Neutrophil's weapons in atherosclerosis

Cellular metabolism changes in atherosclerosis and the impact of comorbidities

Cell activation and nutrient dysregulation are common consequences of atherosclerosis and its preceding risk factors, such as hypertension, dyslipidemia, and diabetes. These diseases may also impact cellular metabolism and consequently cell function, and the other way around, altered cellular metabolism can impact disease development and progression through altered cell function. Understanding the contribution of altered cellular metabolism to atherosclerosis and how cellular metabolism may be altered by co-morbidities and atherosclerosis risk factors could support the development of novel strategies to lower the risk of CVD. Therefore, we briefly review disease pathogenesis and the principles of cell metabolic pathways, before detailing changes in cellular metabolism in the context of atherosclerosis and comorbidities. In the hypoxic, inflammatory and hyperlipidemic milieu of the atherosclerotic plaque riddled with oxidative stress, metabolism shifts to increase anaerobic glycolysis, the pentose-phosphate pathway and amino acid use. We elaborate on metabolic changes for macrophages, neutrophils, vascular endothelial cells, vascular smooth muscle cells and lymphocytes in the context of atherosclerosis and its co-morbidities hypertension, dyslipidemia, and diabetes. Since causal relationships of specific key genes in a metabolic pathway can be cell type-specific and comorbidity-dependent, the impact of cell-specific metabolic changes must be thoroughly explored in vivo, with a focus on also systemic effects. When cell-specific treatments become feasible, this information will be crucial for determining the best metabolic intervention to improve atherosclerosis and its interplay with co-morbidities.

Relationships Between Inflammatory Parameters Derived From Complete Blood Count and Quantitative Flow Ratio in Patients With Stable Coronary Artery Disease

To investigate the relationships between inflammatory parameters, including neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), monocyte-to-lymphocyte ratio (MLR) and systemic immune-inflammation index (SII), and quantitative flow ratio (QFR) in stable coronary artery disease (CAD) patients (n = 450) enrolled in this cross-sectional study. Logistic regression was performed to evaluate the associations of NLR, PLR, MLR, and SII evaluated as continuous and binary variables with QFR ≤0.80. When treated as continuous variables, lnNLR was associated with QFR ≤0.80 with borderline significance in univariable (odds ratio (OR) = 1.60, p = .05) and multivariable analysis (OR = 1.72, p = .05), while lnMLR was associated with QFR ≤0.80 significantly in univariable analysis (OR = 1.87, p = .03) and with borderline significance in multivariable analysis (OR = 1.91, p = .05). When treated as binary variables, high levels of MLR and SII were significantly associated with QFR ≤0.80 in univariable (MLR: OR = 1.91, p = .02; SII: OR = 2.42, p = .006) and multivariable analysis (MLR: OR = 1.83, p = .04; SII: OR = 2.19, p = .02). NLR, MLR, and SII, but not PLR, were significantly associated with the severity of coronary physiology in stable CAD patients.

NETs-Induced Thrombosis Impacts on Cardiovascular and Chronic Kidney Disease

Arterial and venous thrombosis constitute a major source of morbidity and mortality worldwide. Association between thrombotic complications and cardiovascular and other chronic inflammatory diseases are well described. Inflammation and subsequent initiation of thrombotic events, termed immunothrombosis, also receive growing attention but are still incompletely understood. Nevertheless, the clinical relevance of aberrant immunothrombosis, referred to as thromboinflammation, is evident by an increased risk of thrombosis and cardiovascular events in patients with inflammatory or infectious diseases. Proinflammatory mediators released from platelets, complement activation, and the formation of NETs (neutrophil extracellular traps) initiate and foster immunothrombosis. In this review, we highlight and discuss prominent and emerging interrelationships and functions between NETs and other mediators in immunothrombosis in cardiovascular disease. Also, with patients with chronic kidney disease suffering from increased cardiovascular and thrombotic risk, we summarize current knowledge on neutrophil phenotype, function, and NET formation in chronic kidney disease. In addition, we elaborate on therapeutic targeting of NETs-induced immunothrombosis. A better understanding of the functional relevance of antithrombotic mediators which do not increase bleeding risk may provide opportunities for successful therapeutic interventions to reduce thrombotic risk beyond current treatment options.

