Vastatins inhibit tissue factor in cultured human macrophages. A novel mechanism of protection against atherothrombosis

Developing a Biomimetic 3D Neointimal Layer as a Prothrombotic Substrate for a Humanized In Vitro Model of Atherothrombosis

Acute cardiovascular events result from clots caused by the rupture and erosion of atherosclerotic plaques. This paper aimed to produce a functional biomimetic hydrogel of the neointimal layer of the atherosclerotic plaque that can support thrombogenesis upon exposure to human blood. A biomimetic hydrogel of the neointima was produced by culturing THP-1-derived foam cells within 3D collagen hydrogels in the presence or absence of atorvastatin. Prothrombin time and platelet aggregation onset were measured after exposure of the neointimal models to platelet-poor plasma and washed platelet suspensions prepared from blood of healthy, medication-free volunteers. Activity of the extrinsic coagulation pathway was measured using the fluorogenic substrate SN-17. Foam cell formation was observed following preincubation of the neointimal biomimetic hydrogels with oxidized LDL, and this was inhibited by pretreatment with atorvastatin. The neointimal biomimetic hydrogel was able to trigger platelet aggregation and blood coagulation upon exposure to human blood products. Atorvastatin pretreatment of the neointimal biomimetic layer significantly reduced its pro-aggregatory and pro-coagulant properties. In the future, this 3D neointimal biomimetic hydrogel can be incorporated as an additional layer within our current thrombus-on-a-chip model to permit the study of atherosclerosis development and the screening of anti-thrombotic drugs as an alternative to current animal models.

HMG-CoA reductase inhibitors and the attenuation of risk for disseminated intravascular coagulation in patients with sepsis

BACKGROUND

Disseminated Intravascular Coagulation (DIC) is a syndrome of dysregulated coagulation. Patients with sepsis are at increased risk for DIC. HMG-CoA Reductase Inhibitors (Statins) are primarily used as lipid-lowering agents; however, studies have suggested statins may possess anti-inflammatory, antithrombotic, anticoagulant, and endothelial stabilizing properties. These mechanisms may oppose those that underlie the pathogenesis of septic DIC.

METHODS

To evaluate whether statins may be protective against the development of DIC, we conducted a multi-center, retrospective case-control study where 86,638 critically ill patients admitted to the ICU with sepsis, severe sepsis or septic shock were identified during a 3-year period. Patients who developed DIC during their hospitalization were identified and stratified by whether they received a statin or not during their hospitalization. Odds ratios for development of DIC was calculated by composite of any statin, as well as low, moderate, and high intensity statins.

RESULTS

2236 patients would develop DIC compared to 84,402 who did not. The use of any statin was associated with a reduced likelihood for developing DIC (odds ratio [OR], 0.69; 95% CI, 0.61-0.78). This was observed with use of both moderate (OR, 0.64; 95% CI, 0.53-0.77) and high (OR, 0.72; 95% CI, 0.61-0.84) but not low intensity statins (OR, 0.84; 95% CI, 0.53-1.32).

CONCLUSIONS

The use of moderate and high intensity statins was associated with a significantly reduced odds of developing DIC in critically ill patients with sepsis. This present study may be the first to suggest that statin medications may independently reduce the frequency of DIC in critically ill patients with severe sepsis or septic shock. More research is needed to investigate the potential for this class of medication to be protective against DIC.

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.

Strategies for Therapeutic Amelioration of Aberrant Plasma Zn2+ Handling in Thrombotic Disease: Targeting Fatty Acid/Serum Albumin-Mediated Effects

The initiation, maintenance and regulation of blood coagulation is inexorably linked to the actions of Zn²⁺ in blood plasma. Zn²⁺ interacts with a variety of haemostatic proteins in the bloodstream including fibrinogen, histidine-rich glycoprotein (HRG) and high molecular weight kininogen (HMWK) to regulate haemostasis. The availability of Zn²⁺ to bind such proteins is controlled by human serum albumin (HSA), which binds 70–85% of plasma Zn²⁺ under basal conditions. HSA also binds and transports non-esterified fatty acids (NEFAs). Upon NEFA binding, there is a change in the structure of HSA which leads to a reduction in its affinity for Zn²⁺. This enables other plasma proteins to better compete for binding of Zn²⁺. In diseases where elevated plasma NEFA concentrations are a feature, such as obesity and diabetes, there is a concurrent increase in hypercoagulability. Evidence indicates that NEFA-induced perturbation of Zn²⁺-binding by HSA may contribute to the thrombotic complications frequently observed in these pathophysiological conditions. This review highlights potential interventions, both pharmaceutical and non-pharmaceutical that may be employed to combat this dysregulation. Lifestyle and dietary changes have been shown to reduce plasma NEFA concentrations. Furthermore, drugs that influence NEFA levels such as statins and fibrates may be useful in this context. In severely obese patients, more invasive therapies such as bariatric surgery may be useful. Finally, other potential treatments such as chelation therapies, use of cholesteryl transfer protein (CETP) inhibitors, lipase inhibitors, fatty acid inhibitors and other treatments are highlighted, which with additional research and appropriate clinical trials, could prove useful in the treatment and management of thrombotic disease through amelioration of plasma Zn²⁺ dysregulation in high-risk individuals.

