In vivo imaging visualizes discoid platelet aggregations without endothelium disruption and implicates contribution of inflammatory cytokine and integrin signaling

Cure of Congenital Purpura Fulminans via Expression of Engineered Protein C Through Neonatal Genome Editing in Mice

BACKGROUND

PC (protein C) is a plasma anticoagulant encoded by PROC; mutation in both PROC alleles results in neonatal purpura fulminans-a fatal systemic thrombotic disorder. In the present study, we aimed to develop a genome editing treatment to cure congenital PC deficiency.

METHODS

We generated an engineered APC (activated PC) to insert a furin-cleaving peptide sequence between light and heavy chains. The engineered PC was expressed in the liver of mice using an adeno-associated virus vector or CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/clustered regularly interspaced short palindromic repeat-associated 9)-mediated genome editing using an adeno-associated virus vector in vivo.

RESULTS

The engineered PC could be released in its activated form and significantly prolonged the plasma coagulation time independent of the cofactor activity of PS (protein S) in vitro. The adeno-associated virus vector-mediated expression of the engineered PC, but not wild-type PC, prolonged coagulation time owing to the inhibition of activated coagulation FV (factor V) in a dose-dependent manner and abolished pathological thrombus formation in vivo in C57BL/6J mice. The insertion of EGFP (enhanced green fluorescent protein) sequence conjugated with self-cleaving peptide sequence at Alb locus via neonatal in vivo genome editing using adeno-associated virus vector resulted in the expression of EGFP in 7% of liver cells, mainly via homology-directed repair, in mice. Finally, we succeeded in improving the survival of PC-deficient mice by expressing the engineered PC via neonatal genome editing in vivo.

CONCLUSIONS

These results suggest that the expression of engineered PC via neonatal genome editing is a potential cure for severe congenital PC deficiency.

Influence of IL-β, IL-1RN, and TNF-α variants on the risk of acetylsalicylic acid-induced upper gastrointestinal bleeding: a case-control study

OBJECTIVE

Forgerini et al. investigated the role of seven genetic variants in the risk of upper gastrointestinal bleeding as an adverse drug reaction. In 289 participants (50 cases and 189 controls), the presence of seven variants in the IL-1β, IL-1RN, and TNF-α genes was not associated with susceptibility to acetylsalicylic acid-induced upper gastrointestinal bleeding. The use of acetylsalicylic acid, even in low doses, may be associated with the onset of upper gastrointestinal bleeding as an idiosyncratic response. Considering the role of the genetic background in inter-individual responses to pharmacotherapy, we aimed to investigate the role of seven variants in the TNF-α, IL-β, and IL-1RN genes in association with the risk of upper gastrointestinal bleeding in users of low-dose acetylsalicylic acid for the prevention of cardiovascular events.

METHODS

A case-control study was conducted in a Brazilian hospital complex. The Case Group comprised patients diagnosed with upper gastrointestinal bleeding who were administered a low dose of acetylsalicylic acid (n=50). Two Control Groups were recruited: 1) low-dose acetylsalicylic acid users without gastrointestinal complaints and under the supervision of a cardiologist (n=50) and 2) healthy controls (n=189). Sociodemographic, clinical, pharmacotherapeutic, and lifestyle data were recorded through face-to-face interviews. Genomic DNA from all participants was genotyped for rs16944 and rs1143634 (IL-β gene), rs4251961 (IL-1RN gene), and rs1799964, rs1799724, rs361525, and rs1800629 (TNF-α gene).

RESULTS

No significant difference was noted in the genotypic frequencies of TNF-α, IL-β, and IL-1RN variants between the Case and Control Groups of low-dose acetylsalicylic acid users (p>0.05). The frequency of rs1800629 genotypes (TNF-α gene) differed significantly between the Case Group and healthy controls (p=0.003). None of the evaluated variants were associated with a risk of upper gastrointestinal bleeding.

CONCLUSION

This study aimed to explore pharmacogenomics biomarkers in low-dose acetylsalicylic acid users. Our data suggest that the presence of IL-1β, IL-1RN, and TNF-α variants was not associated with an increased risk of upper gastrointestinal bleeding.

Oxidative stress-induced fibrinogen modifications in liver transplant recipients: unraveling a novel potential mechanism for cardiovascular risk

Background

Cardiovascular events represent a major cause of non-graft-related death after liver transplant. Evidence suggest that chronic inflammation associated with a remarkable oxidative stress in the presence of endothelial dysfunction and procoagulant environment plays a major role in the promotion of thrombosis. However, the underlying molecular mechanisms are not completely understood.

Objectives

In order to elucidate the mechanisms of posttransplant thrombosis, the aim of the present study was to investigate the role of oxidation-induced structural and functional fibrinogen modifications in liver transplant recipients.

Methods

A case-control study was conducted on 40 clinically stable liver transplant recipients and 40 age-matched, sex-matched, and risk factor-matched controls. Leukocyte reactive oxygen species (ROS) production, lipid peroxidation, glutathione content, plasma antioxidant capacity, fibrinogen oxidation, and fibrinogen structural and functional features were compared between patients and controls.

Results

Patients displayed enhanced leukocyte ROS production and an increased plasma lipid peroxidation with a reduced total antioxidant capacity compared with controls. This systemic oxidative stress was associated with fibrinogen oxidation with fibrinogen structural alterations. Thrombin-catalyzed fibrin polymerization and fibrin resistance to plasmin-induced lysis were significantly altered in patients compared with controls. Moreover, steatotic graft and smoking habit were associated with high fibrin degradation rate.

Conclusion

ROS-induced fibrinogen structural changes might increase the risk of thrombosis in liver transplant recipients.

Aprotinin (II): Inhalational Administration for the Treatment of COVID-19 and Other Viral Conditions

Aprotinin is a broad-spectrum inhibitor of human proteases that has been approved for the treatment of bleeding in single coronary artery bypass surgery because of its potent antifibrinolytic actions. Following the outbreak of the COVID-19 pandemic, there was an urgent need to find new antiviral drugs. Aprotinin is a good candidate for therapeutic repositioning as a broad-spectrum antiviral drug and for treating the symptomatic processes that characterise viral respiratory diseases, including COVID-19. This is due to its strong pharmacological ability to inhibit a plethora of host proteases used by respiratory viruses in their infective mechanisms. The proteases allow the cleavage and conformational change of proteins that make up their viral capsid, and thus enable them to anchor themselves by recognition of their target in the epithelial cell. In addition, the activation of these proteases initiates the inflammatory process that triggers the infection. The attraction of the drug is not only its pharmacodynamic characteristics but also the possibility of administration by the inhalation route, avoiding unwanted systemic effects. This, together with the low cost of treatment (≈2 Euro/dose), makes it a good candidate to reach countries with lower economic means. In this article, we will discuss the pharmacodynamic, pharmacokinetic, and toxicological characteristics of aprotinin administered by the inhalation route; analyse the main advances in our knowledge of this medication; and the future directions that should be taken in research in order to reposition this medication in therapeutics.

NET-targeted nanoparticles for antithrombotic therapy in pregnancy

Pulmonary embolism caused by deep vein thrombosis (DVT) is a major contributor to maternal morbidity and mortality. There is still an unmet need for safe and effective treatment options for DVT during pregnancy. Recent research has shown that neutrophil extracellular trap (NET) formation plays a very vital role in thrombosis. We created nanoparticles surface-modified by neutrophil elastase (NE)-binding peptide that can target activated neutrophils specifically in vitro and in vivo. Prussian blue nanoparticles (PB NPs) designed in the core scavenges abnormally elevated reactive oxygen species (ROS) in the vascular microenvironment and acts as a photothermal agent to mediate photothermal therapy (PTT) to damage fibrin network structure. Based on the data we have included, this noninvasive therapeutic approach is considered safe for both mothers and the fetus. Furthermore, our findings indicate that this therapeutic approach has a significant alleviation effect on intrauterine growth restriction caused by maternal thrombosis.

