FeCl3 Injury Research Articles

Berberine Decreases Thrombosis Potential Induced by a High-choline Diet by Inhibiting CutC Enzyme.

Gut microbes influence thrombosis potential by generating trimethylamine N-oxide (TMAO). However, whether the antithrombotic effect of berberine is associated with TMAO generation remains unclear. The present study was designed to explore whether berberine decreases the TMAO-induced thrombosis potential and the possible mechanism underneath it. C57BL/6J female mice under a high-choline diet or standard diet were treated with/without berberine for 6 weeks. The TMAO level, carotid artery occlusion time following FeCl3 injury and platelet responsiveness were measured. The binding of berberine to the CutC enzyme was analysed with molecular docking, and molecular dynamics simulations were verified with enzyme activity assays. The results showed that berberine increased the carotid artery occlusion time following FeCl3 injury and decreased the platelet hyperresponsiveness induced by a high-- choline diet, both offset by intraperitoneal injection of TMAO. The effect of berberine on thrombosis potential was associated with decreasing the generation of TMAO by inhibiting the CutC enzyme. Targeting TMAO generation with berberine might be a promising therapy for ischaemic cardiac-cerebral vascular diseases.

Abstract 154: Hierarchical Redundancy And Contextual Roles Of Vesicle-associated Membrane Proteins (VAMPs) In Platelet Function

Background: Platelet granule secretion, driven by the SNARE complex involving Vesicle-Associated Membrane Proteins (VAMPs) and t-SNAREs, is essential for vascular integrity. We dissected individual and combinatorial contributions of all four platelet VAMPs to granule secretion, hemostasis, and intracellular cargo trafficking. Research Questions: 1. Are specific VAMPs critical for granule fusion, or does total VAMP quantity (mass action) dictate secretion? 2. How do differential VAMP deficiencies impact hemostasis in arterial and venous microenvironments? 3. Do VAMPs influence platelet cargo loading and gene expression? Goals: Investigate individual and combinatorial roles of VAMPs in platelet biology and their context dependent contributions to hemostasis. Approach: We generated V7 -/- 8 -/- and V2 Δ 3 Δ 7 -/- 8 -/- mice, assessing granule secretion (dense, alpha, lysosomal) via ATP, PF4/P-selectin, and β-hexosaminidase/LAMP1 release assays, respectively. Hemostasis in arterial and venous models was evaluated with tail bleeding, FeCl3, and venous puncture injury assays. Cargo levels were analyzed using proteomic arrays, and platelet RNA sequencing identified transcriptional changes. Results: Global V7/V8 deletion modestly reduced secretion compared to isolated V8 deficiency. Surprisingly, while platelet-specific V2 Δ 3 Δ 7 -/- 8 -/- exhibited the most dramatic decrease, complete abolition was absent (p<0.01). Alpha and lysosomal secretion were more affected than densegranule release. Both knockout models bled profusely and failed to form stable arterial thrombi (p<0.01). Notably, only V2 Δ 3 Δ 7 -/- 8 -/- mice displayed significantly prolonged venous bleeding (p<0.01). RNA sequencing revealed >800 upregulated and >500 downregulated transcripts in V7 - /- 8 -/- and V2 Δ 3 Δ 8 -/- platelets, suggesting shared transcriptional control by V7 and secondary VAMPs (V2 and V3). Conclusions: VAMP functions exhibit hierarchical redundancy, with V8 presence minimally impacting dense granule secretion and arterial hemostasis. Alpha granule release is more sensitive to VAMP loss. The requirements for platelet granule secretion for hemostasis are context dependent. The deletion of VAMPs disrupts platelet cargo trafficking and transcription.

Anti-thrombotic Effects Mediated by a Novel Dual-Target Peptide Inhibiting Both Platelet Aggregation and Thrombin Activity without Causing Bleeding.