Biological Actions, Implications, and Cautions of Statins Therapy in COVID-19

The Coronavirus Disease 2019 (COVID-19) showed worse prognosis and higher mortality in individuals with obesity. Dyslipidemia is a major link between obesity and COVID-19 severity. Statins as the most common lipid regulating drugs have shown favorable effects in various pathophysiological states. Importantly, accumulating observational studies have suggested that statin use is associated with reduced risk of progressing to severe illness and in-hospital death in COVID-19 patients. Possible explanations underlie these protective impacts include their abilities of reducing cholesterol, suppressing viral entry and replication, anti-inflammation and immunomodulatory effects, as well as anti-thrombosis and anti-oxidative properties. Despite these benefits, statin therapies have side effects that should be considered, such as elevated creatinine kinase, liver enzyme and serum glucose levels, which are already elevated in severe COVID-19. Concerns are also raised whether statins interfere with the efficacy of COVID-19 vaccines. Randomized controlled trials are being conducted worldwide to confirm the values of statin use for COVID-19 treatment. Generally, the results suggest no necessity to discontinue statin use, and no evidence suggesting interference between statins and COVID-19 vaccines. However, concomitant administration of statins and COVID-19 antiviral drug Paxlovid may increase statin exposure and the risk of adverse effects, because most statins are metabolized mainly through CYP3A4 which is potently inhibited by ritonavir, a major component of Paxlovid. Therefore, more clinical/preclinical studies are still warranted to understand the benefits, harms and mechanisms of statin use in the context of COVID-19.

The Immunomodulatory Effects of Statins on Macrophages

Statins are 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors used worldwide to manage dyslipidaemia and thus limit the development of atherosclerotic disease and its complications. These atheroprotective drugs are now known to exert pleiotropic actions outside of their cholesterol-lowering activity, including altering immune cell function. Macrophages are phagocytic leukocytes that play critical functional roles in the pathogenesis of atherosclerosis and are directly targeted by statins. Early studies documented the anti-inflammatory effects of statins on macrophages, but emerging evidence suggests that these drugs can also enhance pro-inflammatory macrophage responses, creating an unresolved paradox. This review comprehensively examines the in vitro, in vivo, and clinical literature to document the statin-induced changes in macrophage polarization and immunomodulatory functions, explore the underlying mechanisms involved, and offer potential explanations for this paradox. A better understanding of the immunomodulatory actions of statins on macrophages should pave the way for the development of novel therapeutic approaches to manage atherosclerosis and other chronic diseases and conditions characterised by unresolved inflammation.

Fluvastatin mitigates SARS-CoV-2 infection in human lung cells

Clinical data of patients suffering from COVID-19 indicates that statin therapy, used to treat hypercholesterolemia, is associated with a better disease outcome. Whether statins directly affect virus replication or influence the clinical outcome through modulation of immune responses is unknown. We therefore investigated the effect of statins on SARS-CoV-2 infection in human lung cells and found that only fluvastatin inhibited low and high pathogenic coronaviruses in vitro and ex vivo in a dose-dependent manner. Quantitative proteomics revealed that fluvastatin and other tested statins modulated the cholesterol synthesis pathway without altering innate antiviral immune responses in infected lung epithelial cells. However, fluvastatin treatment specifically downregulated proteins that modulate protein translation and viral replication. Collectively, these results support the notion that statin therapy poses no additional risk to individuals exposed to SARS-CoV-2 and that fluvastatin has a moderate beneficial effect on SARS-CoV-2 infection of human lung cells.

Antithrombotics and new interventions for venous thromboembolism: Exploring possibilities beyond factor IIa and factor Xa inhibition

Direct oral anti-activated factor X and antithrombin agents have largely replaced vitamin K antagonists as the standard of care in treatment of venous thromboembolism. However, gaps in efficacy and safety persist, notably in end-stage renal disease, implantable heart valves or assist devices, extracorporeal support of the circulation, and antiphospholipid syndrome. Inhibition of coagulation factor XI (FXI) emerges as a promising new therapeutic target. Antisense oligonucleotides offer potential advantages as a prophylactic or therapeutic modality, with one dose-finding trial in orthopedic surgery already published. In addition, monoclonal antibodies blocking activation and/or activity of activated factor XI are investigated, as are small-molecule inhibitors with rapid offset of action. Further potential targets include upstream components of the contact pathway such as factor XII, polyphosphates, or kallikrein. Finally, catheter-directed, pharmacomechanical antithrombotic strategies have been developed for high- and intermediate-risk pulmonary embolism, and large randomized trials aiming to validate their efficacy, safety, and prognostic impact are about to start.

