Inhibition of tissue-factor-mediated thrombin generation by simvastatin

Atorvastatin-mediated inhibition of prenylation of Rab27b and Rap1a in platelets attenuates their prothrombotic capacity and modulates clot structure

Statins inhibit the mevalonate pathway by impairing protein prenylation via depletion of lipid geranylgeranyl diphosphate (GGPP). Rab27b and Rap1a are small GTPase proteins involved in dense granule secretion, platelet activation, and regulation. We analyzed the impact of statins on prenylation of Rab27b and Rap1a in platelets and the downstream effects on fibrin clot properties. Whole blood thromboelastography revealed that atorvastatin (ATV) delayed clot formation time (P < .005) and attenuated clot firmness (P < .005). ATV pre-treatment inhibited platelet aggregation and clot retraction. Binding of fibrinogen and P-selectin exposure on stimulated platelets was significantly lower following pre-treatment with ATV (P < .05). Confocal microscopy revealed that ATV significantly altered the structure of platelet-rich plasma clots, consistent with the reduced fibrinogen binding. ATV enhanced lysis of Chandler model thrombi 1.4-fold versus control (P < .05). Western blotting revealed that ATV induced a dose-dependent accumulation of unprenylated Rab27b and Rap1a in the platelet membrane. ATV dose-dependently inhibited ADP release from activated platelets. Exogenous GGPP rescued the prenylation of Rab27b and Rap1a, and partially restored the ADP release defect, suggesting these changes arise from reduced prenylation of Rab27b. These data demonstrate that statins attenuate platelet aggregation, degranulation, and binding of fibrinogen thereby having a significant impact on clot contraction and structure.

Statins Effects on Blood Clotting: A Review

Statins are powerful lipid-lowering drugs that inhibit cholesterol biosynthesis via downregulation of hydroxymethylglutaryl coenzyme-A reductase, which are largely used in patients with or at risk of cardiovascular disease. Available data on thromboembolic disease include primary and secondary prevention as well as bleeding and mortality rates in statin users during anticoagulation for VTE. Experimental studies indicate that statins alter blood clotting at various levels. Statins produce anticoagulant effects via downregulation of tissue factor expression and enhanced endothelial thrombomodulin expression resulting in reduced thrombin generation. Statins impair fibrinogen cleavage and reduce thrombin generation. A reduction of factor V and factor XIII activation has been observed in patients treated with statins. It is postulated that the mechanisms involved are downregulation of factor V and activated factor V, modulation of the protein C pathway and alteration of the tissue factor pathway inhibitor. Clinical and experimental studies have shown that statins exert antiplatelet effects through early and delayed inhibition of platelet activation, adhesion and aggregation. It has been postulated that statin-induced anticoagulant effects can explain, at least partially, a reduction in primary and secondary VTE and death. Evidence supporting the use of statins for prevention of arterial thrombosis-related cardiovascular events is robust, but their role in VTE remains to be further elucidated. In this review, we present biological evidence and experimental data supporting the ability of statins to directly interfere with the clotting system.

Monocyte Tissue Factor Expression: Lipopolysaccharide Induction and Roles in Pathological Activation of Coagulation

The coagulation system is a part of the mammalian host defense system. Pathogens and pathogen components, such as bacterial lipopolysaccharide (LPS), induce tissue factor (TF) expression in circulating monocytes that then activates the coagulation protease cascade. Formation of a clot limits dissemination of pathogens, enhances the recruitment of immune cells, and facilitates killing of pathogens. However, excessive activation of coagulation can lead to thrombosis. Here, we review studies on the mechanism of LPS induction of TF expression in monocytes and its contribution to thrombosis and disseminated intravascular coagulation. Binding of LPS to Toll-like receptor 4 on monocytes induces a transient expression of TF that involves activation of intracellular signaling pathways and binding of various transcription factors, such as c-rel/p65 and c-Fos/c-Jun, to the TF promoter. Inhibition of TF in endotoxemia and sepsis models reduces activation of coagulation and improves survival. Studies with endotoxemic mice showed that hematopoietic cells and myeloid cells play major roles in the activation of coagulation. Monocyte TF expression is also increased after surgery. Activated monocytes release TF-positive extracellular vesicles (EVs) and levels of circulating TF-positive EVs are increased in endotoxemic mice and in patients with sepsis. More recently, it was shown that inflammasomes contribute to the induction of TF expression and activation of coagulation in endotoxemic mice. Taken together, these studies indicate that monocyte TF plays a major role in activation of coagulation. Selective inhibition of monocyte TF expression may reduce pathologic activation of coagulation in sepsis and other diseases without affecting hemostasis.

The role of monocytes in thrombotic diseases: a review

Cardiovascular and cerebrovascular diseases are the number one killer threatening people's life and health, among which cardiovascular thrombotic events are the most common. As the cause of particularly serious cardiovascular events, thrombosis can trigger fatal crises such as acute coronary syndrome (myocardial infarction and unstable angina), cerebral infarction and so on. Circulating monocytes are an important part of innate immunity. Their main physiological functions are phagocytosis, removal of injured and senescent cells and their debris, and development into macrophages and dendritic cells. At the same time, they also participate in the pathophysiological processes of pro-coagulation and anticoagulation. According to recent studies, monocytes have been found to play a significant role in thrombosis and thrombotic diseases of the immune system. In this manuscript, we review the relationship between monocyte subsets and cardiovascular thrombotic events and analyze the role of monocytes in arterial thrombosis and their involvement in intravenous thrombolysis. Finally, we summarize the mechanism and therapeutic regimen of monocyte and thrombosis in hypertension, antiphospholipid syndrome, atherosclerosis, rheumatic heart disease, lower extremity deep venous thrombosis, and diabetic nephropathy.

Statins and risk of venous thromboembolic diseases: A two-sample mendelian randomization study

BACKGROUND AND AIMS

In observational studies, statins have been suggested to have protective effects on venous thromboembolism (VTE), including deep vein thrombosis (DVT) and pulmonary embolism (PE). To this aim, we performed a two-sample mendelian randomization (MR) analysis to determine whether these associations were causal.

METHODS AND RESULTS

Data on the single nucleotide polymorphisms (SNPs) related to statin medication were obtained from the FinnGen study, and data for VTE, PE and DVT of lower extremities (LEDVT) were from the UK Biobank study, respectively. Inverse variance weighted (IVW) method was used as the principal analysis of MR, and sensitivity analysis was performed to detect horizontal pleiotropy and heterogeneity. MR estimates showed an inverse causal association between statin medication and the risk of VTE (odds ratio [OR]: 0.999, 95% CI: 0.998-1.000, P = 0.004), PE (OR: 0.999, 95% CI: 0.999-1.000, P = 0.011) and LEDVT (OR: 0.999, 95% CI: 0.999-1.000, P = 0.008).

CONCLUSION

Our findings provide direct evidence that statins might decrease the risk of VTE, PE and LEDVT in agreement with observational studies. The specific mechanism of statin therapy for venous thromboembolism needs to be further studied.

