Cooperative Action of Oxidized Low-Density Lipoproteins and Neutrophils on Endothelial Inflammatory Responses Through Neutrophil Extracellular Trap Formation

Association of neutrophil extracellular traps burden with clinical and angiographic characteristics in patients with ST-elevation myocardial infarction

BACKGROUND

The precise triggers for atherosclerotic plaque rupture and the underlying pathophysiology of coronary thrombogenesis remain elusive. Polymorphonuclear neutrophils, particularly their formation of neutrophil extracellular traps (NETs), have garnered attention in the context of coronary atherothrombosis. This study sought to explore the association of NETs burden with clinical and angiographic characteristics in ST-elevation myocardial infarction (STEMI) patients undergoing primary percutaneous coronary intervention (pPCI) and thrombus aspiration (TA).

METHODS

For this study, 336 consecutive STEMI patients undergoing pPCI were considered for TA. Aspirated thrombi underwent histological analysis and NETs quantification via immunohistochemistry. Potential associations of clinical variables and angiographic outcomes with NETs burden were assessed.

RESULTS

Manual TA was selectively performed in 72 cases with increased thrombotic burden, and 60 thrombi were suitable for analysis and included in the current study. Most thrombi specimens displayed lytic features (63%), and almost three out of four were identified as white thrombi. Increased NETs burden was significantly associated with prolonged pain-to-balloon time (>300 min), OR = 10.29 (95% CI 2.11-42.22, p = 0.001), and stress-induced hyperglycemia OR = 6.58 (95% CI 1.23-52.63, p < 0.01) after multivariate regression analysis. Additionally, distal embolization, and left ventricular ejection fraction ≤40% were more frequent among patients with an elevated NETs burden OR = 16.9 (95% CI 4.23-44.52, p < 0.01) and OR = 3.2 (95% CI 1.05-12.1, p = 0.05), respectively.

CONCLUSION

Elevated NETs burden in STEMI thrombi may be due to delayed reperfusion and stress-induced hyperglycemia, and it is associated with an increased risk of distal embolization and lower left ventricular ejection fraction. Further research is needed to elucidate the role of NETs as a potential therapeutic target in acute atherothrombosis.

Suppressive effect of resveratrol, catechin and their conformationally constrained analogs on neutrophil extracellular trap formation by HL-60-derived neutrophils

Neutrophil extracellular trap (NET) formation is a unique self-defense mechanism of neutrophils; however, it is also involved in many diseases, including atherosclerosis. Resveratrol and catechin are antioxidants with anti-atherosclerotic properties. Here, we examined the effects of resveratrol, catechin, and other related compounds on NET formation. HL-60-derived neutrophils were pretreated with resveratrol and other compounds before stimulation with phorbol-myristate acetate (PMA). DNA and myeloperoxidase released from neutrophils were determined. Resveratrol suppressed the DNA release from neutrophils in a dose-dependent manner. NET formation was enhanced by 1-palmitoyl-2-oxovaleroyl phosphatidylcholine (POVPC), a truncated form of oxidized phospholipid, and resveratrol suppressed NET formation induced by POVPC and PMA. Furthermore, we designed several analogs of resveratrol or catechin whose conformation was restricted by the inhibition of the free rotation of aromatic rings. The conformationally constrained analogs were more effective at inhibiting NET formation; however, their inhibitory function decreased when compound was a large, hydrophobic analog. The most potent compounds, planar catechin and resveratrol, suppressed myeloperoxidase release from activated neutrophils. In addition, these compounds suppressed DNA release from neutrophils stimulated with calcium ionophore. These results suggest that resveratrol, catechin and their analogs exert anti-NET effects, and that constraining the geometry of these compounds enhanced their inhibitory effects.

