Thrombus Formation In Carotid Artery Research Articles

Ref-1 protects against FeCl3-induced thrombosis and tissue factor expression via the GSK3β-NF-κB pathway.

Arterial thrombosis and its associated diseases are considered to constitute a major healthcare problem. Arterial thrombosis, defined as blood clot formation in an artery that interrupts blood circulation, is associated with many cardiovascular diseases. Oxidative stress is one of many important factors that aggravates the pathophysiological process of arterial thrombosis. Apurinic/apyrimidinic endonuclease 1/redox factor-1 (Ref-1) has a multifunctional role in cells that includes the regulation of oxidative stress and anti-inflammatory function. The aim of this study was to investigate the therapeutic effect of adenovirus-mediated Ref-1 overexpression on arterial thrombosis induced by 60% FeCl3 solution in rats. Blood flow was measured to detect the time to occlusion, thrombus formation was detected by hematoxylin and eosin staining, reactive oxygen species (ROS) levels were detected by high-performance liquid chromatography, and the expression of tissue factor and other proteins was detected by Western blot. FeCl3 aggravated thrombus formation in carotid arteries and reduced the time to artery occlusion. Ref-1 significantly delayed arterial obstruction via the inhibition of thrombus formation, especially by downregulating tissue factor expression through the Akt-GSK3β-NF-κB signaling pathway. Ref-1 also reduced the expression of vascular inflammation markers ICAM-1 and VCAM-1, and reduced the level of ROS that contributed to thrombus formation. The results showed that adenovirus-mediated Ref-1 overexpression reduced thrombus formation in the rat carotid artery. In summary, Ref-1 overexpression had anti-thrombotic effects in a carotid artery thrombosis model and could be a target for the treatment of arterial thrombosis.

Изучение нового производного бензимидазола, имеющего в своей структуре пространственно затрудненный фенольный заместитель, на моделях артериального и венозного тромбоза

Введение: Тромбоциты являются ключевыми медиаторами патогенеза артериальных тромбозов и атеросклероза. Поэтому изучение антиагрегантных средств на предмет антитромботической активности на различных моделях артериальных и венозных тромбозов является актуальным. Цель исследования: изучение антитромботической активности соединения РУ-1144 (производного бензимидазола) в сравнении с ацетилсалициловой кислотой (АСК) и клопидогрелом на моделях артериального и венозного тромбозов. Материалы и методы: Артериальный тромбоз моделировали на сонной артерии крыс-самцов аппликацией постоянного электрического тока. Воздействие на сосуд выполняли до момента полной окклюзии, регистрируемой на мониторе доплерографа. Венозной тромбоз моделировали на крысах-самцах полной перевязкой нижней полой вены на 24 ч; через сутки проводили изъятие тромба из сосуда и его взвешивание. В экспериментальных группах животным внутрижелудочно вводили соединение РУ-1144 и препараты сравнения — АСК и клопидогрел, в контрольной группе животным внутрижелудочно вводили дистиллированную воду. Для подтверждения отсутствия влияния хирургических манипуляций на организм животного в исследование модели венозного тромбоза была включена группа ложнооперированных крыс. Результаты: На модели артериального тромбоза установлена более высокая антитромботическая активность соединения РУ-1144 по сравнению с АСК и клопидогрелом в 2,5 и 7,4 раза соответственно. В модели венозного тромбоза соединение РУ-1144 уменьшало среднюю массу венозных тромбов в 5,3 раза по сравнению с группой контроля и превосходило по антитромботической активности АСК и клопидогрел в 3,5 и 1,9 раза. Заключение: Соединение РУ-1144 способно предотвращать патологические процессы, связанные с тромбообразованием, не только в сонной артерии, но и в нижней полой вене. Background: Platelets are key mediators of the pathogenesis of arterial thrombosis and atherosclerosis. So, that is actual to study antithrombotic activity of antiplatelet agents in various models of arterial and venous thromboses. Objectives: to study the antithrombotic activity of RU-1144 compound (benzimidazole derivative) as compared with acetylsalicylic acid (ASA) and clopidogrel on models of arterial and venous thromboses. Materials/Methods: Arterial thrombosis was modeled on the carotid artery of male rats by application of direct electric current. Exposure was performed until full vessel occlusion recorded by Dopplerograf. Venous thrombosis was modeled on male rats by complete ligation of vena cava inferior for 24 hours; a day later the thrombus was removed from the vessel and weighed. In the experimental groups the animals were injected intragastrically with the compound RU-1144 and the comparison drugs — ASA and clopidogrel; in the control group the animals were administered distilled water intragastrically. To confirm the absence of the effect of surgical manipulations on the animal’s organism, a group of false-operated rats was included in the study of venous thrombosis model. Results: In arterial thrombosis model RU-1144 compound had a higher antithrombotic activity as compared with ASA and clopidogrel by 2.5 and 7.4 times, respectively. In venous thrombosis model RU-1144 compound reduced the average weight of venous clots by 5.3 times as compared with the control group and exceeded antithrombotic activity of ASA and clopidogrel by 3.5 and 1.9 times. Conclusions: RU-1144 compound capable to prevent the pathological processes associated with thrombus formation in carotid artery as well as in vena cava inferior.