Targeting Cysteine Oxidation in Thrombotic Disorders

Oxidative stress increases the risk for clinically significant thrombotic events, yet the mechanisms by which oxidants become prothrombotic are unclear. In this review, we provide an overview of cysteine reactivity and oxidation. We then highlight recent findings on cysteine oxidation events in oxidative stress-related thrombosis. Special emphasis is on the signaling pathway induced by a platelet membrane protein, CD36, in dyslipidemia, and by protein disulfide isomerase (PDI), a member of the thiol oxidoreductase family of proteins. Antioxidative and chemical biology approaches to target cysteine are discussed. Lastly, the knowledge gaps in the field are highlighted as they relate to understanding how oxidative cysteine modification might be targeted to limit thrombosis.

The impact of platelets on pulmonary microcirculation throughout COVID-19 and its persistent activating factors

Patients with COVID-19 often have hypoxemia, impaired lung function, and abnormal imaging manifestations in acute and convalescent stages. Alveolar inflammation, pulmonary vasculitis, and thromboembolism synergistically damage the blood-air barrier, resulting in increased pulmonary permeability and gas exchange disorders. The incidence of low platelet counts correlates with disease severity. Platelets are also involved in the impairment of pulmonary microcirculation leading to abnormal lung function at different phases of COVID-19. Activated platelets lose the ability to protect the integrity of blood vessel walls, increasing the permeability of pulmonary microvasculature. High levels of platelet activation markers are observed in both mild and severe cases, short and long term. Therefore, the risk of thrombotic events may always be present. Vascular endothelial injury, immune cells, inflammatory mediators, and hypoxia participate in the high reactivity and aggregation of platelets in various ways. Microvesicles, phosphatidylserine (PS), platelets, and coagulation factors are closely related. The release of various cell-derived microvesicles can be detected in COVID-19 patients. In addition to providing a phospholipid surface for the synthesis of intrinsic factor Xase complex and prothrombinase complex, exposed PS also promotes the decryption of tissue factor (TF) which then promotes coagulant activity by complexing with factor VIIa to activate factor X. The treatment of COVID-19 hypercoagulability and thrombosis still focuses on early intervention. Antiplatelet therapy plays a role in relieving the disease, inhibiting the formation of the hypercoagulable state, reducing thrombotic events and mortality, and improving sequelae. PS can be another potential target for the inhibition of hypercoagulable states.

Multimodal microscopy for the simultaneous visualization of five different imaging modalities using a single light source

Optical microscopy has been widely used in biomedical research as it provides photophysical and photochemical information of the target in subcellular spatial resolution without requiring physical contact with the specimen. To obtain a deeper understanding of biological phenomena, several efforts have been expended to combine such optical imaging modalities into a single microscope system. However, the use of multiple light sources and detectors through separated beam paths renders previous systems extremely complicated or slow for in vivo imaging. Herein, we propose a novel high-speed multimodal optical microscope system that simultaneously visualizes five different microscopic contrasts, i.e., two-photon excitation, second-harmonic generation, backscattered light, near-infrared fluorescence, and fluorescence lifetime, using a single femtosecond pulsed laser. Our proposed system can visualize five modal images with a frame rate of 3.7 fps in real-time, thereby providing complementary optical information that enhances both structural and functional contrasts. This highly photon-efficient multimodal microscope system enables various properties of biological tissues to be assessed.

Hemostatic abnormalities in COVID-19: A guided review

The spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has already taken on pandemic proportions, affecting over 213 countries in a matter of weeks. In this context, several studies correlating hemostatic disorders with the infection dynamics of the new coronavirus have emerged. These studies have shown that a portion of the patients affected by Coronavirus Disease 2019 (COVID-19) have prolonged prothrombin time (PT) and activated partial thromboplastin time (APTT), elevated D-dimer levels and other fibrinolytic products, antithrombin (AT) activity reduced and decrease of platelet count. Based on these hallmarks, this review proposes to present possible pathophysiological mechanisms involved in the hemostatic changes observed in the pathological progression of COVID-19. In this analysis, it is pointed the relationship between the downregulation of angiotensin-converting enzyme 2 (ACE2) and storm cytokines action with the onset of hypercoagulability state, other than the clinical events involved in thrombocytopenia and hyperfibrinolysis progression.

Macrophages fine-tune pupil shape during development

Tissue macrophages, which are ubiquitously present innate immune cells, play versatile roles in development and organogenesis. During development, macrophages prune transient or unnecessary synapses in neuronal development, and prune blood vessels in vascular development, facilitating appropriate tissue remodeling. In the present study, we identified that macrophages contributed to the development of pupillary morphology. Csf1^op/op mutant mice, in which ocular macrophages are nearly absent, exhibited abnormal pupillary edges, with abnormal protrusions of excess iris tissue into the pupillary space. Macrophages located near the pupillary edge engulfed pigmented debris, which likely consisted of unnecessary iris protrusions that emerge during smoothening of the pupillary edge. Indeed, pupillary edge macrophages phenotypically possessed some features of M2 macrophages, consistent with robust tissue engulfment and remodeling activities. Interestingly, protruding irises in Csf1^op/op mice were only detected in gaps between regressing blood vessels. Taken together, our findings uncovered a new role for ocular macrophages, demonstrating that this cell population is important for iris pruning during development.

Statistical analysis of 3D localisation microscopy images for quantification of membrane protein distributions in a platelet clot model

We present the software platform 2CALM that allows for a comparative analysis of 3D localisation microscopy data representing protein distributions in two biological samples. The in-depth statistical analysis reveals differences between samples at the nanoscopic level using parameters such as cluster-density and -curvature. An automatic classification system combines multiplex and multi-level statistical approaches into one comprehensive parameter for similarity testing of the compared samples. We demonstrated the biological importance of 2CALM, comparing the protein distributions of CD41 and CD62p on activated platelets in a 3D artificial clot. Additionally, using 2CALM, we quantified the impact of the inflammatory cytokine interleukin-1β on platelet activation in clots. The platform is applicable to any other cell type and biological system and can provide new insights into biological and medical applications.

In Vivo Imaging of Venous Thrombus and Pulmonary Embolism Using Novel Murine Venous Thromboembolism Model

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We established a novel clinically relevant murine DVT model at femoral/saphenous vein induced by flow restriction and light illumination.

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Our model newly succeeded in inducing DVT in a valve pocket and enabled spontaneous pulmonary embolism of fibrin-rich thrombus from lower extremity vein, reproducing the clinical VTE scenario.

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This model is suitable for motion-free in vivo high-resolution imaging of fibrin-rich DVT development and organization using 2-photon microscopy, enabling the real-time imaging of migration of platelets and leukocytes into the erythrocyte-rich DVT.

This work established a new murine venous thromboembolism (VTE) model. This model has multiple novel features representing clinical VTE that include the following: 1) deep venous thrombosis (DVT) was formed and extended in the long axis of femoral/saphenous vein; 2) thrombus was formed in a venous valve pocket; 3) deligation of suture-induced spontaneous pulmonary emboli of fibrin-rich DVT; and 4) cardiac motion-free femoral/saphenous vein allowed high-resolution intravital microscopic imaging of fibrin-rich DVT. This new model requires only commercially available epifluorescence microscopy. Therefore, this model has significant potential for better understanding of VTE pathophysiology.

Mouse laser injury models: variations on a theme

A confluence of technological advances in genetic manipulation and molecular-based fluorescence imaging has led to the widespread adoption of laser injury models to study hemostasis and thrombosis in mice. In all animal models of hemostasis and thrombosis, detailing the nature of experimentally induced vascular injury is paramount in enabling appropriate interpretation of experimental results. A careful appraisal of the literature shows that direct laser-induced injury can result in variable degrees of vascular damage. This review will compare and contrast models of laser injury utilized in the field, with an emphasis on the mechanism and extent of injury, the use of laser injury in different vascular beds and the molecular mechanisms regulating the response to injury. All of these topics will be discussed in the context of how distinct applications of laser injury models may be viewed as representing thrombosis and/or hemostasis.