Neutrophil Extracellular Traps in Cardiovascular and Aortic Disease: A Narrative Review on Molecular Mechanisms and Therapeutic Targeting

Neutrophil extracellular traps (NETs), composed of DNA, histones, and antimicrobial proteins, are released by neutrophils in response to pathogens but are also recognized for their involvement in a range of pathological processes, including autoimmune diseases, cancer, and cardiovascular diseases. This review explores the intricate roles of NETs in different cardiovascular conditions such as thrombosis, atherosclerosis, myocardial infarction, COVID-19, and particularly in the pathogenesis of abdominal aortic aneurysms. We elucidate the mechanisms underlying NET formation and function, provide a foundational understanding of their biological significance, and highlight the contribution of NETs to inflammation, thrombosis, and tissue remodeling in vascular disease. Therapeutic strategies for preventing NET release are compared with approaches targeting components of formed NETs in cardiovascular disease. Current limitations and potential avenues for clinical translation of anti-NET treatments are discussed.

Oral biosciences: The annual review 2023

BACKGROUND

The Journal of Oral Biosciences is dedicated to advancing and disseminating fundamental knowledge with regard to every aspect of oral biosciences. This review features review articles in the fields of "bone regeneration," "periodontitis," "periodontal diseases," "salivary glands," "sleep bruxism," and "Sjögren's syndrome."

HIGHLIGHT

This review focuses on human demineralized dentin and cementum matrices for bone regeneration, oxidized low-density lipoprotein in periodontal disease and systemic conditions, the relationship between inflammatory mediators in migraine and periodontitis, phosphoinositide signaling molecules in the salivary glands, and the pathophysiologies of sleep bruxism and Sjögren's syndrome.

CONCLUSION

The review articles featured in the Journal of Oral Biosciences have broadened the knowledge of readers regarding various aspects of oral biosciences. The current editorial review discusses the findings and significance of these review articles.

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.

Mechanisms of neutrophil extracellular trap in chronic inflammation of endothelium in atherosclerosis

Cardiovascular diseases are a primary cause of morbidity and mortality around the world. In addition, atherosclerosis (AS)-caused cardiovascular disease is the primary cause of death in human diseases, and almost two billion people suffer from carotid AS worldwide. AS is caused by chronic inflammation of the arterial vessel and is initiated by dysfunction of vascular endothelial cells. Neutrophils protect against pathogen invasion because they function as a component of the innate immune system. However, the contribution of neutrophils to cardiovascular disease has not yet been clarified. Neutrophil extracellular traps (NETs) represent an immune defense mechanism that is different from direct pathogen phagocytosis. NETs are extracellular web-like structures activated by neutrophils, and they play important roles in promoting endothelial inflammation via direct or indirect pathways. NETs consist of DNA, histones, myeloperoxidase, matrix metalloproteinases, proteinase 3, etc. Most of the components of NETs have no direct toxic effect on endothelial cells, such as DNA, but they can damage endothelial cells indirectly. In addition, NETs play a critical role in the process of AS; therefore, it is important to clarify the mechanisms of NETs in AS because NETs are a new potential therapeutic target AS. This review summarizes the possible mechanisms of NETs in AS.

Effect of Vitamin E on Apoptosis of the Endothelial Cells of the Carotid Arteries in Hypercholesterolemic Male Rabbits

INTRODUCTION

Cardiovascular disease is the principal cause of mortality and morbidity in developed countries, leading to the formation of atherosclerosis plaques and thrombosis. Apoptosis of endothelial cells is one of the primary factors in vascular thrombosis. Lipids, when oxidized by endothelial cells, result in an increased thickness of the arterial wall. Iron is also recognized as an atherogenic element that induces atherosclerosis. There remains uncertainty about the antioxidative role of vitamin E in the formation of atherosclerosis. In this study, the authors evaluated the effect of iron and vitamin E on the apoptosis of endothelial cells in the carotid arteries of hypercholesterolemic male rabbits.

METHOD

Thirty white male rabbits were randomly divided into five groups and fed the following diet for six weeks: Group 1: control, Group 2: cholesterol (1%), Group 3: cholesterol (1%) + vitamin E (50 mg/kg), Group 4: cholesterol (1%) + Iron (50 mg/kg), and Group 5: cholesterol (1%) + vitamin E (50 mg/kg) + Iron (50 mg/kg). Serum cholesterol, TG, HDL, and LDL levels were assessed after six weeks. Finally, the animals were sacrificed with ketamine, and carotid arteries were removed. The samples were fixed in 10% formalin, and TUNEL staining was used after the tissue processing. Cell counts were carried out under a light microscope.