Novel potent antiplatelet thrombotic agent derived from biguanide for ischemic stroke

Platelet thrombosis is the main pathogeny resulting in the low curability of ischemic stroke, a leading cause of mortality and disability worldwide. Metformin, a biguanide derivative that is the first-line oral medicine for type 2 diabetes, alleviates the severity of ischemic stroke in diabetic patients and suppresses platelet activation in experimental animal model. However, the clinical implementation of commercial biguanide analogs for stroke related to platelet thrombosis remains challenging due to its weak potency, poor pharmacokinetic characteristics and possible hypoglycemia. Here, twenty-three biguanide derivatives were designed and synthesized based on the principles of bioisosteres. These derivatives were evaluated for the activity of antiplatelet thrombosis in vivo. We found that N-trifluoromethanesulfonyl biguanide derivative, compound b10, uniquely prevented cerebral infarction as well as neuronal function injury, and significantly decrease the mortality rate of ischemic stroke in the middle cerebral artery occlusion mice without significant side effects. We verified that b10 directly inhibited platelets thrombus formation and decreased the compactness of stroke thrombi. Particularly, b10 exhibited good potency to inhibit human platelet activation including platelet aggregation, adhesion, pseudopodia formation, integrin GPIIb/IIIa activation, CD62P expression and clot retraction. Meanwhile, the pharmacokinetics assessment showed that b10 had satisfying pharmacological characteristics including a longer duration and a higher oral absorption ratio than its parent compound. In addition, b10 remarkably ameliorated not only stroke related to platelet thrombosis but also carotid artery thrombus formation. It is concluded that the novel potent antiplatelet thrombotic agent derived from biguanide is a promising candidate for stroke treatment.

Factor XIII deficiency does not prevent FeCl3‐induced carotid artery thrombus formation in mice

BackgroundThe compositions of venous (red blood cell–rich) and arterial (platelet‐rich) thrombi are mediated by distinct pathophysiologic processes; however, fibrin is a major structural component of both. The transglutaminase factor XIII (FXIII) stabilizes fibrin against mechanical and biochemical disruption and promotes red blood cell retention in contracted venous thrombi. Previous studies have shown factor XIII (FXIII) inhibition decreases whole blood clot mass and therefore, may be a therapeutic target for reducing venous thrombosis. The role of FXIII in arterial thrombogenesis is less studied, and the particular contribution of platelet FXIII remains unresolved. ObjectiveTo determine whether FXIII reduction prevents experimental arterial thrombogenesis. MethodsUsing wild‐type mice and mice with genetically imposed deficiency in FXIII, we measured thrombus formation and stability following ferric chloride–induced arterial thrombosis. We also determined the impact of FXIII on the mass of contracted platelet‐rich plasma clots. ResultsFollowing vessel injury, F13a+/+, F13a+/−, and F13a−/− mice developed occlusive arterial thrombi. FXIII deficiency did not significantly reduce the incidence or prolong the time to occlusion. FXIII deficiency also did not alter the timing of reflow events or decrease platelet‐rich clot mass. ConclusionsFXIII does not significantly alter the underlying pathophysiology of experimental arterial thrombus formation.