Classical anticoagulants and antiplatelets are associated with high frequencies of bleeding complications or treatment failure when used as single agents. Thrombin plays an important role in the blood coagulation system. GP IIb/IIIa is the central receptor of platelets, which can recognize the Arg-Gly-Asp (RGD) sequence and activate platelets. Molecular simulation and homology modeling were performed to design a novel dual-target anticoagulant short peptide (PTIP ). The activities of PTIP on coagulation and platelet in vitro were analyzed. The antithrombotic activity of PTIP was determined by pulmonary thromboembolism model, ferric chloride injury model and arteriovenous bypass thrombosis model. Bleeding effect and toxicity of PTIP were evaluated. We have constructed a novel dual-target peptide (PTIP) based on the direct thrombin inhibitor peptide (DTIP). PTIP was expressed at high levels in Pichia pastoris. PTIP interfered with thrombin-mediated coagulation and ADP-induced platelet aggregation in vitro. When injected intravenously or subcutaneously, PTIP showed potent and dose-dependent extension of aPTT and PT which were similar to DTIP; but only PTIP was capable of inhibiting platelet aggregation. PTIP (1.0 mg/kg) decelerated thrombosis formation in venous and arterial vessels induced by FeCl3 injury. PTIP (1.0 mg/kg) also prevented deep venous thrombosis and increased the survival rate associated with pulmonary thromboembolism. And PTIP effectively reduced thrombus length in arteriovenous bypass thrombosis model. Moreover, the antithrombotic dose of PTIP could not induce bleeding. These data establish that PTIP represents a novel antithrombotic agent whose effects involve both inhibition of platelet activation and reduction of fibrin generation. And PTIP not only can be used in venous thrombosis and arterial thrombosis, it can also replace the combined treatment of antiplatelet and anticoagulant drugs in thrombotic diseases.

Mitochondrial calcium uniporter b deletion inhibits platelet function and reduces susceptibility to arterial thrombosis

BackgroundMitochondrial calcium uniporter b (MCUb) is a negative regulator of the mitochondrial calcium uniporter (MCU) and is known to limit mitochondrial calcium ion (Ca2+) uptake. The role of MCUb in platelet function remains unclear. ObjectivesUtilizing MCUb−/− mice, we examined the role of MCUb in regulating platelet function and thrombosis. MethodsPlatelet activation was evaluated in agonist-induced standardized in vitro assays. Susceptibility to arterial thrombosis was evaluated in FeCl3 injury–induced carotid artery and laser injury–induced mesenteric artery thrombosis models. The glycolytic proton efflux rate and oxygen consumption rate were measured to evaluate aerobic glycolysis. ResultsUpon stimulation, MCUb−/− platelets exhibited reduced cytoplasmic Ca2+ responses concomitant with increased mitochondrial Ca2+ uptake. MCUb−/− platelets displayed reduced agonist-induced platelet aggregation and spreading on fibrinogen and decreased α and dense-granule secretion and clot retraction. MCUb−/− mice were less susceptible to arterial thrombosis in FeCl3 injury–induced carotid and laser injury–induced mesenteric thrombosis models with unaltered tail bleeding time. In adoptive transfer experiments, thrombocytopenic hIL-4Rα/GPIbα-transgenic mice transfused with MCUb−/− platelets were less susceptible to FeCl3 injury-induced carotid thrombosis compared with hIL-4Rα/GPIbα-Tg mice transfused with wild type platelets, suggesting a platelet-specific role of MCUb in thrombosis. MCUb−/− stimulated platelets exhibited reduced glucose uptake, decreased glycolytic rate, and lowered pyruvate dehydrogenase phosphorylation, suggesting that mitochondrial Ca2+ mediates bioenergetic changes in platelets. ConclusionOur findings suggest that mitochondrial Ca2+ signaling and glucose oxidation are functionally linked in activated platelets and reveal a novel role of MCUb in platelet activation and arterial thrombosis.

Soluble endoglin reduces thrombus formation and platelet aggregation via interaction with αIIbβ3 integrin

BackgroundThe circulating form of human endoglin (sEng) is a cleavage product of membrane-bound endoglin present on endothelial cells. Because sEng encompasses an RGD motif involved in integrin binding, we hypothesized that sEng would be able to bind integrin αIIbβ3, thereby compromising platelet binding to fibrinogen and thrombus stability. MethodsIn vitro human platelet aggregation, thrombus retraction, and secretion-competition assays were performed in the presence of sEng. Surface plasmon resonance (SPR) binding and computational (docking) analyses were carried out to evaluate protein-protein interactions. A transgenic mouse overexpressing human sEng (hsEng+) was used to measure bleeding/rebleeding, prothrombin time (PT), blood stream, and embolus formation after FeCl3-induced injury of the carotid artery. ResultsUnder flow conditions, supplementation of human whole blood with sEng led to a smaller thrombus size. sEng inhibited platelet aggregation and thrombus retraction, interfering with fibrinogen binding, but did not affect platelet activation. SPR binding studies demonstrated that the specific interaction between αIIbβ3 and sEng and molecular modeling showed a good fitting between αIIbβ3 and sEng structures involving the endoglin RGD motif, suggesting the possible formation of a highly stable αIIbβ3/sEng. hsEng+ mice showed increased bleeding time and number of rebleedings compared to wild-type mice. No differences in PT were denoted between genotypes. After FeCl3 injury, the number of released emboli in hsEng+ mice was higher and the occlusion was slower compared to controls. ConclusionsOur results demonstrate that sEng interferes with thrombus formation and stabilization, likely via its binding to platelet αIIbβ3, suggesting its involvement in primary hemostasis control.