Recognition of PF4-VWF complexes by heparin-induced thrombocytopenia antibodies contributes to thrombus propagation

Heparin-induced thrombocytopenia (HIT) is a prothrombotic disorder mediated by complexes between platelet factor 4 (PF4) and heparin or other polyanions, but the risk of thrombosis extends beyond exposure to heparin implicating other PF4 partners. We recently reported that peri-thrombus endothelium is targeted by HIT antibodies, but the binding site(s) has not been identified. We now show that PF4 binds at multiple discrete sites along the surface of extended strings of von Willebrand factor (VWF) released from the endothelium following photochemical injury in an endothelialized microfluidic system under flow. The HIT-like monoclonal antibody KKO and HIT patient antibodies recognize PF4-VWF complexes, promoting platelet adhesion and enlargement of thrombi within the microfluidic channels. Platelet adhesion to the PF4-VWF-HIT antibody complexes is inhibited by antibodies that block FcγRIIA or the glycoprotein Ib-IX complex on platelets. Disruption of PF4-VWF-HIT antibody complexes by drugs that prevent or block VWF oligomerization attenuate thrombus formation in a murine model of HIT. Together, these studies demonstrate assembly of HIT immune complexes along VWF strings released by injured endothelium that might propagate the risk of thrombosis in HIT. Disruption of PF4-VWF complex formation may provide a new therapeutic approach to HIT.

Experimental pathology by intravital microscopy and genetically encoded fluorescent biosensors

The invention of two‐photon excitation microscopes widens the potential application of intravital microscopy (IVM) to the broad field of experimental pathology. Moreover, the recent development of fluorescent protein‐based, genetically encoded biosensors provides an ideal tool to visualize the cell function in live animals. We start from a brief review of IVM with two‐photon excitation microscopes and genetically encoded biosensors based on the principle of Förster resonance energy transfer (FRET). Then, we describe how IVM using biosensors has revealed the pathogenesis of several disease models.

In vivo analysis of thrombus formation in arthritic mice

OBJECTIVES

Rheumatoid arthritis (RA) is characterized by inflammation in multiple joints. In addition to causing joint destruction, the persistent systemic inflammation with RA increases the risk of cardiovascular disease. Although there are in vitro studies showing the prothrombotic effect of inflammatory cytokines, especially TNF, in vivo experimental evidence is lacking due to the complexity of in vivo modeling and observation. In this study, we aimed to model in vivo thrombus formation in arthritic mice and to determine whether the arthritic condition would further promote thrombotic formation.

METHODS

Human TNF-transgenic mice were used as the arthritis model. Thrombus formation was observed on the testicular arterioles. Thrombus formation was induced by reactive oxygen species generated from hematoporphyrin under laser irradiation.

RESULTS

Platelet thrombus formation was observed in real-time using a laser confocal microscopy in both wild-type and arthritic mice. Quantitative analyses revealed that no significant differences were observed in thrombus formation, represented by platelet attachment time and vascular obstruction time, in our experimental setting.

CONCLUSION

Although we confirmed the usefulness of this novel technique for in vivo studies, further investigation is required to conclude the possible mechanism of prothrombotic phenotypes under inflammatory conditions.

Effects of huoxin formula on the arterial functions of patients with coronary heart disease

Context: Huoxin formula is a Traditional Chinese Medicine for coronary heart disease (CHD) treatment. Objective: To explore the therapeutic mechanism of the Huoxin formula on arterial functions in CHD patients. Materials and methods: Fifty-eight CHD patients receiving cardiovascular drugs including β-receptor blocker, statins, and antiplatelet medications or others were randomized into intervention [additionally 13.5 g Huoxin formula granules dissolved in 150 mL warm water per time, twice a day (n = 30)] and control [only cardiovascular drugs (n = 28)] groups. Serum biomarkers (hs-CRP, IL-18, IL-17, TNF-α, MMP-9), and cardiovascular indicators of the common and internal carotid arteries (ICAs) were monitored before and after the treatments. Results: After 3 months of treatment, the increases of intima-media thicknesses (IMT) of the left and right common carotid arteries (CCAs) as well as of the left and right ICAs and the increases of the left and right cardio-ankle vascular index were all significantly (all p < 0.001) less in the intervention than in control group (all p < 0.001). Serum concentrations reductions of hs-CRP, IL-18, IL-17 and MMP9 (all p < 0.001) levels were higher in the intervention compared to the control group, which correlated with the changes of left ICA (hs-CRP: r = 0.581, p = 0.009; IL-18: r = 0.594, p = 0.007; IL-17: r = 0.575, p = 0.006). Discussion and conclusion: Since the Huoxin formula improved arterial functions and reduced inflammatory factor activities in CHD patients, a large-scale clinical trial is warranted.

Neutrophils promote venular thrombosis by shaping the rheological environment for platelet aggregation

In advanced inflammatory disease, microvascular thrombosis leads to the interruption of blood supply and provokes ischemic tissue injury. Recently, intravascularly adherent leukocytes have been reported to shape the blood flow in their immediate vascular environment. Whether these rheological effects are relevant for microvascular thrombogenesis remains elusive. Employing multi-channel in vivo microscopy, analyses in microfluidic devices, and computational modeling, we identified a previously unanticipated role of leukocytes for microvascular clot formation in inflamed tissue. For this purpose, neutrophils adhere at distinct sites in the microvasculature where these immune cells effectively promote thrombosis by shaping the rheological environment for platelet aggregation. In contrast to larger (lower-shear) vessels, this process in high-shear microvessels does not require fibrin generation or extracellular trap formation, but involves GPIbα-vWF and CD40-CD40L-dependent platelet interactions. Conversely, interference with these cellular interactions substantially compromises microvascular clotting. Thus, leukocytes shape the rheological environment in the inflamed venular microvasculature for platelet aggregation thereby effectively promoting the formation of blood clots. Targeting this specific crosstalk between the immune system and the hemostatic system might be instrumental for the prevention and treatment of microvascular thromboembolic pathologies, which are inaccessible to invasive revascularization strategies.

Contribution of the TNF-α (Tumor Necrosis Factor-α)-TNF-Rp55 (Tumor Necrosis Factor Receptor p55) Axis in the Resolution of Venous Thrombus

Objective- Deep vein thrombosis results from a combination of risk factors including genetic conditions, obesity, drugs, pregnancy, aging, and malignancy. We examined pathophysiological roles of the TNF-α (tumor necrosis factor-α)-TNF-Rp55 (tumor necrosis factor receptor p55) axis in thrombus resolution using Tnfrp55^-/- (TNF-Rp55-deficient) mice. Approach and Results- On ligating the inferior vena cava of wild-type (WT) mice, venous thrombi formed and grew progressively until 5 days but shrunk to <50% of the thrombus weight at day 14. Concomitantly, inferior vena cava ligation enhanced intrathrombotic gene expression of Tnfa and Tnfrp55, and intrathrombotic macrophages expressed both TNF-α and TNF-Rp55 proteins. In Tnfrp55^-/- mice treated with the same manner, thrombus formed at a similar rate for 5 days, but shrinking was delayed compared with WT mice. Moreover, the blood flow recovery in thrombosed inferior vena cava was suspended in Tnfrp55^-/- mice compared with WT mice. Intrathrombotic Plau (urokinase-type plasminogen activator), Mmp2 (matrix metalloproteinase 2), and Mmp9 (matrix metalloproteinase 9) mRNA expression was significantly reduced in Tnfrp55^-/- mice, compared with WT ones. Supportingly, the administration of anti-TNF-α antibody or TNF-α inhibitor (etanercept) delayed the thrombus resolution in WT mice. Furthermore, TNF-α treatment enhanced gene expression of Plau, Mmp2, and Mmp9 in WT macrophages but not Tnfrp55^-/- macrophages. These effects were significantly suppressed by ERK (extracellular signal regulated kinase) and NF-κB (nuclear factor-kappa B) inhibitors. Therefore, the lack of TNF-Rp55 has detrimental roles in the thrombus resolution by suppressing PLAU, MMP-2, and MMP-9 expression. In contrast, TNF-α administration accelerated thrombus resolution in WT but not Tnfrp55^-/- mice. Conclusions- The TNF-α-TNF-Rp55 axis may have essential roles in the resolution of venous thrombus in mice.

