High-dose recombinant apolipoprotein A-I(milano) mobilizes tissue cholesterol and rapidly reduces plaque lipid and macrophage content in apolipoprotein e-deficient mice. Potential implications for acute plaque stabilization

BACKGROUND

Repeated doses of recombinant apolipoprotein A-I(Milano) phospholipid complex (apoA-I(m)) reduce atherosclerosis and favorably change plaque composition in rabbits and mice. In this study, we tested whether a single high dose of recombinant apoA-I(m) could rapidly mobilize tissue cholesterol and reduce plaque lipid and macrophage content in apoE-deficient mice.

METHODS AND RESULTS

High cholesterol-fed, 26-week-old apoE-deficient mice received a single intravenous injection of saline (n=16), 1080 mg/kg dipalmitoylphosphatidylcholine (DPPC; n=14), or 400 mg/kg of recombinant apoA-I(m) complexed with DPPC (1:2.7 weight ratio; n=18). Blood was sampled before and 1 and 48 hours after injection, and aortic root plaques were evaluated for lipid content and macrophage content after oil-red O and immunostaining, respectively. One hour after injection, the plasma cholesterol efflux-promoting capacity was nearly 2-fold higher in recombinant apoA-I(m)-treated mice compared with saline and DPPC-treated mice (P<0.01). Compared with baseline values, serum free cholesterol, an index of tissue cholesterol mobilization, increased 1.6-fold by 1 hour after recombinant apoA-I(m) injection, and it remained significantly elevated at 48 hours (P<0.01). Mice receiving recombinant apoA-I(m) had 40% to 50% lower lipid content (P<0.01) and 29% to 36% lower macrophage content (P<0.05) in their plaques compared with the saline- and DPPC-treated mice, respectively.

CONCLUSIONS

A single high dose of recombinant apoA-I(m) rapidly mobilizes tissue cholesterol and reduces plaque lipid and macrophage content in apoE-deficient mice. These findings suggest that this strategy could rapidly change plaque composition toward a more stable phenotype.

Absence of CD40 signaling is associated with an increase in intimal thickening after arterial injury

Immune-mediator CD40 ligand is expressed on a variety of cell types involved in the immune response and on the cells of the vascular system. Inhibition of CD40 signaling has been associated with reduction of experimental atherosclerosis and transplant-associated vasculopathy. Immune response also plays a cardinal role in intimal thickening after acute arterial-wall injury. After carotid artery injury in CD40 ligand knockout (CD40L(-/-)) mice, the intimal thickening was increased 3-fold compared with the thickening in background B6/129 mice. The extent of thickening was similar to the thickening in B6/129 mice depleted of T lymphocytes with anti-CD4 and anti-CD8 antibodies. Injection of splenocytes from B6/129 mice into the CD40L(-/-) mice reduced the intimal thickening to the level comparable to the thickening in background B6/129 mice. These data suggest that CD40 signaling plays a significant role in the inhibitory effect of T lymphocytes on intimal thickening after arterial injury.

Role of inflammation in atherothrombosis

Acute coronary syndromes result from thrombosis on a disrupted atherosclerotic plaque. Plaques prone to rupture contain cellular elements and their secreted products that are characteristic of active inflammation. Multiple triggers may be involved in the activation of inflammatory response. Therapeutic strategies toward these triggers have been proposed and tested. Here the authors review the evidence for the involvement of inflammation in atherothrombosis and possible therapies for the triggers of inflammation.

Pravastatin treatment increases collagen content and decreases lipid content, inflammation, metalloproteinases, and cell death in human carotid plaques: implications for plaque stabilization

BACKGROUND

The clinical benefits of lipid lowering with statins are attributed to changes in plaque composition leading to lesion stability, but supporting clinical data from human studies are lacking. Therefore, we investigated the effect of 3 months of pravastatin treatment on composition of human carotid plaques removed during carotid endarterectomy.