Phosphorylation on Syk Y342 is important for both ITAM and hemITAM signaling in platelets

Immune cells express receptors bearing an immune tyrosine activation motif (ITAM) containing two YXXL motifs or hemITAMs containing only one YXXL motif. Phosphorylation of the ITAM/hemITAM is mediated by Src family kinases allowing for the binding and activation of spleen tyrosine kinase (Syk). It is believed that Syk must be phosphorylated on tyrosine residues for activation, and Tyr342, а conserved tyrosine in the interdomain B region, has been shown to be critical for regulating Syk in FcεR1-activated mast cells. Syk is a key mediator of signaling pathways downstream of several platelet pathways including the ITAM bearing glycoprotein VI (GPVI)/Fc receptor gamma chain collagen receptor and the hemITAM containing C-type lectin-like receptor-2 (CLEC-2). Since platelet activation is a crucial step in both hemostasis and thrombosis, we evaluated the importance of Syk Y342 in these processes by producing an Syk Y342F knock-in mouse. When using a CLEC-2 antibody as an agonist, reduced aggregation and secretion were observed in Syk Y342F mouse platelets when compared with control mouse platelets. Platelet reactivity was also reduced in response to the GPVI agonist collagen-related peptide. Signaling initiated by either GPVI or CLEC-2 was also greatly inhibited, including Syk Y519/520 phosphorylation. Hemostasis, as measured by tail bleeding time, was not altered in Syk Y342F mice, but thrombus formation in response to FeCl3 injury was prolonged in Syk Y342F mice. These data demonstrate that phosphorylation of Y342 on Syk following stimulation of either GPVI or CLEC-2 receptors is important for the ability of Syk to transduce a signal.

Prenylcysteine Oxidase 1 (PCYOX1), a New Player in Thrombosis.

Prenylcysteine Oxidase 1 (PCYOX1) is an enzyme involved in the degradation of prenylated proteins. It is expressed in different tissues including vascular and blood cells. We recently showed that the secretome from Pcyox1-silenced cells reduced platelet adhesion both to fibrinogen and endothelial cells, suggesting a potential contribution of PCYOX1 into thrombus formation. Here, we show that in vivo thrombus formation after FeCl3 injury of the carotid artery was delayed in Pcyox1−/− mice, which were also protected from collagen/epinephrine induced thromboembolism. The Pcyox1−/− mice displayed normal blood cells count, vascular procoagulant activity and plasma fibrinogen levels. Deletion of Pcyox1 reduced the platelet/leukocyte aggregates in whole blood, as well as the platelet aggregation, the alpha granules release, and the αIIbβ3 integrin activation in platelet-rich plasma, in response to adenosine diphosphate (ADP) or thrombin receptor agonist peptide (TRAP). Washed platelets from the Pcyox1−/− and WT animals showed similar phosphorylation pathway activation, adhesion ability and aggregation. The presence of Pcyox1−/− plasma impaired agonist-induced WT platelet aggregation. Our findings show that the absence of PCYOX1 results in platelet hypo-reactivity and impaired arterial thrombosis, and indicates that PCYOX1 could be a novel target for antithrombotic drugs.

Novel venous thromboembolism mouse model to evaluate the role of complete and partial factor XIII deficiency in pulmonary embolism risk