Regulation of pseurotin A biosynthesis by GliZ and zinc in Aspergillus fumigatus

Recently, we reported that zinc regulates gliotoxin biosynthesis via ZafA, which is a zinc-responsive transcriptional activator. From an HPLC analysis of culture media of Aspergillus fumigatus, we found a trend of decreasing gliotoxin production but increasing pseurotin A and fumagillin production in proportion to the zinc concentration. The expression of the genes involved in pseurotin A biosynthesis was upregulated under high zinc concentrations. Furthermore, upregulated expression of pseurotin A biosynthetic genes and higher production of pseurotin A were observed in the zafA deletion strain. Interestingly, the deletion of gliZ, a transcriptional activator of gliotoxin biosynthesis genes, resulted in upregulated expression of pseurotin A biosynthetic genes and increased production of pseurotin A. We detected upregulation of fumR expression in the gliZ and zafA deletion mutants. The overexpression of gliZ observed in the zafA deletion mutant resulted in the failure of the mutant to increase pseurotin A production, which is a phenotype of the zafA deletion mutant. These results suggest that ZafA sequentially regulates pseurotin A biosynthesis through GliZ. Finally, we found through a murine virulence test that the gliZ and fumR double-deletion mutants showed a delayed death rate compared with the single-deletion mutants of either gliZ or fumR. Taken together, these results suggested that the biosynthesis of gliotoxin and pseurotin A are regulated in opposite ways by zinc utilization and that each secondary metabolite is synthesized when the synthesis of another secondary metabolite fails to protect it against the defense system of the host.

The role of platelets, neutrophils and endothelium in COVID-19 infection

INTRODUCTION

COVID-19 is associated to an increased risk of thrombosis, as a result of a complex process that involves the activation of vascular and circulating cells, the release of soluble inflammatory and thrombotic mediators and blood clotting activation.

AREAS COVERED

This article reviews the pathophysiological role of platelets, neutrophils and the endothelium, and of their interactions, in the thrombotic complications of COVID-19 patients, and the current and future therapeutic approaches targeting these cell types.

EXPERT OPINION

Virus-induced platelet, neutrophil and endothelial cell changes are crucial triggers of the thrombotic complications and of the adverse evolution of COVID-19. Both the direct interaction with the virus and the associated cytokine storm concur to trigger cell activation in a classical thromboinflammatory vicious circle. Although heparin has proven to be an effective prophylactic and therapeutic weapon for the prevention and treatment of COVID-19-associated thrombosis, it acts downstream of the cascade of events triggered by SARS-CoV-2. The identification of specific molecular targets interrupting the thromboinflammatory cascade upstream, and more specifically acting either on the interaction of SARS-CoV-2 with blood and vascular cells or on the specific signalling mechanisms associated with their COVID-19-associated activation, might theoretically offer greater protection with potentially lesser side effects.

Research Progress on the Immunogenicity and Regeneration of Acellular Adipose Matrix: A Mini Review

Acellular adipose matrix (AAM) has received increasing attention for soft tissue reconstruction, due to its abundant source, high long-term retention rate and in vivo adipogenic induction ability. However, the current decellularization methods inevitably affect native extracellular matrix (ECM) properties, and the residual antigens can trigger adverse immune reactions after transplantation. The behavior of host inflammatory cells mainly decides the regeneration of AAM after transplantation. In this review, recent knowledge of inflammatory cells for acellular matrix regeneration will be discussed. These advancements will inform further development of AAM products with better properties.

