Involvement of peptidylarginine deiminase 4 in eosinophil extracellular trap formation and contribution to citrullinated histone signal in thrombi

Background: Extracellular traps formed by neutrophils (NETs) and eosinophils (EETs) have been described in coronary thrombi, contributing to thrombus stability. A key mechanism during NET formation is histone modification by the enzyme PAD4. Citrullinated histones, the product of PAD4 activity, are often attributed to neutrophils. Eosinophils also express high levels of PAD4. Objectives: We aimed to explore the contribution of PAD4 to EET formation. Methods: We performed immunohistological analyses on thrombi, including a large, intact, and eosinophil-containing thrombus retrieved from the right coronary artery using an aspiration catheter and stroke thrombi from thrombectomy retrieval. We studied eosinophils for their capability to form PAD4-dependent EETs in response to strong ET-inducing agonists as well as activated platelets and bacteria. Results: Histopathology and immunofluorescence microscopy identified a coronary thrombus rich in platelets and neutrophils, with distinct areas containing von Willebrand factor and citrullinated histone H3 (H3Cit). Eosinophils were also identified in leukocyte-rich areas. The majority of the H3Cit+ signal colocalized with myeloperoxidase, but some colocalized with eosinophil peroxidase, indicating EETs. Eosinophils isolated from healthy volunteers produced H3Cit+ EETs, indicating an involvement of PAD4 activity. The selective PAD4 inhibitor GSK484 blocked this process, supporting PAD4 dependence of H3Cit+ EET release. Citrullinated histones were also present in EETs produced in response to live Staphylococci. However, limited evidence for EETs was found in mouse models of venous thrombosis or infective endocarditis. Conclusion: As in NETosis, PAD4 can catalyze the formation of EETs. Inhibition of PAD4 decreases EET formation, supporting the future utility of PAD4 inhibitors as possible antithrombotic agents

Hypofibrinolysis in diabetes: a therapeutic target for the reduction of cardiovascular risk

An enhanced thrombotic environment and premature atherosclerosis are key factors for the increased cardiovascular risk in diabetes. The occlusive vascular thrombus, formed secondary to interactions between platelets and coagulation proteins, is composed of a skeleton of fibrin fibres with cellular elements embedded in this network. Diabetes is characterised by quantitative and qualitative changes in coagulation proteins, which collectively increase resistance to fibrinolysis, consequently augmenting thrombosis risk. Current long-term therapies to prevent arterial occlusion in diabetes are focussed on anti-platelet agents, a strategy that fails to address the contribution of coagulation proteins to the enhanced thrombotic milieu. Moreover, antiplatelet treatment is associated with bleeding complications, particularly with newer agents and more aggressive combination therapies, questioning the safety of this approach. Therefore, to safely control thrombosis risk in diabetes, an alternative approach is required with the fibrin network representing a credible therapeutic target. In the current review, we address diabetes-specific mechanistic pathways responsible for hypofibrinolysis including the role of clot structure, defects in the fibrinolytic system and increased incorporation of anti-fibrinolytic proteins into the clot. Future anti-thrombotic therapeutic options are discussed with special emphasis on the potential advantages of modulating incorporation of the anti-fibrinolytic proteins into fibrin networks. This latter approach carries theoretical advantages, including specificity for diabetes, ability to target a particular protein with a possible favourable risk of bleeding. The development of alternative treatment strategies to better control residual thrombosis risk in diabetes will help to reduce vascular events, which remain the main cause of mortality in this condition

Both sunitinib and sorafenib are effective treatments for pheochromocytoma in a xenograft model