2182Sirtuin 5 regulates arterial thrombosis by modulating endothelial plasminogen activator inhibitor-1

Abstract Introduction Arterial thrombosis as a result of plaque rupture or erosion is a crucial event in myocardial infarction and stroke. Oxidative stress and inflammation promote endothelial dysfunction and play a pivotal role in destabilization of the atherosclerotic plaque. Sirtuin 5 (SIRT5) is a member of the sirtuin protein family with function as a NAD+-dependent protein desuccinylase and demalonylase. Being implicated in the regulation of different pathophysiological processes among which production of reactive oxygen species and transcription of inflammatory mediators, SIRT5 plays a role in the development of several cardiovascular diseases such as myocardial infarction and stroke. To date, the possible involvement of SIRT5 as a mediator of arterial thrombosis remains to be investigated. Purpose In this study we investigate the putative role of this protein in arterial thrombosis by using an established in vivo mouse model. The translational value of animal findings as well as the molecular mechanism underlying the observed effect will be investigated also in primary human aortic endothelial cells (HAECs). Methods SIRT5 knockout (KO) as well as SIRT5 transgenic (TG) animals were used for in vivo experiments. HAECs treated with SIRT5 silencing RNA (si-SIRT5) and stimulated with tumor necrosis factor (TNF)-α were used for in vitro assays. Results When compared to WT animals, SIRT5 KO mice display blunted carotid artery thrombus formation as underlined by delayed time to occlusion in a photochemical injury model. Oppositely, in SIRT5 TG mice the formation of an occlusive thrombus is accelerated (Fig 1). Mechanistically, SIRT5 KO and WT animals show no difference in terms of vascular tissue factor (TF) activity, TF concentration in plasma and expression of TF pathway inhibitor (TFPI) in the aorta. In line with the observed reduced thrombogenicity, SIRT5 KO animal express reduced level of the pro-thrombotic plasminogen activator-1 (PAI-1), as assessed by western blot in aorta lysate. Of interest, SIRT5 genetic deletion does not affect platelet aggregation, as assessed by ex-vivo collagen-induced aggregometry. In HAECs, SIRT5-silencing inhibits PAI-1 expression in response to TNF-α. Real-time polymerase chain reaction revealed that inhibition of PAI-1 expression occurs at the mRNA level. This effect is mediated by reduced activation of the MAP kinase Erk 1/2, but not JNK (Fig 1). Conclusions SIRT5 mediates arterial thrombosis by increasing endothelial PAI-1 expression. Hence, SIRT5 may be an effective therapeutic target in the context of atherothrombosis.

Isolation and Characterization of Poecistasin, an Anti-Thrombotic Antistasin-Type Serine Protease Inhibitor from Leech Poecilobdella manillensis.

Antistasin, first identified as a potent inhibitor of the blood coagulation factor Xa, is a novel family of serine protease inhibitors. In this study, we purified a novel antistasin-type inhibitor from leech Poecilobdella manillensis called poecistasin. Amino acid sequencing of this 48-amino-acid protein revealed that poecistasin was an antistasin-type inhibitor known to consist of only one domain. Poecistasin inhibited factor XIIa, kallikrein, trypsin, and elastase, but had no inhibitory effect on factor Xa and thrombin. Poecistasin showed anticoagulant activities. It prolonged the activated partial thromboplastin time and inhibited FeCl3-induced carotid artery thrombus formation, implying its potent function in helping Poecilobdella manillensis to take a blood meal from the host by inhibiting coagulation. Poecistasin also suppressed ischemic stroke symptoms in transient middle cerebral artery occlusion mice model. Our results suggest that poecistasin from the leech Poecilobdella manillensis plays a crucial role in blood-sucking and may be an excellent candidate for the development of clinical anti-thrombosis and anti-ischemic stroke medicines.