BackgroundVenous thrombosis (VT) and pulmonary embolism (PE), collectively venous thromboembolism (VTE), cause high mortality and morbidity. Factor XIII (FXIII) crosslinks fibrin to enhance thrombus stability and consequently may influence PE risk. Elucidating mechanisms contributing to PE is limited by a lack of models that recapitulate human PE characteristics. ObjectiveWe aimed to develop a mouse model that permits embolization of red blood cell (RBC)‐ and fibrin‐rich VT and determine the contribution of FXIII to PE risk. Methods and ResultsIn a thrombin‐infusion PE model, F13a+/+, F13a+/−, and F13a−/− mice had similar incidence of microthrombi in the lungs; however, thrombi were small, with low RBC content (≤7%), unlike human PEs (~70%). To identify a model producing PE consistent with histological characteristics of human PE, we compared mouse femoral vein electrolytic injury, femoral vein FeCl3 injury, and infrarenal vena cava (IVC) stasis models of VT. Electrolytic and FeCl3 models produced small thrombi with few RBCs (5% and 4%, respectively), whereas IVC stasis produced large thrombi with higher RBC content (68%) that was similar to human PEs. After IVC stasis and ligature removal (de‐ligation) to permit thrombus embolization, compared to F13a+/+ mice, F13a+/− and F13a−/− mice had similar and increased PE incidence, respectively. ConclusionsCompared to thrombin infusion‐, electrolytic injury‐, and FeCl3‐based models, IVC stasis produces thrombi that are more histologically similar to human thrombi. IVC stasis followed by de‐ligation permits embolization of existing RBC‐ and fibrin‐rich thrombi. Complete FXIII deficiency increases PE incidence, but partial deficiency does not.

The metabolic enzyme pyruvate kinase M2 regulates platelet function and arterial thrombosis

Very little is known about the role of metabolic regulatory mechanisms in platelet activation and thrombosis. Dimeric pyruvate kinase M2 (PKM2) is a crucial regulator of aerobic glycolysis that facilitates the production of lactate and metabolic reprogramming. Herein, we report that limiting PKM2 dimer formation, using the small molecule inhibitor ML265, negatively regulates lactate production and glucose uptake in human and murine stimulated platelets. Furthermore, limiting PKM2 dimer formation reduced agonist-induced platelet activation, aggregation, clot retraction, and thrombus formation under arterial shear stress in vitro in both human and murine platelets. Mechanistically, limiting PKM2 dimerization downregulated phosphatidylinositol 3-kinase (PI3K)-mediated protein kinase B or serine/threonine-specific protein kinase (Akt)/glycogen synthase kinase 3 (GSK3) signaling in human and murine platelets. To provide further evidence for the role of PKM2 in platelet function, we generated a megakaryocyte or platelet-specific PKM2−/− mutant strain (PKM2fl/flPF4Cre+). Platelet-specific PKM2-deficient mice exhibited impaired agonist-induced platelet activation, aggregation, clot retraction, and PI3K-mediated Akt/GSK3 signaling and were less susceptible to arterial thrombosis in FeCl3 injury–induced carotid- and laser injury–induced mesenteric artery thrombosis models, without altering hemostasis. Wild-type mice treated with ML265 were less susceptible to arterial thrombosis with unaltered tail bleeding times. These findings reveal a major role for PKM2 in coordinating multiple aspects of platelet function, from metabolism to cellular signaling to thrombosis, and implicate PKM2 as a potential target for antithrombotic therapeutic intervention.

Combined thrombogenic effects of vessel injury, pregnancy and procoagulant immune globulin administration in mice

BackgroundPregnant women are at increased risk of thrombotic adverse events. Plasma derived immune globulin (IG) products, which are used in pregnancy for various indications, may contain procoagulant impurity activated coagulation factor XI (FXIa). Procoagulant IG products have been associated with increased thrombogenicity but their effect in pregnancy is unknown.MethodsLate pregnant (gestation days 17–20) or early lactation (days 1–3) and control female mice were treated with IGs supplemented with human FXIa then subjected to ferric chloride (FeCl3) vessel injury. Occlusion of blood vessel was assessed by recording blood velocity in the femoral vein for 20 min using doppler ultrasound laser imaging. FXIa dose was selected by the ability to increase thrombin generation in mouse plasma in vitro.ResultsFXIa produced robust thrombin generation in mouse plasma ex vivo. Following FeCl3 injury, pregnant and non-pregnant mice receiving IG + FXIa exhibited faster reduction of blood velocity in femoral vein compared to IG alone or untreated controls. In vitro, thrombin generation in plasma samples collected after thrombosis in FXIa-treated animals was elevated and could be reduced by anti-FXI antibody.ConclusionsOur results suggest that intravenously-administered FXIa may contribute to thrombosis at the site of vascular injury in both pregnant and non-pregnant animals.