Effects of simvastatin on tissue factor pathway of blood coagulation in STATCOPE (Simvastatin in the prevention of COPD exacerbations) trial

BACKGROUND

Statins are widely used to lower lipids and reduce cardiovascular events. In vitro studies and small studies in patients with hyperlipidemias show statins inhibit tissue factor (TF) and blood coagulation mechanisms. We assessed the effects of simvastatin on TF and coagulation biomarkers in patients entered in STATCOPE, a multicenter, randomized, placebo-controlled trial of simvastatin (40 mg daily) versus placebo on exacerbation rates in patients with chronic obstructive pulmonary disease (COPD).

METHODS

In 227 patients (114 simvastatin, 113 placebo; mean [± standard error of the mean] age 62 ± 0.53 years, 44.5% women) we measured (baseline, and 6 and 12 months): whole blood membrane TF-procoagulant activity (TF-PCA) and plasma factors VIIa, VII, VIII, fibrinogen, TF antigen, tissue factor pathway inhibitor (TFPI), thrombin-antithrombin complexes (TAT), and D-dimer. We excluded patients with diabetes, cardiovascular disease, and those taking or requiring a statin.

RESULTS

In the statin group, there was a small increase in TF-PCA (from 25.18 ± 1.08 to 30.36 ± 1.10 U/ml; p = .03) over 12 months; factors VIIa and VIII, fibrinogen, TAT, and D-dimer did not change. Plasma TFPI (from 52.4 ± 1.75 to 44.7 ± 1.78 ng/ml; p < .0001) and FVIIC (1.23 ± 0.04 to 1.15 ± 0.03 U/ml; p = .03) decreased and correlated with total cholesterol levels. No changes in biomarkers were observed with placebo.

CONCLUSIONS

In contrast to previous studies on statins, in COPD patients without diabetes, cardiovascular disease, or requiring a statin treatment, simvastatin (40 mg per day) did not decrease TF or factors VIIa and VIII, fibrinogen, TAT, or D-dimer. The decreases in TFPI and factor VII reflect the decrease in serum lipids.

Protein disulfide isomerase enhances tissue factor-dependent thrombin generation

Protein disulfide isomerase (PDI) plays an important role in fibrin generation in vivo, but the underlying mechanism remains largely unknown. In this study, using thrombin generation assay (TGA), we investigated whether PDI contributes to tissue factor (TF)-mediated thrombin generation. Human peripheral blood mononuclear cells (PBMCs) were treated with 100 ng/ml lipopolysaccharide (LPS), the expression of TF on cell surface was analyzed by flow cytometry. After incubation with an inhibitory anti-TF antibody, recombinant PDI protein or a PDI inhibitor PACMA31, LPS-stimulated human PBMCs were incubated with human plasma, and thrombin generation was assessed by Ceveron Alpha TGA and a fluorescent thrombin substrate. Bone marrow mononuclear cells isolated from PDI-knockout and wild-type mice were stimulated by LPS, followed by measurement of thrombin generation. LPS stimulation increased expression of TF on PBMCs, and thrombin generation. Inhibitory anti-TF antibody almost completely suppressed thrombin generation of LPS-stimulated PBMCs, suggesting that thrombin generation was TF-dependent. Recombinant PDI protein increased thrombin generation, while PACMA31 attenuated thrombin generation. Compared with control cells, PDI-deficient marrow mononuclear cells had less capacity in thrombin generation. Taken together, these data suggest that PDI enhances TF-dependent thrombin generation.

Atherothrombosis and Oxidative Stress: Mechanisms and Management in Elderly

SIGNIFICANCE

The incidence of cardiovascular events (CVEs) increases with age, representing the main cause of death in an elderly population. Aging is associated with overproduction of reactive oxygen species (ROS), which may affect clotting and platelet activation, and impair endothelial function, thus predisposing elderly patients to thrombotic complications. Recent Advances: There is increasing evidence to suggest that aging is associated with an imbalance between oxidative stress and antioxidant status. Thus, upregulation of ROS-producing enzymes such as nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and myeloperoxidase, along with downregulation of antioxidant enzymes, such as superoxide dismutase and glutathione peroxidase, occurs during aging. This imbalance may predispose to thrombosis by enhancing platelet and clotting activation and eliciting endothelial dysfunction. Recently, gut-derived products, such as trimethylamine N-oxide (TMAO) and lipopolysaccharide, are emerging as novel atherosclerotic risk factors, and gut microbiota composition has been shown to change by aging, and may concur with the increased cardiovascular risk in the elderly.

CRITICAL ISSUES

Antioxidant treatment is ineffective in patients at risk or with cardiovascular disease. Further, anti-thrombotic treatment seems to work less in the elderly population.

FUTURE DIRECTIONS

Interventional trials with antioxidants targeting enzymes implicated in aging-related atherothrombosis are warranted to explore whether modulation of redox status is effective in lowering CVEs in the elderly. Antioxid. Redox Signal. 27, 1083-1124.

Gut-Derived Serum Lipopolysaccharide is Associated With Enhanced Risk of Major Adverse Cardiovascular Events in Atrial Fibrillation: Effect of Adherence to Mediterranean Diet

Background

Gut microbiota is emerging as a novel risk factor for atherothrombosis, but the predictive role of gut‐derived lipopolysaccharide (LPS) is unknown. We analyzed (1) the association between LPS and major adverse cardiovascular events (MACE) in atrial fibrillation (AF) and (2) its relationship with adherence to a Mediterranean diet (Med‐diet).

Methods and Results

This was a prospective single‐center study including 912 AF patients treated with vitamin K antagonists (3716 patient‐years). The primary end point was a composite of MACE. Baseline serum LPS, adherence to Med‐diet (n=704), and urinary excretion of 11‐dehydro‐thromboxane B₂ (TxB₂, n=852) were investigated. Mean age was 73.5 years; 42.9% were women. A total of 187 MACE (5.0% per year) occurred: 54, 59, and 74 in the first, second, and third tertile of LPS, respectively (log‐rank test P=0.004). Log‐LPS (hazard ratio 1.194, P=0.009), age (hazard ratio 1.083, P<0.001), and previous cerebrovascular (hazard ratio 1.634, P=0.004) and cardiac events (hazard ratio 1.822, P<0.001) were predictors of MACE. In the whole cohort, AF (versus sinus rhythm) (β 0.087, P=0.014) and low‐density lipoprotein cholesterol (β 0.069, P=0.049) were associated with circulating LPS. Furthermore, Med‐diet score (β −0.137, P<0.001) was predictive of log‐LPS, with fruits (β −0.083, P=0.030) and legumes (β −0.120, P=0.002) negatively associated with log‐LPS levels. Log‐LPS and log‐TxB₂ were highly correlated (r=0.598, P<0.001). Log‐LPS (β 0.574, P<0.001) and Med‐diet score (β −0.218, P<0.001) were significantly associated with baseline urinary excretion of TxB₂.

Conclusions

In this cohort of AF patients, LPS levels were predictive of MACE and negatively affected by high adherence to Med‐diet. LPS may contribute to MACE incidence in AF by increasing platelet activation.

