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

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.

Toll-like Receptors as Pro-Thrombotic Drivers in Viral Infections: A Narrative Review

Toll-like receptors (TLRs) have a critical role in the pathogenesis and disease course of viral infections. The induced pro-inflammatory responses result in the disturbance of the endovascular surface layer and impair vascular homeostasis. The injury of the vessel wall further promotes pro-thrombotic and pro-coagulatory processes, eventually leading to micro-vessel plugging and tissue necrosis. Moreover, TLRs have a direct role in the sensing of viruses and platelet activation. TLR-mediated upregulation of von Willebrand factor release and neutrophil, as well as macrophage extra-cellular trap formation, further contribute to (micro-) thrombotic processes during inflammation. The following review focuses on TLR signaling pathways of TLRs expressed in humans provoking pro-thrombotic responses, which determine patient outcome during viral infections, especially in those with cardiovascular diseases.

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.

The procoagulant activity of tissue factor expressed on fibroblasts is increased by tissue factor-negative extracellular vesicles

Tissue factor (TF) is critical for the activation of blood coagulation. TF function is regulated by the amount of externalised phosphatidylserine (PS) and phosphatidylethanolamine (PE) on the surface of the cell in which it is expressed. We investigated the role PS and PE in fibroblast TF function. Fibroblasts expressed 6–9 x 10⁴ TF molecules/cell but had low specific activity for FXa generation. We confirmed that this was associated with minimal externalized PS and PE and characterised for the first time the molecular species of PS/PE demonstrating that these differed from those found in platelets. Mechanical damage of fibroblasts, used to simulate vascular injury, increased externalized PS/PE and led to a 7-fold increase in FXa generation that was inhibited by annexin V and an anti-TF antibody. Platelet-derived extracellular vesicles (EVs), that did not express TF, supported minimal FVIIa-dependent FXa generation but substantially increased fibroblast TF activity. This enhancement in fibroblast TF activity could also be achieved using synthetic liposomes comprising 10% PS without TF. In conclusion, despite high levels of surface TF expression, healthy fibroblasts express low levels of external-facing PS and PE limiting their ability to generate FXa. Addition of platelet-derived TF-negative EVs or artificial liposomes enhanced fibroblast TF activity in a PS dependent manner. These findings contribute information about the mechanisms that control TF function in the fibroblast membrane.

Preventive Effects of Neuroprotective Agents in a Neonatal Rat of Photothrombotic Stroke Model

Neonatal ischemic stroke has a higher incidence than childhood stroke. Seizures are the first sign for the need for clinical assessment in neonates, but many questions remain regarding treatments and follow-up modalities. In the absence of a known pathophysiological mechanism, only supportive care is currently provided. Stroke-induced microglia activation and neuroinflammation are believed to play a central role in the pathological progression of neonatal ischemic stroke. We induced a photothrombotic infarction with Rose Bengal in neonatal rats to investigate the effects of pre- and post-treatment with Aspirin (ASA), Clopidogrel (Clop), and Coenzyme Q10 (CoQ10), which are known for their neuroprotective effects in adult stroke. Pre-stroke medication ameliorates cerebral ischemic injury and reduces infarct volume by reducing microglia activation, cellular reactive oxygen species (ROS) production, and cytokine release. Post-stroke administration of ASA, Clop, and CoQ10 increased motor function and reduced the volume of infarction, and the statistical evidence was stronger than that seen in the pre-stroke treatment. In this study, we demonstrated that ASA, Clop, and CoQ10 treatment before and after the stroke reduced the scope of stroke lesions and increased behavioral activity. It suggests that ASA, Clop, and CoQ10 medication could significantly have neuroprotective effects in the neonates who have suffered strokes.

