Thrombosis is the most feared complication of cardiovascular diseases and a main cause of death worldwide, making it a major health-care challenge. Platelets and the coagulation cascade are ...effectively targeted by antithrombotic approaches, which carry an inherent risk of bleeding. Moreover, antithrombotics cannot completely prevent thrombotic events, implicating a therapeutic gap due to a third, not yet adequately addressed mechanism, namely inflammation. In this Review, we discuss how the synergy between inflammation and thrombosis drives thrombotic diseases. We focus on the huge potential of anti-inflammatory strategies to target cardiovascular pathologies. Findings in the past decade have uncovered a sophisticated connection between innate immunity, platelet activation and coagulation, termed immunothrombosis. Immunothrombosis is an important host defence mechanism to limit systemic spreading of pathogens through the bloodstream. However, the aberrant activation of immunothrombosis in cardiovascular diseases causes myocardial infarction, stroke and venous thromboembolism. The clinical relevance of aberrant immunothrombosis, referred to as thromboinflammation, is supported by the increased risk of cardiovascular events in patients with inflammatory diseases but also during infections, including in COVID-19. Clinical trials in the past 4 years have confirmed the anti-ischaemic effects of anti-inflammatory strategies, backing the concept of a prothrombotic function of inflammation. Targeting inflammation to prevent thrombosis leaves haemostasis mainly unaffected, circumventing the risk of bleeding associated with current approaches. Considering the growing number of anti-inflammatory therapies, it is crucial to appreciate their potential in covering therapeutic gaps in cardiovascular diseases.
Thrombosis is the most frequent cause of mortality worldwide and is closely linked to haemostasis, which is the biological mechanism that stops bleeding after the injury of blood vessels. Indeed, ...both processes share the core pathways of blood coagulation and platelet activation. Here, we summarize recent work suggesting that thrombosis under certain circumstances has a major physiological role in immune defence, and we introduce the term immunothrombosis to describe this process. Immunothrombosis designates an innate immune response induced by the formation of thrombi inside blood vessels, in particular in microvessels. Immunothrombosis is supported by immune cells and by specific thrombosis-related molecules and generates an intravascular scaffold that facilitates the recognition, containment and destruction of pathogens, thereby protecting host integrity without inducing major collateral damage to the host. However, if uncontrolled, immunothrombosis is a major biological process fostering the pathologies associated with thrombosis.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Platelets are small anucleate cellular fragments that are released by megakaryocytes and safeguard vascular integrity through a process termed 'haemostasis'. However, platelets have important roles ...beyond haemostasis as they contribute to the initiation and coordination of intravascular immune responses. They continuously monitor blood vessel integrity and tightly coordinate vascular trafficking and functions of multiple cell types. In this way platelets act as 'patrolling officers of the vascular highway' that help to establish effective immune responses to infections and cancer. Here we discuss the distinct biological features of platelets that allow them to shape immune responses to pathogens and tumour cells, highlighting the parallels between these responses.
Coronavirus disease 2019 (COVID-19) is a clinical syndrome caused by infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Patients with severe disease show hyperactivation of ...the immune system, which can affect multiple organs besides the lungs. Here, we propose that SARS-CoV-2 infection induces a process known as immunothrombosis, in which activated neutrophils and monocytes interact with platelets and the coagulation cascade, leading to intravascular clot formation in small and larger vessels. Microthrombotic complications may contribute to acute respiratory distress syndrome (ARDS) and other organ dysfunctions. Therapeutic strategies aimed at reducing immunothrombosis may therefore be useful. Several antithrombotic and immunomodulating drugs have been proposed as candidates to treat patients with SARS-CoV-2 infection. The growing understanding of SARS-CoV-2 infection pathogenesis and how it contributes to critical illness and its complications may help to improve risk stratification and develop targeted therapies to reduce the acute and long-term consequences of this disease.
Abstract
Atherothrombosis is a frequent cause of cardiovascular mortality. It is mostly triggered by plaque rupture and exposure of the thrombogenic subendothelial matrix, which initiates platelet ...aggregation and clot formation. Current antithrombotic strategies, however, target both thrombosis and physiological hemostasis and thereby increase bleeding risk. Thus, there is an unmet clinical need for optimized therapies. Neutrophil activation and consecutive interactions of neutrophils and platelets contribute mechanistically to thromboinflammation and arterial thrombosis, and thus present a potential therapeutic target. Platelet–neutrophil interactions are mediated through adhesion molecules such as P-selectin and P-selectin glycoprotein ligand 1 as well as glycoprotein Ib and macrophage-1 antigen, which mediate physical cell interactions and intracellular signaling. Release of soluble mediators as well as direct signaling between platelets and neutrophils lead to their reciprocal activation and neutrophil release of extracellular traps, scaffolds of condensed chromatin that play a prothrombotic role in atherothrombosis. In this article, we review the role of neutrophils and neutrophil-derived prothrombotic molecules in platelet activation and atherothrombosis, and highlight potential therapeutic targets.
PURPOSE OF REVIEWThis review highlights recent insights into the role of platelets in acute inflammation and infection.
RECENT FINDINGSPlatelets exhibit intravascular crawling behavior and can ...collect and bundle bacteria. In addition, platelets are key in promoting intravascular thrombus formation in infection, a process termed ‘immunothrombosis’, which contributes to pathogen containment, but also potentially damages the host. Platelets are at the nexus of leukocyte recruitment and activation, yet they are at the same time crucial in preventing inflammation-associated hemorrhage and tissue damage. This multitasking requires specific receptors and pathways, depending on stimulus, organ and effector function.
SUMMARYNew findings highlight the complex interplay of innate immunity, coagulation and platelets in inflammation and infection, and unravel novel molecular pathways and effector functions. These offer new potential therapeutic approaches, but require further extensive research to distinguish treatable proinflammatory from host–protective pathways.