Antiphospholipid syndrome and tissue factor: a thrombotic couple

The antiphospholipid syndrome (APS) is characterized by thrombosis and/or pregnancy morbidity in the presence of antiphospholipid antibodies (aPL). Among the thrombogenic mechanisms proposed, it has been suggested that aPL can stimulate tissue factor (TF) expression by endothelial cells (ECs) and monocytes. Moreover, our in vivo studies have shown that APS patients (particularly those with thrombosis) have increased monocyte TF expression. Yet, the molecular mechanism(s) by which aPL induce TF expression has not been completely underscored. In a recent study, we have demonstrated that aPL induces TF expression in monocytes from APS patients by activating, simultaneously and independently, the phosphorylation of MEK-1/ERK proteins, and the p38 MAP kinase-depenent nuclear translocation and activation of NFκB/Rel proteins. Understanding the intracellular mechanism(s) of aPL-mediated monocyte activation may help to establish new therapeutic approaches, such as selective inhibition of MAP kinases, to reverse the prothrombotic state in APS. Furthermore, the contribution of TF to a protrombotic state in the APS provides a renewed focus on antithrombotic therapies in current use, including the oral anticoagulation and, more recently, the use of statins, which have been proven to be effective in the inhibition of EC and monocyte TF-expression.

Early High-dosage Atorvastatin Treatment Improved Serum Immune-inflammatory Markers and Functional Outcome in Acute Ischemic Strokes Classified as Large Artery Atherosclerotic Stroke: A Randomized Trial

Statins have beneficial effects on cerebral circulation and brain parenchyma during ischemic stroke and reperfusion. The primary hypothesis of this randomized parallel trial was that treatment with 80 mg/day of atorvastatin administered early at admission after acute atherosclerotic ischemic stroke could reduce serum levels of markers of immune-inflammatory activation of the acute phase and that this immune-inflammatory modulation could have a possible effect on prognosis of ischemic stroke evaluated by some outcome indicators. We enrolled 42 patients with acute ischemic stroke classified as large arteries atherosclerosis stroke (LAAS) randomly assigned in a randomized parallel trial to the following groups: Group A, 22 patients treated with atorvastatin 80 mg (once-daily) from admission day until discharge; Group B, 20 patients not treated with atorvastatin 80 mg until discharge, and after discharge, treatment with atorvastatin has been started. At 72 hours and at 7 days after acute ischemic stroke, subjects of group A showed significantly lower plasma levels of tumor necrosis factor-α, interleukin (IL)-6, vascular cell adhesion molecule-1, whereas no significant difference with regard to plasma levels of IL-10, E-Selectin, and P-Selectin was observed between the 2 groups. At 72 hours and 7 days after admission, stroke patients treated with atorvastatin 80 mg in comparison with stroke subjects not treated with atorvastatin showed a significantly lower mean National Institutes of Health Stroke Scale and modified Rankin scores. Our findings provide the first evidence that atorvastatin acutely administered immediately after an atherosclerotic ischemic stroke exerts a lowering effect on immune-inflammatory activation of the acute phase of stroke and that its early use is associated to a better functional and prognostic profile.

Tissue Factor and Atherothrombosis

Atherosclerosis is a progressive disease characterized by the accumulation of lipids in medium to large sized arteries. Atherothrombosis is a term used to describe formation of a thrombus after rupture of an atherosclerotic plaque. Thrombosis can lead to myocardial infarction and stroke. Risk factors for atherosclerosis include hyperlipidemia, diabetes, smoking and hypertension all of which increase tissue factor (TF) expression. High levels of TF are present in atherosclerotic plaques due to expression by macrophages and vascular smooth muscle cells and the presence of cell-derived TF-positive microvesicles (MVs). In addition, hyperlipidemia leads to the formation of oxidized LDL, which induces TF expression in circulating monocytes and the release of TF-positive MVs. The major source of TF that drives thrombosis after plaque rupture is TF within the plaque. However, TF in the blood on monocytes and MVs may also contribute the thrombosis. Inhibition of the TF/factor VIIa complex is unlikely to be an effective strategy to reduce atherothrombosis due the essential role of the complex in hemostasis. However, selective blockade of pathologic TF without affecting protective TF may be effective in reducing atherothrombosis. For instance, statins have been shown to reduce TF expression in the plaque and in circulating monocytes, which would be expected to reduce thrombosis. Further studies are needed to determine safe strategies to reduce pathologic TF expression and atherothrombosis.

Particulate matter phagocytosis induces tissue factor in differentiating macrophages

Airborne exposure to particulate matter with diameter < 10 mcM (PM10) has been linked to an increased risk of thromboembolic events, but the mechanisms are not completely understood. The aim of this study was to evaluate the effect of PM10 phagocytosis on the release of procoagulant molecules in human differentiating macrophages, and that of PM10 inhalation in an experimental model in rats. Human monocytes were separated from the peripheral blood by the lymphoprep method, differentiated in vitro and treated with standard PM10 or vehicle. Sprague-Dawley rats were instilled intratracheally with PM10 or vehicle alone. The outcome was expression of proinflammatory genes and of tissue factor (TF). In human differentiating macrophages, PM10 exposure upregulated inflammatory genes, but most consistently induced TF mRNA and protein levels, but not TF protein inhibitor, resulting in increased TF membrane expression and a procoagulant phenotype. Differentiation towards the anti-inflammatory M2 phenotype inhibited PM10 -mediated TF expression. TF induction required phagocytosis of PM10 , whereas phagocytosis of inert particles was less effective. PM10 phagocytosis was associated with a gene expression profile consistent with intracellular retention of iron, inducing oxidative stress. Both PM10 and iron activated the stress kinases ERK1/2 pathway, involved in the induction of TF expression. In rats, alveolar exposure to PM10 was associated with pulmonary recruitment of inflammatory cells and resulted in local, but not systemic, induction of TF expression, which was sufficient to increase circulating TF levels. In conclusion, TF induction by differentiating lung macrophages, activated following phagocytosis, contributes to the increased risk of thromboembolic complications associated with PM10 exposure.

The antithrombotic effects of statins

Hypercholesterolemia is considered the primary risk factor for cardiovascular disease. An estimated 200 million prescriptions are issued per year for statins to treat hypercholesterolemia. Importantly, statins have additional beneficial effects independent of their effects on lipids. Recent studies have shown that statins reduce thrombosis via multiple pathways, including inhibiting platelet activation and reducing the pathologic expression of the procoagulant protein tissue factor. Many of the antithrombotic effects of statins are attributed to inhibiting prenylation of RhoA and effects on other intracellular signaling molecules such as NF-κB and KLF2. These antithrombotic activities of statins likely contribute to the ability of statins to reduce the incidence of cardiovascular death.

Statins decrease thrombin generation in patients with hypercholesterolemia

OBJECTIVE

Statins are cholesterol-lowering agents with antithrombotic effect possibly unrelated to their lipid-lowering properties. Traditional global coagulation tests failed, however, to reveal clinically relevant change after treatment. We therefore sought to investigate whether statins were able to modify thrombin generation in hypercholesterolemia.

METHODS

Fifty-one patients who needed treatment with statins were enrolled in this study. Thrombin generation, assessed as endogenous thrombin potential (the amount of thrombin generated after triggering coagulation with small amount of tissue factor) was measured at pre- and two months post-treatment with statins.

RESULTS

The median (inter-quartile range) level of total cholesterol that was 325 mg/dL (278-405) decreased significantly [211 mg/dL (197-247)] at post-treatment (p<0.001); the median level of HDL cholesterol that was 49 mg/dL (43-56) increased significantly [55 mg/dL (47-66)] at post-treatment (p<0.001). The median endogenous thrombin potential (inter-quartile range) before treatment was 2372 nM·min (2008-2617) and decreased to 2,048 nM·min (1764-2375) (p<0.001) after treatment.