Role of GRK6 in the Regulation of Platelet Activation through Selective G Protein-Coupled Receptor (GPCR) Desensitization

Platelet G protein-coupled receptors (GPCRs) regulate platelet function by mediating the response to various agonists, including adenosine diphosphate (ADP), thromboxane A2, and thrombin. Although GPCR kinases (GRKs) are considered to have the crucial roles in most GPCR functions, little is known regarding the regulation of GPCR signaling and mechanisms of GPCR desensitization by GRKs in platelets. In this study, we investigated the functional role of GRK6 and the molecular basis for regulation of specific GPCR desensitization by GRK6 in platelets. We used GRK6 knockout mice to evaluate the functional role of GRK6 in platelet activation. Platelet aggregation, dense- and α-granule secretion, and fibrinogen receptor activation induced by 2-MeSADP, U46619, thrombin, and AYPGKF were significantly potentiated in GRK6−/− platelets compared to the wild-type (WT) platelets. However, collagen-related peptide (CRP)-induced platelet aggregation and secretion were not affected in GRK6−/− platelets. Interestingly, platelet aggregation induced by co-stimulation of serotonin and epinephrine which activate Gq-coupled 5HT2A and Gz-coupled α2A adrenergic receptors, respectively, was not affected in GRK6−/− platelets, suggesting that GRK6 was involved in specific GPCR regulation. In addition, platelet aggregation in response to the second challenge of ADP and AYPGKF was restored in GRK6−/− platelets whereas re-stimulation of the agonist failed to induce aggregation in WT platelets, indicating that GRK6 contributed to P2Y1, P2Y12, and PAR4 receptor desensitization. Furthermore, 2-MeSADP-induced Akt phosphorylation and AYPGKF-induced Akt, extracellular signal-related kinase (ERK), and protein kinase Cδ (PKCδ) phosphorylation were significantly potentiated in GRK6−/− platelets. Finally, GRK6−/− mice exhibited an enhanced and stable thrombus formation after FeCl3 injury to the carotid artery and shorter tail bleeding times, indicating that GRK6−/− mice were more susceptible to thrombosis and hemostasis. We conclude that GRK6 plays an important role in regulating platelet functional responses and thrombus formation through selective GPCR desensitization.

Role of arrestin1 in regulation of GPCR signaling in platelet activation

The arrestins are a class of soluble proteins that function in concert with the GPCR kinases to stop or arrest GPCR‐mediated intracellular signaling. Although β‐arrestins function in the desensitization of most GPCRs, the functional differences of β‐arrestin1 (arrestin2, BARR1) versus β‐arrestin2 (arrestin1, BARR2) in the regulation of GPCR signaling in platelets and the mechanisms of desensitization of platelets to GPCR agonists by β‐arrestins have not been understood. In this study, we identify the role of BARR2 in the regulation of platelet function and GPCR signaling in platelets. We used mice lacking BARR1 and BARR2 to evaluate the functional role of BARR2 in platelet activation. Platelet aggregation, dense‐granule secretion, and fibrinogen receptor activation induced by 2‐MeSADP, U46619, thrombin, and AYPGKF were significantly potentiated in BARR2 −/− platelets compared to WT platelets. In contrast to BARR2 −/− platelets, AYPGKF‐, thrombin‐, and U46619‐induced platelet aggregation and secretion were significantly inhibited in BARR1 −/− platelets compared to WT platelets, while 2‐MeSADP‐induced platelet aggregation and secretion were minimally affected in BARR1 −/−platelets. However, CRP‐induced platelet aggregation and secretion were not affected in both BARR1 −/− and BARR2 −/− platelets. These results suggest that BARR2 functions as the predominant regulator in the termination of GPCR signaling in platelets. In addition, platelet aggregation was restored in response to second challenge of 2‐MeSADP and AYPGKF in BARR2 −/− platelets whereas re‐stimulation of agonist failed to induce aggregation in WT and b‐arrestin1 −/− platelets, indicating BARR2 contributes to P2Y1, P2Y12, and PAR receptor desensitization. Furthermore, 2MeSADP‐ and AYPGKF‐induced Akt and ERK phosphorylations were significantly potentiated in BARR2 −/− platelets. Finally, BARR2 −/− mice show an enhanced and stable thrombus formation after FeCl3 injury to the carotid artery, indicating BARR2 is critical for thrombus formation in vivo. We conclude that BARR2 plays an important role in regulation of platelet function through selective GPCR desensitization.Support or Funding InformationThis work was supported by the National Research Foundation of Korea (NRF) Grant of the Korean government (NRF‐2016R1D1A1B01010310) and the Global Research and Development Center (GRDC) Program through the NRF funded by the Ministry of Education, Science and Technology (2017K1A4A3014959).