Association between TNF-α polymorphisms and the risk of upper gastrointestinal bleeding induced by aspirin in patients with coronary heart disease

OBJECTIVE

To investigate the correlation of tumor necrosis factor α (TNF-α) polymorphisms with upper gastrointestinal bleeding (UGIB) induced by enteric-coated aspirin in coronary heart disease (CHD) patients.

METHODS

In total, 154 CHD patients taking enteric-coated aspirin were enrolled in this study. Patients were divided into the UGIB group (n = 57) and non-UGIB group (n = 97) based on the presence or absence of signs of UGIB, respectively. TNF-α polymorphism (-857C > T, -863C > A, and -1031T > C) genotyping was performed using polymerase chain reaction (PCR) amplification with sequence-specific primers (PCR-SSP).

RESULTS

Patients who had the CC genotype and C allele of -1031T > C exhibited a significantly increase risk of UGIB after receiving enteric-coated aspirin (CC vs. TT: odds (OR) (95% confidence interval (CI)): 7.568 (1.527-37.49), P = 0.005; C vs. T: OR (95% CI): 1.852 (1.036-3.312), P = 0.036). Patients who had CA and CA + AA genotypes and the A allele of -863C > A also exhibited an increased risk of aspirin-induced UGIB (CA vs. CC: OR (95% CI): 2.415 (1.143-5.101), P = 0.019: CA + AA vs. CC: OR (95% CI): 2.218 (1.123-4.381), P = 0.021; A vs. C: OR (95% CI): 1.788 (1.039-3.078), P = 0.035). However, the TNF-α -857 C > T polymorphism was unrelated to the induction of UGIB by enteric-coated aspirin in CHD patients (P > 0.05). In addition, the haplotypes of CCC (-1031T > C, -863C > A, and -857C > T) markedly reduced the risk of aspirin-induced UGIB in CHD patients.

CONCLUSION

TNF-α -863A and -1031C increased the risk of UGIB induction by enteric-coated aspirin in CHD patients, whereas TNF-α -857C > T was not correlated with the UGIB risk.

Turbulence Activates Platelet Biogenesis to Enable Clinical Scale Ex Vivo Production

The ex vivo generation of platelets from human-induced pluripotent cells (hiPSCs) is expected to compensate donor-dependent transfusion systems. However, manufacturing the clinically required number of platelets remains unachieved due to the low platelet release from hiPSC-derived megakaryocytes (hiPSC-MKs). Here, we report turbulence as a physical regulator in thrombopoiesis in vivo and its application to turbulence-controllable bioreactors. The identification of turbulent energy as a determinant parameter allowed scale-up to 8 L for the generation of 100 billion-order platelets from hiPSC-MKs, which satisfies clinical requirements. Turbulent flow promoted the release from megakaryocytes of IGFBP2, MIF, and Nardilysin to facilitate platelet shedding. hiPSC-platelets showed properties of bona fide human platelets, including circulation and hemostasis capacities upon transfusion in two animal models. This study provides a concept in which a coordinated physico-chemical mechanism promotes platelet biogenesis and an innovative strategy for ex vivo platelet manufacturing.

Transplantation of bioengineered rat lungs recellularized with endothelial and adipose-derived stromal cells

Bioengineered lungs consisting of a decellularized lung scaffold that is repopulated with a patient's own cells could provide desperately needed donor organs in the future. This approach has been tested in rats, and has been partially explored in porcine and human lungs. However, existing bioengineered lungs are fragile, in part because of their immature vascular structure. Herein, we report the application of adipose-derived stem/stromal cells (ASCs) for engineering the pulmonary vasculature in a decellularized rat lung scaffold. We found that pre-seeded ASCs differentiated into pericytes and stabilized the endothelial cell (EC) monolayer in nascent pulmonary vessels, thereby contributing to EC survival in the regenerated lungs. The ASC-mediated stabilization of the ECs clearly reduced vascular permeability and suppressed alveolar hemorrhage in an orthotopic transplant model for up to 3 h after extubation. Fibroblast growth factor 9, a mesenchyme-targeting growth factor, enhanced ASC differentiation into pericytes but overstimulated their proliferation, causing a partial obstruction of the vasculature in the regenerated lung. ASCs may therefore provide a promising cell source for vascular regeneration in bioengineered lungs, though additional work is needed to optimize the growth factor or hormone milieu for organ culture.

Abnormal von Willebrand factor secretion, factor VIII stabilization and thrombus dynamics in type 2N von Willebrand disease mice

Essentials Type 2N von Willebrand disease involves impaired von Willebrand factor to factor VIII binding. Type 2N von Willebrand disease mutations exhibit qualitative and mild quantitative deficiencies. Type 2N von Willebrand disease mice exhibit unstable venous hemostatic thrombi. The factor VIII-binding ability of von Willebrand factor regulates arteriole thrombosis dynamics.

SUMMARY

Background von Willebrand factor (VWF) and factor VIII (FVIII) circulate as a non-covalent complex, with VWF serving as the carrier for FVIII. VWF indirectly influences secondary hemostasis by stabilizing FVIII and transporting it to the site of primary hemostasis. Type 2N von Willebrand disease involves impaired binding of VWF to FVIII, resulting in decreased plasma levels of FVIII. Objectives In these studies, we characterize the impact of three type 2N VWD variants (R763A, R854Q, R816W) on VWF secretion, FVIII stabilization and thrombus formation in a murine model. Methods Type 2N VWD mice were generated by hydrodynamic injections of mutant murine VWF cDNAs and the influence of these variants on VWF secretion and FVIII binding was evaluated. In vivo hemostasis and the dynamics of thrombus formation and embolization were assessed using a murine tail vein transection hemostasis model and an intravital thrombosis model in the cremaster arterioles. Results Type 2N VWD variants were associated with decreased VWF secretion using cell and animal-based models. FVIII-binding to type 2N variants was impaired in vitro and was variably stabilized in vivo by expressed or infused 2N variant VWF protein. Both transgenic type 2N VWD and FVIII knockout (KO) mice demonstrated impaired thrombus formation associated with decreased thrombus stability. Conclusions The type 2N VWD phenotype can be recapitulated in a murine model and is associated with both quantitative and qualitative VWF deficiencies and impaired thrombus formation. Patients with type 2N VWD may have normal primary hemostasis formation but decreased thrombus stability related to ineffective secondary hemostasis.

Live imaging of extracellular signal-regulated kinase and protein kinase A activities during thrombus formation in mice expressing biosensors based on Förster resonance energy transfer

Essentials Spatiotemporal regulation of protein kinases during thrombus formation remains elusive in vivo. Activities of protein kinases were live imaged in mouse platelets at laser-ablated arterioles. Protein kinase A was activated in the dislodging platelets at the downstream side of the thrombus. Extracellular signal-regulated kinase was activated at the core of contracting platelet aggregates.

SUMMARY

Background The dynamic features of thrombus formation have been visualized by conventional video widefield microscopy or confocal microscopy in live mice. However, owing to technical limitations, the precise spatiotemporal regulation of intracellular signaling molecule activities, which have been extensively studied in vitro, remains elusive in vivo. Objectives To visualize, by the use of two-photon excitation microscopy of transgenic mice expressing Förster resonance energy transfer (FRET) biosensors for extracellular signal-regulated kinase (ERK) and protein kinase A (PKA), ERK and PKA activities during thrombus formation in laser-injured subcutaneous arterioles. Results When a core of densely packed platelets had developed, ERK activity was increased from the basal region close to the injured arterioles. PKA was activated at the downstream side of an unstable shell overlaying the core of platelets. Intravenous administration of a MEK inhibitor, PD0325901, suppressed platelet tethering and dislodged platelet aggregates, indicating that ERK activity is indispensable for both initiation and maintenance of the thrombus. A cAMP analog, dbcAMP, inhibited platelet tethering but failed to dislodge the preformed platelet aggregates, suggesting that PKA can antagonize thrombus formation only in the early phase. Conclusion In vivo imaging of transgenic mice expressing FRET biosensors will open a new opportunity to visualize the spatiotemporal changes in signaling molecule activities not only during thrombus formation but also in other hematologic disorders.