Protective effect of microRNA‑381 against inflammatory damage of endothelial cells during coronary heart disease by targeting CXCR4

Coronary heart disease (CHD) is the leading cause of human morbidity and mortality worldwide. MicroRNA (miRNA) profiling is an innovative method of identifying biomarkers for many diseases and may be a powerful tool in the diagnosis and treatment of CHD. The present study aimed to analyze the effects of miRNA (miR)‑381 on the inflammatory damage of endothelial cells during CHD. A total of 21 patients with CHD and 21 healthy control patients were enrolled in this study. Reverse transcription‑quantitative PCR, western blotting and immunofluorescence assays were conducted to examine the expression levels of miR‑381, C‑X‑C chemokine receptor type 4 (CXCR4), Bcl‑2, Bax, Cleaved‑Caspases‑3 and ‑9, p38, ERK1/2 and JNK. Cell Counting Kit‑8, EdU and flow cytometry experiments were performed to evaluate cell proliferation and apoptosis. An ELISA was adopted to determine the expressions of inflammatory factors (interleukins‑8, ‑6 and ‑1β, and tumor necrosis factor‑α). In addition, a dual‑luciferase reporter assay was used to determine the relationship between miR‑381 and CXCR4. Decreased miR‑381 expression and increased CXCR4 expression in the plasma were observed in the CHD group compared with the normal group, which indicated a negative relationship between miR‑381 and CXCR4. Overexpression of miR‑381 significantly promoted the proliferation and inhibited the apoptosis of oxidized low‑density lipoprotein (OX‑LDL)‑induced human umbilical vein endothelial cells (HUVECs) through mitogen‑activated protein kinase pathway by targeting and inhibiting CXCR4. Furthermore, overexpression of miR‑381 reduced the release of inflammatory factors in OX‑LDL‑induced HUVECs. By contrast, reduced expression of miR‑381 exerted the opposite effects, which were subsequently reversed by silencing CXCR4 expression. Results from the present study indicated that miR‑381 was a CHD‑related factor that may serve as a potential molecular target for CHD treatment.

Oxidative burden in familial hypercholesterolemia

Familial hypercholesterolemia (FH) is a genetic disorder characterized by high serum levels of low-density lipoprotein cholesterol (LDL-c). FH is characterized by accelerated development of atherosclerosis and represents the most frequent hereditary cause of premature coronary heart disease. Mutations of the LDL receptor gene are the genetic signature of FH, resulting in abnormal levels of circulating LDLs. Moreover, FH promotes the generation of reactive oxygen species (ROS) which is another key mechanism involved in atherosclerosis development and progression. The aim of this narrative review is to update the current knowledge on the pathophysiological mechanisms linking FH to ROS generation and their detrimental impact on atherosclerotic pathophysiology. With this purpose, we reviewed experimental and clinical data on the association between FH and OS and the functional role of OS as a promoter of inflammation and atherosclerosis. In this regard, oxidant species such as oxidized LDL, malondialdehyde, ROS, and isoprostanes emerged as leading mediators of the oxidative injury in FH. In conclusion, targeting oxidative stress may be a promising therapeutic strategy to reduce atherogenesis in patients with FH.

Tissue Factor: An Essential Mediator of Hemostasis and Trigger of Thrombosis

Tissue factor (TF) is the high-affinity receptor and cofactor for factor (F)VII/VIIa. The TF-FVIIa complex is the primary initiator of blood coagulation and plays an essential role in hemostasis. TF is expressed on perivascular cells and epithelial cells at organ and body surfaces where it forms a hemostatic barrier. TF also provides additional hemostatic protection to vital organs, such as the brain, lung, and heart. Under pathological conditions, TF can trigger both arterial and venous thrombosis. For instance, atherosclerotic plaques contain high levels of TF on macrophage foam cells and microvesicles that drives thrombus formation after plaque rupture. In sepsis, inducible TF expression on monocytes leads to disseminated intravascular coagulation. In cancer patients, tumors release TF-positive microvesicles into the circulation that may contribute to venous thrombosis. TF also has nonhemostatic roles. For instance, TF-dependent activation of the coagulation cascade generates coagulation proteases, such as FVIIa, FXa, and thrombin, which induce signaling in a variety of cells by cleavage of protease-activated receptors. This review will focus on the roles of TF in protective hemostasis and pathological thrombosis.