METHODS AND RESULTS

Consecutive patients with symptomatic carotid artery stenosis received 40 mg/d pravastatin (n=11) or no lipid-lowering therapy (n=13; control subjects) for 3 months before scheduled carotid endarterectomy. Carotid plaque composition was assessed with special stains and immunocytochemistry with quantitative image analysis. Plaques from the pravastatin group had less lipid by oil red O staining (8.2+/-8.4% versus 23.9+/-21.1% of the plaque area, P<0.05), less oxidized LDL immunoreactivity (13.3+/-3.6% versus 22.0+/-6.5%, P<0.001), fewer macrophages (15.0+/-10.2% versus 25.3+/-12.5%, P<0.05), fewer T cells (11.2+/-9.3% versus 24.3+/-13.4%, P<0.05), less matrix metalloproteinase 2 (MMP-2) immunoreactivity (3.6+/-3.9% versus 8.4+/-5.3%, P<0.05), greater tissue inhibitor of metalloproteinase 1 (TIMP-1) immunoreactivity (9.0+/-6.2% versus 3.1+/-3.9%, P<0.05), and a higher collagen content by Sirius red staining (12.4+/-3.1% versus 7.5+/-3.5%, P<0.005). Cell death by TUNEL staining was reduced in the pravastatin group (17.7+/-7.8% versus 32.0+/-12.6%, P<0.05).

CONCLUSIONS

-Pravastatin decreased lipids, lipid oxidation, inflammation, MMP-2, and cell death and increased TIMP-1 and collagen content in human carotid plaques, confirming its plaque-stabilizing effect in humans.

Adventitial remodeling after angioplasty is associated with expression of tenascin mRNA by adventitial myofibroblasts

OBJECTIVES

The purpose of this study was to determine the temporospatial expression of tenascin-C (TnC) in balloon-injured rat and porcine arteries.

BACKGROUND

Recent studies suggest that cell migration, in addition to cell proliferation, is a critical component of neointima formation after vascular injury. We have previously shown that adventitial myofibroblasts synthesize growth factors that contribute to the formation of neointima after arterial injury. We have also shown that the extracellular matrix protein, TnC, regulates cell migration. Consequently, we investigated the temporospatial expression of TnC by myofibroblasts after vascular injury.

METHODS

In situ hybridization and immunohistochemistry were used to investigate the temporospatial expression of TnC in injured arteries. Northern and Western blots were used to determine the in vitro expression of TnC.

RESULTS

In situ hybridization revealed that the major site of TnC expression early after vascular injury was the adventitial myofibroblasts. Immunohistochemical staining demonstrated that TnC expression began in adventitial myofibroblasts three days after injury. Tenascin-C expression, however, did not persist in this region. Rather, it moved progressively across the vascular wall toward the luminal surface. By one week, TnC expression reached the developing neointima. In vitro, myofibroblasts did not express TnC mRNA under basal conditions. In contrast, angiotensin II and PDGF-BB, factors that have been implicated in remodeling of balloon-injured arteries, markedly upregulated TnC mRNA.

CONCLUSIONS

Tenascin-C is expressed in response to balloon injury. Tenascin-C expression begins with adventitial myofibroblasts. Over a period of 7 to 14 days, expression moves progressively across the vessel wall to the neointima. We hypothesize that adventitial myofibroblasts are actively involved in the formation of neointima and that TnC facilitates migration of these cells during adventitial remodeling.

Remnant-like particle (RLP) cholesterol is an independent cardiovascular disease risk factor in women: results from the Framingham Heart Study

Remnants of triglyceride-rich lipoproteins (TRL) of both intestinal and liver origin are considered to be atherogenic, but separation of remnant lipoproteins from other TRL is difficult. An assay has been developed that allows immunoseparation of remnant-like particles (RLP) and measurement of cholesterol (RLP-C) and triglyceride (RLP-TG). We measured RLP-C and RLP-TG in fast plasma samples obtained from 1567 women participating in cycle 4 of the Framingham heart study (FHS). When values from 83 women with cardiovascular disease (CVD) were compared with the values from 1484 women without disease, concentrations in women with CVD were found to be significantly higher for both RLP-C (0.215+/-0.102 vs. 0.186+/-0.162 mmol/l; +15.6%; P<0.0001) and RLP-TG (0.319+/-0.352 vs. 0.251+/-0. 716 mmol/l; +27.0%; P<0.0002). Logistic regression analysis revealed that RLP-C was significantly associated with prevalent CVD in women (P<0.002) after adjustment with other major risk factors. In conclusion, we have documented that RLP-C is an independent risk factor for CVD in women, and provides significantly more information than do triglycerides.