Protection from Psoriasis-Related Thrombosis after Inhibition of IL-23 or IL-17A

Psoriasis patients experience chronic systemic skin inflammation and develop cardiovascular comorbidities that shorten their lifespan. Whether cardiovascular disease is improved by treatment with current biologics that target disease-specific pathways is unclear. KC-Tie2 mice develop psoriasiform skin inflammation with increases in IL-23 and IL-17A and proinflammatory monocytosis and neutrophilia that precedes development of carotid artery thrombus formation. To examine whether targeted blockade of IL-23 or IL-17A in KC-Tie2 psoriasis mice improves cardiovascular outcomes, mice were treated systemically for 6 weeks with antibodies targeting IL-17A, IL-17RA, IL-12/23p40, or IL-23p19. Skin inflammation; thrombosis clotting times; and percentage of splenic monocytes, neutrophils, and CD4 T cells were examined. Skin inflammation significantly improved in KC-Tie2 mice treated with each of the antibodies targeting IL-23, IL-17A, or IL-17RA, consistent with clinical efficacy observed in psoriasis patients. The time to occlusive thrombus formation lengthened in these mice and correlated with attenuated acanthosis. This decrease in skin inflammation paralleled decreases in splenic neutrophils (CD11b+Ly6G+) but not monocytes (CD11b+Ly6Chigh) or T cells (CD4+). Our data show that targeted inhibition of IL-23 or IL-17A improves psoriasis-like skin disease and also improves cardiovascular disease in mice.

0416 : Vascular smooth muscle cells are responsible for a prothrombotic phenotype of spontaneously hypertensive rat arteries

The hypothesis that hypertension confers a hypercoagulable state arises from the complications associated with hypertension, stroke and myocardial infarction. Our objective was to determine whether spontaneous hypertension causes changes in the thrombin generating capacity of the vascular wall. We used spontaneously hypertensive rats (SHR) compared with Wistar rats. The addition of thoracic aorta rings of SHR to a Wistar or SHR plasma pool resulted in a greater increase in thrombin generation compared to the addition of equivalent rings from Wistar. Comparison of 5 week-old and 12 week-old rats indicate that established hypertension is required to induce increased thrombin generation within the vessel wall. Whereas no difference was observed for endothelial cells, thrombin formation was higher at the surface of cultured aortic smooth muscle cells (SMCs) from SHR than from Wistar. Exposure of negatively-charged phospholipids was higher on SHR than on Wistar aortic rings as well as on SMCs. Tissue factor activity was higher in SHR SMCs. Twelve week-old SHR exhibited accelerated FeCl3-induced thrombus formation in carotid arteries and the resulting occlusive thrombi are disaggregated by blockade of glycoprotein Ibα-von Willebrand factor interactions. SHR SMCs were more sensitive to thrombininduced proliferation than Wistar SMCs. This cellular effect was totally abolished by a protease-activated receptor 1 inhibitor. The prothrombotic phenotype of the SHR vessel wall was due to the ability of SMCs to support greater thrombin generation and resulted in accelerated occlusive thrombus formation after arterial injury, which is sensitive to glycoprotein Ibα-von Willebrand factor inhibitors.

Vascular smooth muscle cells are responsible for a prothrombotic phenotype of spontaneously hypertensive rat arteries.

