum antibiotics.

Tissue factor expression by endothelial cells in sickle cell anemia

The role of the vascular endothelium in activation of the coagulation system, a fundamental homeostatic mechanism of mammalian biology, is uncertain because there is little evidence indicating that endothelial cells in vivo express tissue factor (TF), the system's triggering mechanism. As a surrogate for vessel wall endothelium, we examined circulating endothelial cells (CEC) from normals and patients with sickle cell anemia, a disease associated with activation of coagulation. We find that sickle CEC abnormally express TF antigen (expressed as percent CEC that are TF-positive), with 66+/-13% positive in sickle patients in steady-state, 83+/-19% positive in sickle patients presenting with acute vasoocclusive episodes, and only 10+/-13% positive in normal controls. Repeated samplings confirmed this impression that TF expression is greater when sickle patients develop acute vasoocclusive episodes. Sickle CEC are also positive for TF mRNA, with excellent concurrence between antigen and mRNA expression. The TF expressed on the antigen-positive CEC is functional, as demonstrated by a binding assay for Factor VIIa and a chromogenic assay sensitive to generation of Factor Xa. By establishing that endothelial cells in vivo can express TF, these data imply that the vast endothelial surface area does provide an important pathophysiologic trigger for coagulation activation.

Low levels of tissue factor are compatible with development and hemostasis in mice

Tissue factor (TF) expression is associated with life-threatening thrombosis in a variety of human diseases, including sepsis, cancer, and atherosclerosis. Recently, it was shown that inactivation of the murine TF (mTF) gene results in embryonic lethality. To date, despite extensive studies on the regulation of the TF promoter in vitro, no studies have examined the cis-acting regulatory elements that control TF gene expression in vivo. Here we report that a human TF (hTF) minigene containing the human TF promoter and human TF cDNA directed a low level (approximately 1% relative to mouse TF) of both constitutive and LPS-inducible human TF expression in transgenic mice. Importantly, the human TF minigene rescued the embryonic lethality of murine TF null embryos, suggesting that human TF substituted for murine TF during embryogenesis. Rescued mice (mTF-/-, hTF+), which expressed low levels (approximately 1%) of TF activity, developed normally with no signs of a bleeding diathesis, suggesting that low TF expression can maintain hemostasis compatible with normal survival. These studies establish a novel mouse model system that can be used to examine the regulation of the human TF gene in vivo and the impact of low TF levels on the hemostatic balance in various thrombotic diseases.

Comparison of plasma tissue factor levels in unstable and stable angina pectoris

We have reported that the plasma levels of plasma fibrinopeptide A and plasminogen activator inhibitor activity increase in patients with unstable angina and acute myocardial infarction. Tissue factor (TF) is a low-molecular-weight glycoprotein that binds to and acts on essential cofactor VII, and the resulting complex activates factors IX and X, initiating the coagulation cascade. We measured plasma TF antigen levels in 21 patients with unstable angina (on admission and after treatment), 27 patients with stable exertional angina, and 27 control subjects. The 3 groups were matched for age, gender, and other clinical variables. The plasma TF antigen levels were higher in the unstable angina group than in the stable exertional angina and control groups (240 +/- 75 vs 184 +/- 46 and 177 +/- 37 pg/ml, p < 0.01). There were no significant differences in the plasma TF antigen levels between the stable exertional angina and the control groups. Furthermore, the plasma TF antigen levels were reexamined after treatment in the 21 patients with unstable angina. The mean level in these 21 patients decreased after 2 weeks of treatment (from 240 +/- 75 to 206 +/- 57 pg/ml, p < 0.01). This study suggests that the plasma TF antigen levels correlate with disease activity in patients with unstable angina. The increased plasma TF antigen levels in patients with unstable angina may reflect intravascular procoagulant activity.

Effects of coronary angioplasty on monocyte tissue factor response in patients with stable or unstable angina

Balloon coronary angioplasty is a revascularization procedure which increases the luminal diameter at a site of arterial stenosis, leading to mechanical disruption of the atherosclerotic plaque and to stretching of the vascular wall (1). This procedure can be complicated by thrombosis or restenosis, which occur in 5% and 30% of the cases respectively (2). These complications probably result from exposure of blood to components of atherosclerotic plaque, subendothelium and components of vascular wall, leading to activation of coagulation (thrombin generation) and platelets (3,4). Recent data point to simultaneous increase of leukocyte adhesive receptors, indicating an additional process of leukocyte activation, which could play a key role in the vascular healing process after angioplasty (5). These elements could also play a role in the thrombotic and stenotic complications.

Increased plasma tissue factor levels in acute myocardial infarction

BACKGROUND

Tissue factor (TF) is a low molecular weight glycoprotein that initiates the clotting cascade and is considered to be a major regulator of coagulation, hemostasis, and thrombosis.