Arrhythmias are common and contribute substantially to cardiovascular morbidity and mortality. The underlying pathophysiology of arrhythmias is complex and remains incompletely understood, which ...explains why mostly only symptomatic therapy is available. The evaluation of the complex interplay between various cell types in the heart, including cardiomyocytes from the conduction system and the working myocardium, fibroblasts and cardiac immune cells, remains a major challenge in arrhythmia research because it can be investigated only in vivo. Various animal species have been used, and several disease models have been developed to study arrhythmias. Although every species is useful and might be ideal to study a specific hypothesis, we suggest a practical trio of animal models for future use: mice for genetic investigations, mechanistic evaluations or early studies to identify potential drug targets; rabbits for studies on ion channel function, repolarization or re-entrant arrhythmias; and pigs for preclinical translational studies to validate previous findings. In this Review, we provide a comprehensive overview of different models and currently used species for arrhythmia research, discuss their advantages and disadvantages and provide guidance for researchers who are considering performing in vivo studies.
Neutrophils, early mediators of the innate immune defense, are recruited to developing thrombi in different types of thrombosis. They amplify intravascular coagulation by stimulating the tissue ...factor-dependent extrinsic pathway via inactivation of endogenous anticoagulants, enhancing factor XII activation or decreasing plasmin generation. Neutrophil-dependent prothrombotic mechanisms are supported by the externalization of decondensed nucleosomes and granule proteins that together form neutrophil extracellular traps. These traps, either in intact or fragmented form, are causally involved in various forms of experimental thrombosis as first indicated by their role in the enhancement of both microvascular thrombosis during bacterial infection and carotid artery thrombosis. Neutrophil extracellular traps can be induced by interactions of neutrophils with activated platelets; vice versa, these traps enhance adhesion of platelets via von Willebrand factor. Neutrophil-induced microvascular thrombus formation can restrict the dissemination and survival of blood-borne bacteria and thereby sustain intravascular immunity. Dysregulation of this innate immune pathway may support sepsis-associated coagulopathies. Notably, neutrophils and extracellular nucleosomes, together with platelets, critically promote fibrin formation during flow restriction-induced deep vein thrombosis. Neutrophil extracellular traps/extracellular nucleosomes are increased in thrombi and in the blood of patients with different vaso-occlusive pathologies and could be therapeutically targeted for the prevention of thrombosis. Thus, during infections and in response to blood vessel damage, neutrophils and externalized nucleosomes are major promoters of intravascular blood coagulation and thrombosis.
Under steady-state conditions, aged neutrophils are removed from the circulation in bone marrow, liver, and spleen, thereby maintaining myeloid cell homeostasis. The fate of these aged immune cells ...under inflammatory conditions, however, remains largely obscure. Here, we demonstrate that in the acute inflammatory response during endotoxemia, aged neutrophils cease returning to the bone marrow and instead rapidly migrate to the site of inflammation. Having arrived in inflamed tissue, aged neutrophils were found to exhibit a higher phagocytic activity as compared with the subsequently recruited nonaged neutrophils. This distinct behavior of aged neutrophils under inflammatory conditions is dependent on specific age-related changes in their molecular repertoire that enable these “experienced” immune cells to instantly translate inflammatory signals into immune responses. In particular, aged neutrophils engage Toll-like receptor-4- and p38 MAPK-dependent pathways to induce conformational changes in β2 integrins that allow these phagocytes to effectively accomplish their mission in the front line of the inflammatory response. Hence, ageing in the circulation might represent a critical process for neutrophils that enables these immune cells to properly unfold their functional properties for host defense.
•Aged neutrophils exhibit a distinct, highly reactive phenotype that depends on age-related changes in their molecular repertoire.•This specific phenotype of aged neutrophils enables them to serve as “first responders” in inflammatory reactions.
Abstract
Aims
Patients with pulmonary hypertension (PHT) are often excluded from surgical therapies for tricuspid regurgitation (TR). Transcatheter tricuspid valve repair (TTVR) with the MitraClip™ ...technique is a novel treatment option for these patients. We aimed to assess the role of PHT in severe TR and its implications for TTVR.
Methods and results
A total of 243 patients underwent TTVR at two centres. One hundred twenty-one patients were grouped as iPHT+ invasive systolic pulmonary artery pressures (PAPs) ≥50 mmHg. Patients were similarly stratified according to echocardiographic PAPs (ePHT). The occurrence of the combined clinical endpoint (death, heart failure hospitalization, and reintervention) was investigated during a follow-up of 330 (interquartile range 175–402) days. iPHT+ patients were at higher preoperative risk (P < 0.01), had more severe symptoms (P = 0.01), higher N-terminal pro-B-type natriuretic peptide levels (P < 0.01), more impaired right ventricular (RV) function (P < 0.01), and afterload corrected RV function (P < 0.01). Procedural TTVR success was similar in iPHT+ and iPHT− patients (84 vs. 84%, P = 0.99). The echocardiographic diagnostic accuracy to detect iPHT was only 55%. During follow-up, 35% of patients reached the combined clinical endpoint. The discordant diagnosis of iPHT+/ePHT− carried the highest risk for the combined clinical endpoint HR 3.76 (CI 2.25–6.37), P < 0.01, while iPHT+/ePHT+ patients had a similar survival-free time from the combined endpoint compared to iPHT− patients (P = 0.48). In patients with isolated tricuspid procedure (n = 131) a discordant iPHT+/ePHT− diagnosis and an impaired afterload corrected RV function (P < 0.01 for both) were independent predictors for the occurrence of the combined endpoint.
Conclusion
The discordant echocardiographic and invasive diagnosis of PHT in severe TR predicts outcomes after TTVR.
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