Beneficial antithrombotic effects of the association of pharmacological oral magnesium therapy with aspirin in coronary heart disease patients

The use of magnesium in the treatment of acute myocardial infarction remains controversial despite preliminary experimental evidence that magnesium plays a beneficial role as a regulator of thrombosis. The aim of our study was to determine whether oral magnesium treatment inhibits platelet-dependent thrombosis (PDT) in stable patients with coronary artery disease (CAD). In a randomized prospective, double-blind, cross-over and placebo controlled study, 42 patients with stable CAD (37 men, 5 women, mean age 68 +/- 9 years) on aspirin received either magnesium oxide tablets (800-1,200 mg/day) or placebo for 3 months (Phase 1) followed by a 4-week washout period, and the cross-over treatment for 3 months (Phase 2). PDT, platelet aggregation, platelet P-selectin flow-cytometry, monocyte tissue factor procoagulant activity (TF-PCA) and adhesion molecules density were assessed before and after each phase. PDT was evaluated by an ex-vivo perfusion model using the Badimon chamber. Median PDT was significantly reduced by 35 percent in patients who received magnesium versus placebo (D change from baseline: -24 vs. 26 microm2/mm; p = 0.02, respectively). There was no significant effect of magnesium treatment on platelet aggregation, P-selectin expression, monocyte TF-PCA or adhesion molecules. Oral magnesium treatment inhibits PDT in patients with stable CAD. This effect appears to be independent of platelet aggregation or P-selectin expression, and is evident despite aspirin therapy. These findings suggest a potential mechanism whereby magnesium may beneficially alter outcomes in patients with CAD.

Elevated troponin I level on admission is associated with adverse outcome of primary angioplasty in acute myocardial infarction

BACKGROUND

In patients with acute myocardial infarction (AMI) undergoing thrombolytic therapy, an elevated troponin level on admission is associated with a lower reperfusion rate and a complicated clinical course. Whether an elevated troponin level on admission similarly predicts an adverse outcome in patients undergoing primary angioplasty is currently unknown and was investigated in the present study.

METHODS AND RESULTS

Cardiac troponin I (cTnI) was determined on admission in 110 consecutive patients with AMI associated with ST-segment elevation or left bundle branch block who underwent primary angioplasty. Fifty-four patients (49%) had an elevated cTnI (>/=0.4 ng/mL) on admission. In patients with elevated cTnI, primary angioplasty was less likely to achieve TIMI 3 flow (as classified by the Thrombolysis in Myocardial Infarction trial) in univariate (76% versus 96%, P:=0.03) or in multivariate (odds ratio 0.1, 95% CI 0.02 to 0.54) analysis. Patients with elevated cTnI were more likely to develop congestive heart failure (23% versus 9%, P:<0.05) and death, heart failure, or shock (30% versus 9%, P:=0.006). Elevated cTnI remained a significant predictor of the composite end point after controlling for other clinical data that were available early in the course, including time to presentation and angiographic results (relative risk 5.2, 95% CI 1.03 to 26.3). During a follow-up of 426+/-50 days, elevated admission cTnI was a predictor of cardiac mortality (11% versus 0%, P:=0.012), adverse cardiac events (cardiac mortality or nonfatal reinfarction; 19% versus 5.4%, P:=0.04), and adverse cardiac events plus target vessel revascularization (32% versus 14%, P:=0.054).

CONCLUSIONS

In patients with ST-segment elevation AMI, an elevated cTnI on admission is associated with an increased risk of primary angioplasty failure and a more complicated clinical course.