Prior Statin Therapy and Mortality After Extracorporeal Membrane Oxygenation Therapy: A Retrospective, Population-Based, Cohort Study

OBJECTIVE

To investigate whether prior statin therapy is associated with an improvement in mortality among patients who undergo extracorporeal membrane oxygenation (ECMO) therapy.

DESIGN

Retrospective, population-based, cohort study.

SETTING

Health records were obtained from the National Health Insurance Service database in South Korea.

PATIENTS

All adult patients (≥18 y) who underwent ECMO therapy in the intensive care unit between 2005 and 2018 were enrolled.

EXPOSURES

Statin users were defined as patients who were prescribed continuous oral statins ≥90 days before ECMO.

MEASUREMENTS AND MAIN RESULTS

The primary endpoint of this study was 90-day mortality. A total of 21,129 adult patients from 128 hospitals were included (4,737 [22.4%] statin users and 16,392 [77.6%] nonusers). After propensity score matching, 9,474 ECMO patients (4,737 in each group) were included in the final analysis. In the propensity-score-matched cohort, statin users exhibited lower 90-day mortality than did nonusers (58.6% [2,774/4,737] in statin users v 65.6% [3,106/4,737] in nonusers). In addition, on Cox regression, 90-day mortality in statin users was 14% less than that in nonusers (hazard ratio 0.86, 95% confidence interval 0.81-0.90; p < 0.001).

CONCLUSION

Among patients who underwent ECMO in South Korea, prior statin therapy was found to be associated with lower 90-day mortality rates after ECMO therapy. However, because this study had a retrospective design, future prospective trials are needed to confirm the findings.

Relationship between lipoproteins, thrombosis and atrial fibrillation

The prothrombotic state in atrial fibrillation (AF) occurs as a result of multifaceted interactions, known as Virchow’s triad of hypercoagulability, structural abnormalities, and blood stasis. More recently, there is emerging evidence that lipoproteins are implicated in this process, beyond their traditional role in atherosclerosis. In this review, we provide an overview of the various lipoproteins and explore the association between lipoproteins and AF, the effects of lipoproteins on haemostasis, and the potential contribution of lipoproteins to thrombogenesis in AF. There are several types of lipoproteins based on size, lipid composition, and apolipoprotein category, namely: chylomicrons, very low-density lipoprotein, low-density lipoprotein (LDL), intermediate-density lipoprotein, and high-density lipoprotein. Each of these lipoproteins may contain numerous lipid species and proteins with a variety of different functions. Furthermore, the lipoprotein particles may be oxidized causing an alteration in their structure and content. Of note, there is a paradoxical inverse relationship between total cholesterol and LDL cholesterol (LDL-C) levels, and incident AF. The mechanism by which this occurs may be related to the stabilizing effect of cholesterol on myocardial membranes, along with its role in inflammation. Overall, specific lipoproteins may interact with haemostatic pathways to promote excess platelet activation and thrombin generation, as well as inhibiting fibrinolysis. In this regard, LDL-C has been shown to be an independent risk factor for thromboembolic events in AF. The complex relationship between lipoproteins, thrombosis and AF warrants further research with an aim to improve our knowledge base and contribute to our overall understanding of lipoprotein-mediated thrombosis.

COVID-19 and Thromboinflammation: Is There a Role for Statins?

The novel coronavirus disease (COVID-19) showed increased morbidity and mortality rates and worse prognosis in individuals with underlying chronic diseases, especially cardiovascular disease and its risk factors, such as hypertension, diabetes, and obesity. There is also evidence of possible links among COVID-19, myocardial infarction, and stroke. Emerging evidence suggests a pro-inflammatory milieu and hypercoagulable state in patients with this infection. Despite anticoagulation, a large proportion of patients requiring intensive care may develop life-threatening thrombotic complications. Indeed, the levels of some markers of hemostatic activation, such as D-dimer, are commonly elevated in COVID-19, indicating potential risk of deep vein thrombosis and pulmonary thromboembolism. In this review, we critically examine and discuss aspects of hypercoagulability and inflammation in COVID-19 and the possible benefits of statins in this scenario, with emphasis on their underlying molecular mechanisms. Moreover, we present recommendations on the use of antiviral drugs in combination with statins.

Statins: Could an old friend help in the fight against COVID-19?

The COVID-19 pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has overwhelmed healthcare systems requiring the rapid development of treatments, at least, to reduce COVID-19 severity. Drug repurposing offers a fast track. Here, we discuss the potential beneficial effects of statins in COVID-19 patients based on evidence that they may target virus receptors, replication, degradation, and downstream responses in infected cells, addressing both basic research and epidemiological information. Briefly, statins could modulate virus entry, acting on the SARS-CoV-2 receptors, ACE2 and CD147, and/or lipid rafts engagement. Statins, by inducing autophagy activation, could regulate virus replication or degradation, exerting protective effects. The well-known anti-inflammatory properties of statins, by blocking several molecular mechanisms, including NF-κB and NLRP3 inflammasomes, could limit the "cytokine storm" in severe COVID-19 patients which is linked to fatal outcome. Finally, statin moderation of coagulation response activation may also contribute to improving COVID-19 outcomes. LINKED ARTICLES: This article is part of a themed issue on The Pharmacology of COVID-19. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.21/issuetoc.