The hypothesis that hypertension induces a hypercoagulable state arises from the complications associated with hypertension: stroke and myocardial infarction. Here, we determine whether hypertension causes changes in the thrombin-generating capacity of the vascular wall. We used spontaneously hypertensive rats (SHR) compared with Wistar rats. The addition of thoracic aortic rings of SHR to a Wistar or SHR plasma pool resulted in a greater increase in thrombin generation compared with equivalent rings from Wistar. This increase occurred in 12- but not 5-week-old rats and was prevented by an angiotensin II-converting enzyme inhibitor, indicating that established hypertension is required to induce increased thrombin generation within the vessel wall. Whereas no difference was observed for endothelial cells, thrombin formation was higher on aortic smooth muscle cells (SMCs) from SHR than on those from Wistar. Exposure of negatively charged phospholipids was higher on SHR than on Wistar rings, as well as on cultured SMCs. Tissue factor activity was higher in SHR SMCs. Twelve-week-old SHR exhibited accelerated FeCl3-induced thrombus formation in carotid arteries, and the resulting occlusive thrombi were disaggregated by blockade of glycoprotein Ibα-von Willebrand factor interactions. SHR SMCs were more sensitive to thrombin-induced proliferation than Wistar SMCs. This effect was totally abolished by a protease-activated receptor 1 inhibitor. The prothrombotic phenotype of the SHR vessel wall was due to the ability of SMCs to support greater thrombin generation and resulted in accelerated occlusive thrombus formation after arterial injury, which was sensitive to glycoprotein Ibα-von Willebrand factor inhibitors.

Inflammatory Cytokine TSLP Stimulates Platelet Secretion and Potentiates Platelet Aggregation via a TSLPR-Dependent PI3K/Akt Signaling Pathway

Aims: Thymic stromal lymphopoietin (TSLP) plays an important role in inflammatory diseases and is over-expressed in human atherosclerotic artery specimens. The present study investigated the role of TSLP in platelet activation and thrombosis models in vitro and in vivo, as well as the underlying mechanism and signaling pathway. Methods and Results: Western blotting and flow cytometry demonstrated that the TSLP receptor was expressed on murine platelets. According to flow cytometry, platelet stimulation with TSLP induced platelet degranulation and integrin αIIbβ3 activation. A TSLPR deficiency caused defective platelet aggregation, defective platelet secretion and markedly blunted thrombus growth in perfusion chambers at both low and high shear rates. TSLPR KO mice exhibited defective carotid artery thrombus formation after exposure to FeCl₃. TSLP increased Akt phosphorylation, an effect that was abrogated by the PI3K inhibitors wortmannin and LY294002. The PI3K inhibitors further diminished TSLP-induced platelet activation. TSLP-mediated platelet degranulation, integrin αIIbβ3 activation and Akt phosphorylation were blunted in platelets that lacked the TSLP receptor. Conclusion: This study demonstrated that the functional TSLPR was surface-expressed on murine platelets. The inflammatory cytokine TSLP triggered platelet activation and thrombus formation via TSLP-dependent PI3K/Akt signaling, which suggests an important role for TSLP in linking vascular inflammation and thrombo-occlusive diseases.

Short- and long-term treatment with folic acid suppresses thrombus formation in atherogenic mice in vivo

In the present study, we examined the effects of short- and long-term treatment with folic acid (FA) on thrombus formation in vivo in atherogenic mice to explore a novel agent for the prevention of atherothrombotic disease. Apolipoprotein E and low-density lipoprotein receptor double deficient (ApoE−/−LDLR−/−) mice were orally administrated a single bolus of FA (20mg/kg) or fed an atherogenic diet with or without FA (0.02, 0.5, and 1.5mg/kg) for 12 weeks. Thrombus formation and endothelial function were assessed in vivo using the He–Ne laser-induced carotid artery thrombus formation test and the flow-mediated vasodilation method. Platelet reactivity was assessed ex vivo using haemostatometry. Short-term treatment with FA markedly increased plasma folate levels and significantly suppressed laser-induced thrombus formation in apoE−/−LDLR−/− mice. Short-term treatment with FA suppressed platelet reactivity in apoE−/−LDLR−/− mice, but FA treatment did not affect endothelial function or plasma homocysteine levels. Long-term treatment with FA increased plasma folate levels dose-dependently. Thrombus formation and endothelial dysfunction were suppressed by treatment with 0.5 and 1.5mg/kg of FA, respectively, but not with 0.02mg/kg of FA, whereas platelet reactivity was not altered by treatment with any dose of FA. Long-term treatment with all doses of FA decreased the plasma homocysteine levels in apoE−/−LDLR−/− mice, although this result was not consistent with its anti-thrombotic action. In conclusion, our data showed that short- and long-term treatment with FA could suppress in vivo thrombus formation in an atherogenic setting, independent of its hypohomocysteinemic action.