Bionic Microbubble Neutrophil Composite for Inflammation-Responsive Atherosclerotic Vulnerable Plaque Pluripotent Intervention

Rupture or erosion of inflammatory atherosclerotic vulnerable plaque is essential to acute coronary events, while the target intervene of vulnerable plaque is very challenging, due to the relatively small volume, high hemodynamic shear stress, and multifactorial nature of the lesion foci. Herein, we utilize the biological functionality of neutrophil and the versatility of microbubble in the acoustic field, to form Neu-balloon through CD11b antibody binding. The Neu-balloon inherits the advantage of neutrophils on firming the endothelium adhesion even at shear stress up to 16 dyne/cm2 and also maintains the acoustic enhancement property from the microbubble, to accumulate at atherosclerotic lesions under acoustic in an atherosclerotic Apo E-/- mice model. Interestingly, Neo-balloon also has high and broad drug loading capacity, which enables the delivery of indocyanine green and miR-126a-5p into vulnerable plagues in vivo. Overall, the bionic Neu-balloon holds great potential to boost on-demand drug transportation into plaques in vivo.

The Role of Cell Derived Microparticles in Cardiovascular Diseases: Current Concepts

Abstract:

Cardiovascular disease remains the main cause of human morbidity and mortality in the developed countries. Microparticles (MPs) are small vesicles originating from the cell membrane as a result of various stimuli and particularly of biological processes that constitute the pathophysiology of atherosclerosis, such as endothelial damage. They form vesicles that can transfer various molecules and signals to remote target cells without direct cell to cell interaction. Circulating microparticles have been associated with cardiovascular diseases. Therefore, many studies have been designed to further investigate the role of microparticles as biomarkers for diagnosis, prognosis, and disease monitoring. To this concept the pro-thrombotic and atherogenic potential of platelets and endothelial derived MPs has gain research interest especially concerning accelerate atherosclerosis and acute coronary syndrome triggering and prognosis. MPs especially of endothelial origin have been investigated in different clinical scenarios of heart failure and in association of left ventricular loading conditions. Finally, most cardiovascular risk factors present unique patterns of circulating MPs population, highlighting their pathophysiologic link to cardiovascular disease progression. In this review article we present a synopsis of the biogenesis and characteristics of microparticles, as well as the most recent data concerning their implication in the cardiovascular settings.

Cryoprotectants-Free Vitrification and Conventional Freezing of Human Spermatozoa: A Comparative Transcript Profiling

Introduction: Spermatozoa cryopreservation is an important technique to preserve fertility for males. This study aimed at exploring the stability of epigenetics information in human spermatozoa, manipulated by two different technologies, freezing and vitrification. Methods: Spermatozoa samples were distributed into three groups: 1. Fresh spermatozoa (control group), 2. Frozen spermatozoa, 3. Vitrified spermatozoa. Epigenetic differences of fresh and cryopreserved spermatozoa were evaluated using high-throughput RNA sequencing. Results: Differentially expressed genes (DEGs) in frozen (1103 genes) and vitrified (333 genes) spermatozoa were evaluated. The bioinformatical analysis identified 8 and 15 significant pathways in groups of frozen and vitrified spermatozoa, respectively. The majority of these pathways are most relevant to immune and infectious diseases. The DEGs of the fertilization process are not detected during vitrification. The freezing process induces more down-regulation of genes and is relevant to apoptosis changes and immune response. Conclusion: Cryopreservation of human spermatozoa is an epigenetically safe method for male fertility preservation. Cryoprotectant-free vitrification can induce more minor biological changes in human spermatozoa, in comparison with conventional freezing.

Lipoxins modulate neutrophil oxidative burst, integrin expression and lymphatic transmigration differentially in human health and atherosclerosis