Focus on HDL: a new treatment paradigm for athero-thrombotic vascular disease

Atherosclerotic vascular disease is the leading cause of mortality and morbidity in much of the Western world. Although advances in lifestyle and risk factor modification, pharmacotherapy, endovascular interventions and surgery have considerably improved clinical outcome, 40 - 50% of adverse cardiovascular events continue to occur despite current strategies. A number of new targets for therapeutic exploitation are currently being investigated that include, among others, apolipoprotein A-I, the major structural component of high density lipoprotein (HDL) particle. The strong negative relationship between HDL-cholesterol levels and coronary heart disease in epidemiological studies, as well as data from experimental models suggest that HDL-based therapies could be an important new paradigm for prevention, treatment and reversal of atherosclerotic vascular disease.

Smoking increases tissue factor expression in atherosclerotic plaques: implications for plaque thrombogenicity

BACKGROUND

Smoking increases the risk of atherothrombotic events. To determine whether smoking influences plaque thrombogenicity, we examined the effect of cigarette smoking and aspirin use on tissue factor (TF) expression in atherosclerotic plaques.

METHODS AND RESULTS

A total of 23 apoE-/- mice were exposed to cigarette smoke with (n=9) or without (n=14) aspirin treatment. Eleven mice who were exposed to filtered room air served as controls. Aortic root plaques of mice exposed to smoke had higher immunoreactivity for TF (14+/-4% versus 6.4+/-3%; P=0.0005), vascular cell adhesion molecule-1 (15+/-4% versus 5+/-2%; P=0.002), and macrophages (16+/-5% versus 6+/-2%; P=0.002) compared with nonsmoking controls. Aspirin treatment attenuated smoking-induced changes in plaque composition. In human plaques obtained by carotid endarterectomy, TF immunoreactivity (8+/-5% versus 2+/-2%; P=0.0002) and activity (P=0. 03) were higher in the plaques from smokers (n=28) than those from nonsmokers (n=28). Aspirin use was associated with reduced TF expression in smokers (9+/-8% versus 3+/-4%; P=0.0017).

CONCLUSIONS

Our results suggest increased plaque TF expression and thrombogenicity as a novel mechanism for the increased risk of atherothrombotic events in smokers. Treatment with aspirin may reduce TF expression.

Low intracellular magnesium levels promote platelet-dependent thrombosis in patients with coronary artery disease

BACKGROUND

Although reduced intracellular levels of magnesium have been described in patients with acute myocardial infarction, its significance as a regulator of thrombosis remains unknown.

METHODS AND RESULTS

To determine whether reduced intracellular levels of magnesium enhance platelet-dependent thrombosis, we evaluated 42 patients with coronary artery disease (CAD) by exposing porcine aortic media to their flowing unanticoagulated venous blood for 5 minutes by using an ex vivo perfusion (Badimon) chamber. Baseline analysis demonstrated significant associations between intracellular levels of magnesium, platelet-dependent thrombosis (P =.02), and platelet P-selectin (CD62P) expression (P <.05). Patients were divided into 2 groups: below (n = 22) and above (n = 20) the median intracellular levels of magnesium (1.12 microg/mg protein). There were no significant differences in age, body mass index, serum lipids, fibrinogen, platelet count, or serum magnesium levels between the two groups. Platelet-dependent thrombosis was significantly higher in patients with intracellular levels of magnesium below compared with above median (150 +/- 128 vs 45 +/- 28 microm(2)/mm, P <.004). Neither platelet aggregation nor CD62P expression was significantly different between the two groups.

CONCLUSIONS

Platelet-dependent thrombosis was significantly increased in patients with stable CAD with low intracellular levels of magnesium, suggesting a potential role for magnesium supplementation in CAD.

Plasma apolipoprotein B levels predict platelet-dependent thrombosis in patients with coronary artery disease

Elevated plasma apolipoprotein B is a known risk factor for atherosclerotic coronary artery disease (CAD), however its relationship to arterial thrombosis is unexplored. We prospectively assessed apolipoprotein B and platelet-dependent thrombosis (PDT) in 42 CAD patients (37 men, 5 women, mean age 68 +/- 9 years), by exposing porcine aortic media to their flowing unanticoagulated venous blood for 5 min using an ex vivo perfusion (Badimon) chamber. PDT was significantly correlated with apolipoprotein B (r = 0.41, p = 0.009), intracellular magnesium levels (r = -0.46, p = 0.003) fasting blood glucose (r = 0.47, p = 0.002), and total cholesterol (r = 0.43, p = 0.006). PDT did not correlate with serum total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, apolipoprotein A-I or fibrinogen levels. These findings suggest that the positive relationship of elevated apolipoprotein B to CAD may be, in part, related to its prothrombotic effects.