Dronedarone reduces arterial thrombus formation

Dronedarone has been associated with a reduced number of first hospitalisation due to acute coronary syndromes. Whether this is only due to the reduction in ventricular heart rate and blood pressure or whether other effects of dronedarone may be involved is currently elusive. This study was designed to investigate the role of dronedarone in arterial thrombus formation. C57Bl/6 mice were treated with dronedarone and arterial thrombosis was investigated using a mouse photochemical injury model. Dronedarone inhibited carotid artery thrombus formation in vivo (P < 0.05). Thrombin- and collagen-induced platelet aggregation was impaired in dronedarone-treated mice (P < 0.05), and expression of plasminogen activator inhibitor-1 (PAI1), an inhibitor of the fibrinolytic system, was reduced in the arterial wall (P < 0.05). In contrast, the level of tissue factor (TF), the main trigger of the coagulation cascade, and that of its physiological inhibitor, TF pathway inhibitor, did not differ. Similarly, coagulation times as measured by prothrombin time and activated partial thromboplastin time were comparable between the two groups. Dronedarone inhibits thrombus formation in vivo through inhibition of platelet aggregation and PAI1 expression. This effect occurs within the range of dronedarone concentrations measured in patients, and may represent a beneficial pleiotropic effect of this drug.

Lufaxin, a novel factor Xa inhibitor from the salivary gland of the sand fly Lutzomyia longipalpis blocks protease-activated receptor 2 activation and inhibits inflammation and thrombosis in vivo.

Blood-sucking arthropods' salivary glands contain a remarkable diversity of antihemostatics. The aim of the present study was to identify the unique salivary anticoagulant of the sand fly Lutzomyia longipalpis, which remained elusive for decades. Several L. longipalpis salivary proteins were expressed in human embryonic kidney 293 cells and screened for inhibition of blood coagulation. A novel 32.4-kDa molecule, named Lufaxin, was identified as a slow, tight, noncompetitive, and reversible inhibitor of factor Xa (FXa). Notably, Lufaxin's primary sequence does not share similarity to any physiological or salivary inhibitors of coagulation reported to date. Lufaxin is specific for FXa and does not interact with FX, Dansyl-Glu-Gly-Arg-FXa, or 15 other enzymes. In addition, Lufaxin blocks prothrombinase and increases both prothrombin time and activated partial thromboplastin time. Surface plasmon resonance experiments revealed that FXa binds Lufaxin with an equilibrium constant ≈3 nM, and isothermal titration calorimetry determined a stoichiometry of 1:1. Lufaxin also prevents protease-activated receptor 2 activation by FXa in the MDA-MB-231 cell line and abrogates edema formation triggered by injection of FXa in the paw of mice. Moreover, Lufaxin prevents FeCl(3)-induced carotid artery thrombus formation and prolongs activated partial thromboplastin time ex vivo, implying that it works as an anticoagulant in vivo. Finally, salivary gland of sand flies was found to inhibit FXa and to interact with the enzyme. Lufaxin belongs to a novel family of slow-tight FXa inhibitors, which display antithrombotic and anti-inflammatory activities. It is a useful tool to understand FXa structural features and its role in prohemostatic and proinflammatory events.