Oxidized Low-Density Lipoprotein Induces Macrophage Production of Prothrombotic Microparticles

Background Activated vascular cells produce submicron prothrombotic and proinflammatory microparticle vesicles. Atherosclerotic plaques contain high levels of microparticles. Plasma microparticle levels increase during acute coronary syndromes and the thrombotic consequences of plaque rupture likely involve macrophage-derived microparticles (MΦMPs). The activation pathways that promote MΦMP production remain poorly defined. This study tested the hypothesis that signals implicated in atherogenesis also stimulate MΦMP production. Methods and Results We stimulated human primary MΦs with proinflammatory cytokines and atherogenic lipids, and measured MΦMP production by flow cytometry. Oxidized low-density lipoprotein (oxLDL; 25 µg/mL) induced MΦMP production in a concentration-dependent manner (293% increase; P<0.001), and these oxLDL MΦMP stimulatory effects were mediated by CD36. OxLDL stimulation increased MΦMP tissue factor content by 78% (P<0.05), and oxLDL-induced MΦMP production correlated with activation of caspase 3/7 signaling pathways. Salvionolic acid B, a CD36 inhibitor and a CD36 inhibitor antibody reduced oxLDL-induced MΦMP by 67% and 60%, respectively. Caspase 3/7 inhibition reduced MΦMP release by 52% (P<0.01) and caspase 3/7 activation increased MΦMP production by 208% (P<0.01). Mevastatin pretreatment (10 µM) decreased oxLDL-induced caspase 3/7 activation and attenuated oxLDL-stimulated MΦMP production and tissue factor content by 60% (P<0.01) and 43% (P<0.05), respectively. Conclusions OxLDL induces the production of prothrombotic microparticles in macrophages. This process depends on caspases 3 and 7 and CD36 and is inhibited by mevastatin pretreatment. These findings link atherogenic signaling pathways, inflammation, and plaque thrombogenicity and identify a novel potential mechanism for antithrombotic effects of statins independent of LDL lowering.

Statins reduce vascular inflammation in atherogenesis: A review of underlying molecular mechanisms

Chronic inflammation enhances the detrimental role of dyslipidaemia during atherogenesis. Statins are among the most effective anti-atherosclerotic medications, being able to impact on both cardiovascular morbidity and mortality. Although these molecules have been first described as lipid-lowering medications, several lines of evidence suggest additional benefits through their "pleiotropic" anti-atherosclerotic activities. Specifically, statins can modulate vascular atherosclerotic inflammation by directly improving functions of endothelial cells, vascular smooth muscle cells, platelets, and immune cells. Here, we discuss basic and clinical evidence to provide an update on the molecular mechanisms underlying the protective anti-inflammatory role of statins in atherogenesis.

Effect of Statins on Recurrent Venous Thromboembolism (from the COMMAND VTE Registry)

Statins, which are considered as essential for primary and secondary prevention of atherosclerotic diseases, were also reported to reduce first venous thromboembolism (VTE). However, the effect of statins on VTE recurrence remains conflicting. We aimed to examine the association between statin use and VTE recurrence in a large observational study in Japan. The COMMAND VTE Registry is a multicenter registry enrolling consecutive 3027 patients with acute symptomatic VTE in 29 centers in Japan between January 2010 and August 2014. In the current study, the entire cohort was divided into statin group (N = 437) and no-statin group (N = 2590) according to the status of statin use at baseline. The statin group as compared with the no-statin group was older (statin group 71.2 vs no-statin group 66.5 years, p <0.001), included more women (67% vs 60%, p = 0.008), and less frequently had active cancer (12% vs 25%, p <0.001). There was no significant difference in the clinical presentation of VTE (pulmonary embolism, 58% vs 56%, p = 0.44). The cumulative 3-year incidence of recurrent VTE was significantly lower in the statin group than the no-statin group (3.8% vs 8.8%, p <0.001). After adjusting for confounders including active cancer, statin use was associated with significantly lower risk for recurrent VTE (Hazard ratio 0.49, 95% confidence interval 0.29 to 0.78, p = 0.002). The results were consistent in a sensitivity sub-group analysis with and without active cancer. In conclusion, statin use was associated with significantly lower risk for the recurrent VTE in patients with VTE.

Rosuvastatin use improves measures of coagulation in patients with venous thrombosis

Aims

Observational studies indicate that statins reduce the risk of recurrent venous thrombosis (VT). However, trials have not been performed and the mechanism is unknown. We aimed to determine whether statin therapy improves the coagulation profile in patients with prior VT.