RESULTS

Vitamin E decreased Serum cholesterol and apoptotic endothelial cells in the hypercholesterolemic + vitamin E diet (P< 0.05). However, they increased significantly in the interference groups compared to the control group (P< 0.05).

CONCLUSION

According to our findings, vitamin E showed to have a beneficial effect on preventing cardiovascular diseases and may play a positive role in the prevention of atherosclerosis.

The etiological consideration of oxidized low-density lipoprotein in periodontitis

BACKGROUND

Epidemiologically, correlations between periodontal disease activity and CVD/serum lipid-related condition have been reported. Known mediators of these links include triglycerides, oxidized LDL (oxLDL) and inflammatory cytokines such as TNF-α supplied by adipocytes as well as oxidative degeneration products of these lipids. In this review, we focused on oxidized LDL and considered the relationship between periodontal disease and systemic conditions.

HIGHLIGHT

The degree of oxidation in the periodontal pocket can be evaluated by analyzing the Gingival Cervicular Fluid (GCF), which can be easily collected with paperpoint. The oxLDL/LDL ratio in GCF has been shown to be 17 times as high as that in blood, and IL-8 and IL-1β were also abundantly found in GCF. Periodontal treatment significantly lowers oxLDL levels in not only GCF but also plasma. In addition, there has been growing body of evidence that periodontal infections by periodontopathic bacteria affect arteriosclerosis. On the other hands, neutrophil extracellular traps (NETs), a form of innate immune responses, reportedly play a role as a defense mechanism in the periodontal pockets. However, the regulatory mechanism of NETs in periodontal pocket is still unknown. Recently, NETs induced by oxidized cholesterol have been reported to be involved in inflammatory damage to vascular endothelial cells.

CONCLUSION

Further understanding of the newly discovered roles of oxLDL in the defense and destruction of periodontal tissues are anticipated.

High-Density Lipoprotein Suppresses Neutrophil Extracellular Traps Enhanced by Oxidized Low-Density Lipoprotein or Oxidized Phospholipids

Neutrophil extracellular traps (NETs) are found in patients with various diseases, including cardiovascular diseases. We previously reported that copper-oxidized low-density lipoprotein (oxLDL) promotes NET formation of neutrophils, and that the resulting NETs increase the inflammatory responses of endothelial cells. In this study, we investigated the effects of high-density lipoproteins (HDL) on NET formation. HL-60-derived neutrophils were treated with phorbol 12-myristate 13-acetate (PMA) and further incubated with oxLDL and various concentrations of HDL for 2 h. NET formation was evaluated by quantifying extracellular DNA and myeloperoxidase. We found that the addition of native HDL partially decreased NET formation of neutrophils induced by oxLDL. This effect of HDL was lost when HDL was oxidized. We showed that oxidized phosphatidylcholines and lysophosphatidylcholine, which are generated in oxLDL, promoted NET formation of PMA-primed neutrophils, and NET formation by these products was completely blocked by native HDL. Furthermore, we found that an electronegative subfraction of LDL, LDL(-), which is separated from human plasma and is thought to be an in vivo oxLDL, was capable of promoting NET formation. These results suggest that plasma lipoproteins and their oxidative modifications play multiple roles in promoting NET formation, and that HDL acts as a suppressor of this response.