Sirt1 inhibition promotes in vivo arterial thrombosis and tissue factor expression in stimulated cells

The mammalian silent information regulator-two 1 (Sirt1) blunts the noxious effects of cardiovascular risk factors such as type 2 diabetes mellitus and obesity. Nevertheless, the role of Sirt1 in regulating the expression of tissue factor (TF), the key trigger of coagulation, and arterial thrombus formation remains unknown. Human as well as mouse cell lines were used for in vitro experiments, and C57Bl/6 mice for in vivo procedures. Sirt1 inhibition by splitomicin or sirtinol enhanced cytokine-induced endothelial TF protein expression as well as surface activity, while TF pathway inhibitor protein expression did not change. Sirt1 inhibition further enhanced TF mRNA expression, TF promoter activity, and nuclear translocation as well as DNA binding of the p65 subunit of nuclear factor-kappa B (NFκB/p65). Sirt1 siRNA enhanced TF protein and mRNA expression, and this effect was reduced in NFκB/p65(-/-) mouse embryonic fibroblasts reconstituted with non-acetylatable Lys(310)-mutant NFκB/p65. Activation of the mitogen-activated protein kinases p38, c-Jun NH(2)-terminal kinase, and p44/42 (ERK) remained unaffected. In vivo, mice treated with the Sirt1 inhibitor splitomicin exhibited enhanced TF activity in the arterial vessel wall and accelerated carotid artery thrombus formation in a photochemical injury model. We provide pharmacological and genetic evidence that Sirt1 inhibition enhances TF expression and activity by increasing NFκB/p65 activation in human endothelial cells. Furthermore, Sirt1 inhibition induces arterial thrombus formation in vivo. Hence, modulation of Sirt1 may offer novel therapeutic options for targeting thrombosis.

TCT-130: The Novel Synthetic Peptide (s

TCT-130: The Novel Synthetic Peptide (s<S) PSRCDCR-NH2, Reduces Carotid Artery Thrombus Formation In Rabbits By Inhibiting Platelet Aggregation

Abstract 4941: Dietary Alpha-Linolenic Acid Supplementation Inhibits Thrombus Formation in vivo

Background. Considering the reduced availability of marine derived long-chain n-3 fatty acids (n-3 FA), the use of the plant-derived n-3 FA α -linolenic acid (ALA) may constitute an attractive cardioprotective alternative. However, despite promising epidemiological data, the effect of dietary ALA supplementation on arterial thrombus formation remains unknown. Methods and Results. 8 week-old male C57Bl/6 mice were fed either a high ALA (7.3g%) or low ALA (0.03g%) diet for 2 weeks. Mice fed a high ALA diet showed delayed carotid artery thrombus formation in a mouse photochemical injury model as compared to mice on a low ALA diet (68±6 vs 40±4.2 minutes; n=7; p&lt;0.05). High dietary ALA supplementation impaired platelet aggregation as determined by whole blood aggregometry in isolated murine platelets (n=5; p&lt;0.005), without affecting PTT and aPTT clotting times (n=7; p=NS). Mice on the high ALA diet exhibited reduced vascular tissue factor (TF) expression and activity, as well as reduced vascular NF kappa B activity (n=7; p&lt;0.05). In human endothelial, vascular smooth muscle, and peripheral blood mononuclear cells ALA (10 –30 μ mol/l) inhibited tumor necrosis factor (TNF)- α and thrombin induced TF expression as well as surface activity (n=4; p&lt;0.01). Real time PCR and analysis of TF promoter activation demonstrated that ALA mediated inhibition of endothelial TF expression occurred at the transcriptional level involving the MAP kinases p38, ERK and JNK1/2 (−62%,−55% and −28% versus TNF- α alone; n=3; p&lt;0.05). In endothelial cells ALA impaired TNF-á induced I kappa B-á degradation and NF kappa B activation (n=3; p&lt;0.05). Conclusions. A diet rich in plant-derived ALA inhibits arterial thrombus formation via impaired platelet aggregation and reduced TF expression. Hence, dietary ALA supplementation represents an attractive antithrombotic nutritional supplement.