International audiencePheochromocytomas and paragangliomas are rare neuroendocrine tumors which develop from chromaf-fin cells of the adrenal medulla and extra-adrenal sites, leading to excess catecholamine release and hypertension. Many of the tumors are characterized by a high vascularity, suggesting the possible implementation of anti-angiogenic therapies for patients. Here, the efficacy of the tyrosine kinase inhibitors sunitinib and sorafenib was investigated in vivo and in vitro. Oral treatment with either sunitinib or sorafenib (40 mg/kg/day) for 14 days induced a marked reduction in the volume and weight of PC12 pheochromocytoma cell tumor xenografts in mice. Assessment of tumoral neo-angiogenesis, assessed by morphometric analysis of the vascular network after CD31 immunolabeling, showed that both suni-tinib and sorafenib reduced the microvessel area (À85% and À80%, respectively) and length (À80% and À78%, respectively) in treated compared to control tumors. In addition, the number of vessel nodes was significantly lower in treated tumors (À95% and À84%, respectively). Furthermore, cleaved caspase 3 immunolabeling revealed a marked increase in the number of apoptotic cells in tumors from treated animals. Sunitinib and sorafenib could exert a direct effect on PC12 cell viability in vitro. While sunitinib induced a rapid (4 h) and pronounced (5-fold) increase in caspase-3/7-dependent apoptosis, sorafenib seems to exert its cytotoxic activity through a different mechanism. Altogether, our data demonstrate that sunitinib and sorafenib have the ability to impair pheochromocytoma development by inhibiting angiogenesis and reducing tumor cell viability. These results strongly suggest that both sunitinib and sorafenib could represent valuable therapeutic tools for pheochromocytoma

Histological stroke clot analysis after thrombectomy: Technical aspects and recommendations

The recent advent of endovascular procedures has created the unique opportunity to collect and analyze thrombi removed from cerebral arteries, instigating a novel subfield in stroke research. Insights into thrombus characteristics and composition could play an important role in ongoing efforts to improve acute ischemic stroke therapy. An increasing number of centers are collecting stroke thrombi. This paper aims at providing guiding information on thrombus handling, procedures, and analysis in order to facilitate and standardize this emerging research field.This work was supported by research grants to S.F.D.M. from the Fonds voor Wetenschappelijk Onderzoek – Vlaanderen (FWO) (research grants G.0A86.13, G.0785.17 and 1509216N), the KU Leuven (OT/14/099 and ISP/14/02L2), the Queen Elisabeth Medical Foundation and by the European Union's Horizon 2020 Research and Innovation Program INSIST under grant agreement No 777072. F.D. is a postdoctoral fellow of the FWO (FWO, 12U7818N). This work is also supported by a research grant to KD from Science Foundation Ireland, co-funded under the European Regional Development fund under Grant Number 13/RC/2073 and Cerenovus.peer-reviewe

The role of platelet and endothelial GARP in thrombosis and hemostasis.

BACKGROUND: Glycoprotein-A Repetitions Predominant protein (GARP or LRRC32) is present on among others human platelets and endothelial cells. Evidence for its involvement in thrombus formation was suggested by full knockout of GARP in zebrafish. OBJECTIVES: To evaluate the role of GARP in platelet physiology and in thrombus formation using platelet and endothelial conditional GARP knock out mice. METHODS: Platelet and endothelial specific GARP knockout mice were generated using the Cre-loxP recombination system. The function of platelets without GARP was measured by flow cytometry, spreading analysis and aggregometry using PAR4-activating peptide and collagen related peptide. Additionally, clot retraction and collagen-induced platelet adhesion and aggregation under flow were analyzed. Finally, in vivo tail bleeding time, occlusion time of the mesenteric and carotid artery after FeCl3-induced thrombosis were determined in platelet and endothelial specific GARP knock out mice. RESULTS: Platelet specific GARP knockout mice had normal surface GPIb, GPVI and integrin αIIb glycoprotein expression. Although GARP expression was increased upon platelet activation, platelets without GARP displayed normal agonist induced activation, spreading on fibrinogen and aggregation responses. Furthermore, absence of GARP on platelets did not influence clot retraction and had no impact on thrombus formation on collagen-coated surfaces under flow. In line with this, neither the tail bleeding time nor the occlusion time in the carotid- and mesenteric artery after FeCl3-induced thrombus formation in platelet or endothelial specific GARP knock out mice were affected. CONCLUSIONS: Evidence is provided that platelet and endothelial GARP are not important in hemostasis and thrombosis in mice. PLoS One 2017 Mar 9; 12(3):e0173329

Mobility characterization in advanced FD-SOI CMOS devices

International audienc