Dysregulated chronic inflammation plays a crucial role in the pathophysiology of atherosclerosis and may be a result of impaired resolution. Thus, restoring levels of specialized pro‐resolving mediators (SPMs) to promote the resolution of inflammation has been proposed as a therapeutic strategy for patients with atherosclerosis, in addition to standard clinical care. Herein, we evaluated the effects of the SPM lipids, lipoxin A₄ (LXA₄) and lipoxin B₄ (LXB₄), on neutrophils isolated from patients with atherosclerosis compared with healthy controls. Patients displayed altered endogenous SPM production, and we demonstrated that lipoxin treatment in whole blood from atherosclerosis patients attenuates neutrophil oxidative burst, a key contributor to atherosclerotic development. We found the opposite effect in neutrophils from healthy controls, indicating a potential mechanism whereby lipoxins aid the endogenous neutrophil function in health but reduce its excessive activation in disease. We also demonstrated that lipoxins attenuated upregulation of the high‐affinity conformation of the CD11b/CD18 integrin, which plays a central role in clot activation and atherosclerosis. Finally, LXB₄ enhanced lymphatic transmigration of human neutrophils isolated from patients with atherosclerosis. This finding is noteworthy, as impaired lymphatic function is now recognized as an important contributor to atherosclerosis. Although both lipoxins modulated neutrophil function, LXB₄ displayed more potent effects than LXA₄ in humans. This study highlights the therapeutic potential of lipoxins in atherosclerotic disease and demonstrates that the effect of these SPMs may be specifically tailored to the need of the individual.

Immune system and atherosclerosis: Hostile or friendly relationship

Coronary artery disease has remained a major health challenge despite enormous progress in prevention, diagnosis, and treatment strategies. Formation of atherosclerotic plaque is a chronic process that is developmentally influenced by intrinsic and extrinsic determinants. Inflammation triggers atherosclerosis, and the fundamental element of inflammation is the immune system. The immune system involves in the atherosclerosis process by a variety of immune cells and a cocktail of mediators. It is believed that almost all main components of this system possess a profound contribution to the atherosclerosis. However, they play contradictory roles, either protective or progressive, in different stages of atherosclerosis progression. It is evident that monocytes are the first immune cells appeared in the atherosclerotic lesion. With the plaque growth, other types of the immune cells such as mast cells, and T lymphocytes are gradually involved. Each cell releases several cytokines which cause the recruitment of other immune cells to the lesion site. This is followed by affecting the expression of other cytokines as well as altering certain signaling pathways. All in all, a mix of intertwined interactions determine the final outcome in terms of mild or severe manifestations, either clinical or subclinical. Therefore, it is of utmost importance to precisely understand the kind and degree of contribution which is made by each immune component in order to stop the growing burden of cardiovascular morbidity and mortality. In this review, we present a comprehensive appraisal on the role of immune cells in the atherosclerosis initiation and development.

Uremic serum damages endothelium by provoking excessive neutrophil extracellular trap formation

Cardiovascular disease (CVD) is the leading cause of death in patients with chronic kidney disease (CKD). Endothelial cell (EC) dysfunction is a key CKD-specific risk factor; however, the mechanisms by which uremia harms the endothelium are still unclear. We report a role for excessive neutrophil extracellular trap (NET) formation induced by uremic serum on EC injury. Level of plasma nucleosome and myeloperoxidase-DNA, established in vivo markers of NETs, as well as intracellular adhesion molecule (ICAM)-1 were measured in hemodialysis (HD) patients and healthy volunteers (HV) and their prognostic role evaluated. For in vitro studies, HV-derived neutrophils and differentiated HL-60 cells by retinoic acid were used to determine the effect of uremic serum-induced NETs on human umbilical vein EC (HUVEC). The level of in vivo NETs was significantly higher in incident HD patients compared to HV, and these markers were strongly associated with ICAM-1. Specifically, nucleosome and ICAM-1 levels were independent predictors of a composite endpoint, all-cause mortality, or vascular access failure. In vitro, HD-derived uremic serum significantly increased NET formation both in dHL-60 and isolated neutrophils compared to control serum, and these NETs decreased EC viability and induced their apoptosis. In addition, the level of ICAM-1, E-selectin and von Willebrand factor in HUVEC supernatant was significantly increased by uremic serum-induced NETs compared to control serum-induced NETs. Dysregulated neutrophil activities in the uremic milieu may play a key role in vascular inflammatory responses. The high mortality and CVD rates in ESRD may be explained in part by excessive NET formation leading to EC damage and dysfunction.