CONCLUSION

The results support the hypothesis of a direct link between statins and coagulation through their capacity to lower thrombin generation in patients with hypercholesterolemia.

PRACTICE IMPLICATIONS

The antithrombotic properties of statins could be mediated (at least in part) by their endogenous thrombin potential lowering effect. This interesting hypothesis warrants evaluation by clinical trials.

The effect of lowering LDL cholesterol on vascular access patency: post hoc analysis of the Study of Heart and Renal Protection

BACKGROUND AND OBJECTIVES

Reducing LDL cholesterol (LDL-C) with statin-based therapy reduces the risk of major atherosclerotic events among patients with CKD, including dialysis patients, but the effect of lowering LDL-C on vascular access patency is unclear.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The Study of Heart and Renal Protection (SHARP) randomized patients with CKD to 20 mg simvastatin plus 10 mg ezetimibe daily versus matching placebo. This study aimed to explore the effects of treatment on vascular access occlusive events, defined as any access revision procedure, access thrombosis, removal of an old dialysis access, or formation of new permanent dialysis access.

RESULTS

Among 2353 SHARP participants who had functioning vascular access at randomization, allocation to simvastatin plus ezetimibe resulted in a 13% proportional reduction in vascular access occlusive events (355 [29.7%] for simvastatin/ezetimibe versus 388 [33.5%] for placebo; risk ratio [RR], 0.87; 95% confidence interval [95% CI], 0.75 to 1.00; P=0.05). There was no evidence that the effects of treatment differed for any of the separate components of this outcome. To test the hypothesis raised by SHARP, comparable analyses were performed using the AURORA (A Study to Evaluate the Use of Rosuvastatin in Subjects on Regular Hemodialysis: An Assessment of Survival and Cardiovascular Events) trial cohort. AURORA did not provide independent confirmation (vascular access occlusive events: 352 [28.9%] for rosuvastatin versus 337 [27.6%] for placebo; RR, 1.06, 95% CI, 0.91 to 1.23; P=0.44). After combining the two trials, the overall effect of reducing LDL-C with a statin-based regimen on vascular access occlusive events was not statistically significant (707 [29.3%] with any LDL-C-lowering therapy versus 725 [30.5%] with placebo; RR, 0.95, 95% CI, 0.85 to 1.05; P=0.29).

CONCLUSIONS

Exploratory analyses from SHARP suggest that lowering LDL-C with statin-based therapy may improve vascular access patency, but there was no evidence of benefit in AURORA. Taken together, the available evidence suggests that any benefits of lowering LDL-C on vascular access patency are likely to be modest.

Anticoagulant effects of statins and their clinical implications

There is evidence indicating that statins (3-hydroxy-methylglutaryl coenzyme A reductase inhibitors) may produce several cholesterol-independent antithrombotic effects. In this review, we provide an update on the current understanding of the interactions between statins and blood coagulation and their potential relevance to the prevention of venous thromboembolism (VTE). Anticoagulant properties of statins reported in experimental and clinical studies involve decreased tissue factor expression resulting in reduced thrombin generation and attenuation of pro-coagulant reactions catalysed by thrombin, such as fibrinogen cleavage, factor V and factor XIII activation, as well as enhanced endothelial thrombomodulin expression, resulting in increased protein C activation and factor Va inactivation. Observational studies and one randomized trial have shown reduced VTE risk in subjects receiving statins, although their findings still generate much controversy and suggest that the most potent statin rosuvastatin exerts the largest effect.

Hyperlipidemia, tissue factor, coagulation, and simvastatin

Hyperlipidemia affects millions of people worldwide and is a major risk factor for cardiovascular disease. People with hyperlipidemia have elevated levels of serum cholesterol and an increased risk of thrombosis. Studies have suggested that oxidized lipoproteins, such as oxidized low-density lipoprotein (oxLDL), contribute to the development of a pro-thrombotic state. In this review, we discuss our recent studies demonstrating a role for hematopoietic cell-derived tissue factor (TF) expression in the activation of coagulation and increased thrombosis associated with hyperlipidemia. In addition, we investigated the effect of simvastatin on TF expression and coagulation. We found that simvastatin reduced leukocyte TF expression, TF⁺ microparticles, and coagulation. These results and earlier studies suggest that the anti-coagulant activity of statins is due, in part, to their ability to reduce monocyte TF expression in patients with cardiovascular disease.

Role of tissue factor in atherothrombosis

Tissue factor (TF) is abundantly present in atherosclerotic plaques and it is the primary source of TF that triggers the rapid activation of the coagulation cascade after plaque rupture. While much of this TF is associated with monocyte/macrophages and vascular smooth muscle cells, recent studies suggests TF-positive microparticles (MPs) are the most abundant source in plaques. Further, while intravascular TF is largely absent in healthy patients, cardiovascular disease patients have increased TF expression in circulating monocytes, which can result in increased levels of TF-positive MPs. This brief review describes how TF is the primary initiator of atherothrombosis and how TF-positive MPs may serve as a biomarker to identify patients at greater risk of forming an occlusive thrombus. In addition, currently used therapeutics, such as statins and inhibitors of the renin angiotensin system, may have additional benefits by reducing TF expression and subsequent thrombosis.

The role of 3-hydroxy-3-methylglutaryl coenzyme a reductase inhibitors (statins) in modern rheumatology

Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase commonly known as statins are widely used for treating hypercholesterolemia. However, there is much evidence to suggest that statins may have other properties in addition to their cholesterol-lowering effect. In particular, statins may neutralize post-translational prenylation of vitally important regulatory small GTPases, which are involved in several processes such as tissue fibrosis, cell maturation, apoptosis, immune cell maturation, and immune response. The beneficial effect of statins has been reported in animal and in vitro models as well as in some clinical studies. As they have an acceptable safety profile, statins may be considered, in selected cases, as a valuable concomitant therapy in the treatment of rheumatic and autoimmune disorders.

New insights into the mechanisms of venous thrombosis

Venous thrombosis is a leading cause of morbidity and mortality in industrialized countries, especially in the elderly. Many risk factors have been identified for venous thrombosis that alter blood flow, activate the endothelium, and increase blood coagulation. However, the precise mechanisms that trigger clotting in large veins have not been fully elucidated. The most common site for initiation of the thrombus appears to be the valve pocket sinus, due to its tendency to become hypoxic. Activation of endothelial cells by hypoxia or possibly inflammatory stimuli would lead to surface expression of adhesion receptors that facilitate the binding of circulating leukocytes and microvesicles. Subsequent activation of the leukocytes induces expression of the potent procoagulant protein tissue factor that triggers thrombosis. Understanding the mechanisms of venous thrombosis may lead to the development of new treatments.