A Novel Role for Piezo1 in Diabetes-Associated Thrombosis

Thrombosis, as the underlying mechanism of coronary heart disease, stroke, and venous thromboembolism, is the leading cause of death. The risk of thrombosis is drastically increased in diabetes. As thrombosis occurs in the blood flow, cells involved undergo dynamic mechanical triggers that can result in downstream cellular responses. One key player of mechano-sensing in blood cells is the Piezo1 channel, which transduces physical stretch to Ca2+ influx in cells. We investigated in the role of Piezo1 in thrombosis and how it is dysregulated in diabetes. We developed a high-throughput imaging-based platform to test Piezo1's function in erythrocytes, leukocytes and platelets from patients’ peripheral blood. The assay utilizes Ca2+ imaging, Piezo1 modulators, and machine-learning-based imaging analysis. To test force-induced Ca2+ entry in vitro, we incorporated microfluidic devices that mimic vessel constrictions. Finally, we used Zebrafish as animal model to assess Piezo1's role in thrombosis in vivo. We found that acute hyperglycemia attenuated Piezo1 activator Yoda1-mediated Ca2+ elevation in erythrocytes by 13.0±3.0% (40 patients, p=0.004). Consistently, we observed in microfluidic devices that hyperglycemia reduced pressure-induced Ca2+ increase in erythrocytes. Conversely, Piezo1-mediated Ca2+ entry in varies blood cells increased in diabetic patients compared to healthy group, suggesting an adaptive regulation of Piezo1 expression in diabetes. To test whether the elevated Piezo1 activity contributes to the prothrombotic state, we tested in WT and Piezo1 knock-down Zebrafish. In vivo clot formation after FeCl3 injury was suppressed in Piezo1 morphants (time to occlusion WT: 64.3±3.5s, Piezo1 morphant: 92.5±4.9s, p=0.0002), suggesting that Piezo1 promotes thrombosis. Overall, we demonstrated that Piezo1's activities in blood cells are modulated in hyperglycemia and diabetes. The upregulated Piezo1 activity in diabetic patients is potentially one of the underlying mechanisms for their increased thrombosis risk, which makes Piezo1 an important diagnostic and therapeutic target.

The slow releasing hydrogen sulfide donor GYY4137 reduces neointima formation upon FeCl3 injury of the carotid artery inmice.

Neointima formation is closely linked to vascular stenosis and occurs after endothelial damage. Hydrogen sulfide is an endogenous pleiotropic mediator with numerous positive effects on the cardio vascular system. This study evaluates the effect of the slow releasing hydrogen sulfide donor GYY4137 (GYY) on neointimal formation in vivo. The effect of GYY on neointimal formation in the carotid artery was studied in the FeCl3 injury model in GYY- or vehicle-treated mice. The carotid arteries were studied at days 7 and 21 after treatment by means of histology and immunohistochemistry for proliferating cell nuclear antigen (PCNA) and alpha smooth muscle actin (α-SMA). GYY treatment significantly reduced the maximal diameter and the area of the newly formed neointima on both days 7 and 21 when compared to vehicle treatment. GYY additionally reduced the number of PCNA- and α-SMA-positive cells within the neointima on day 21 after FeCl3 injury of the carotid artery. Summarizing, single treatment with the slow releasing hydrogen sulfide donor GYY reduced the extent of the newly formed neointima by affecting the cellular proliferation at the site of vascular injury.

Histone-induced thrombotic thrombocytopenic purpura in adamts13 -/- zebrafish depends on von Willebrand factor.

Thrombotic thrombocytopenic purpura (TTP) is caused by severe deficiency of ADAMTS13 (A13), a plasma metalloprotease that cleaves endothelium-derived von Willebrand factor (VWF). However, severe A13 deficiency alone is often not sufficient to cause an acute TTP; additional factors may be required to trigger the disease. Using CRISPR/Cas9, we created and characterized several novel zebrafish lines carrying a null mutation in a13−/−, vwf, and both. We further used these zebrafish lines to test the hypothesis that inflammation that results in neutrophil activation and release of histone/DNA complexes may trigger TTP. As shown, a13−/− zebrafish exhibit increased levels of plasma VWF antigen, multimer size, and ability of thrombocytes to adhere to a fibrillar collagen-coated surface under flow. The a13−/−zebrafish also show an increased rate of occlusive thrombus formation in the caudal venules after FeCl3 injury. More interestingly, a13−/− zebrafish exhibit ~30% reduction in the number of total, immature, and mature thrombocytes with increased fragmentation of erythrocytes. Administration of a lysine-rich histone results in more severe and persistent thrombocytopenia and a significantly increased mortality rate in a13−/−zebrafish than in wildtype (wt) ones. However, both spontaneous and histone-induced TTP in a13−/− zebrafish are rescued by the deletion of vwf. These results demonstrate a potentially mechanistic link between inflammation and the onset of TTP in light of severe A13 deficiency; the novel zebrafish models of TTP may help accelerate our understanding of pathogenic mechanisms and the discoveries of novel therapeutics for TTP and perhaps other arterial thrombotic disorders.