Redox regulation of the immune response

The immune-inflammatory response is associated with increased nitro-oxidative stress. The aim of this mechanistic review is to examine: (a) the role of redox-sensitive transcription factors and enzymes, ROS/RNS production, and the activity of cellular antioxidants in the activation and performance of macrophages, dendritic cells, neutrophils, T-cells, B-cells, and natural killer cells; (b) the involvement of high-density lipoprotein (HDL), apolipoprotein A1 (ApoA1), paraoxonase-1 (PON1), and oxidized phospholipids in regulating the immune response; and (c) the detrimental effects of hypernitrosylation and chronic nitro-oxidative stress on the immune response. The redox changes during immune-inflammatory responses are orchestrated by the actions of nuclear factor-κB, HIF1α, the mechanistic target of rapamycin, the phosphatidylinositol 3-kinase/protein kinase B signaling pathway, mitogen-activated protein kinases, 5' AMP-activated protein kinase, and peroxisome proliferator-activated receptor. The performance and survival of individual immune cells is under redox control and depends on intracellular and extracellular levels of ROS/RNS. They are heavily influenced by cellular antioxidants including the glutathione and thioredoxin systems, nuclear factor erythroid 2-related factor 2, and the HDL/ApoA1/PON1 complex. Chronic nitro-oxidative stress and hypernitrosylation inhibit the activity of those antioxidant systems, the tricarboxylic acid cycle, mitochondrial functions, and the metabolism of immune cells. In conclusion, redox-associated mechanisms modulate metabolic reprogramming of immune cells, macrophage and T helper cell polarization, phagocytosis, production of pro- versus anti-inflammatory cytokines, immune training and tolerance, chemotaxis, pathogen sensing, antiviral and antibacterial effects, Toll-like receptor activity, and endotoxin tolerance.

Autophagy-driven neutrophil extracellular traps: The dawn of sepsis

Sepsis is a systemic inflammatory syndrome caused by infection disorders. The core mechanism of sepsis is immune dysfunction. Neutrophils are the most abundant circulating white blood cells, which play a crucial role in mediating the innate immune response. Previous studies have shown that an effective way to treat sepsis is through the regulation of neutrophil functions. Autophagy, a highly conserved degradation process, is responsible for removing denatured proteins or damaged organelles within cells and protecting cells from external stimuli. It is a key homeostasis process that promotes neutrophil function and differentiation. Autophagy has been shown to be closely associated with inflammation and immunity. Neutrophils, the first line of innate immunity, migrate to inflammatory sites upon their activation. Neutrophil-mediated autophagy may participate in the clinical course of sepsis. In this review, we summarized and analyzed the latest research findings on the changes in neutrophil external traps during sepsis, the regulatory role of autophagy in neutrophil, and the potential application of autophagy-driven NETs in sepsis, so as to guide clinical treatment of sepsis.

Modified Lipoproteins Induce Arterial Wall Inflammation During Atherogenesis

Circulating apolipoprotein B-containing lipoproteins, notably the low-density lipoproteins, enter the inner layer of the arterial wall, the intima, where a fraction of them is retained and modified by proteases, lipases, and oxidizing agents and enzymes. The modified lipoproteins and various modification products, such as fatty acids, ceramides, lysophospholipids, and oxidized lipids induce inflammatory reactions in the macrophages and the covering endothelial cells, initiating an increased leukocyte diapedesis. Lipolysis of the lipoproteins also induces the formation of cholesterol crystals with strong proinflammatory properties. Modified and aggregated lipoproteins, cholesterol crystals, and lipoproteins isolated from human atherosclerotic lesions, all can activate macrophages and thereby induce the secretion of proinflammatory cytokines, chemokines, and enzymes. The extent of lipoprotein retention, modification, and aggregation have been shown to depend largely on differences in the composition of the circulating lipoprotein particles. These properties can be modified by pharmacological means, and thereby provide opportunities for clinical interventions regarding the prevention and treatment of atherosclerotic vascular diseases.