Sources of tissue factor that contribute to thrombosis after rupture of an atherosclerotic plaque

Hyperlipidemia leads to the formation of oxidized LDL (oxLDL), vessel dysfunction, atherosclerotic disease, and ultimately to plaque rupture and thrombosis. OxLDL induces tissue factor (TF) expression in various cell types, including monocytes and macrophages. High levels of TF are present in atherosclerotic plaques and this represents that major source of TF that triggers thrombosis after plaque rupture. In addition, increased levels of "circulating TF" are observed in hyperlipidemic animals and patients. This is due to induced TF expression in monocytes and release of monocyte-derived, TF(+) microparticles, which represents a minor source of TF that likely contributes to thrombosis after plaques rupture. This review will summarize the connections between hyperlipidemia and TF expression within atherosclerotic plaques and circulating monocytes, as well as its inhibition by statins.

Monocyte tissue factor-dependent activation of coagulation in hypercholesterolemic mice and monkeys is inhibited by simvastatin

Hypercholesterolemia is a major risk factor for atherosclerosis. It also is associated with platelet hyperactivity, which increases morbidity and mortality from cardiovascular disease. However, the mechanisms by which hypercholesterolemia produces a procoagulant state remain undefined. Atherosclerosis is associated with accumulation of oxidized lipoproteins within atherosclerotic lesions. Small quantities of oxidized lipoproteins are also present in the circulation of patients with coronary artery disease. We therefore hypothesized that hypercholesterolemia leads to elevated levels of oxidized LDL (oxLDL) in plasma and that this induces expression of the procoagulant protein tissue factor (TF) in monocytes. In support of this hypothesis, we report here that oxLDL induced TF expression in human monocytic cells and monocytes. In addition, patients with familial hypercholesterolemia had elevated levels of plasma microparticle (MP) TF activity. Furthermore, a high-fat diet induced a time-dependent increase in plasma MP TF activity and activation of coagulation in both LDL receptor-deficient mice and African green monkeys. Genetic deficiency of TF in bone marrow cells reduced coagulation in hypercholesterolemic mice, consistent with a major role for monocyte-derived TF in the activation of coagulation. Similarly, a deficiency of either TLR4 or TLR6 reduced levels of MP TF activity. Simvastatin treatment of hypercholesterolemic mice and monkeys reduced oxLDL, monocyte TF expression, MP TF activity, activation of coagulation, and inflammation, without affecting total cholesterol levels. Our results suggest that the prothrombotic state associated with hypercholesterolemia is caused by oxLDL-mediated induction of TF expression in monocytes via engagement of a TLR4/TLR6 complex.

Atorvastatin neutralises the thrombin-induced tissue factor expresion in endothelial cells via geranylgeranyl pyrophosphate

Statins may have beneficial effects in atherogenesis given their antithrombotic properties involving non-lipid mechanisms that modify endothelial function of tissue factor induction by thrombin. In this study, we investigate the effect of atorvastatin on tissue factor (TF) activity in thrombin-stimulated endothelial cells and its regulation through mevalonate or its derivatives. First subculture of human umbilical endothelial cells was used for this study. Cells were treated with thrombin and atorvastatin for different time intervals and dosage. Tissue factor activity was measured as Factor Xa generation induced by Tissue Factor-Factor VIIa complex on confluent cells. Our results show that atorvastatin prevents the thrombin-induced up-regulation of tissue factor activity in a concentration-dependent manner. Mevalonate and geranylgeranyl pyrophosphate reversed this inhibitory effect of atorvastatin on tissue factor activity, while the presence of farnesyl pyrophosphate did not prevent the atorvastatin effect on thrombin-induced tissue factor activity. Rho-kinase inhibitor did not affect the thrombin stimulation of tissue factor activity. High amount of hydrophobic isoprenoid groups decreases the thrombin-induced TF activity and may promote endothelial cell anti-thrombotic action. Rho kinase pathways do not have a major role in the thrombin-mediated TF activity. The inhibitory effect of atorvastatin on thrombin-induced TF activity was partially reversed by MVA and GGPP but not FPP.

Postoperative Statin Therapy Attenuates the Intensity of Systemic Inflammation and Increases Fibrinolysis After Coronary Artery Bypass Grafting

A total of 25 patients undergoing coronary artery bypass grafting (CABG) were included in the study. Patients received statin (20 mg daily) postoperatively for 2 weeks. All analyses were performed at 2 different time points: preoperatively (group 1) and 2 weeks after operation (group 2). Interleukin (IL)-6, IL-8, plasminogen activator inhibitor 1 (PAI-1), tumor necrosis factor α (TNF-α), tissue plasminogen activator (t-PA) levels, and tissue factor pathway inhibitor (TFPI) were evaluated. Statin treatment caused a significant reduction in the plasma level of PAI-1 (preop: 15.04 ± 0.13 ng/mL vs postop: 13.89 ± 2.14 ng/mL; P < .05) and increased t-PA levels (preop: 109.74 ± 0.13 vs postop: 231.40 ± 1.22 ng/mL; P < .001). Plasma TNF-α and IL-6 levels did not change with treatment. Statin treatment caused a significant reduction in plasma IL-8 level (279.70 ± 3.42 ng/mL vs postop: 207.18 ± 3.63 ng/mL, P < .05), and TFPI (4.87 ± 2.05 ng/mL vs postop: 6.27 ± 1.25 ng/mL; P < .05). The results demonstrate that atorvastatin attenuates systemic inflammatory reaction after cardiac surgery.

Inhibition of platelet-rich arterial thrombus in vivo: acute antithrombotic effect of intravenous HMG-CoA reductase therapy

OBJECTIVE

To test the hypothesis that statins will acutely inhibit platelet thrombus formation, intravenous lovastatin was assessed in our well-characterized porcine carotid injury model.

METHODS AND RESULTS

The first carotid artery was crush-injured and harvested after 30 minutes. Pigs then received intravenous lovastatin (100 microg/kg bolus+100 microg/kg/h infusion, n=6) or saline (n=11) before injury of the second carotid artery. Thrombus size was quantified by scintillation detection of autologous (111)In-platelets. Sequential carotid injury produced a thrombus more than 50% greater in volume in the second (3149+/-2053 x 10(6)/cm(2)) relative to the first injured artery (2081+/-1552 x 10(6)/cm(2); P=0.04) in control pigs. This augmentation was inhibited by intravenous lovastatin which acutely reduced platelet deposition (944+/-246 x 10(6)/cm(2)) relative to saline control (P=0.02). Flow chamber closure times increased on average by 2.45-fold in response to whole blood lovastatin incubation. Lovastatin (P<0.05) and simvastatin (P<0.05) reduced platelet dense granule secretion in vitro.

CONCLUSIONS

Sequential arterial injury augments the thrombotic response suggesting that the propensity for arterial thrombosis is at least partially acquired. This thrombotic augmentation can be acutely attenuated by intravenous lovastatin which may result from a pleiotropic impact on platelet function. These results appear to be a class effect of 3-hydroxy-3-methyl-glutaryl-CoA reductase inhibitors.

Can we use statins to prevent stroke in Fabry disease?

Fabry disease is a rare, X-linked lysosomal storage disease caused by an inborn deficiency of alpha-galactosidase A, which results in the progressive accumulation of globotriaosylceramide and other neutral glycolipids in a range of cells and tissues. In association with the renal and cardiac insufficiency, cerebrovascular complications can result in the death of the patients. Several mechanisms causing vascular damage that leads to the development of deep-white matter lesions have been described. Recent clinical trials strongly suggest that statins protect against stroke by neuroprotective properties or pleiotropic effects.