Methods and results

Randomized clinical trial (NCT01613794). Patients were randomized to rosuvastatin 20 mg/day for 4 weeks or no intervention. Blood was drawn at baseline and at end of study. The primary outcome was factor (F) VIII:C. In total, five coagulation factors were measured: FVIII:C, von Willebrand factor:Ag, FVII:C, FXI:C, and D-dimer. Among 247 randomized participants, mean age was 58 years, 62% were women and 49% had unprovoked VT. For all tested coagulation factors, mean levels were clearly decreased at end of study in rosuvastatin users, whereas they hardly differed in non-statin users. Results were most consistent for FVIII:C where mean FVIII:C levels were 7.2 IU/dL [95% CI (confidence interval) 2.9-11.5] lower in rosuvastatin users, while among non-users, no change in FVIII:C was observed (mean difference -0.1; 95% CI -3.0 to 2.9). The mean age and sex adjusted difference in FVIII:C change was -6.7 IU/dL (95% CI -12.0 to -1.4) in rosuvastatin users vs. non-users. Subgroup analyses revealed that the decrease in coagulation factors by rosuvastatin was more pronounced in participants with unprovoked VT and in those with cardiovascular risk factors.

Conclusion

Rosuvastatin 20 mg/day substantially improved the coagulation profile among patients with prior VT. These results suggest that statin therapy might be beneficial in patients at risk of recurrent VT.

A revised systematic review and meta-analysis on the effect of statins on D-dimer levels

BACKGROUND

D-dimers are generated during endogenous fibrinolysis of a blood clot and have a central role in diagnostic algorithms to rule out venous thromboembolism. HMG-CoA reductase inhibitors, more commonly called statins, are known to have effects independent of LDL-cholesterol lowering, including antithrombotic properties. An effect of statins on D-dimer levels has been reported in a prior systematic review and meta-analysis, but methodological shortcomings might have led to an overestimated effect. To re-evaluate the association between statins and D-dimer levels, we systematically reviewed all published articles on the influence of statins on D-dimer levels and conducted a novel meta-analysis (PROSPERO registration number CRD42017058932).

MATERIALS AND METHODS

We electronically searched EMBASE, Medline Epub, Cochrane, Web of Science and Google Scholar (100 top relevance) (date of last search: 5 October 2017). We included randomized controlled trials, cohort studies and cross-sectional studies. Two reviewers independently screened all articles retrieved and extracted data on study and patient characteristics, study quality and D-dimer levels.

RESULTS

Study-level meta-analysis involving 18,052 study participants showed lower D-dimer levels in those receiving statin treatment than controls (SMD: -0.165, 95% CI -0.234; -0.096, P = <0.001). Sensitivity analyses and additional analyses on treatment duration (<12 weeks vs ≥12 weeks) and type of statin (lipophilic or hydrophilic) did not modify this overall result.

CONCLUSION

This meta-analysis suggests an association between use of statins and reduction of D-dimer levels, independent of treatment duration and type of statin used. This effect is small but robust, and should be interpreted with caution.

Statin Use and Gastrointestinal Hemorrhage: A Large Retrospective Cohort Study

BACKGROUND

Nearly 70% of Americans with cardiovascular disease use statins, which have documented bleeding effects independent of their cholesterol-lowering activities. However, the literature is conflicting regarding the association between statin use and gastrointestinal hemorrhage.

OBJECTIVES

The aim of this study was to investigate the risk of gastrointestinal hemorrhage in statin users.

METHODS

In this retrospective cohort study, data from the Truven Health MarketScan^® Research Database (2009-2015) were used to investigate the risk of gastrointestinal hemorrhage amongst statin users aged 30-65 years at the initial prescription claim. Statin users and a group of negative controls (i.e. other chronic medication users) were followed until first gastrointestinal hemorrhage event (both inpatient and outpatient, as well as restricted to inpatient), and were censored at treatment discontinuation, disenrollment from coverage, or the end of the study period.

RESULTS

Statin users had an elevated risk of gastrointestinal hemorrhage, which was especially apparent in the first year of treatment (1-year adjusted hazard ratio 1.19; 95% confidence interval (CI) 1.15-1.23). The risk of gastrointestinal hemorrhage leading to hospitalization was even higher (1-year adjusted hazard ratio 1.38; 95% CI 1.30-1.69). High-intensity statin users had a greater rate of gastrointestinal hemorrhage than moderate-intensity users (incidence rates per 1000 subject-years 22.2 (95% CI 21.9-22.8) vs. 21.5 (95% CI 21.3-21.8), respectively).

CONCLUSIONS

In a population of commercially insured subjects aged 30-65 years, statin users had a higher risk for gastrointestinal hemorrhage than other chronic medication users. These findings are important when treating patients at a high risk for bleeding events.

Statins, haemostatic factors and thrombotic risk

PURPOSE OF REVIEW

Statins reduce cholesterol synthesis and promote low-density lipoprotein clearance from circulation. Beyond their cholesterol-lowering action, statins may interfere with haemostasis. This review aims to provide an update on the impact of statin treatment on markers of haemostasis and platelet function and on thrombosis-related outcomes.