Monoclonal antibody against vascular cell adhesion molecule-1 inhibits neointimal formation after periadventitial carotid artery injury in genetically hypercholesterolemic mice

Vascular cell adhesion molecule (VCAM)-1 is induced in smooth muscle cells after arterial injury, in which it has been implicated in the recruitment of inflammatory cells to the site of injury. To investigate the effect of hypercholesterolemia on VCAM-1 induction after injury and the role of VCAM-1 in neointimal response to injury, we injured the carotid artery of wild-type and apolipoprotein E null (KO) mice fed normal and high cholesterol chow. We demonstrate a graded response of VCAM-1 induction as well as monocyte/macrophage infiltration by immunohistochemistry 3 days after injury that correlated with increasing circulating cholesterol levels. Three weeks after injury, KO mice fed high cholesterol chow (KO HC group) had a significantly greater neointimal formation compared with wild-type and KO mice fed normal chow (P<0.05). Inhibition of VCAM-1 function in the KO HC group by monoclonal antibody treatment significantly reduced monocyte/macrophage infiltration and neointimal formation. There was reduced alpha-actin expression in KO HC mice 7 days after injury that was partially inhibited by VCAM-1 antibody treatment. Cell migration in an in vitro injury model was partially inhibited by monoclonal VCAM-1 antibody treatment. We propose an additional role for VCAM-1 in smooth muscle cell activation and neointimal formation after injury.

Collaborative multidisciplinary workshop report: clinical antimicrobial trials for primary and secondary prevention of atherosclerotic cardiovascular disease

The task assigned to the working group on Clinical Antimicrobial Trials for Primary and/or Secondary Prevention of Atherosclerotic Cardiovascular Disease was to evaluate the need for additional clinical antibiotic trials of a primary or secondary nature for the treatment of atherosclerotic heart disease and to suggest possible designs for future trials. In addition, the working group was to define the role of collaboration in answering research questions.

Low molecular weight heparin in acute coronary syndrome: evidence for superior or equivalent efficacy compared with unfractionated heparin?

This article will review the results of recent clinical trials evaluating low molecular weight heparins (LMWHs) in the management of patients with acute coronary syndromes of unstable angina and non-ST segment elevation MI. Low molecular weight heparins are a new class of anticoagulants that have a number of advantages over unfractionated heparin (UFH) leading to their increasing use for thrombotic vascular disorders. There is convincing evidence that LMWH is more effective than placebo and at least as effective as UFH in reducing the hard end points of death and recurrent myocardial infarction. Convincing evidence for a superior efficacy is mostly limited to the least robust but most prevalent end point of recurrent angina, and benefits appear to be confined predominantly to high-risk patients. The benefits are sustained long-term, but there appears to be no incremental benefit with prolonged treatment. The risk for major bleeding is approximately equivalent to UFH, but minor hemorrhage is clearly increased, especially with vascular instrumentation. The increased bleeding risk together with its long half-life and absence of specific antidote warrants exercising caution when using LMWH with coronary intervention. Low molecular weight heparins have the potential of being cost-neutral or even cost-saving by reducing resource utilization, especially in the setting of aggressive interventional practice pattern. Last, the issue of whether one LMWH preparation is more effective and cost-effective than others remains an open question that can be answered only by direct head-to-head comparison of different LMWH preparations in randomized trials. In conclusion, subcutaneous weight-adjusted LMWH is as effective and safe as intravenous UFH in the management of patients with acute coronary syndromes. The logistic ease of administration without the need for monitoring anticoagulation appears to be the major advantage over UFH.