N-acetylcysteine in preclinical mouse and baboon models of thrombotic thrombocytopenic purpura

Prophylactic administration of NAC was effective in preventing severe TTP signs in mice by reducing the VWF multimer size. In both mice and baboons, NAC was not effective in resolving preexisting TTP signs, as thrombus resolution could not be achieved.

Endothelial antigen assembly leads to thrombotic complications in heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a prothrombotic disorder initiated by antibodies against complexes between human platelet factor 4 (hPF4) and heparin. A better understanding of the events that initiate the prothrombotic state may improve approaches to antithrombotic management. Here, we visualized thrombus formation in an in vivo murine model and an endothelialized microfluidic system that simulate the pathogenesis of HIT. hPF4 released from platelets predominantly bound to peri-injury endothelium and formed HIT antigenic complexes that were dissociated by heparin. In mice expressing both hPF4+ and human platelet IgG Fc receptor IIA (FcγRIIA), infusion of the HIT-like monoclonal antibody KKO increased fibrin and platelet deposition at sites of injury, followed immediately by antigen formation on proximate endothelial cells. After a few minutes, HIT antigen was detected within the thrombus itself at the interface between the platelet core and the surrounding shell. We observed similar results in the humanized, endothelialized microfluidic system. hPF4 and KKO selectively bound to photochemically injured endothelium at sites where surface glycocalyx was reduced. These studies support the concept that the perithrombus endothelium is the predominant site of HIT antigen assembly. This suggests that disrupting antigen formation along the endothelium or protecting the endothelium may provide a therapeutic opportunity to prevent thrombotic complications of HIT, while sparing systemic hemostatic pathways.

Thrombocytopathy leading to impaired in vivo haemostasis and thrombosis in platelet type von Willebrand disease

Platelet defects due to hyper-responsive GPIbα causing enhanced VWF interaction, counter-intuitively result in bleeding rather than thrombosis. The historical explanation of platelet/VWF clearance fails to explain mechanisms of impaired haemostasis particularly in light of reported poor platelet binding to fibrinogen. This study aimed to evaluate the defects of platelets with hyper-responsive GPIbα and their contribution to impaired in vivo thrombosis. Using the PT-VWD mouse model, platelets from the hTg^G233V were compared to control hTg^WT mice. Platelets' pro-coagulant capacity was evaluated using flowcytometry assessment of P-selectin and annexin V. Whole blood platelet aggregation in response to ADP, collagen and thrombin was tested. Clot kinetics using laser injury thrombosis model and the effect of GPIbα inhibition in vivo using 6B4; a monoclonal antibody, were evaluated. Thrombin-induced platelet P-selectin and PS exposure were significantly reduced in hTg^G233V compared to hTg^WT and not significantly different when compared to unstimulated platelets. The hTg^G233V platelets aggregated normally in response to collagen, and had a delayed response to ADP and thrombin, when compared to hTg^WT platelets. Laser injury showed significant impairment of in vivo thrombus formation in hTg^G233V compared to hTg^WT mice. There was a significant lag in in vitro clot formation in turbidity assay but no impairment in thrombin generation was observed using thromboelastography. The in vivo inhibition of GPIbα facilitated new - unstable - clot formation but did not improve the lag. We conclude platelets with hyper-responsive GPIbα have complex intrinsic defects beyond the previously described mechanisms. Abnormal signalling through GPIbα and potential therapy using inhibitors require further investigations.

Histones link inflammation and thrombosis through the induction of Weibel-Palade body exocytosis

Essentials Dysregulated DNA and histone release can promote pathological immunothrombosis. Weibel-Palade bodies (WPBs) are sentinel-like organelles that respond to proinflammatory stimuli. Histones induce WPB exocytosis in a caspase, calcium and charge-dependent mechanism. A targetable axis may exist between DNA/histones and WPBs in inflammation and immunothrombosis.

SUMMARY

Background Damage-associated molecular patterns (DAMPs), including molecules such as DNA and histones, are released into the blood following cell death. DAMPs promote a procoagulant phenotype through enhancement of thrombin generation and platelet activation, thereby contributing to immunothrombosis. Weibel-Palade bodies (WPBs) are dynamic endothelial cell organelles that contain procoagulant and proinflammatory mediators, such as von Willebrand factor (VWF), and are released in response to cell stresses. VWF mediates platelet adhesion and aggregation, and has been implicated as a procoagulant component of the innate immune response. Objective To determine the influence of histones and DNA on WPB release, and characterize their association in models of inflammation. Methods We treated C57BL/6J mice and cultured endothelial cells with histones (unfractionated, lysine-rich or arginine-rich) and DNA, and measured WPB exocytosis. We used inhibitors to determine a mechanism of histone-induced WPB release in vitro. We characterized the release of DAMPs and WPBs in response to acute and chronic inflammation in human and murine models. Results and conclusions Histones, but not DNA, induced the release of VWF (1.46-fold) from WBPs and caused thrombocytopenia (0.74-fold), which impaired arterial thrombus formation in mice. Histones induced WPB release from endothelial cells in a caspase-dependent, calcium-dependent and charge-dependent manner, and promoted platelet capture in a flow chamber model of VWF-platelet string formation. The levels of DAMPs and WPB-released proteins were elevated during inflammation, and were positively correlated in chronic inflammation. These studies showed that DAMPs can regulate the function and level of VWF by inducing its release from endothelial WPBs. This DAMP-WPB axis may propagate immunothrombosis associated with inflammation.

Selective Inhibition of ADAM17 Efficiently Mediates Glycoprotein Ibα Retention During Ex Vivo Generation of Human Induced Pluripotent Stem Cell-Derived Platelets

Donor‐independent platelet concentrates for transfusion can be produced in vitro from induced pluripotent stem cells (iPSCs). However, culture at 37°C induces ectodomain shedding on platelets of glycoprotein Ibα (GPIbα), the von Willebrand factor receptor critical for adhesive function and platelet lifetime in vivo, through temperature‐dependent activation of a disintegrin and metalloproteinase 17 (ADAM17). The shedding can be suppressed by using inhibitors of panmetalloproteinases and possibly of the upstream regulator p38 mitogen‐activated protein kinase (p38 MAPK), but residues of these inhibitors in the final platelet products may be accompanied by harmful risks that prevent clinical application. Here, we optimized the culture conditions for generating human iPSC‐derived GPIbα⁺ platelets, focusing on culture temperature and additives, by comparing a new and safe selective ADAM17 inhibitor, KP‐457, with previous inhibitors. Because cultivation at 24°C (at which conventional platelet concentrates are stored) markedly diminished the yield of platelets with high expression of platelet receptors, 37°C was requisite for normal platelet production from iPSCs. KP‐457 blocked GPIbα shedding from iPSC platelets at a lower half‐maximal inhibitory concentration than panmetalloproteinase inhibitor GM‐6001, whereas p38 MAPK inhibitors did not. iPSC platelets generated in the presence of KP‐457 exhibited improved GPIbα‐dependent aggregation not inferior to human fresh platelets. A thrombus formation model using immunodeficient mice after platelet transfusion revealed that iPSC platelets generated with KP‐457 exerted better hemostatic function in vivo. Our findings suggest that KP‐457, unlike GM‐6001 or p38 MAPK inhibitors, effectively enhances the production of functional human iPSC‐derived platelets at 37°C, which is an important step toward their clinical application. Stem Cells Translational Medicine2017;6:720–730

Platelets in Pulmonary Immune Responses and Inflammatory Lung Diseases

Platelets are essential for physiological hemostasis and are central in pathological thrombosis. These are their traditional and best known activities in health and disease. In addition, however, platelets have specializations that broaden their functional repertoire considerably. These functional capabilities, some of which are recently discovered, include the ability to sense and respond to infectious and immune signals and to act as inflammatory effector cells. Human platelets and platelets from mice and other experimental animals can link the innate and adaptive limbs of the immune system and act across the immune continuum, often also linking immune and hemostatic functions. Traditional and newly recognized facets of the biology of platelets are relevant to defensive, physiological immune responses of the lungs and to inflammatory lung diseases. The emerging view of platelets as blood cells that are much more diverse and versatile than previously thought further predicts that additional features of the biology of platelets and of megakaryocytes, the precursors of platelets, will be discovered and that some of these will also influence pulmonary immune defenses and inflammatory injury.