Antithrombotic Effect of Oral Administration of Mozuku (Cladosiphon okamuranus, Brown Seaweed) Extract in Rat.

Dysfunction of vascular endothelial cells causes the risk of thrombosis. Aim of this study is to evaluate the antithrombotic effect of Okinawa mozuku (brown seaweed, Cladosiphon okamuranus) extract by using cultured vascular endothelial cells and rat carotid arterial thrombosis model induced by ferric chloride (FeCl3). The cell line (TKM-33) established from human umbilical vein endothelial cells were cultured with or without Okinawa mozuku extract. After incubation for 24 h, the conditioned medium was collected to evaluate urokinase-type plasminogen activator (u-PA) activity. Next, rats were fed with water or water containing 5% of Okinawa mozuku extract for 8 wk. After 8 wk of treatments, the rats were provided for the carotid arterial thrombosis model, and fibrinolytic factor and coagulation factor in blood were measured. Okinawa mozuku extract significantly augmented u-PA activity in the conditioned medium. The decrease of carotid artery blood flow induced by 40% FeCl3 injury in rats fed with Okinawa mozuku extract was less than that in control rats. Thus, oral administration of Okinawa mozuku extract prevented thrombus formation in this model. Oral administration of Okinawa mozuku extract significantly increased u-PA activity in euglobulin fraction, compared with control group. On the other hand, platelet aggregation activity, activated partial thromboplastin time, and active PAI-1 level in plasma exhibited no significant differences between control and Okinawa mozuku groups. These results indicate that oral administration of Okinawa mozuku enhances fibrinolytic activity in plasma and prevents thrombus formation which is induced by injury of vascular endothelial cells.

The mode of anesthesia influences outcome in mouse models of arterial thrombosis

BackgroundArterial thrombosis models are important for preclinical evaluation of antithrombotics but how anesthetic protocol can influence experimental results is not studied. ObjectivesWe studied how three most commonly used rodent anesthetics affect the induction of thrombosis and thrombus resolution with antiplatelet agent integrilin (Eptifibatide). MethodsThe Folts, electrolytic, and FeCl3 models of carotid artery thrombosis were evaluated. The extent of blood flow reduction required to elicit cyclic flow reductions (CFR) was examined in the Folts model. The occlusion time and stability following electrolytic or FeCl3 injury was assessed. The efficacy of Eptifibatide was studied in each cohort and clot composition following FeCl3 application was assessed histologically. ResultsIsoflurane and ketamine‐xylazine (ket‐x) elicited higher basal blood flow velocities. For reliable CFR in the Folts model, a higher degree of blood flow reduction was required under ket‐x and isoflurane. For the FeCl3 and electrolytic models, injury severity had to be increased in mice under ket‐x anesthesia to achieve rapid occlusion. FeCl3‐injured artery sections from ket‐x and isoflurane‐treated mice showed vessel dilatation and clots that were more fibrin/red‐cell rich compared to pentobarbitone. Integrilin led to cycle abolishment for all three Folts‐injury cohorts but for the electrolytic model a 2.5‐fold higher dose was required to restore blood flow under pentobarbitone. Integrilin after FeCl3 arterial injury was partially ineffective in isoflurane‐treated mice. ConclusionsAnesthesia impacts rodent carotid artery occlusion experiments and alters integrilin efficacy. It is important to consider anesthetic protocols in animal experiments involving pharmacological agents for treatment of atherothrombosis.