RECENT FINDINGS

Different coagulation factors are modulated by statins, leading to inhibition of coagulation and increased fibrinolysis. Also, an impact of statins on platelet function has been documented. From a clinical perspective, several observational studies have revealed a reduced incidence of venous thromboembolism in patients receiving statins, which has been argued in some available studies and meta-analyses. Furthermore, a beneficial effect of early statin initiation following acute coronary syndrome for short-term prevention of thrombosis-related events has been documented, but the available data are still not consistent.

SUMMARY

Although statins influence the levels of a multitude of haemostatic factors in an antithrombotic direction, data supporting their use for venous thromboembolism prevention are not consistent, and the impact of statins on early vascular events following acute coronary syndrome is still debated. Whether the robust long-term beneficial effects of statins in reducing cardiovascular risk may be also explained by persistent changes in haemostatic factors needs further exploration.

Usefulness of Statins for Prevention of Venous Thromboembolism

Venous thromboembolism (VTE), including deep venous thrombosis and pulmonary embolism, is common with an annual incidence of 1 to 5 per 1,000, resulting in major morbidity, mortality, and increased health care costs. It is more common in the elderly, obese, those with cancer, those undergoing surgery, and those with previous VTE. Strategy to reduce its occurrence has important public health implications. Pleotropic effects of statins may have beneficial effects on a number of potential targets associated with VTE. Statins have excellent safety profile and seem to be associated with beneficial effects in VTE in case-control studies, large observational studies, meta-analyses, and a randomized trial. In conclusion, after critically reviewing the clinical data supporting statin use in the prevention of VTE, we presented clinical recommendations for the use of statins in reducing VTE occurrence, especially in high-risk situations.

The beneficial effects of HMG-CoA reductase inhibitors in the processes of neurodegeneration

Statins, cholesterol lowering drugs, have been demonstrated to exert beneficial effects in other conditions such as primary and progressing neurodegenerative diseases beyond their original role. Observation that statins ameliorate the neurodegenerative diseases such as Parkinson's disease (PD), Alzheimer's disease (AD), multiple sclerosis (MS) and cerebral ischemic stroke, the neuroprotective effects of these drugs are thought to be linked to their anti-inflammatory, anti-oxidative, and anti-excitotoxic properties. Despite the voluminous literature on the clinical advantages of 3-hydroxy-3-methylglutaryl Co-enzyme A reductase (HMGCR) inhibitors (statins) in cardiovascular system, the neuroprotective effects and the underlying mechanisms are little understood. Hence, the present review tries to provide a critical overview on the statin-induced neuroprotection, which are presumed to be associated with the ability to reduce cholesterol, Amyloid-β and apolipoprotein E (ApoE) levels, decrease reactive oxygen and nitrogen species (ROS and RNS) formation, inhibit excitotoxicity, modulate matrix metalloproteinases (MMPs), stimulate endothelial nitric oxide synthase (eNOS), and increase cerebral blood perfusion. This review is also aimed to illustrate that statins protect neurons against the neuro-inflammatory processes through balancing pro-inflammatory/anti-inflammatory cytokines. Ultimately, the beneficial role of statins in ameliorating the development of PD, AD, MS and cerebral ischemic stroke has been separately reviewed.

Influence of statin therapy at time of stroke onset on functional outcome among patients with atrial fibrillation

BACKGROUND

Statin pretreatment has been associated with reduced infarct volume in nonlacunar strokes. The effect of statins on functional outcomes of strokes related to atrial fibrillation (AF) is unknown. We aimed to define the influence of prestroke statin use on functional outcome in AF.

METHODS

We assembled a cohort of consecutive ischemic stroke patients from 2006 to 2010. All patients underwent CT or MRI and were adjudicated by site investigators. AF was confirmed by electrocardiogram in 100% of patients. Site neurologists blinded to the study hypothesis affirmed the type of stroke and assessed the severity of disability at the time of hospital discharge. The frequency of death at 30-days was calculated.

RESULTS

Ischemic stroke (n=1030) resulted in a severe neurological deficit or death (modified Rankin scale ≥4) at 30days in 711 patients (69%). Using multivariable logistic regression models adjusting for factors associated with statin treatment and factors associated with functional outcome, prestroke statin use was associated with a 32% reduction in frequency of severe stroke (odds ratio [OR], 0.68; 95% confidence interval [CI], 0.50-0.92; P=0.011). Other independent factors associated with severe stroke included older age, female sex, non-White race, diabetes mellitus, prior ischemic stroke, prior venous thromboembolism, and dementia.

CONCLUSION

Ischemic strokes in AF are associated with high mortality and morbidity. Statin use at time of stroke onset among patients with AF was associated in this study with less severe stroke and warrant validation.

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.