Tau polymorphisms are not associated with Alzheimer's disease

Alzheimer's disease (AD) is one of a number of neurodegenerative conditions including frontotemporal dementia and progressive supranuclear palsy that are associated with abnormal tau protein aggregates in neurons. Mutations in the tau gene cause familial forms of frontotemporal dementia and alleles of the tau gene have been associated with risk for progressive supranuclear palsy. However, studies evaluating whether polymorphic variation in tau is associated with AD have produced conflicting results. We investigated the role of the tau exon 2 polymorphism in a large sample of AD cases and controls and found no evidence that polymorphic variation in tau is associated AD.

Polymeric-based perivascular delivery of a nitric oxide donor inhibits intimal thickening after balloon denudation arterial injury: role of nuclear factor-kappaB

OBJECTIVES

To examine the effect of a polymeric-based periadventitial delivery of a nitric oxide (NO)-releasing diazeniumdiolate, spermine/NO (SPER/NO), on balloon injury-induced neointimal hyperplasia in rat ileofemoral arteries.

BACKGROUND

Reduced local bioavailability and adverse side effects limit systemic administration of NO to modulate vascular response to injury.

METHODS

A polylactic-polyglycolic acid polymeric matrix containing 2.5% SPER/NO (w/w) was applied around the injured arteries. Quantitative histomorphometry was performed at day 14, proliferating cell nuclear antigen (PCNA) immunohistochemistry at day 3 to assess effects on smooth muscle proliferation and electrophoretic mobility shift assay to evaluate effects on transcription factor, nuclear factor-kappaB (NF-kappaB).

RESULTS

Treatment with SPER/NO reduced the intimal area (0.011 +/- 0.009 vs. 0.035 +/- 0.006 mm2 control, p < 0.01) and the intima to media ratio (0.089 +/- 0.062 vs. 0.330 +/- 0.057 control, p < 0.005). Spermine/nitric oxide produced a profound inhibition of PCNA-positive cells (>75%, p < 0.005) and significantly suppressed the injury-induced activation of NF-kappaB. Vascular cyclic guanosine monophosphate (cGMP) levels were elevated after treatment with the SPER/NO (0.28 +/- 0.03 vs. 0.17 +/- 0.02 pmol/mg tissue control, p < 0.01). The inhibitory effects on neointimal proliferation were localized to the site of application of SPER/NO and were not associated with any changes in platelet aggregation or bleeding time. Neither SPER nor polymer alone had any significant effects on any of the variables examined.

CONCLUSIONS

Polymeric-based perivascular delivery of a NO donor produces a marked localized inhibition of neointimal proliferation in balloon-injured arteries. This phenomenon is associated with suppression of NF-kappaB activation and elevation of the vascular cGMP at the site of injury.

Plaque disruption and thrombosis: potential role of inflammation and infection

Acute coronary syndromes (unstable angina, acute myocardial infarction, and ischemic sudden death) result from coronary thrombosis superimposed on an atherosclerotic plaque. Thrombosis is generally a consequence of disruption of the atherosclerotic plaque in the form of a fissure/rupture in the fibrous cap overlying a lipid-rich pool or superficial endothelial erosion covering a smooth muscle and proteoglycan-rich matrix with or without a lipid-core. Approximately 2/3 of acute coronary syndromes evolve from atherosclerotic plaques that are minimally or mildly obstructive of the lumen before the acute event. Inflammation with accumulation of activated mononuclear cells may play a potential role in plaque disruption through the elaboration of proteases, such as matrix degrading neutral metalloproteinases and other proteases, inhibition of function and/or survival, or promotion of apoptosis of matrix synthesizing smooth muscle cells. Inflammation may also contribute to thrombosis after plaque disruption by providing a source for tissue factor in the plaque. Inflammation in the plaque may result from accumulation of modified lipids, oxidant and hemodynamic stress, and infectious agents, such as Chlamydia pneumoniae or pro-inflammatory triggers from distant sites of infection and inflammation (eg, chronic gingivitis and chronic bronchitis). Improved insights into the pathophysiology of plaque disruption and thrombosis are likely to provide new and improved methods of stabilizing atherosclerotic disease process.