Decellularized scaffold and its elicited immune response towards the host: the underlying mechanism and means of immunomodulatory modification

The immune response of the host towards a decellularized scaffold is complex. Not only can a number of immune cells influence this process, but also the characteristics, preparation and modification of the decellularized scaffold can significantly impact this reaction. Such factors can, together or alone, trigger immune cells to polarize towards either a pro-healing or pro-inflammatory direction. In this article, we have comprehensively reviewed factors which may influence the immune response of the host towards a decellularized scaffold, including the source of the biomaterial, biophysical properties or modifications of the scaffolds with bioactive peptides, drugs and cytokines. Furthermore, the underlying mechanism has also been recapitulated.

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.

Appreciating the First Line of the Human Innate Immune Defense: A Strategy to Model and Alleviate the Neutrophil Elastase-Mediated Attack toward Bioactivated Biomaterials

Biointerface engineering is a wide-spread strategy to improve the healing process and subsequent tissue integration of biomaterials. Especially the integration of specific peptides is one promising strategy to promote the regenerative capacity of implants and 3D scaffolds. In vivo, these tailored interfaces are, however, first confronted with the innate immune response. Neutrophils are cells with pronounced proteolytic potential and the first recruited immune cells at the implant site; nonetheless, they have so far been underappreciated in the design of biomaterial interfaces. Herein, an in vitro approach is introduced to model and analyze the neutrophil interaction with bioactivated materials at the example of nano-bioinspired electrospun surfaces that reveals the vulnerability of a given biointerface design to the contact with neutrophils. A sacrificial, transient hydrogel coating that demonstrates optimal protection for peptide-modified surfaces and thus alleviates the immediate cleavage by neutrophil elastase is further introduced.

Neutrophil-mediated immune response as a possible mechanism of acute unilateral vestibulopathy

OBJECTIVE

This study aimed to investigate the underlying pathogenesis of acute unilateral vestibulopathy (AUV) using gene expression profiling combined with bioinformatics analysis.

METHODS

Total RNA was extracted from the peripheral blood mononuclear cells of ten AUV patients in the acute phase and from ten controls. The differentially expressed genes (DEGs) between these two groups were screened using microarray analysis with the cut-off criteria (|fold changes| > 1.5 and p-value < 0.05). Functional enrichment analysis of DEGs was performed using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis, and the protein-protein interaction (PPI) network was constructed using the STRING (Search Tool for the Retrieval of Interacting Genes) database.

RESULTS

There were 57 DEGs (50 up-regulated and 7 down-regulated) identified in the AUV group. Functional enrichment analysis showed that most of the up-regulated DEGs were significantly enriched in terms related to the neutrophil-mediated immune pathway. From the PPI network, the top ten hub genes were extracted by calculating four topological properties, and most of them were related to the innate immune system, inflammatory processes and vascular disorders. The complete blood count tests showed that the neutrophil-to-lymphocyte ratio was significantly higher in the 72 AUV patients than in the age-matched controls (2.93±2.25 vs 1.54±0.61, p < 0.001).

CONCLUSIONS

This study showed that the neutrophil-mediated immune pathway may contribute to the development of AUV by mediating inflammatory and thrombotic changes in the vestibular organ.

Prolonged Cardiopulmonary Bypass is Associated With Endothelial Glycocalyx Degradation

BACKGROUND

The endothelial glycocalyx (EG) is involved in critical regulatory mechanisms that maintain endothelial vascular integrity. We hypothesized that prolonged cardiopulmonary bypass (CPB) may be associated with EG degradation. We performed an analysis of soluble syndecan-1 levels in relation to duration of CPB, as well as factors associated with cell stress and damage, such as mitochondrial DNA (mtDNA) and inflammation.

METHODS

Blood samples from subjects undergoing cardiac surgery with CPB (n = 54) were obtained before and during surgery, 4-8 h and 24 h after completion of CPB, and on postoperative day 4. Flow cytometry was used to determine subpopulations of white blood cells. Plasma levels of mtDNA were determined using quantitative polymerase chain reaction and plasma content of shed syndecan-1 was measured. To determine whether syndecan-1 was signaling white blood cells, the effect of recombinant syndecan-1 on mobilization of neutrophils from bone marrow was tested in mice.