Different Effect of Statins on Platelet Oxidized-LDLReceptor (CD36 and LOX-1) Expressionin Hypercholesterolemic Subjects

Hydroxymethyl-glutaryl-CoA-reductase inhibitors (statins) reduce cardiovascular mortality by decreasing cholesterol as well as by non-lipid-related actions. Oxidized low-density lipoproteins (ox-LDL) are pro-atherogenic molecules and potent platelet agonists. CD36 and lectin-like ox-LDL receptor-1 (LOX-1) are specific ox-LDL receptors also expressed in platelets. This study was planned to address whether treatment with atorvastatin 10 mg/day, pravastatin 40 mg/day or simvastatin 20 mg/day could affect platelet CD36 and LOX-1 expression. Twenty-four patients for each treatment were evaluated after 3, 6, and 9 days and at 6 weeks for complete lipid profile (chromogenic), ox-LDL (ELISA), platelet P-selectin (P-sel), CD36, LOX-1 (FACS), and intracellular citrullin recovery (iCit) (HPLC). Data show hyperactivated platelets (P-sel absolute values, percent variation in activated cells, all p < 0.001), and CD36 and LOX-1 overexpression (all p < 0.001) in patients at baseline. P-sel, CD36, and LOX-1 were significantly decreased by atorvastatin and simvastatin (all p < 0.01) and related with iCit increase (r = 0.58,p < 0.001) and platelet-associated ox-LDL (r = 0.51, p < 0.01) at 9 days. Pravastatin reduced LOX-1 and P-sel (p < 0.05) at 6 weeks in relation with decreased LDL and ox-LDL (r = 0.39, p < 0.01 and r = 0.37, p < 0.01, respectively). These data suggest that atorvastatin and simvastatin reduce platelet activity by exposure of CD36 and LOX-1 before significant LDL reduction, whereas pravastatin action is detected later and in relation with LDL and ox-LDL lowering. Rapid and consistent reduction of CD36 and LOX-1 could be considered a direct anti-atherothrombotic mechanism related to the role of ox-LDL in platelet activation, platelet-endothelium interactions, and NO synthase activity.

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.

Do statins prevent Alzheimer's disease? A narrative review

Alzheimer's disease is the most common cause of dementia and occurs commonly in patients 65 and older. There is an urgent need to find an effective management that could help prevent or at least slow down the progress of this major public health problem. Cholesterol related pathways might play a role in the pathogenesis of Alzheimer's disease. Treatment with 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins) has been suggested to promote the prevention of Alzheimer's disease. In this review, we discuss potential pathogenetic pathways for the development of Alzheimer's disease and review the evidence regarding the value of statins as a strategy to prevent or delay progression of Alzheimer's disease.

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.

Is lipid lowering therapy an independent risk factor for venous thromboembolism? A population-based case-control study

INTRODUCTION

The independent effect of lipid lowering therapy (LLT) on venous thromboembolism (VTE) risk is uncertain.

OBJECTIVE

To test statin and non-statin LLT as potential VTE risk factors.

METHODS

Using Rochester Epidemiology Project resources, we identified all Olmsted County, MN residents with objectively diagnosed incident VTE (cases) over the 13-year period, 1988-2000 (n=1340), and one to two matched controls (n=1538). We reviewed their complete medical records for baseline characteristics previously identified as independent VTE risk factors, and for statin and non-statin LLT. Using conditional logistic regression, we tested the overall effect of LLT on VTE risk and also separately explored the role of statin versus that of non-statin LLT, adjusting for other baseline characteristics.

RESULTS

Among cases and controls, 74 and 111 received statin LLT, and 32 and 50 received non-statin LLT, respectively. Univariately, and after individually controlling for other potential VTE risk factors (i.e., BMI, trauma/fracture, leg paresis, hospitalization for surgery or medical illness, nursing home residence, active cancer, central venous catheter, varicose veins, prior superficial vein thrombosis, diabetes, congestive heart failure, angina/myocardial infarction, stroke, peripheral vascular disease, smoking, anticoagulation), LLT was associated with decreased odds of VTE (unadjusted OR=0.73; p=0.03). When considered separately, statin and non-statin LLT were each associated with moderate, non-significant lower odds of VTE. After adjusting for angina/myocardial infarction, each was significantly associated with decreased odds of VTE (OR=0.63, p<0.01 and OR=0.61, p=0.04, respectively).

CONCLUSIONS

LLT is associated with decreased VTE risk after adjusting for known risk factors.

Statins meditate anti-atherosclerotic action in smooth muscle cells by peroxisome proliferator-activated receptor-γ activation

The peroxisome proliferator-activated receptor-γ (PPARγ) is an important regulator of lipid and glucose metabolism, and its activation is reported to suppress the progression of atherosclerosis. We have reported that 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) activate PPARγ in macrophages. However, it is not yet known whether statins activate PPARγ in other vascular cells. In the present study, we investigated whether statins activate PPARγ in smooth muscle cells (SMCs) and endothelial cells (ECs) and thus mediate anti-atherosclerotic effects. Human aortic SMCs (HASMCs) and human umbilical vein ECs (HUVECs) were used in this study. Fluvastatin and pitavastatin activated PPARγ in HASMCs, but not in HUVECs. Statins induced cyclooxygenase-2 (COX-2) expression in HASMCs, but not in HUVECs. Moreover, treatment with COX-2-siRNA abrogated statin-mediated PPARγ activation in HASMCs. Statins suppressed migration and proliferation of HASMCs, and inhibited lipopolysaccharide-induced expression of monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor-α (TNF-α) in HASMCs. These effects of statins were abrogated by treatment with PPARγ-siRNA. Treatment with statins suppressed atherosclerotic lesion formation in Apoe(-/-) mice. In addition, transcriptional activity of PPARγ and CD36 expression were increased, and the expression of MCP-1 and TNF-α was decreased, in the aorta of statin-treated Apoe(-/-) mice. In conclusion, statins mediate anti-atherogenic effects through PPARγ activation in SMCs. These effects of statins on SMCs may be beneficial for the prevention of atherosclerosis.