Decreased neointimal thickening after arterial wall injury in inducible nitric oxide synthase knockout mice

Mechanical injury in vivo results in the expression of the inducible form of nitric oxide synthase (iNOS) in vascular smooth muscle cells. However, the role of iNOS in modulating neointima formation after arterial wall injury is not clear. To determine whether the induction of iNOS gene expression promotes or attenuates the neointimal response to injury, we used a murine model of perivascular injury induced by placing a periadventitial collar around the carotid arteries in both wild-type and iNOS knockout mice (iNOS-KO mice). Periadventitial injury induced iNOS expression in the wild-type but not the iNOS-KO mice. Neointimal area and the intima/media ratio were significantly less in the iNOS-KO mice compared with the wild-type mice at 21 days. Injury-induced proliferation of medial cells and vascular cell adhesion molecule-1 expression were also attenuated in iNOS-KO mice compared with wild-type mice. The induction of iNOS and the activation of the nuclear factor-kappaB-mediated pathway were also demonstrated in an in vitro injury model. We conclude that mechanical injury in vivo and in vitro induces iNOS expression and that lack of iNOS expression attenuates neointima formation after perivascular arterial injury. Taken together, these findings suggest that iNOS expression after vascular injury may promote neointima formation.

Leukaemia inhibitory factor enhances tissue factor expression in human monocyte-derived macrophages: a gp130-mediated mechanism

Leukaemia inhibitory factor (LIF) and interleukin (IL)-6 are members of a cytokine group that share a common signal transducer gp130 and induce pleiotropic biological effects in cells of diverse lineage. In monocytes, LIF facilitates differentiation, which may stimulate the biosynthesis of tissue factor (TF) that initiates the coagulation cascade. We tested the hypothesis that LIF would enhance TF expression in human monocyte-derived macrophages (MDMs). Human peripheral blood mononuclear cells separated from whole blood by density centrifugation were allowed to differentiate into MDMs in primary culture, and were then exposed to LIF, IL-6 and oncostatin M (OSM) for 24 h. LIF and IL-6 receptors, and gp130 were demonstrated in MDMs by immunocytochemistry and RT-PCR. TF procoagulant activity (TF-PCA) was measured by recalcification clotting time and TF protein by Western blotting. The results show that both TF procoagulant activity and TF protein increased significantly in response to LIF over the concentration range of 1-100 nM (P < 0.03). Although OSM and IL-6 tended to enhance TF expression by MDMs, the increase did not reach statistical significance. Anti-LIF receptor and anti-gp130 antibodies attenuated the effect of LIF on TF expression as assayed by both bioassay and flow-cytometry. In conclusion, LIF increases TF-PCA and TF protein in MDMs, and specific anti-LIF receptor antibodies attenuate this effect. Thus, LIF may regulate by a gp130-dependent pathway macrophage-mediated procoagulant function in diverse pathological states involving inflammation and thrombosis and seems to serve as an important mediator at the interface between these processes.

Effect of glycoprotein IIb/IIIa inhibition without thrombolytic therapy on reperfusion in acute myocardial infarction: results of ReoMI pilot study

The efficacy of abciximab and moderate dose heparin in attaining reperfusion in acute MI was tested in a multicenter pilot study. Patients with acute MI of less than 6-hr onset triaged to primary PTCA received intravenous abciximab bolus and infusion and heparin (70 u/kg) in the emergency room. Mean time to angiography from administration of abciximab was 34 +/- 23 min. TIMI flow rates were: grade 0-62%, grade I-20%, grade II-9%, and grade III-9%. Primary PTCA was performed with 100% success rate. Access site bleeding occurred in 10% of patients with no incidence of intracranial bleeding. TIMI II/III flow rates were 50% in a patient subset where angiography was delayed by 45 min. While not an alternative to thrombolytics in AMI, abciximab administration in the emergency room in patients triaged to PTCA may be beneficial in situation where door to needle time is delayed as TIMI II/III flows may be attained in some patients. Cathet. Cardiovasc. Intervent. 48:430-434, 1999.