Association of Lipoproteins with Neutrophil Extracellular Traps in Patients with Abdominal Aortic Aneurysm

Neutrophil extracellular traps (NETs) are DNA–protein structures released by neutrophils in response to various stimuli, including oxidized, low-density lipoprotein (oxLDL). Accumulating evidence suggests a role for NETs in the pathogenesis of abdominal aortic aneurysm (AAA). In this study, we investigated the potential association of lipoprotein particles and NETs in AAA in comparison to non-AAA control groups. The concentrations of neutrophil myeloperoxidase (MPO), the NET parameters citrullinated histone H3 (citH3) and circulating cell-free DNA (cfDNA), as well as of blood lipids were determined in plasma or serum of patients with AAA (n = 40), peripheral artery occlusive disease (PAD; n = 40) and healthy donors (n = 29). A sandwich ELISA detecting oxidized phosphatidylcholine in association with apolipoprotein B-100 (oxPL/apoB) was applied to measure oxidized phospholipids in circulation. The effect of lipoparticles on NET formation was tested using a DNA release assay with isolated human neutrophils. Plasma MPO, citH3 and cfDNA levels were significantly increased in AAA patients in comparison to healthy donors and PAD patients. Plasma concentrations of citH3 positively correlated with serum oxPL/apoB in AAA patients. In functional in vitro assays, the addition of oxLDL induced NET formation in pre-stimulated neutrophils. In conclusion, our data suggest a promoting role of oxLDL on NET formation in AAA patients.

Neutrophil extracellular traps modulate inflammatory markers and uptake of oxidized LDL by human and murine macrophages

Neutrophil extracellular traps (NETs) are web-like structures, which are released upon neutrophil activation. It has previously been demonstrated that NETs are present in atherosclerotic lesions of both humans and animal models thus playing a decisive role in atherosclerosis. Besides, macrophages have a crucial role in disease progression, whereby classically activated M1 macrophages sustain inflammation and alternatively activated M2 macrophages display anti-inflammatory effects. Although NETs and macrophages were found to colocalize in atherosclerotic lesions, the impact of NETs on macrophage function is not fully understood. In the present study, we aimed to investigate the effect of NETs on human and murine macrophages in respect to the expression of pro-inflammatory cytokines, matrix metalloproteinases (MMPs) and uptake of oxidized LDL (oxLDL) in vitro. Human THP-1 and murine bone marrow-derived macrophages were cultured under M1 (LPS + IFN-γ)- and M2a (IL-4)-polarizing culture conditions and treated with NETs. To mimic intraplaque regions, cells were additionally cultured under hypoxic conditions. NETs significantly increased the expression of IL-1β, TNF-α and IL-6 in THP-M1 macrophages under normoxia but suppressed their expression in murine M1 macrophages under hypoxic conditions. Notably, NETs increased the number of oxLDL-positive M1 and M2 human and murine macrophages under normoxia, but did not influence formation of murine foam cells under hypoxia. However, oxLDL uptake did not strongly correlate with the expression of the LDL receptor CD36. Besides, upregulated MMP-9 expression and secretion by macrophages was detected in the presence of NETs. Again, hypoxic culture conditions dampened NETs effects. These results suggest that NETs may favor foam cell formation and plaque vulnerability, but exert opposite effects in respect to the inflammatory response of human and murine M1 macrophages. Moreover, effects of NETs on macrophages’ phenotype are altered under hypoxia.

Inflammatory Mechanisms Contributing to Endothelial Dysfunction

Maintenance of endothelial cell integrity is an important component of human health and disease since the endothelium can perform various functions including regulation of vascular tone, control of hemostasis and thrombosis, cellular adhesion, smooth muscle cell proliferation, and vascular inflammation. Endothelial dysfunction is encompassed by complex pathophysiology that is based on endothelial nitric oxide synthase uncoupling and endothelial activation following stimulation from various inflammatory mediators (molecular patterns, oxidized lipoproteins, cytokines). The downstream signaling via nuclear factor-κB leads to overexpression of adhesion molecules, selectins, and chemokines that facilitate leukocyte adhesion, rolling, and transmigration to the subendothelial space. Moreover, oscillatory shear stress leads to pro-inflammatory endothelial activation with increased monocyte adhesion and endothelial cell apoptosis, an effect that is dependent on multiple pathways and flow-sensitive microRNA regulation. Moreover, the role of neutrophil extracellular traps and NLRP3 inflammasome as inflammatory mechanisms contributing to endothelial dysfunction has recently been unveiled and is under further investigation. Consequently, and following their activation, injured endothelial cells release inflammatory mediators and enter a pro-thrombotic state through activation of coagulation pathways, downregulation of thrombomodulin, and an increase in platelet adhesion and aggregation owing to the action of von-Willebrand factor, ultimately promoting atherosclerosis progression.