Role of oxidative stress on platelet hyperreactivity during aging

Thrombotic events are common causes of morbidity and mortality in the elderly. Age-accelerated vascular injury is commonly considered to result from increased oxidative stress. There is abundant evidence that oxidative stress regulate several components of thrombotic processes, including platelet activation. Thus oxidative stress can trigger platelet hyperreactivity by decreasing nitric oxide bioavailability. Therefore oxidative stress measurement may help in the early identification of asymptomatic subjects at risk of thrombosis. In addition, oxidative stress inhibitors and platelet-derived nitric oxide may represent a novel anti-aggregation/-activation approach. In this article the relative contribution of oxidative stress and platelet activation in aging is explored.

Neutrophil Activation Promotes Fibrinogen Oxidation and Thrombus Formation in Behçet Disease

Background—

Behçet disease (BD) is a systemic vasculitis with a broad range of organ involvement, characterized by a multisystemic, immune-inflammatory disorder involving vessels of all sizes and often complicated by thrombosis. Systemic redox imbalance and circulating neutrophil hyperactivation have been observed in BD patients and are thought to be responsible for impaired coagulation. We here focused on the pathogenetic mechanisms potentially linking immune cell activation and thrombosis, and specifically examined whether neutrophil activation can affect fibrinogen modifications and consequently elicit thrombosis.

Methods and Results—

Blood samples were collected from 98 consecutive BD patients attending our dedicated Center and from 70 age- and sex-matched healthy controls; in all patients fibrinogen function and structure, fibrin susceptibility to plasmin-lysis, plasma redox status, leukocyte oxidative stress markers, and possible reactive oxygen species sources were examined. Thrombin-catalyzed fibrin formation and fibrin susceptibility to plasmin-induced lysis were significantly impaired in BD patients ( P <0.001). These findings were associated with increased plasma oxidative stress markers ( P <0.001) and with a marked carbonylation of fibrinogen ( P <0.001), whose secondary structure appeared deeply modified. Neutrophils displayed an enhanced NADPH oxidase activity and increased reactive oxygen species production ( P <0.001), which significantly correlated with fibrinogen carbonylation level ( r 2 =0.33, P <0.0001), residual β-band intensity ( r 2 =0.07, P <0.01), and fibrinogen clotting ability ( r 2 =0.073, P <0.01)

Conclusions—

In BD patients, altered fibrinogen structure and impaired fibrinogen function are associated with neutrophil activation and enhanced reactive oxygen species production whose primary source is represented by neutrophil NADPH oxidase.

The C-terminal CGHC motif of protein disulfide isomerase supports thrombosis

Protein disulfide isomerase (PDI) has two distinct CGHC redox-active sites; however, the contribution of these sites during different physiologic reactions, including thrombosis, is unknown. Here, we evaluated the role of PDI and redox-active sites of PDI in thrombosis by generating mice with blood cells and vessel wall cells lacking PDI (Mx1-Cre Pdifl/fl mice) and transgenic mice harboring PDI that lacks a functional C-terminal CGHC motif [PDI(ss-oo) mice]. Both mouse models showed decreased fibrin deposition and platelet accumulation in laser-induced cremaster arteriole injury, and PDI(ss-oo) mice had attenuated platelet accumulation in FeCl3-induced mesenteric arterial injury. These defects were rescued by infusion of recombinant PDI containing only a functional C-terminal CGHC motif [PDI(oo-ss)]. PDI infusion restored fibrin formation, but not platelet accumulation, in eptifibatide-treated wild-type mice, suggesting a direct role of PDI in coagulation. In vitro aggregation of platelets from PDI(ss-oo) mice and PDI-null platelets was reduced; however, this defect was rescued by recombinant PDI(oo-ss). In human platelets, recombinant PDI(ss-oo) inhibited aggregation, while recombinant PDI(oo-ss) potentiated aggregation. Platelet secretion assays demonstrated that the C-terminal CGHC motif of PDI is important for P-selectin expression and ATP secretion through a non-αIIbβ3 substrate. In summary, our results indicate that the C-terminal CGHC motif of PDI is important for platelet function and coagulation.

Spatiotemporal regulation of coagulation and platelet activation during the hemostatic response in vivo

The hemostatic response requires the tightly regulated interaction of the coagulation system, platelets, other blood cells and components of the vessel wall at a site of vascular injury. The dysregulation of this response may result in excessive bleeding if the response is impaired, and pathologic thrombosis with vessel occlusion and tissue ischemia if the response is overly robust. Extensive studies over the past decade have sought to unravel the regulatory mechanisms that coordinate the multiple biochemical and cellular responses in time and space to ensure that an optimal response to vascular damage is achieved. These studies have relied in part on advances in in vivo imaging techniques in animal models, allowing for the direct visualization of various molecular and cellular events in real time during the hemostatic response. This review summarizes knowledge gained with these in vivo imaging and other approaches that provides new insights into the spatiotemporal regulation of coagulation and platelet activation at a site of vascular injury.

TMEM16F is required for phosphatidylserine exposure and microparticle release in activated mouse platelets

Phosphatidylserine (PtdSer) exposure on the surface of activated platelets requires the action of a phospholipid scramblase(s), and serves as a scaffold for the assembly of the tenase and prothrombinase complexes involved in blood coagulation. Here, we found that the activation of mouse platelets with thrombin/collagen or Ca(2+) ionophore at 20 °C induces PtdSer exposure without compromising plasma membrane integrity. Among five transmembrane protein 16 (TMEM16) members that support Ca(2+)-dependent phospholipid scrambling, TMEM16F was the only one that showed high expression in mouse platelets. Platelets from platelet-specific TMEM16F-deficient mice exhibited defects in activation-induced PtdSer exposure and microparticle shedding, although α-granule and dense granule release remained intact. The rate of tissue factor-induced thrombin generation by TMEM16F-deficient platelets was severely reduced, whereas thrombin-induced clot retraction was unaffected. The imaging of laser-induced thrombus formation in whole animals showed that PtdSer exposure on aggregated platelets was TMEM16F-dependent in vivo. The phenotypes of the platelet-specific TMEM16F-null mice resemble those of patients with Scott syndrome, a mild bleeding disorder, indicating that these mice may provide a useful model for human Scott syndrome.

Inflammasome in platelets: allying coagulation and inflammation in infectious and sterile diseases?

Platelets are crucial effector cells in hemostasis. In addition, platelets are increasingly recognized as major inflammatory cells with key roles in innate and adaptive immune responses. Activated platelets have key thromboinflammatory activities linking coagulation to inflammatory response in a variety of coagulation disorders and vasculopathies. Recently identified inflammatory activities of platelets include the synthesis of IL-1β from spliced pre-RNA, as well as the presence and assembly of inflammasome which intermediate IL-1β secretion. Here we review the mechanisms by which platelets activate translation machinery and inflammasome assembly to synthesize and release IL-1β. The contributions of these processes to protective and pathogenic responses during infectious and inflammatory diseases are discussed.