RESULTS

CPB is associated with increased mtDNA during surgery, increased syndecan-1 blood levels at 4-8 h, and increased white blood cell count at 4-8 h and 24 h. Correlation analysis revealed significant positive associations between time on CPB and syndecan-1 (r_s = 0.488, P < 0.001) and level of syndecan-1 and neutrophil count (r_s = 0.351, P = 0.038) at 4-8 h. Intravenous administration of recombinant syndecan-1 in mice resulted in a 2.5-fold increase in the number of circulating neutrophils, concurrent with decreased bone marrow neutrophil number.

CONCLUSIONS

Longer duration of CPB is associated with increased plasma levels of soluble syndecan-1, a signal for EG degradation, which can induce neutrophil egress from the bone marrow. Development of therapy targeting EG shedding may be beneficial in patients with prolonged CPB.

Neutrophil activation and neutrophil derived neutrophil extracellular trap formation in patients with coronary artery ectasia

BACKGROUND

This study investigated neutrophil activation and neutrophil-derived extracellular traps formation in coronary artery ectasia.

METHODS

We enrolled 90 patients who underwent coronary angiography, and included 30 patients with coronary artery ectasia (CAE), 30 patients with obstructive coronary artery disease (CAD) and 30 patients with normal coronary arteries (CON). Intra-neutrophil mean myeloperoxidase index (MPXI) was determined using an automated blood cell counter (ADVIA2120 Hematology System). Serum concentrations of plasma adhesion molecules, cytokines, and neutrophil-derived extracellular traps were quantified.

RESULTS

The intra-neutrophil mean myeloperoxidase index was reduced in CAE patients compared to CAD and CON patients (1.02 ± 3.01, 3.22 ± 3.03, 3.52 ± 4.25, respectively; CAE vs CAD, p = 0.016 and CAE vs CON, p = 0.007). Multiple logistic regression analysis showed that MPXI and dsDNA were independent factors that predicted the presence of CAE. CAE patients had higher levels of plasma adhesion molecules (P-selectin glycoprotein ligand-1, E-selectin, L-selectin) and interleukin 1 beta levels. Neutrophil extracellular trap concentrations were significantly higher in the CAE group compared to CAD and CON patients (284.31(258.33-449.91) ng/mL, 225.12(203.34-257.13) ng/mL, and 247.37(231.04-273.01) ng/mL, respectively; CAE vs CAD, p = 0.000 and CAE vs CON, p = 0.001).

CONCLUSIONS

Peripheral neutrophils from CAE patients were activated and neutrophil extracellular traps were elevated in the plasma. IL-1β and soluble adhesion molecules may be the causal factors for neutrophil activation.

Fibrillar conformation of an apolipoprotein A-I variant involved in amyloidosis and atherosclerosis

BACKGROUND

Different protein conformations may be involved in the development of clinical manifestations associated with human amyloidosis. Although a fibrillar conformation is usually the signature of damage in the tissues of patients, it is not clear whether this species is per se the cause or the consequence of the disease. Hereditary amyloidosis due to variants of apolipoprotein A-I (apoA-I) with a substitution of a single amino acid is characterized by the presence of fibrillar protein within the lesions. Thus mutations result in increased protein aggregation. Here we set up to characterize the folding of a natural variant with a mutation leading to a deletion at position 107 (apoA-I Lys107-0). Patients carrying this variant show amyloidosis and severe atherosclerosis.

METHODS

We oxidized this variant under controlled concentrations of hydrogen peroxide and analyzed the structure obtained after 30-day incubation by fluorescence, circular dichroism and microscopy approaches. Neutrophils activation was characterized by confocal microscopy.

RESULTS

We obtained a high yield of well-defined stable fibrillar structures of apoA-I Lys107-0. In an in vitro neutrophils system, we were able to detect the induction of Neutrophils Extracellular Traps (NETs) when we incubated with oxidized apoA-I variants. This effect was exacerbated by the fibrillar structure of oxidized Lys 107-0.