Neutrophil Extracellular Traps Affecting Cardiovascular Health in Infectious and Inflammatory Diseases

Neutrophil extracellular traps (NETs) are web-like structures of decondensed extracellular chromatin fibers and neutrophil granule proteins released by neutrophils. NETs participate in host immune defense by entrapping pathogens. They are pro-inflammatory in function, and they act as an initiator of vascular coagulopathies by providing a platform for the attachment of various coagulatory proteins. NETs are diverse in their ability to alter physiological and pathological processes including infection and inflammation. In this review, we will summarize recent findings on the role of NETs in bacterial/viral infections associated with vascular inflammation, thrombosis, atherosclerosis and autoimmune disorders. Understanding the complex role of NETs in bridging infection and chronic inflammation as well as discussing important questions related to their contribution to pathologies outlined above may pave the way for future research on therapeutic targeting of NETs applicable to specific infections and inflammatory disorders.

The Role of Neutrophil Extracellular Traps in Periodontitis

Periodontitis is a chronic, destructive disease of periodontal tissues caused by multifaceted, dynamic interactions. Periodontal bacteria and host immunity jointly contribute to the pathological processes of the disease. The dysbiotic microbial communities elicit an excessive immune response, mainly by polymorphonuclear neutrophils (PMNs). As one of the main mechanisms of PMN immune response in the oral cavity, neutrophil extracellular traps (NETs) play a crucial role in the initiation and progression of late-onset periodontitis. NETs are generated and released by neutrophils stimulated by various irritants, such as pathogens, host-derived mediators, and drugs. Chromatin and proteins are the main components of NETs. Depending on the characteristics of the processes, three main pathways of NET formation have been described. NETs can trap and kill pathogens by increased expression of antibacterial components and identifying and trapping bacteria to restrict their spread. Moreover, NETs can promote and reduce inflammation, inflicting injuries on the tissues during the pro-inflammation process. During their long-term encounter with NETs, periodontal bacteria have developed various mechanisms, including breaking down DNA of NETs, degrading antibacterial proteins, and impacting NET levels in the pocket environment to resist the antibacterial function of NETs. In addition, periodontal pathogens can secrete pro-inflammatory factors to perpetuate the inflammatory environment and a friendly growth environment, which are responsible for the progressive tissue damage. By learning the strategies of pathogens, regulating the periodontal concentration of NETs becomes possible. Some practical ways to treat late-onset periodontitis are reducing the concentration of NETs, administering anti-inflammatory therapy, and prescribing broad-spectrum and specific antibacterial agents. This review mainly focuses on the mechanism of NETs, pathogenesis of periodontitis, and potential therapeutic approaches based on interactions between NETs and periodontal pathogens.

The Potential of Hydrogen Sulfide Donors in Treating Cardiovascular Diseases

Hydrogen sulfide (H2S) has long been considered as a toxic gas, but as research progressed, the idea has been updated and it has now been shown to have potent protective effects at reasonable concentrations. H2S is an endogenous gas signaling molecule in mammals and is produced by specific enzymes in different cell types. An increasing number of studies indicate that H2S plays an important role in cardiovascular homeostasis, and in most cases, H2S has been reported to be downregulated in cardiovascular diseases (CVDs). Similarly, in preclinical studies, H2S has been shown to prevent CVDs and improve heart function after heart failure. Recently, many H2S donors have been synthesized and tested in cellular and animal models. Moreover, numerous molecular mechanisms have been proposed to demonstrate the effects of these donors. In this review, we will provide an update on the role of H2S in cardiovascular activities and its involvement in pathological states, with a special focus on the roles of exogenous H2S in cardiac protection.