Shaping the platelet response to vascular injury

PURPOSE OF REVIEW

Several decades of work by many investigators have elucidated the major signaling pathways responsible for platelet activation. Still to be fully understood is how these pathways are integrated into a single network and how changing conditions within a growing thrombus affect that network. In this review we will consider some of the recent studies that address these issues and describe a model that provides insights into platelet activation as it occurs in vivo.

RECENT FINDINGS

Genetic and pharmacologic studies performed in vivo have demonstrated that platelet activation during hemostasis and thrombosis is heterogeneous. Those studies indicate that distinct platelet activation pathways are not merely redundant, but are coordinated in time and space to achieve an optimal response. This coordination is achieved at least in part by the evolving distribution of platelet agonists and changes in solute transport within a hemostatic plug.

SUMMARY

Studies examining the coordination of platelet signaling in time and space continue to increase our understanding of hemostasis and thrombosis. In addition to helping to decipher platelet biology, the results have implications for the understanding of new and existing antiplatelet agents and their potential risks.

Simultaneous downregulation of KLF5 and Fli1 is a key feature underlying systemic sclerosis

Systemic sclerosis (SSc) is manifested by fibrosis, vasculopathy and immune dysregulation. So far, a unifying hypothesis underpinning these pathological events remains unknown. Given that SSc is a multifactorial disease caused by both genetic and environmental factors, we focus on the two transcription factors, which modulate the fibrotic reaction and are epigenetically suppressed in SSc dermal fibroblasts, Friend leukemia integration 1 (Fli1) and Krüppel-like factor 5 (KLF5). In addition to Fli1 silencing-dependent collagen induction, simultaneous knockdown of Fli1 and KLF5 synergistically enhances expression of connective tissue growth factor. Notably, mice with double heterozygous deficiency of Klf5 and Fli1 mimicking the epigenetic phenotype of SSc skin spontaneously recapitulate all the three features of SSc, including fibrosis and vasculopathy of the skin and lung, B cell activation, and autoantibody production. These studies implicate the epigenetic downregulation of Fli1 and KLF5 as a central event triggering the pathogenic triad of SSc.

Inactivation of a common OGG1 variant by TNF-alpha in mammalian cells

Reactive oxygen species threaten genomic integrity by inducing oxidative DNA damage. One common form of oxidative DNA damage is the mutagenic lesion 8-oxoguanine (8-oxodG). One driver of oxidative stress that can induce 8-oxodG is inflammation, which can be initiated by the cytokine tumor necrosis factor alpha (TNF-α). Oxidative DNA damage is primarily repaired by the base excision repair pathway, initiated by glycosylases targeting specific DNA lesions. 8-oxodG is excised by 8-oxoguanine glycosylase 1 (OGG1). A common Ogg1 allelic variant is S326C-Ogg1, prevalent in Asian and Caucasian populations. S326C-Ogg1 is associated with various forms of cancer, and is inactivated by oxidation. However, whether oxidative stress caused by inflammatory cytokines compromises OGG1 variant repair activity remains unknown. We addressed whether TNF-α causes oxidative stress that both induces DNA damage and inactivates S326C-OGG1 via cysteine 326 oxidation. In mouse embryonic fibroblasts, we found that S326C-OGG1 was inactivated only after exposure to H2O2 or TNF-α. Treatment with the antioxidant N-acetylcysteine prior to oxidative stress rescued S326C-OGG1 activity, demonstrated by in vitro and cellular repair assays. In contrast, S326C-OGG1 activity was unaffected by potassium bromate, which induces oxidative DNA damage without causing oxidative stress, and presumably cysteine oxidation. This study reveals that Cys326 is vulnerable to oxidation that inactivates S326C-OGG1. Physiologically relevant levels of TNF-α simultaneously induce 8-oxodG and inactivate S326C-OGG1. These results suggest a mechanism that could contribute to increased risk of cancer among S326C-Ogg1 homozygous individuals.

Assessment of changes in membrane properties of platelets from patients with chronic myeloid leukaemia in different stages of the disease

Patients with chronic myeloproliferative leukemia (CML) have frequent haemorrhage and/or thrombosis in their medical history. The mechanisms of these major and life-threatening complications remain unclear. Membrane organization influences many of the unique cellular functions and is strongly correlated, among other factors, to the membrane lipid composition; it may be evaluated by following up the membrane fluidity and aggregation properties of the platelet. In this study, we evaluated the platelet aggregation, the expression of platelet surface receptors, the membrane fluidity (as evaluated by fluorescence anisotropy) and its correlation to reactive oxygen species (ROS) production, in patients with chronic myeloid leukaemia (CML). It was found that the patients in accelerated and blastic phase of CML present an altered platelet aggregation response to all reagents except for ristocetin as compared with chronic phase group, which shows only epinephrine-altered response. We also found that BCR/ABL transcript leads to higher levels of ROS in accelerated and blastic CML phases. Patients without molecular remission have lower platelet membrane fluidity. We obtained a positive correlation between ROS level and membrane fluorescence anisotropy changes. The CD41 expression was decreased in CML patients and P selectin expression was found to be higher in these patients than in healthy volunteers. Platelets of CML patients have altered aggregation parameters in accelerated and blastic phases, in which BCR/ABL transcript level is increased. The increased level of ROS in CML patients without molecular remission is associated with a decrease in fluidity of platelet membrane and expression of CD41/CD61 receptors. These findings may contribute to understanding the mechanism of the altered platelet response reported in CML patients.

Discovery of prognostic biomarker candidates of lacunar infarction by quantitative proteomics of microvesicles enriched plasma

Background

Lacunar infarction (LACI) is a subtype of acute ischemic stroke affecting around 25% of all ischemic stroke cases. Despite having an excellent recovery during acute phase, certain LACI patients have poor mid- to long-term prognosis due to the recurrence of vascular events or a decline in cognitive functions. Hence, blood-based biomarkers could be complementary prognostic and research tools.

Methods and Finding

Plasma was collected from forty five patients following a non-disabling LACI along with seventeen matched control subjects. The LACI patients were monitored prospectively for up to five years for the occurrence of adverse outcomes and grouped accordingly (i.e., LACI-no adverse outcome, LACI-recurrent vascular event, and LACI-cognitive decline without any recurrence of vascular events). Microvesicles-enriched fractions isolated from the pooled plasma of four groups were profiled by an iTRAQ-guided discovery approach to quantify the differential proteome. The data have been deposited to the ProteomeXchange with identifier PXD000748. Bioinformatics analysis and data mining revealed up-regulation of brain-specific proteins including myelin basic protein, proteins of coagulation cascade (e.g., fibrinogen alpha chain, fibrinogen beta chain) and focal adhesion (e.g., integrin alpha-IIb, talin-1, and filamin-A) while albumin was down-regulated in both groups of patients with adverse outcome.

Conclusion

This data set may offer important insight into the mechanisms of poor prognosis and provide candidate prognostic biomarkers for validation on larger cohort of individual LACI patients.

Rapamycin promoted thrombosis and platelet adhesion to endothelial cells by inducing membrane remodeling

BACKGROUND

Recently, evidence indicated that the rapamycin-eluting stent which was used worldwide may contribute to an increased risk for thrombosis. On the contrary, other researchers found it was safe. Thus, it is necessary to clarify the effect of rapamycin on thrombosis and the corresponding mechanisms.

RESULTS

The effects of rapamycin in vivo were evaluated by modified deep vein thrombosis animal model. The platelets were from healthy volunteers and the platelet-endothelium (purchased from ATCC) adhesion in cultured endothelial cells was assessed. Membrane rufflings in endothelial cells were examined by confocal and electron microscope. Thrombus formation increased in rats that were injected with rapamycin. Electron microscope analysis exhibited microvilli on the rapamycin-treated endothelium in rats. Rapamycin enhanced membrane ruffling in human umbilical vein endothelial cells (HUVECs) and adhesion of platelets to HUVECs. The platelet-HUVECs adhesion was attenuated when cells were treated with cytochalacin B. Inhibition of autophagy by 3-methyladenine led to suppression of membrane ruffles in HUVECs and augmentation of platelet-endothelial adhesion.

