Neutrophil Extracellular Traps in Atherosclerosis and Thrombosis

The role of immune system in atherosclerosis: Molecular mechanisms, controversies, and future possibilities

Numerous cardiovascular disorders have atherosclerosis as their pathological underpinning. Numerous studies have demonstrated that, with the aid of pattern recognition receptors, cytokines, and immunoglobulins, innate immunity, represented by monocytes/macrophages, and adaptive immunity, primarily T/B cells, play a critical role in controlling inflammation and abnormal lipid metabolism in atherosclerosis. Additionally, the finding of numerous complement components in atherosclerotic plaques suggests yet again how heavily the immune system controls atherosclerosis. Therefore, it is essential to have a thorough grasp of how the immune system contributes to atherosclerosis. The specific molecular mechanisms involved in the activation of immune cells and immune molecules in atherosclerosis, the controversy surrounding some immune cells in atherosclerosis, and the limitations of extrapolating from relevant animal models to humans were all carefully reviewed in this review from the three perspectives of innate immunity, adaptive immunity, and complement system. This could provide fresh possibilities for atherosclerosis research and treatment in the future.

Association of Periprocedural Inflammatory Activation With Increased Risk for Early Coronary Stent Thrombosis

BACKGROUND

Stent thrombosis is a rare but deleterious event. Routine coronary angiography with percutaneous coronary intervention (PCI) is often deferred in the presence of laboratory markers of acute inflammation to prevent complications. The aim of this study was to investigate whether an acute inflammatory state is associated with an increased risk of early stent thrombosis.

METHODS AND RESULTS

Within a prospective single-center registry, the association between preprocedural acute inflammatory activation, defined as C-reactive protein plasma levels >50 mg/L or a leukocyte count >12 g/L, and occurrence of early (≤30 days) stent thrombosis was evaluated. In total, 11 327 patients underwent PCI and of those, 6880 patients had laboratory results available. 49.6% of the study population received PCI for an acute coronary syndrome and 50.4% for stable ischemic heart disease. In patients with signs of acute inflammatory activation (24.9%), PCI was associated with a significantly increased risk for stent thrombosis (hazard ratio, 2.89; P<0.00001), independent of age, sex, kidney function, number and type of stents, presence of multivessel disease, choice of P2Y12 inhibitor, and clinical presentation. Elevated laboratory markers of acute inflammation were associated with the occurrence of stent thrombosis in both patients with acute coronary syndrome (hazard ratio, 2.63; P<0.001) and in patients with stable ischemic heart disease (hazard ratio, 3.57; P<0.001).

CONCLUSIONS

An acute inflammatory state at the time of PCI was associated with a significantly increased risk of early stent thrombosis. Evidence of acute inflammation should result in deferred PCI in elective patients, while future studies are needed for patients with acute coronary syndrome.

Role of neutrophil extracellular trap and immune infiltration in atherosclerotic plaque instability: Novel insight from bioinformatics analysis and machine learning

The instability of atherosclerotic plaques increases the risk of acute coronary syndrome. Neutrophil extracellular traps (NETs), mesh-like complexes consisting of extracellular DNA adorned with various protein substances, have been recently discovered to play an essential role in atherosclerotic plaque formation and development. This study aimed to investigate novel diagnostic biomarkers that can identify unstable plaques for early distinction and prevention of plaque erosion or disruption. Differential expression analysis was used to identify the differentially expressed NET-related genes, and Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses were performed. We filtered the characteristic genes using machine learning and estimated diagnostic efficacy using receiver operating characteristic curves. Immune infiltration was detected using single-sample gene set enrichment analysis and the biological signaling pathways involved in characteristic genes utilizing gene set enrichment analysis were explored. Finally, miRNAs- and transcription factors-target genes networks were established. We identified 8 differentially expressed NET-related genes primarily involved in immune-related pathways. Four were identified as capable of distinguishing unstable plaques. More immune cells infiltrated unstable plaques than stable plaques, and these cells were predominantly positively related to characteristic genes. These 4 diagnostic genes are involved in immune responses and the modulation of smooth muscle contractility. Several miRNAs and transcription factors were predicted as upstream regulatory factors, providing further information on the identification and prevention of atherosclerotic plaques rupture. We identified several promising NET-related genes (AQP9, C5AR1, FPR3, and SIGLEC9) and immune cell subsets that may identify unstable atherosclerotic plaques at an early stage and prevent various complications of plaque disruption.