METHODS AND RESULTS

We examined plasma TF levels in 31 consecutive patients with acute myocardial infarction (AMI) (within 6 hours after the onset of symptoms), 27 patients with stable exertional angina, and 27 control subjects. Ten patients with AMI had a history of unstable angina before infarction, and 21 had a sudden onset of infarction. The plasma TF level was higher in the AMI group than in the stable exertional angina and control groups (240 +/- 112 vs 184 +/- 46 pg/ml [p < 0.05] vs 177 +/- 37 pg/ml, p < 0.01, respectively). TF levels were decreased in the chronic phase (2 weeks after admission) compared with the acute phase of infarction (from 240 +/- 112 pg/ml to 222 +/- 97 pg/ml, p < 0.05). In addition, plasma TF levels were higher in patients with AMI with prodromal unstable angina than in patients with a sudden onset of infarction (300 +/- 169 pg/ml vs 212 +/- 57 pg/ml, p < 0.05). TF levels were similar in the acute and chronic phases in the patients with AMI with prodromal unstable angina (300 +/- 169 pg/ml vs 290 +/- 136 pg/ml, p = not significant) but were decreased in the chronic phase in the patients with AMI with sudden onset (from 212 +/- 57 pg/ml to 190 +/- 49 pg/ml, p < 0.05).

CONCLUSION

Increased plasma TF levels in patients with AMI may reflect enhanced intravascular procoagulant activity. The higher TF levels in patients with AMI with prodramol unstable angina may be associated with repeated episodes of myocardial ischemia and reperfusion.

Suppression of human monocyte tissue factor synthesis by antisense oligodeoxynucleotide

Tissue factor (TF) is a cellular receptor and cofactor for factor V11/V11a which initiates the blood coagulation cascade. An understanding of TF cell biology is therefore of critical importance to the pathophysiology of many disorders. We have utilized an antisense oligodeoxynucleotide (aODN), directed against human blood monocyte TF mRNA, to investigate the feasibility of inhibiting the synthesis of TF. CD14 receptor-mediated endocytosis was used as a means of delivering TF aODN to monocytes. This DNA carrier system consists of the fab portion of anti-CD14 antibody covalently linked to poly (L-lysine). Co-treatment of monocytes with TF aODN and endotoxin resulted in 80.4 +/- 2.2% suppression of TF activity when compared with control endotoxin stimulated cells. Control experiments with TF sense ODN, mismatched aODN, and an irrelevant aODN were performed to exclude nonspecific inhibitory effects. The cytotoxicity of the DNA carrier complex was also evaluated. These results demonstrate that this TF mRNA antisense ODN specifically suppressed the synthesis of biologically active monocyte TF and that antisense ODNs might therefore represent a useful tool in the investigation of monocyte/macrophage TF function.

Effects of enalapril on tissue factor in patients with uncomplicated acute myocardial infarction

In a randomized, double-blind, placebo-controlled study beginning 4 weeks after uncomplicated acute myocardial infarction, it was established that the baseline plasma tissue factor antigen level was significantly higher in patients with myocardial infarction than in control subjects, and enalapril therapy significantly reduced the elevated plasma tissue factor antigen level. This may be associated with the reduction in the risk of coronary thrombosis seen with the use of angiotensin-converting enzyme inhibitors.

Pathophysiology and inflammatory aspects of plaque rupture

Atherosclerotic plaque disruption with superimposed thrombosis is the main cause of acute coronary events. At present it is not known specifically how various risk factors influence the development and configuration of coronary plaques. The risk of plaque disruption depends more on plaque composition and vulnerability (plaque type) than on the degree of stenosis (plaque size). Lipid accumulation and chronic inflammation, particularly macrophage activities, seem to influence the development and the stability of a plaque and thus its propensity to rupture. Macrophages have the ability to secrete proteolytic enzymes and often infiltrate the region of imminent plaque rupture, and disruption may be associated with a generalized inflammatory reaction. Further, plaque disruption tends to occur at points where the plaque surface is weakest, corresponding to locations where mechanical and hemodynamic forces have their highest impact. The risk of plaque disruption is a function of both plaque vulnerability (intrinsic disease) and rupture triggers (extrinsic forces). The former predisposes the plaque to rupture; the latter may precipitate rupture. The danger of vulnerable plaques, however, is not related to disruption as such but to the resulting thrombosis. The magnitude of this thrombotic response and the ensuing flow obstruction depends on the contents and quantity of exposed thrombogenic plaque material, the degree of pre-existing stenosis, and the systemic thrombotic tendency. The thrombotic response is a dynamic process that is decisive for the clinical presentation and the outcome.