Oxidation-specific epitopes are major targets of innate immunity in atherothrombosis

Atherosklerose ist eine chronisch-entzündliche Erkrankung der Gefäßwände, die durch das Zusammenspiel von Dyslipidämie und vermehrtem oxidativen Stress verursacht wird. Die damit verbundene Lipidperoxidation führt zu einer Reihe von Abbauprodukten von Membranlipiden, sogenannten oxidations-spezifischen Epitopen (OSE). OSE finden sich in oxidierten Lipoproteinen und auf der Oberfläche absterbender Zellen, und ihre Fähigkeit inflammatorische und thrombogene Reaktionen auszulösen ist weithin bekannt. Jüngste Studien konnten zeigen, daß OSE spezifische Zielstrukturen für eine Reihe von zellulären und humoralen Rezeptoren des angeborenen Immunsystems darstellen. Dadurch kann das Immunsystem, metabolische Abbaubprodukte erkennen und wichtige physiologische “Haushaltsfunktionen” vermitteln, z.B. durch die kontrollierte Entsorgung abgestorbener Zellen und oxidierten Moleküle. So wurde gezeigt, daß natürliche IgM Antikörper mit Spezifität für OSE Mäuse vor der Entstehung atherosklerotischer Läsionen schützen. So können spezifische natürliche IgM Antikörper die pro-inflammatorischen und pro-thrombotischen Effekte von OSE neutralisieren, währenddessen niedrige Plasmaspiegel OSE-spezifischer IgM Antikörper mit einem erhöhten Risiko für Myokardinfarkt assoziiert sind. Schlussfolgerung: Das Verständnis der molekularen Komponenten und Mechanismen, die an diesem Prozess beteiligt sind, werden in Zukunft dazu beitragen, Personen mit einem erhöhten Risiko für Atherothrombose besser zu identifizieren und möglicherweise neue therapeutische Ansatzpunkte zu definieren.

General mechanisms of coagulation and targets of anticoagulants (Section I)

Contrary to previous models based on plasma, coagulation processes are currently believed to be mostly cell surface-based, including three overlapping phases: initiation, when tissue factor-expressing cells and microparticles are exposed to plasma; amplification, whereby small amounts of thrombin induce platelet activation and aggregation, and promote activation of factors (F)V, FVIII and FXI on platelet surfaces; and propagation, in which the Xase (tenase) and prothrombinase complexes are formed, producing a burst of thrombin and the cleavage of fibrinogen to fibrin. Thrombin exerts a number of additional biological actions, including platelet activation, amplification and self-inhibition of coagulation, clot stabilisation and anti-fibrinolysis, in processes occurring in the proximity of vessel injury, tightly regulated by a series of inhibitory mechanisms. ″Classical″ anticoagulants, including heparin and vitamin K antagonists, typically target multiple coagulation steps. A number of new anticoagulants, already developed or under development, target specific steps in the process, inhibiting a single coagulation factor or mimicking natural coagulation inhibitors.

Puerarin inhibits expression of tissue factor induced by oxidative low-density lipoprotein through activating the PI3K/Akt/eNOS pathway and inhibiting activation of ERK1/2 and NF-κB

AIMS

The present study aimed to investigate whether puerarin regulated tissue factor (TF) expression induced by oxidative low-density lipoprotein (ox-LDL), an independent risk factor for atherosclerosis, and its mechanisms.

MAIN METHODS

TF expression at the mRNA level was determined by reverse transcription-quantitative polymerase chain reaction, and its expression at the protein level, as well as other target proteins, was assessed by western blotting. Nitric oxide (NO) production was measured by a nitrate reduction method.