AIM

To evaluate evidence and potential beneficial effects of statins in the vasculopathy of Fabry disease.

Statins: mechanisms of neuroprotection

Clinical trials report that the class of drugs known as statins may be neuroprotective in Alzheimer's and Parkinson's disease, and further trials are currently underway to test whether these drugs are also beneficial in multiple sclerosis and acute stroke treatment. Since statins are well tolerated and have relatively few side effects, they may be considered as viable drugs to ameliorate neurodegenerative diseases. However, the mechanism of their neuroprotective effects is only partly understood. In this article, we review the current data on the neuroprotective effects of statins and their underlying mechanisms. In the first section, we detail the mechanisms by which statins affect cellular signalling. The primary action of statins is to inhibit cellular cholesterol synthesis. However, the cholesterol synthesis pathway also has several by-products, the non-sterol isoprenoids that are also important in cellular functioning. Furthermore, reduced cholesterol levels may deplete the cholesterol-rich membrane domains known as lipid rafts, which in turn could affect cellular signalling. In the second section, we summarize how the effects on signalling translate into general neuroprotective effects through peripheral systems. Statins improve blood-flow, reduce coagulation, modulate the immune system and reduce oxidative damage. The final section deals with the effects of statins on the central nervous system, particularly during Alzheimer's and Parkinson's disease, stroke and multiple sclerosis.

Tissue factor in the antiphospholipid syndrome

Antiphospholipid (aPL) antibodies are clinically important acquired risk factors for thrombosis and pregnancy loss and are thought to have a direct prothrombotic effect in vivo. Data suggest that a major mechanism by which aPL antibodies contribute to thrombophilia is the upregulation of tissue factor (TF) (CD142) on blood cells and vascular endothelium. TF is the physiological trigger of normal blood coagulation and thrombosis in many hypercoagulable conditions. This article reviews the physiology of TF, the molecular regulation of TF expression and the effects of aPL antibodies on intravascular TF regulation and expression. Inhibition of TF and the pathways by which aPL antibodies induce TF expression are potentially attractive therapeutic targets in the antiphospholipid syndrome.

Statins and stroke

Statins play an important role in brain ischemia. These drugs reduce cholesterol levels, which have been related to a reduction in vascular event risk, but they also have other functions besides cholesterol metabolism, called pleiotropic effects. Statins play an important role during the acute phase of ischemia, and might have neuroprotective effects, as they act in several mechanisms during the acute phase of stroke, such as in nitric oxide (NO) and glutamate metabolism, inflammation, platelet aggregation, immune responses and apoptosis. They also have other functions that can be related, with better long-term outcome, to neurorepair mechanisms. Statins promote angiogenesis, endogenous cell proliferation, neurogenesis and new synapse formation.

Tissue factor +5466A>G polymorphism determines thrombin formation following vascular injury and thrombin-lowering effects of simvastatin in patients with ischemic heart disease

OBJECTIVE

We examined the hypothesis that the +5466A>G variant (rs3917643) of the tissue factor (TF) gene is associated with thrombin formation following simvastatin in patients with ischemic heart disease (IHD).

METHODS AND RESULTS

Prothrombin 1.2 fragments (F1.2) and thrombin-antithrombin complexes (TAT) were assessed in 95 men with stable IHD, aged 54.4+/-6.8 years, in blood collected every 60s from the bleeding-time wounds before and after a 3-month simvastatin administration (40 mg/day). We identified 16 patients with the TF +5466AG genotype and 79 subjects with the +5466AA genotype. Baseline maximum rates of F1.2 and TAT formation and their maximum levels at the site of vascular injury, but not in venous blood, were higher in +5466G allele carriers than in those with +5466AA genotype (P<0.0001). The magnitude of reduction in maximum rates of F1.2 and TAT formation following simvastatin was larger (P<0.001) in +5466G allele carriers than in +5466AA subjects. The degree of decrease in maximum local levels of F1.2 and TAT after simvastatin was similar in both genotype groups. The presence of the +5466G allele was independently associated with the maximum velocity of F1.2 and TAT generation and maximum levels of both markers before and after simvastatin in multiple regression models (P<0.01 for all analyses). Local thrombin generation, in +5466AG and +5466AA subjects, showed no significant correlations with lipid variables.

CONCLUSIONS

Thrombin formation following vascular injury and thrombin-lowering effect of statins in patients with IHD are at least in part genetically determined by the TF +5466A>G polymorphism.

Statins inhibit toll-like receptor 4-mediated lipopolysaccharide signaling and cytokine expression

OBJECTIVE

Toll-like receptor 4 (TLR4) is the main receptor for Lipopolysaccharide (LPS). Two relatively common variants of the TLR4 gene are present, resulting in changes from aspartic acid (D) to glycine (G) at residue 299 and from threonine (T) to isoleucine (I) at residue 399, respectively. It has been shown that statins have a greater effect on lowering risk of cardiovascular events in individuals carrying the 299G allele than in those not carrying this allele. We investigated possible mechanisms underlying this synergy of statin treatment and TLR4 genotype.

METHODS AND RESULTS

In cells expressing the 299D-399T TLR4, LPS activated the transcription factor NFkappaB and increased the expression of interleukin-6 and tumor necrosis factor-alpha, and these effects were reduced by pretreatment of the cells with pravastatin or simvastatin. LPS-induced NFkappaB activation and interleukin-6 and tumor necrosis factor-alpha expression were substantially reduced in cell expressing the 299G-399T or 299D-399I variant, and undetectable in cells expressing the 299G-399I TLR4. The 3-hydroxy-3-methylglutaryl coenzyme A pathway inhibitors, Y27632 and GGTI-286, exhibited a similar effect to statins, suggesting that the inhibitory effect of statins was mediated by the 3-hydroxy-3-methylglutaryl coenzyme A pathway.

CONCLUSION

The results of this study indicate that the TLR4 variations and statins have an additive inhibitory effect on TLR4-mediated inflammatory response, providing a potential explanation for the finding that the beneficial effect of statins on cardiovascular risk is dependent on TLR4 genotype.

Spectrum of pleiotropic effects of statins in heart failure

The syndrome of heart failure is characterized by increased levels of circulating inflammatory mediators, which have been implicated in the pathogenesis of heart failure. Recently, a number of studies have suggested that statins may exert salutary effects in patients who have heart failure by virtue of their pleiotropic (non-lipid lowering) actions. This article focuses on the non-lipid lowering effects of statins, with an emphasis on the anti-inflammatory properties of these agents.

Antiphospholipid antibody effects on monocytes

Although the presence of autoantibodies is known to increase the risk of thrombosis in the antiphospholipid syndrome, the mechanism by which these antibodies exert their effects is poorly understood. Several studies suggest that autoantibody-mediated dysregulation of monocytes is one pathobiologic mechanism of this disease. Recent studies have focused on extra- and intracellular interactions involved in monocyte activation and expression of procoagulant activity. Agents specifically targeting monocyte activation and activity may provide a novel and efficacious approach that is safer than current antithrombotics.