Neutrophil extracellular traps mediate deep vein thrombosis: from mechanism to therapy

Deep venous thrombosis (DVT) is a part of venous thromboembolism (VTE) that clinically manifests as swelling and pain in the lower limbs. The most serious clinical complication of DVT is pulmonary embolism (PE), which has a high mortality rate. To date, its underlying mechanisms are not fully understood, and patients usually present with clinical symptoms only after the formation of the thrombus. Thus, it is essential to understand the underlying mechanisms of deep vein thrombosis for an early diagnosis and treatment of DVT. In recent years, many studies have concluded that Neutrophil Extracellular Traps (NETs) are closely associated with DVT. These are released by neutrophils and, in addition to trapping pathogens, can mediate the formation of deep vein thrombi, thereby blocking blood vessels and leading to the development of disease. Therefore, this paper describes the occurrence and development of NETs and discusses the mechanism of action of NETs on deep vein thrombosis. It aims to provide a direction for improved diagnosis and treatment of deep vein thrombosis in the near future.

Physical Exercise Promotes DNase Activity Enhancing the Capacity to Degrade Neutrophil Extracellular Traps

(1) Background: An unhealthy lifestyle is a significant contributor to the development of chronic diseases. Physical activity can benefit primary and secondary prevention. Higher DNase activity is associated with favourable outcomes after cardiovascular (CV) events. In this study, we aimed to investigate the influence of consequent endurance exercise on DNase activity. (2) Methods: 98 subjects with at least one CV risk factor but the physical ability to perform endurance training were included. Individuals performed a bicycle stress test at the beginning and after 8 months to assess physical performance. In between, all participants were instructed to engage in guideline-directed physical activity. Blood samples were drawn in two-month intervals to assess routine laboratory parameters, cell-free DNA (cfDNA), and DNase activity. (3) Results: Prevailing CV risk factors were overweight (65.9%), a positive family history (44.9%), hypertension (32.7%) and smoking (20.4%). Performance changed by 7.8 ± 9.1% after 8 months. Comparison of baseline to 8 months revealed a decrease in cfDNA and an increase in DNase activity. This effect was driven by participants who achieved a performance gain. (4) Conclusions: Regular physical activity might improve CV health by increasing DNase activity and thereby, the capacity to lower pro-inflammatory signalling, complementing measures of primary and secondary prevention.

Antigen-Presenting Cell-Like Neutrophils Foster T Cell Response in Hyperlipidemic Patients and Atherosclerotic Mice

Neutrophils constitute abundant cellular components in atherosclerotic plaques. Most of the current studies are focused on the roles of granular proteins released by neutrophils in atherosclerosis. Here, we revealed a unique subset of neutrophils which exhibit the characteristics of antigen-presenting cell (APC) (which were called APC-like neutrophils afterwards) in atherosclerosis. The roles of APC-like neutrophils and relevant mechanisms were investigated in hyperlipidemic patients and atherosclerotic mice. Higher percentages of neutrophils and APC-like neutrophils were found in peripheral blood of hyperlipidemic patients than that of healthy donors. Meanwhile, we also identified higher infiltration of neutrophils and APC-like neutrophils in atherosclerotic mice. Ox-LDL induced Phorbol-12-myristate-13-acetate (PMA)-activated neutrophils to acquire the APC-like phenotype. Importantly, upon over-expression of APC-like markers, neutrophils acquired APC functions to promote the proliferation and interferon-γ production of CD3⁺ T cells via HLA-DR/CD80/CD86. In accordance with what found in vitro, positive correlation between neutrophils and CD3⁺ T cells was observed in hyperlipidemic patients. In conclusion, our work identifies a proinflammatory neutrophil subset in both hyperlipidemic patients and atherosclerotic mice. This unique phenotype of neutrophils could activate the adaptive immune response to promote atherosclerosis progression. Thus, this neutrophil subset may be a new target for immunotherapy of atherosclerosis.

The Emerging Role of Neutrophil Extracellular Traps in Arterial, Venous and Cancer-Associated Thrombosis

Neutrophils play a vital role in the formation of arterial, venous and cancer-related thrombosis. Recent studies have shown that in a process known as NETosis, neutrophils release proteins and enzymes complexed to DNA fibers, collectively called neutrophil extracellular traps (NETs). Although NETs were originally described as a way for the host to capture and kill bacteria, current knowledge indicates that NETs also play an important role in thrombosis. According to recent studies, the destruction of vascular microenvironmental homeostasis and excessive NET formation lead to pathological thrombosis. In vitro experiments have found that NETs provide skeletal support for platelets, red blood cells and procoagulant molecules to promote thrombosis. The protein components contained in NETs activate the endogenous coagulation pathway to promote thrombosis. Therefore, NETs play an important role in the formation of arterial thrombosis, venous thrombosis and cancer-related thrombosis. This review will systematically summarize and explain the study of NETs in thrombosis in animal models and in vivo experiments to provide new targets for thrombosis prevention and treatment.