CONCLUSIONS

In conclusion, we found that endothelial membrane remodeling induced by rapamycin is crucial for the adhesion of platelets to endothelial cells and thereby for thrombosis in vivo, and that the endothelial membrane remodeling is autophagy dependent.

GpIbα-VWF blockade restores vessel patency by dissolving platelet aggregates formed under very high shear rate in mice

Interactions between platelet glycoprotein (Gp) IIb/IIIa and plasma proteins mediate platelet cross-linking in arterial thrombi. However, GpIIb/IIIa inhibitors fail to disperse platelet aggregates after myocardial infarction or ischemic stroke. These results suggest that stability of occlusive thrombi involves additional and as-yet-unidentified mechanisms. In the present study, we investigated the mechanisms driving platelet cross-linking during occlusive thrombus formation. Using computational fluid dynamic simulations and in vivo thrombosis models, we demonstrated that the inner structure of occlusive thrombi is heterogeneous and primarily determined by the rheological conditions that prevailed during thrombus growth. Unlike the first steps of thrombus formation, which are GpIIb/IIIa-dependent, our findings reveal that closure of the arterial lumen is mediated by GpIbα-von Willebrand Factor (VWF) interactions. Accordingly, disruption of platelet cross-linking using GpIbα-VWF inhibitors restored vessel patency and improved outcome in a mouse model of ischemic stroke, although the thrombi were resistant to fibrinolysis or traditional antithrombotic agents. Overall, our study demonstrates that disruption of GpIbα-VWF interactions restores vessel patency after occlusive thrombosis by specifically disaggregating the external layer of occlusive thrombi, which is constituted of platelet aggregates formed under very high shear rates.

Expandable megakaryocyte cell lines enable clinically applicable generation of platelets from human induced pluripotent stem cells

The donor-dependent supply of platelets is frequently insufficient to meet transfusion needs. To address this issue, we developed a clinically applicable strategy for the derivation of functional platelets from human pluripotent stem cells (PSCs). This approach involves the establishment of stable immortalized megakaryocyte progenitor cell lines (imMKCLs) from PSC-derived hematopoietic progenitors through the overexpression of BMI1 and BCL-XL to respectively suppress senescence and apoptosis and the constrained overexpression of c-MYC to promote proliferation. The resulting imMKCLs can be expanded in culture over extended periods (4-5 months), even after cryopreservation. Halting the overexpression of c-MYC, BMI1, and BCL-XL in growing imMKCLs led to the production of CD42b(+) platelets with functionality comparable to that of native platelets on the basis of a range of assays in vitro and in vivo. The combination of robust expansion capacity and efficient platelet production means that appropriately selected imMKCL clones represent a potentially inexhaustible source of hPSC-derived platelets for clinical application.

Paxillin is an intrinsic negative regulator of platelet activation in mice

Background

Paxillin is a LIM domain protein localized at integrin-mediated focal adhesions. Although paxillin is thought to modulate the functions of integrins, little is known about the contribution of paxillin to signaling pathways in platelets. Here, we studied the role of paxillin in platelet activation in vitro and in vivo.

Methods and results

We generated paxillin knockdown (Pxn-KD) platelets in mice by transplanting bone marrow cells transduced with a lentiviral vector carrying a short hairpin RNA sequence, and confirmed that paxillin expression was significantly reduced in platelets derived from the transduced cells. Pxn-KD platelets showed a slight increased in size and augmented integrin αIIbβ3 activation following stimulation of multiple receptors including glycoprotein VI and G protein-coupled receptors. Thromboxane A₂ biosynthesis and the release of α-granules and dense granules in response to agonist stimulation were also enhanced in Pxn-KD platelets. However, Pxn-KD did not increase tyrosine phosphorylation or intracellular calcium mobilization. Intravital imaging confirmed that Pxn-KD enhanced thrombus formation in vivo.

Conclusions

Our findings suggest that paxillin negatively regulates several common platelet signaling pathways, resulting in the activation of integrin αIIbβ3 and release reactions.

Differentiating haemostasis from thrombosis for therapeutic benefit

The central role of platelets in the formation of the primary haemostatic plug as well as in the development of arterial thrombosis is well defined. In general, the molecular events underpinning these processes are broadly similar. Whilst it has long been known that disturbances in blood flow, changes in platelet reactivity and enhanced coagulation reactions facilitate pathological thrombus formation, the precise details underlying these events remain incompletely understood. Intravital microscopy studies have highlighted the dynamic and heterogeneous nature of thrombus development and demonstrated that there are considerable spatiotemporal differences in the activation states of platelets within a forming thrombus. In this review we will consider the factors regulating the activation state of platelets in a developing thrombus and discuss how specific prothrombotic factors may influence this process, leading to excessive thrombus propagation. We will also discuss some potentially novel therapeutic approaches that may reduce excess thrombus development whilst minimising bleeding risk.

Contrast-enhanced imaging of SPIO-labeled platelets using magnetomotive ultrasound

The ability to image platelets in vivo can provide insight into blood clotting processes and coagulopathies, and aid in identifying sites of vascular endothelial damage related to trauma or cardiovascular disease. Toward this end, we have developed a magnetomotive ultrasound (MMUS) system that provides contrast-enhanced imaging of superparamagnetic iron oxide (SPIO) labeled platelets via magnetically-induced vibration. Platelets are a promising platform for functional imaging contrast because they readily take up SPIOs and are easily harvested from blood. Here we report a novel MMUS system that accommodates an arbitrarily thick sample while maintaining portability. We employed a frequency- and phase-locked motion detection algorithm based on bandpass filtering of the differential RF phase, which allows for the detection of sub-resolution vibration amplitudes on the order of several nanometers. We then demonstrated MMUS in homogenous tissue phantoms at SPIO concentrations as low as 0.09 mg ml(-1) Fe (p < 0.0001, n = 6, t-test). Finally, we showed that our system is capable of three-dimensional imaging of a 185 µL simulated clot containing SPIO-platelets. This highlights the potential utility for non-invasive imaging of platelet-rich clots, which would constitute a fundamental advance in technology for the study of hemostasis and detection of clinically relevant thrombi.

Crossroads of coagulation and innate immunity: the case of deep vein thrombosis

Deep vein thrombosis (DVT) is a common condition characterized by the formation of an occlusive blood clot in the venous vascular system, potentially complicated by detachment and embolization of thrombi into the lung. Recent evidence from mouse models has shed light on the sequence of events and on the cellular (innate immune cells, platelets) and molecular (hematopoietic tissue factor, nucleic acids) components involved. In response to decreased blood flow, circulating neutrophils and monocytes adhere to the activated endothelium within hours. They initiate and propagate DVT by interacting with platelets and by the exposure and activation of circulating tissue factor and FXII. Intravascular blood coagulation is also induced by extracellular nucleosomes released mainly from activated neutrophils. Interestingly, these mechanisms are closely linked to an evolutionary conserved immune defense mechanism activated in response to infections. In this review, we will give an overview of DVT and the role of innate immune pathways supporting this process. While the latter are aimed at preserving tissue integrity and function, uncontrolled blood coagulation and activation of immune cells may result in pathological thrombus formation and vascular occlusion. Understanding the molecular and cellular players triggering occlusion of large veins, and their distinction from physiological hemostasis, is important for the development of strategies to prevent and treat DVT.

Harnessing the platelet signaling network to produce an optimal hemostatic response

Once released into the circulation by megakaryocytes, circulating platelets can undergo rapid activation at sites of vascular injury and resist unwarranted activation, which can lead to heart attacks and strokes. Historically, the signaling mechanisms underlying the regulation of platelet activation have been approached as a collection of individual pathways unique to agonist. This review takes a different approach, casting platelet activation as the product of a signaling network, in which activating and restraining mechanisms interact in a flexible network that regulates platelet adhesiveness, cohesion between platelets, granule secretion, and the formation of a stable hemostatic thrombus.