A synthesis approach of mouse studies to identify genes and proteins in arterial thrombosis and bleeding

AbstractAntithrombotic therapies reduce cardiovascular diseases by preventing arterial thrombosis and thromboembolism, but at expense of increased bleeding risks. Arterial thrombosis studies using genetically modified mice have been invaluable for identification of new molecular targets. Because of low sample sizes and heterogeneity in approaches or methodologies, a formal meta-analysis to compare studies of mice with single-gene defects encountered major limitations. To overcome these, we developed a novel synthesis approach to quantitatively scale 1514 published studies of arterial thrombus formation (in vivo and in vitro), thromboembolism, and tail-bleeding of genetically modified mice. Using a newly defined consistency parameter (CP), indicating the strength of published data, comparisons were made of 431 mouse genes, of which 17 consistently contributed to thrombus formation without affecting hemostasis. Ranking analysis indicated high correlations between collagen-dependent thrombosis models in vivo (FeCl3 injury or ligation/compression) and in vitro. Integration of scores and CP values resulted in a network of protein interactions in thrombosis and hemostasis (PITH), which was combined with databases of genetically linked human bleeding and thrombotic disorders. The network contained 2946 nodes linked to modifying genes of thrombus formation, mostly with expression in megakaryocytes. Reactome pathway analysis and network characteristics revealed multiple novel genes with potential contribution to thrombosis/hemostasis. Studies with additional knockout mice revealed that 4 of 8 (Apoe, Fpr2, Ifnar1, Vps13a) new genes were modifying in thrombus formation. The PITH network further: (i) revealed a high similarity of murine and human hemostatic and thrombotic processes and (ii) identified multiple new candidate proteins regulating these processes.

Lysine Histone-Induced Thrombocytopenia in Zebrafish Depends on Endothelial Von Willebrand Factor

Thrombotic thrombocytopenic purpura (TTP), a potentially fatal blood disorder, is caused by severe deficiency of plasma ADAMTS13 activity, primarily resulting from acquired autoantibodies that inhibit ADAMTS13's ability to cleave von Willebrand factor (VWF). However, severe deficiency of plasma ADAMTS13 activity alone is often not sufficient to cause an acute episode of TTP; additional environmental or genetic factors may be required for the development of acute TTP. Here, we report a creation and characterization of a novel zebrafish model of TTP and use the model to identify a potential mechanistic link between an innate immunity and onset of TTP. Using CRISPR/cas9, we generated adamts13-/-,vwf-/-, and adamts13-/-vwf-/-zebrafish on a double transgenic (Fli1-eGFP/Gata1-dsRed) background in which erythrocytes, thrombocytes, and endothelial cells were uniquely labeled with an endogenously expressed fluorescent protein. Our results demonstrated that adamts13-/-zebrafish larvae (5-dpf) had an increased rate of developing occlusive thrombi in the caudal venues after FeCl3 injury; also, adamts13-/- adult zebrafish (3-4 months) exhibited ~27% reduction of their total or mature thrombocyte counts with a significantly increased number of fragmented erythrocytes; moreover, an intraperitoneal administration of a lysine-rich histone resulted in severe and more persistent thrombocytopenia with an increased mortality in adamts13-/-zebrafish than their wild-type littermate; finally, both spontaneous and histone-induced thrombocytopenia and thrombotic microangiopathy in adamts13-/-was eliminated when endothelial vwf was genetically deleted from zebrafish. Together, these results provide experimental evidences to support a mechanistic link of acute infection or inflammation to acute onset of TTP in patients lacking plasma ADAMTS13 activity. DisclosuresZheng:Alexion: Research Funding, Speakers Bureau.

Optimizing outcome measurement with murine ferric chloride-induced thrombosis.

: The murine FeCl3 model is a widely used model for studying arterial thrombosis, yet provides limited information from each mouse, often only a single time point for the onset of occlusion (defined as the time to occlusion; TTO). To optimize data from the murine ferric chloride model of thrombosis. FeCl3 injury was induced in the carotid arteries of wild-type and Factor IX (FIX) knockout mice, with infusion of recombinant FIX (rFIX) to normalize FIX deficiency at various times around FeCl3 injury. The TTO was recorded as a percentage of baseline flow as occlusion continued to zero flow, with identification of reflow events. The TTO among the treatment groups of FIX-deficient mice showed no statistical differences, except with physiological saline-treated FIX-deficient mice and those receiving delayed treatment. Incidences of occlusion were 100% for wild-type mice and FIX-deficient mice receiving slow infusions of rFIX at early times around the FeCl3 application. In contrast, only 68% of FIX-deficient mice achieved occlusion with preinfusion of rFIX and none occluded with delayed rFIX infusion. A majority of occluded vessels exhibited reflow events, with significantly lower incidence for slow infusion of rFIX starting 4 min after FeCl3 application in comparison with preinjury bolus, demonstrating characterization of a differential response to timing and infusion rates of treatment. Simple use of the time to occlusion may not maximize data available from the FeCl3 arterial thrombosis model. Inclusion of documenting reflow events can extend the useful data obtained with application of this model.