Differentiation of HL-60 cells in serum-free hematopoietic cell media enhances the production of neutrophil extracellular traps

Neutrophil extracellular traps (NETs) are web-like structures made of chromatin and have been identified to have a role in the host's immune defense. Differentiated human promyelocytic leukemia HL-60 cells (dHL-60) have been used to study the mechanisms of NETs formation, as neutrophils have a short lifespan that limits their use. However, dHL-60 cells are inefficient at generating NETs and therefore are not ideal replacements for neutrophils in studying of NET formation. In the present study, the optimal cell culture conditions and differentiation time that result in the most effective release of NETs from dHL-60 cells upon stimulation were determined. HL-60 cells were cultured in serum (FBS) or serum-free (X-VIVO) medium and differentiated using all-trans retinoic acid (ATRA) or dimethyl sulfoxide (DMSO). dHL-60 cells were stimulated with phorbol 12-myristate 13-acetate (PMA) or Ca²⁺ ionophore (CI). Cell differentiation and apoptosis, as well as the formation of reactive oxygen species (ROS) and citrullinated histone H3 (citH3) were analyzed using flow cytometry. NETs were visualized using fluorescence microscopy and NET quantification was performed using PicoGreen. Induction of HL-60 cells for five days produced the best results in terms of differentiation markers and cell viability. Both ATRA- and DMSO-induced dHL-60 cells were able to release NETs upon PMA and CI stimulation; dHL-60 cells in serum-free medium produced more NETs than those in serum-containing medium. DMSO-dHL-60 (X-VIVO) cells were most efficient at producing NETs and ROS upon stimulation with PMA, while ATRA-dHL-60 (X-VIVO) cells were most efficient at producing NETs and citH3 upon stimulation with CI. It was concluded that DMSO-dHL-60 (X-VIVO) may be a model for the study of ROS-high NETosis and ATRA-dHL-60 (X-VIVO) may be suitable for ROS-low NETosis.

Neutrophil Extracellular Traps and Their Implications in Cardiovascular and Inflammatory Disease

Neutrophils are primary effector cells of innate immunity and fight infection by phagocytosis and degranulation. Activated neutrophils also release neutrophil extracellular traps (NETs) in response to a variety of stimuli. These NETs are net-like complexes composed of cell-free DNA, histones and neutrophil granule proteins. Besides the evolutionarily conserved mechanism to capture and eliminate pathogens, NETs are also associated with pathophysiological processes of various diseases. Here, we elucidate the mechanisms of NET formation and their different implications in disease. We focused on autoinflammatory and cardiovascular disorders as the leading cause of death. Neutrophil extracellular traps are not only present in various cardiovascular diseases but play an essential role in atherosclerotic plaque formation, arterial and venous thrombosis, as well as in the development and progression of abdominal aortic aneurysms. Furthermore, NETosis can be considered as a source of autoantigens and maintains an inflammatory milieu promoting autoimmune diseases. Indeed, there is further need for research into the balance between NET induction, inhibition, and degradation in order to pharmacologically target NETs and their compounds without impairing the patient’s immune defense. This review may be of interest to both basic scientists and clinicians to stimulate translational research and innovative clinical approaches.

Scavenger Receptors as Biomarkers and Therapeutic Targets in Cardiovascular Disease

The process of atherosclerosis leads to the formation of plaques in the arterial wall, resulting in a decreased blood supply to tissues and organs and its sequelae: morbidity and mortality. A class of membrane-bound proteins termed scavenger receptors (SRs) are closely linked to the initiation and progression of atherosclerosis. Increasing interest in understanding SR structure and function has led to the idea that these proteins could provide new routes for cardiovascular disease diagnosis, management, and treatment. In this review, we consider the main classes of SRs that are implicated in arterial disease. We consider how our understanding of SR-mediated recognition of diverse ligands, including modified lipid particles, lipids, and carbohydrates, has enabled us to better target SR-linked functionality in disease. We also link clinical studies on vascular disease to our current understanding of SR biology and highlight potential areas that are relevant to cardiovascular disease management and therapy.