KEY FINDINGS

Results demonstrated that treatment with ox-LDL (50mg/l) for 24h significantly increased (P<0.01) TF expression at the mRNA and protein levels in human umbilical vein endothelial cells (HUVECs). Such an ox-LDL exposure also triggered the dephosphorylation of Akt, resulting in a reduction of NO production and activated the extracellular signal-regulated kinase (ERK)1/2 and nuclear factor (NF)-κB signaling pathways. Pre-treatment with puerarin (50-200μM) for 1h significantly attenuated the ox-LDL-induced TF expression, augmented the phosphorylation of Akt, with a resultant increase of the NO production, and inhibited the activation of ERK1/2 and NF-κB (P<0.01). However, this beneficial effect of puerarin (100μM) was abolished by LY294002 (10μM), an inhibitor of phosphoinositide 3-kinase (PI3K), or NG-nitro-L-arginine methyl ester (100μM), an inhibitor of NO synthase.

SIGNIFICANCE

These results suggested that puerarin suppressed TF expression in HUVECs through activating the PI3K/Akt/endothelial nitric oxide synthase signaling pathway and inhibiting the activation of ERK1/2 and NF-κB. These findings suggested that puerarin possessed certain anticoagulation and may be a potential novel therapeutic drug for thrombosis in coronary artery disease.

Protective and detrimental effects of neuroectodermal cell-derived tissue factor in mouse models of stroke

Within the CNS, a dysregulated hemostatic response contributes to both hemorrhagic and ischemic strokes. Tissue factor (TF), the primary initiator of the extrinsic coagulation cascade, plays an essential role in hemostasis and also contributes to thrombosis. Using both genetic and pharmacologic approaches, we characterized the contribution of neuroectodermal (NE) cell TF to the pathophysiology of stroke. We used mice with various levels of TF expression and found that astrocyte TF activity reduced to ~5% of WT levels was still sufficient to maintain hemostasis after hemorrhagic stroke but was also low enough to attenuate inflammation, reduce damage to the blood-brain barrier, and improve outcomes following ischemic stroke. Pharmacologic inhibition of TF during the reperfusion phase of ischemic stroke attenuated neuronal damage, improved behavioral deficit, and prevented mortality of mice. Our data demonstrate that NE cell TF limits bleeding complications associated with the transition from ischemic to hemorrhagic stroke and also contributes to the reperfusion injury after ischemic stroke. The high level of TF expression in the CNS is likely the result of selective pressure to limit intracerebral hemorrhage (ICH) after traumatic brain injury but, in the modern era, poses the additional risk of increased ischemia-reperfusion injury after ischemic stroke.

The Impact of Lipoprotein-Associated Oxidative Stress on Cell-Specific Microvesicle Release in Patients with Familial Hypercholesterolemia

Objective. Microvesicles (MVs) are small cell-derived particles shed upon activation. Familial hypercholesterolemia (FH) particularly when associated with Achilles tendon xanthomas (ATX) predisposes to atherosclerosis, possibly through oxLDL-C interaction with the CD36 receptor. To investigate the hypothesis that MVs derived from cells involved in atherosclerosis are increased in FH and that CD36 expressing MVs (CD36+ MVs) may be markers of oxLDL-C-induced cell activation, cell-specific MVs were measured in FH patients with and without ATX and their association with atherogenic lipid profile was studied. Approach and Results. Thirty FH patients with and without ATX and twenty-three controls were included. Plasma concentrations of MVs and CD36+ MVs derived from platelets (PMVs), erythrocytes (ErytMVs), monocytes (MMVs), and endothelial cells (EMVs), as well as tissue factor-positive cells (TF+ MVs), were measured by flow cytometry. Total MVs, MMVs, EMVs, ErytMVs, and TF+ MVs were significantly increased in FH patients, compared to controls. CD36+ MVs derived from endothelial cells and monocytes were significantly higher in FH patients and oxLDL-C predicted all the investigated cell-specific CD36+ MVs in FH patients with ATX. Conclusions. MVs derived from cells involved in atherosclerosis were increased in FH and may contribute to elevated atherothrombosis risk. The increased cell-specific CD36+ MVs observed in FH may represent markers of oxLDL-C-induced cell activation.