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.

Statins and venous thromboembolic disease prophylaxis

Statins have dramatically improved the treatment of hyperlipidemia and cardiovascular disease through its inhibition of hydroxymethylglutaryl-coenzyme A reductase. Although its main effect has long been known, much is yet to be understood about the wide and varied pleiotropic properties of statins. Some studies have demonstrated that statins contain antiplatelet, antithrombotic, antiinflammatory, cardioprotective, and neuroprotective properties independent of their ability to lower plasma low-density lipoprotein cholesterol. More recently, statins have been used in novel ways in the treatment of Alzheimer disease, sepsis, pneumonia, and bacteremia. In 2000, it was first suggested that statins could decrease the incidence of venous thromboembolisms (VTEs). A recent publication showed that not only do statins lower the incidence of deep vein thrombosis and pulmonary embolism, but they do so in a dose-dependent manner. Although there is certainly strong evidence demonstrating that statins do indeed lower VTEs, the mechanism is not understood. Possible hypotheses include their antiinflammatory and antithrombotic properties. With only one randomized clinical trial available, further studies must be conducted before routinely recommending statins for prophylaxis of VTEs.

Clinical evidence of statin therapy in non-dyslipidemic disorders

The clinical benefits of statins are strongly related to their low density lipoprotein cholesterol (LDL-C) lowering properties. However, considering that the pharmacological target of statins, the 3-hydroxy-3-methyl-3-glutaryl coenzyme A (HMG-CoA) reductase, is one of the upstream enzyme of the mevalonate pathway, its inhibition may determine a substantial impoverishment of additional lipid moieties required for a proper cellular function. From this hypothesis, several experimental and clinical evidences have been reported indicating additional effects of statins beyond the LDL-C lowering, in particular anti-inflammatory and immunomodulatory effects. Thus statin therapy, indicated for hyperlipidemic patients for primary and secondary prevention of coronary heart disease (CHD) has begun to be considered effective in other diseases not necessarily linked to altered lipid profile. In the present review we summarized the current clinical evidence of the efficacy and safety profile of statins in a variety of diseases, such as rheumatoid arthritis, venous thromboembolism, liver diseases, polycystic ovary syndrome, and age-related macular degeneration. As discussed in the review, pending large, well designed, randomized trials, it is reasonable to conclude that there is no definitive evidence for the use of statins in the aforementioned diseases.

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.

Tissue factor and atherosclerosis: not only vessel wall-derived TF, but also platelet-associated TF

In the last ten years the contribution of both vessel wall-derived tissue factor (TF) and platelets to atherosclerosis has been revisited. At the beginning of the 2000 a circulating blood-borne TF has been proposed to sustain coagulation activation and propagation on the edge of a growing thrombus. Concomitantly with the observation that platelets not only contribute to thrombus formation, but also take part to the onset of the atherosclerotic lesion, evidences have been provided that they express functionally active TF, making them able to trigger the coagulation cascade.

Do statins have a role in reduction/prevention of post-PCI restenosis?

The pathophysiology of post-PCI restenosis involves neointimal formation that consists of three phases: thrombosis (within 24 h), recruitment (3-8 days), and proliferation, which starts on day 8 of PCI. Various factors suggested to be predictors/risks for restenosis include C-reactive protein (CRP), inflammatory mediators (cytokines and adhesion molecules), oxygen radicals, advanced glycation end products (AGEs) and their receptors (RAGE), and soluble RAGE (sRAGE). The earlier noted factors produce thrombogenesis, vascular smooth muscle cell proliferation, and extracellular matrix formation. Statins have pleiotropic effects. Besides lowering serum cholesterol, they have various other biological effects including antiinflammatory, antithrombotic, CRP-lowering, antioxidant, antimitotic, and inhibition of smooth muscle cell proliferation. They inhibit matrix metalloproteinase and cyclooxygenase-2, lower AGEs, decrease expression of RAGE and increase levels of serum sRAGE. They also increase the synthesis of nitric oxide (NO) by increasing endothelial NO synthase expression and activity. Preprocedural statin therapy is known to reduce peri- and post-PCI myonecrosis and reduce the need for repeat revascularization. There is evidence that statin-eluting stents inhibit in-stent restenosis in animal models. It is concluded that because of the above attributes of statins, they are suitable candidates for reduction of post-PCI restenosis and post-PCI myonecrosis. The future directions for the use of statins in reduction of post-PCI restenosis and myonecrosis have been discussed.