Prevention of stroke and dementia by statin therapy: Experimental and clinical evidence of their pleiotropic effects

Stroke and dementia are major causes of disability in most countries. Epidemiological studies have demonstrated that statins (3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors) are likely to reduce the risk for developing these formidable disorders. The favorable outcomes in statin users may be attributable to not only cholesterol-dependent actions, but also various cholesterol-independent actions called "pleiotropic effects." Several clinical trials have suggested that statins decrease the incidence of stroke, especially ischemic stroke. Statins improve endothelial function, inhibit platelet activation, reduce blood coagulability, and suppress inflammatory reactions, all of which may contribute to the beneficial effects of the therapy. Statins also reduce the risk of vasospasm caused by subarachnoid hemorrhage (SAH). In addition, statins might inhibit the development and progression of Alzheimer's disease (AD), the dominant type of dementia in most industrialized countries, upstream of the amyloid cascade. In vitro studies have shown that statins modulate the metabolism of the beta-amyloid precursor protein (APP) and reduce the extracellular level of its proteolytic product, amyloid-beta (Abeta). The aggregated Abeta is cytotoxic, leading to formation of neurofibrillary tangles and neuronal loss in the brain. Inflammatory processes are active in AD and may contribute significantly to AD pathology. We review the experimental background regarding the pleiotropic effects of statins and summarize clinical trials that examined the preventative effects of statin therapy on stroke and dementia. We include current trials in which statin therapy is initiated within 24 hr of onset of acute ischemic stroke.

From pathophysiology to targeted therapy for atherothrombosis: A role for the combination of statin and aspirin in secondary prevention

Atherothrombosis results from direct interaction between the atherosclerotic plaque and arterial thrombosis, and underlies most forms of cardiovascular disease (CVD). The pathophysiology of atherosclerosis is now recognised to involve endothelial dysfunction and dyslipidemia with cholesterol accumulation, as well as critical immuno-inflammatory and apoptotic dimensions. Erosion or rupture of a vulnerable, lipid-rich, inflammatory atherosclerotic plaque triggers the formation of a platelet-rich thrombus that may partially or completely occlude the artery, with resultant clinical scenarios including stable and unstable angina, acute myocardial infarction (MI) and ischaemic stroke. Insight into the pathophysiology of atherothrombosis indicates that an integrated risk factor approach, focusing particularly on management of dyslipidaemia (with a statin) and thrombosis (with aspirin), may constitute an optimal therapeutic approach. Both agents have established roles in secondary prevention. Statin action on atherogenic lipoproteins mediates plaque stabilisation, modification of plaque morphology and attenuation of inflammation, and may lead to plaque regression, while aspirin reduces platelet activation and aggregation, decreases release of inflammatory cytokines at sites of vascular injury and attenuates vasoconstriction. Given these complementary modes of action, this combination would be a logical choice for reducing atherothrombotic risk in patients with CVD. Meta-analysis of 5 major clinical studies has demonstrated that the combination of pravastatin plus aspirin was significantly more effective than either agent alone in reducing the relative risk of key cardiovascular endpoints including MI and ischaemic stroke. This combination may therefore represent an important, cost-efficient therapeutic approach to reduction of cardiovascular risk and prevention of recurrent events in stable CVD.

Combined therapy with ramipril and simvastatin has beneficial additive effects on tissue factor activity and prothrombin fragment 1+2 in patients with type 2 diabetes

Tissue factor (TF) plays a pivotal role in thrombus formation. Statins and angiotensin converting enzyme inhibitors attenuate expression of TF by distinct mechanism. Therefore, we hypothesized that combined therapy with simvastatin and ramipril may have additive beneficial anti-atherogenic effects to lower TF activity when compared with either drug alone. This was a randomized, double-blind, placebo-controlled cross-over trial with three treatment arms (each 2 months) and two washout periods (each 2 months). Fifty patients with type 2 diabetes were given simvastatin 20 mg and placebo, simvastatin 20 mg and ramipril 10 mg, or ramipril 10 mg and placebo daily during each treatment period. Simvastatin and ramipril monotherapy tended to reduce TF activity (0.53 to 0.46 nM, P=0.056; 0.54 to 0.50 nM, P=0.167, respectively) while combined therapy had a significant effect (0.64 to 0.43 nM, P<0.001). All three therapies significantly reduced prothrombin fragment 1+2 (F1+2) levels from their respective baselines (P=0.037, P<0.001, and P=0.057, respectively). Combined therapy significantly reduced TF activity and F1+2 levels to a greater extent than either simvastatin or ramipril alone (P=0.029 and P=0.040 by ANOVA, respectively). Percent changes in TF activity and percent changes in F1+2 levels were significantly correlated. All three therapies reduced CD40 ligand levels from their respective baselines (P=0.098, P<0.001, and P=0.002, respectively) with no significant differences among these three therapies (P=0.204 by ANOVA). Ramipril combined with simvastatin significantly reduces plasma TF activity and F1+2 levels to a greater extent than monotherapy with either drug in patients with type 2 diabetes.

Low-Density Lipoprotein-Lowering Medication and Platelet Function

Elevated low-density lipoprotein (LDL) cholesterol (LDL-C) levels represent one of the most important risk factors for atherosclerosis and therefore cardiovascular morbidity and mortality. LDL-C operates at different levels and through various classic and non-classic mechanisms. In particular, increased or modified LDL enhances platelet function and increases sensitivity of platelets to several naturally occurring agonists. Agents that lower LDL-C in hypercholesterolemic patients have been shown to interfere with platelet function. Several studies, in fact, suggested that statins exert anti-thrombotic effects largely as a result of an anti-platelet activity. Among the other LDL-C-lowering agents those acting by interfering with cholesterol reabsorption from the gut (cholestyramine, colestipol) do not appear to interfere with platelet function, whereas peroxisome proliferator-activated receptor agonists (such as fibrates) can inhibit platelet function. The full potential of these drugs in vascular protection is only just being realized. Further studies are still needed to elucidate the full therapeutic benefits of these agents in plaque stabilization and thrombosis.

Increased Levels of Soluble CD40L in African Tick Bite Fever: Possible Involvement of TLRs in the Pathogenic Interaction betweenRickettsia africae, Endothelial Cells, and Platelets

The pathophysiological hallmark of spotted fever group rickettsioses comprises infection of endothelial cells with subsequent infiltration of inflammatory cells. Based on its ability to promote inflammation and endothelial cell activation, we investigated the role of CD40L in African tick bite fever (ATBF), caused by Rickettsia africae, using different experimental approaches. Several significant findings were revealed. 1) Patients with ATBF (n = 15) had increased serum levels of soluble CD40 ligand (sCD40L), which decreased during follow-up. 2) These enhanced sCD40L levels seem to reflect both direct and indirect (through endothelial cell activation involving CX3CL1-related mechanisms) effects of R. africae on platelets. 3) In combination with sCD40L, R. africae promoted a procoagulant state in endothelial cells by up-regulating tissue factor and down-regulating thrombomodulin expression. 4) Although the R. africae-mediated activation of platelets involved TLR2, the combined procoagulant effects of R. africae and sCD40L on endothelial cells involved TLR4. 5) Doxycycline counteracted the combined procoagulant effects of R. africae and sCD40L on endothelial cells. Our findings suggest an inflammatory interaction between platelets and endothelial cells in ATBF, involving TLR-related mechanisms. This interaction, which includes additive effects between sCD40L and R. africae, may contribute to endothelial inflammation and hypercoagulation in this disorder.