Rose Bengal Photothrombosis by Confocal Optical Imaging In Vivo: A Model of Single Vessel Stroke

In vivo imaging techniques have increased in utilization due to recent advances in imaging dyes and optical technologies, allowing for the ability to image cellular events in an intact animal. Additionally, the ability to induce physiological disease states such as stroke in vivo increases its utility. The technique described herein allows for physiological assessment of cellular responses within the CNS following a stroke and can be adapted for other pathological conditions being studied. The technique presented uses laser excitation of the photosensitive dye Rose Bengal in vivo to induce a focal ischemic event in a single blood vessel. The video protocol demonstrates the preparation of a thin-skulled cranial window over the somatosensory cortex in a mouse for the induction of a Rose Bengal photothrombotic event keeping injury to the underlying dura matter and brain at a minimum. Surgical preparation is initially performed under a dissecting microscope with a custom-made surgical/imaging platform, which is then transferred to a confocal microscope equipped with an inverted objective adaptor. Representative images acquired utilizing this protocol are presented as well as time-lapse sequences of stroke induction. This technique is powerful in that the same area can be imaged repeatedly on subsequent days facilitating longitudinal in vivo studies of pathological processes following stroke.

PARP-14 combines with tristetraprolin in the selective posttranscriptional control of macrophage tissue factor expression

Tissue factor (TF) (CD142) is a 47 kDa transmembrane cell surface glycoprotein that triggers the extrinsic coagulation cascade and links thrombosis with inflammation. Although macrophage TF expression is known to be regulated at the RNA level, very little is known about the mechanisms involved. Poly(adenosine 5'-diphosphate [ADP]-ribose)-polymerase (PARP)-14 belongs to a family of intracellular proteins that generate ADP-ribose posttranslational adducts. Functional screening of PARP-14-deficient macrophages mice revealed that PARP-14 deficiency leads to increased TF expression and functional activity in macrophages after challenge with bacterial lipopolysaccharide. This was related to an increase in TF messenger RNA (mRNA) stability. Ribonucleoprotein complex immunoprecipitation and biotinylated RNA pull-down assays demonstrated that PARP-14 forms a complex with the mRNA-destabilizing protein tristetraprolin (TTP) and a conserved adenylate-uridylate-rich element in the TF mRNA 3' untranslated region. TF mRNA regulation by PARP-14 was selective, as tumor necrosis factor (TNF)α mRNA, which is also regulated by TTP, was not altered in PARP-14 deficient macrophages. Consistent with the in vitro data, TF expression and TF activity, but not TNFα expression, were increased in Parp14(-/-) mice in vivo. Our study provides a novel mechanism for the posttranscriptional regulation of TF expression, indicating that this is selectively regulated by PARP-14.

Sevelamer does not decrease lipopolysaccharide or soluble CD14 levels but decreases soluble tissue factor, low-density lipoprotein (LDL) cholesterol, and oxidized LDL cholesterol levels in individuals with untreated HIV infection

Abnormal levels of inflammation are associated with cardiovascular disease and mortality in human immunodeficiency virus (HIV)-infected patients. Microbial translocation, which may cause inflammation, is decreased by sevelamer in patients undergoing hemodialysis. In this single-arm study, we evaluated the effects of 8 weeks of sevelamer therapy on 36 HIV-infected subjects who were not receiving antiretroviral therapy. Sevelamer did not significantly change markers of microbial translocation, inflammation, or T-cell activation. During sevelamer treatment, however, levels of soluble tissue factor, low-density lipoprotein (LDL) cholesterol, and oxidized LDL cholesterol decreased significantly, whereas D-dimer levels increased. Thus, in this study population, sevelamer did not reduce microbial translocation but may have yielded cardiovascular benefits.

CLINICAL TRIALS REGISTRATION

NCT 01543958.

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.