Amiodarone Inhibits Arterial Thrombus Formation and Tissue Factor Translation

In patients with coronary artery disease and reduced ejection fraction, amiodarone reduces mortality by decreasing sudden death. Because the latter may be triggered by coronary artery thrombosis as much as ventricular arrhythmias, amiodarone might interfere with tissue factor (TF) expression and thrombus formation. Clinically relevant plasma concentrations of amiodarone reduced TF activity and impaired carotid artery thrombus formation in a mouse photochemical injury model in vivo. PTT, aPTT, and tail bleeding time were not affected; platelet number was slightly decreased. In human endothelial and vascular smooth muscle cells, amiodarone inhibited tumor necrosis factor (TNF)-alpha and thrombin-induced TF expression as well as surface activity. Amiodarone lacking iodine and the main metabolite of amiodarone, N-monodesethylamiodarone, inhibited TF expression. Amiodarone did not affect mitogen-activated protein kinase activation, TF mRNA expression, and TF protein degradation. Metabolic labeling confirmed that amiodarone inhibited TF protein translation. Amiodarone impairs thrombus formation in vivo; in line with this, it inhibits TF protein expression and surface activity in human vascular cells. These pleiotropic actions occur within the range of amiodarone concentrations measured in patients, and thus may account at least in part for its beneficial effects in patients with coronary artery disease.

Serglycin proteoglycan deletion induces defects in platelet aggregation and thrombus formation in mice

AbstractSerglycin (SG), the hematopoietic cell secretory granule proteoglycan, is crucial for storage of specific secretory proteins in mast cells, neutrophils, and cytotoxic T lymphocytes. We addressed the role of SG in platelets using SG−/− mice. Wild-type (WT) but not SG−/− platelets contained chondroitin sulfate proteoglycans. Electron microscopy revealed normal α-granule structure in SG−/− platelets. However, SG−/− platelets and megakaryocytes contained unusual scroll-like membranous inclusions, and SG−/− megakaryocytes showed extensive emperipolesis of neutrophils. SG−/− platelets had reduced ability to aggregate in response to low concentrations of collagen or PAR4 thrombin receptor agonist AYPGKF, and reduced fibrinogen binding after AYPGKF, but aggregated normally to ADP. 3H-serotonin and ATP secretion were greatly reduced in SG−/− platelets. The α-granule proteins platelet factor 4, β-thromboglobulin, and platelet-derived growth factor were profoundly reduced in SG−/− platelets. Exposure of P-selectin and αIIb after thrombin treatment was similar in WT and SG−/− platelets. SG−/− mice exhibited reduced carotid artery thrombus formation after exposure to FeCl3. This study demonstrates that SG is crucial for platelet function and thrombus formation. We propose that SG−/− platelet function deficiencies are related to inadequate packaging and secretion of selected α-granule proteins and reduced secretion of dense granule contents critical for platelet activation.

Platelet PECAM-1 inhibits thrombus formation in vivo

AbstractPlatelet endothelial cell adhesion molecule-1 (PECAM-1) is a cell surface glycoprotein receptor expressed on a range of blood cells, including platelets, and on vascular endothelial cells. PECAM-1 possesses adhesive and signaling properties, the latter being mediated by immunoreceptor tyrosine-based inhibitory motifs present on the cytoplasmic tail of the protein. Recent studies in vitro have demonstrated that PECAM-1 signaling inhibits the aggregation of platelets. In the present study we have used PECAM-1–deficient mice and radiation chimeras to investigate the function of this receptor in the regulation of thrombus formation. Using intravital microscopy and laser-induced injury to cremaster muscle arterioles, we show that thrombi formed in PECAM-1–deficient mice were larger, formed more rapidly than in control mice, and were more stable. Larger thrombi were also formed in control mice that received transplants of PECAM-1–deficient bone marrow, in comparison to mice that received control transplants. A ferric chloride model of thrombosis was used to investigate thrombus formation in carotid arteries. In PECAM-1–deficient mice the time to 75% vessel occlusion was significantly shorter than in control mice. These data provide evidence for the involvement of platelet PECAM-1 in the negative regulation of thrombus formation.