Neutrophils as a Novel Target of Modified Low-Density Lipoproteins and an Accelerator of Cardiovascular Diseases

Neutrophil extracellular traps (NETs) significantly contribute to various pathophysiological conditions, including cardiovascular diseases. NET formation in the vasculature exhibits inflammatory and thrombogenic activities on the endothelium. NETs are induced by various stimulants such as exogenous damage-associated molecular patterns (DAMPs). Oxidatively modified low-density lipoprotein (oxLDL) has been physiologically defined as a subpopulation of LDL that comprises various oxidative modifications in the protein components and oxidized lipids, which could act as DAMPs. oxLDL has been recognized as a crucial initiator and accelerator of atherosclerosis through foam cell formation by macrophages; however, recent studies have demonstrated that oxLDL stimulates neutrophils to induce NET formation and enhance NET-mediated inflammatory responses in vascular endothelial cells, thereby suggesting that oxLDL may be involved in cardiovascular diseases through neutrophil activation. As NETs comprise myeloperoxidase and proteases, they have the potential to mediate oxidative modification of LDL. This review summarizes recent updates on the analysis of NETs, their implications for cardiovascular diseases, and prospects for a possible link between NET formation and oxidative modification of lipoproteins.

Lipoproteins and the Tumor Microenvironment

The tumor microenvironment (TME) plays a key role in enhancing the growth of malignant tumors and thus contributing to "aggressive phenotypes," supporting sustained tumor growth and metastasis. The precise interplay between the numerous components of the TME that contribute to the emergence of these aggressive phenotypes is yet to be elucidated and currently under intense investigation. The purpose of this article is to identify specific role(s) for lipoproteins as part of these processes that facilitate (or oppose) malignant growth as they interact with specific components of the TME during tumor development and treatment. Because of the scarcity of literature reports regarding the interaction of lipoproteins with the components of the tumor microenvironment, we were compelled to explore topics that were only tangentially related to this topic, to ensure that we have not missed any important concepts.

Neutrophil Extracellular Traps Participate in Cardiovascular Diseases: Recent Experimental and Clinical Insights

Neutrophil extracellular traps (NETs) have recently emerged as a newly recognized contributor to venous and arterial thrombosis. These strands of DNA extruded by activated or dying neutrophils, decorated with various protein mediators, become solid-state reactors that can localize at the critical interface of blood with the intimal surface of diseased arteries and propagate and amplify the regional injury. NETs thus furnish a previously unsuspected link between inflammation, innate immunity, thrombosis, oxidative stress, and cardiovascular diseases. In response to disease-relevant stimuli, neutrophils undergo a specialized series of reactions that culminate in NET formation. DNA derived from either nuclei or mitochondria can contribute to NET formation. The DNA liberated from neutrophils forms a reticular mesh that resembles morphologically a net, rendering the acronym NETs particularly appropriate. The DNA backbone of NETs not only presents intrinsic neutrophil proteins (eg, MPO [myeloperoxidase] and various proteinases) but can gather other proteins found in blood (eg, tissue factor procoagulant). This review presents current concepts of neutrophil biology, the triggers to and mechanisms of NET formation, and the contribution of NETs to atherosclerosis and to thrombosis. We consider the use of markers of NETs in clinical studies. We aim here to integrate critically the experimental literature with the growing body of clinical information regarding NETs.

Cross-Talk between Lipoproteins and Inflammation: The Role of Microvesicles

Atherothrombosis is the principal underlying cause of cardiovascular disease (CVD). Microvesicles (MV) are small blebs originated by an outward budding at the cell plasma membranes, which are released in normal conditions. However, MV release is increased in pathophysiologic conditions such as CVD. Low density lipoprotein (LDL) and MV contribute to atherothrombosis onset and progression by promoting inflammation and leukocyte recruitment to injured endothelium, as well as by increasing thrombosis and plaque vulnerability. Moreover, (oxidized)LDL induces MV release and vice-versa, perpetuating endothelium injury leading to CVD progression. Therefore, MV and lipoproteins exhibit common features, which should be considered in the interpretation of their respective roles in the pathophysiology of CVD. Understanding the pathways implicated in this process will aid in developing novel therapeutic approaches against atherothrombosis.