C-reactive protein contributes to the hypercoagulable state in coronary artery disease

OBJECTIVES

Elevated plasma C-reactive protein (CRP) levels predict coronary events, but it is unclear whether CRP plays a role in thrombosis associated with these events. We investigated tissue factor (TF) induction by CRP on peripheral blood mononuclear cells (PBMC) from patients with coronary disease.

PATIENTS AND METHODS

PBMC from 35 patients with stable angina (SA) in study 1, 10 male patients with SA, 10 with unstable angina (UA) and 10 matched controls in study 2, and 25 patients with inflammatory disorders (ID) and 24 normal controls in study 3 were stimulated with CRP, interferon-gamma (IFN) or lipopolysaccharide (LPS), or their combination. PBMC from additional normal donors were also stimulated with CRP in adherent and non-adherent conditions, and TF activity, antigen and mRNA expression detected.

RESULTS

CRP (5-25 microg mL(-1)) dose dependently induced more TF on PBMC from SA patients than 42 contemporary controls (P = 0.001, study 1). Compared with controls, patients with SA or UA had higher basal, and much higher CRP- or CRP/LPS-induced monocyte TF activity although serum CRP levels were similar (study 2). IFN induced monocyte TF activity in patients with angina, but not in controls. Basal or CRP-induced TF levels did not differ between controls and ID, even though ID patients had much higher serum CRP levels (study 3). CRP-induced monocyte TF activity correlated with serum CRP levels in controls (P = 0.005) and ID (P = 0.007) in study 3, but not in patients with angina (P =0.84) in study 2. CRP induced more TF activity, protein and mRNA under adherent than non-adherent conditions implying that it may mainly target macrophages in lymphocyte-rich lesions.

CONCLUSIONS

Our results indicate that monocytes from patients with angina are preactivated and express TF but CRP is unlikely to be a major priming factor in vivo. IFN and CRP further increase TF levels that may contribute to the hypercoagulable state in coronary disease.

Simvastatin blunts endotoxin-induced tissue factor in vivo

BACKGROUND

Beyond lipid lowering, various antiinflammatory properties have been ascribed to statins. Moreover, in vitro studies have suggested the presence of anticoagulant effects of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, as lipopolysaccharide (LPS)-induced monocyte tissue factor (TF) was suppressed. In this study, we examined the role of statins in experimental endotoxemia on inflammatory and procoagulant responses in vivo.

METHODS AND RESULTS

In this double-blind, placebo-controlled, parallel-group study, 20 healthy, male subjects were randomized to receive either simvastatin (80 mg/d) or placebo for 4 days before intravenous administration of LPS (20 IU/kg IV). Plasma high-sensitive C-reactive protein (hsCRP), monocyte chemoattractant protein (MCP-1), sCD40L, sCD40, and prothrombin fragment F1+2 (F1.2) were determined by ELISAs at baseline and at 4 and 8 hours after LPS administration. Monocyte TF expression and monocyte-platelet aggregates were measured by whole-blood flow cytometry over the same time course. The increases in hsCRP and MCP-1, both known inducers of TF, were significantly suppressed by statin treatment after LPS challenge. Statin premedication blunted the increase of monocyte TF expression in response to LPS. In parallel, endotoxin-induced formation of F1.2 was significantly reduced by simvastatin after 4 and 8 hours. LPS infusion affected neither the formation and activation of monocyte-platelet aggregates nor plasma levels of sCD40 and sCD40L.

CONCLUSIONS

Simvastatin suppresses the inflammatory response to endotoxin and blunts monocyte TF expression but does not affect platelet activation.

The case for intensive statin therapy after acute coronary syndromes

Acute coronary syndromes (ACS) consist of unstable angina or acute myocardial infarction and are associated with a high risk of early recurrent ischemic events. Revascularization procedures do not modify underlying pathophysiology and only modestly reduce early ischemic events after an index episode of ACS. Although statins improve dyslipidemia and cardiovascular risk over the long term, efforts to identify new ACS treatments are focusing on the ability of statins to modify the arterial wall-blood interface and reduce the risk of early recurrent ischemic events. Statins have been shown to reduce circulating markers of inflammation within days of an acute ischemic event. Short-term statin therapy also has been associated with improved coronary endothelial function, reversal of prothrombotic states, and reduction in atherosclerotic plaque volume. Findings from 6 randomized, controlled intervention trials were evaluated to determine if risk reduction is associated with the intensity of statin therapy. In addition, the predictive ability of baseline lipid levels and inflammatory markers were examined. High-intensity statin therapy (atorvastatin 80 mg) reduced early recurrent ischemic events after ACS compared with moderate-intensity treatment (eg, pravastatin 40 mg) or placebo. Moderate-intensity regimens (simvastatin 40 mg, pravastatin 20 to 40 mg, fluvastatin 80 mg, cerivastatin 0.4 mg) provided minimal benefit compared with placebo. Although there was no apparent relation between low-density lipoprotein (LDL) cholesterol levels before or during randomized treatment and short-term (4-month) risk of recurrent events, the degree of LDL cholesterol reduction with statin treatment after ACS may be related to longer-term event reduction. Moreover, evidence suggests that anti-inflammatory effects of high-intensity statin treatment are associated with clinical benefit.

Losartan and simvastatin inhibit platelet activation in hypertensive patients

BACKGROUND

Diabetic patients also show hypercoagulability and platelet hyperaggregability, with increased levels of platelet activation-markers such as P-selectin (CD62P) and platelet-derived microparticles. We investigated the effects of losartan and simvastatin on circulating levels of platelet activation markers, microparticles, soluble selectins, and soluble cell adhesion molecules in hypertensive and hyperlipidemic patients with or without Type 2 diabetes.

METHODS

The subjects included 25 normotensive healthy controls and 41 hypertensive patients. The 41 hypertensive patients were divided into three groups: group A had hypertension and hyperlipidemia (n = 11), group B had hypertension and Type 2 diabetes (n = 14), and group C had hypertension, hyperlipidemia, and diabetes (n = 16). Losartan was administered to all of the patients at a dose of 50 mg/day for 24 weeks. In addition, simvastatin was administered to the hyperlipidemic patients at a dose of 10 mg/day for 24 weeks.

RESULTS

There were significant differences in the levels of CD62P, CD63, PAC-1, platelet microparticles, endothelial microparticles, sE-selectin, and sVCAM-1 between the hypertensive patients and healthy controls. These markers were all significantly increased in hypertensive and hyperlipidemic patients with Type 2 diabetes. In hypertensive patients with diabetes, CD62P, CD63, PAC-1, platelet and endothelial microparticles, and soluble adhesion markers were all decreased by losartan monotherapy. The decrease of each marker in hypertensive and hyperlipidemic patients given combined therapy with losartan plus simvastatin was greater among those with than without Type 2 diabetes. Low-density lipoprotein was decreased significantly by simvastatin and was correlated with CD62P or platelet microparticles in all of the patients.

CONCLUSION

Administration of losartan plus simvastatin to hypertensive and hyperlipidemic patients with Type 2 diabetes may prevent the development of cardiovascular complications caused by activated platelets and microparticles via another mechanism in addition to reduction of the blood pressure or lipid levels.