Activation of mitogen-activated protein kinase pathways by cyclic GMP and cyclic GMP-dependent protein kinase in contractile vascular smooth muscle cells

Vascular smooth muscle cells (VSMC) exist in either a contractile or a synthetic phenotype in vitro and in vivo. The molecular mechanisms regulating phenotypic modulation are unknown. Previous studies have suggested that the serine/threonine protein kinase mediator of nitric oxide (NO) and cyclic GMP (cGMP) signaling, the cGMP-dependent protein kinase (PKG) promotes modulation to the contractile phenotype in cultured rat aortic smooth muscle cells (RASMC). Because of the potential importance of the mitogen-activated protein kinase (MAP kinase) pathways in VSMC proliferation and phenotypic modulation, the effects of PKG expression in PKG-deficient and PKG-expressing adult RASMC on MAP kinases were examined. In PKG-expressing adult RASMC, 8-para-chlorophenylthio-cGMP activated extracellular signal- regulated kinases (ERK1/2) and c-Jun N-terminal kinase (JNK). The major effect of PKG activation was increased activation by MAP kinase kinase (MEK). The cAMP analog, 8-Br-cAMP inhibited ERK1/2 activation in PKG-deficient and PKG-expressing RASMC but had no effect on JNK activity. The effects of PKG on ERK and JNK activity were additive with those of platelet-derived growth factor (PDGF), suggesting that PKG activates MEK through a pathway not used by PDGF. The stimulatory effects of cGMP on ERK and JNK activation were also observed in low-passaged, contractile RASMC still expressing endogenous PKG, suggesting that the effects of PKG expression were not artifacts of cell transfections. These results suggest that in contractile adult RASMC, NO-cGMP signaling increases MAP kinase activity. Increased activation of these MAP kinase pathways may be one mechanism by which cGMP and PKG activation mediate c-fos induction and increased proliferation of contractile adult RASMC.

Evidence that high-density lipoprotein cholesterol is an independent predictor of acute platelet-dependent thrombus formation

Plasma total and low-density lipoprotein (LDL) cholesterol are established risk factors for atherosclerotic vascular disease and may also contribute to a prothrombotic risk via enhanced platelet reactivity. This study examines whether high-density lipoprotein (HDL) cholesterol, which is inversely correlated with coronary artery disease, is associated with a reduced thrombogenic potential. Platelet thrombus formation was evaluated by exposing porcine aortic media placed in Badimon perfusion chambers to flowing nonanticoagulated venous blood for 5 minutes at a shear rate of 1,000 s(-1). Forty-five subjects, 23 normal (LDL 104 +/- 31, HDL 50 +/- 15 mg/dl) and 22 hypercholesterolemic (LDL 181 +/- 45, HDL 41 +/- 10 mg/dl) patients without coronary artery disease were studied. Platelet aggregation and CD62 antigen expression, and assay for circulating prothrombotic factors were also performed. In univariate analysis platelet thrombus formation correlated with weight (r = 0.33, p = 0.03), diastolic blood pressure (r = 0.39, p = 0.01), HDL cholesterol (r = -0.45, p = 0.003), total/HDL cholesterol (r = 0.43, p = 0.004) and LDL/HDL (r = 0.38, p = 0.01) ratios, and platelet CD62 expression (r = 0.41, p = 0.02). In multiple regression analysis only HDL cholesterol showed significant correlation with platelet thrombus formation (p = 0.03). Platelet aggregation and circulating prothrombotic factors did not correlate with platelet thrombus formation. A comparison between normal and hypercholesterolemic subjects revealed enhanced thrombus area (0.026 +/- 0.20 vs 0.045 +/- 0.039 mm2/mm; p = 0.04), resting CD62 expression (6 +/- 7% vs 15 +/- 10% positive platelets, p = 0.02), and platelet aggregation (16.7 +/- 5.2 vs 21.7 +/- 6.7 ohms, p = 0.04) in hypercholesterolemic subjects. Our results demonstrate that HDL cholesterol is a significant independent predictor of ex vivo platelet thrombus formation.