CONCLUSIONS

We conclude that a pro-inflammatory microenvironment could result in the formation of aggregation-prone species, which, in addition may induce a positive feed-back in the activation of an inflammatory response.

GENERAL SIGNIFICANCE

These events may explain a close association between amyloidosis due to apoA-I Lys107-0 and atherosclerosis.

Neutrophils in Psoriasis

Neutrophils are the most abundant innate immune cells. The pathogenic roles of neutrophils are related to chronic inflammation and autoimmune diseases. Psoriasis is a chronic systemic inflammatory disease affecting ~2–3% of the world population. The abundant presence of neutrophils in the psoriatic skin lesions serves as a typical histopathologic hallmark of psoriasis. Recent reports indicated that oxidative stress, granular components, and neutrophil extracellular traps from psoriatic neutrophils are related to the initial and maintenance phases of psoriasis. This review provides an overview on the recent (up to 2019) advances in understanding the role of neutrophils in the pathophysiology of psoriasis, including the effects of respiratory burst, degranulation, and neutrophil extracellular trap formation on psoriatic immunity and the clinical relationships.

Neutrophil Extracellular Traps Induce Endothelial Cell Activation and Tissue Factor Production Through Interleukin-1α and Cathepsin G

Objective- Coronary artery thrombosis can occur in the absence of plaque rupture because of superficial erosion. Erosion-prone atheromata associate with more neutrophil extracellular traps (NETs) than lesions with stable or rupture-prone characteristics. The effects of NETs on endothelial cell (EC) inflammatory and thrombogenic properties remain unknown. We hypothesized that NETs alter EC functions related to erosion-associated thrombosis. Approach and Results- Exposure of human ECs to NETs increased VCAM-1 (vascular cell adhesion molecule 1) and ICAM-1 (intercellular adhesion molecule 1) mRNA and protein expression in a time- and concentration-dependent manner. THP-1 monocytoid cells and primary human monocytes bound more avidly to NET-treated human umbilical vein ECs than to unstimulated cells under flow. Treatment of human ECs with NETs augmented the expression of TF (tissue factor) mRNA, increased EC TF activity, and hastened clotting of recalcified plasma. Anti-TF-neutralizing antibody blocked NET-induced acceleration of clotting by ECs. NETs alone did not exhibit TF activity or acceleration of clotting in cell-free assays. Pretreatment of NETs with anti-interleukin (IL)-1α-neutralizing antibody or IL-1Ra (IL-1 receptor antagonist)-but not with anti-IL-1β-neutralizing antibody or control IgG-blocked NET-induced VCAM-1, ICAM-1, and TF expression. Inhibition of cathepsin G, a serine protease abundant in NETs, also limited the effect of NETs on EC activation. Cathepsin G potentiated the effect of IL-1α on ECs by cleaving the pro-IL-1α precursor and releasing the more potent mature IL-1α form. Conclusions- NETs promote EC activation and increased thrombogenicity through concerted action of IL-1α and cathepsin G. Thus, NETs may amplify and propagate EC dysfunction related to thrombosis because of superficial erosion.

The Phenomenon of Neutrophil Extracellular Traps in Vascular Diseases

Vascular diseases constitute a global health issue due to the increasing number of cases of patients with these diseases. The pathogenesis of the majority of these diseases, including atherosclerosis and thrombosis, is complex and not yet fully understood. One of the major causes for their occurrence can be immune disorders resulting in the development of a chronic inflammation within the vessels. In recent years, studies have placed emphasis on the role of neutrophils in the development of these diseases, i.e., the discovery of neutrophil extracellular traps (NETs) demonstrated that the structures released by the cells may contribute to the enhancement of inflammatory reactions and cell damage. This article summarizes current knowledge on the role of NETs during atherosclerosis, thrombosis and small-vessel vasculitis, especially in antineutrophil cytoplasmic antibody (ANCA)-associated small-vessel vasculitis (AAV).

The Yin and Yang of Tyrosine Kinase Inhibition During Experimental Polymicrobial Sepsis

Neutrophils are the first cells of our immune system to arrive at the site of inflammation. They release cytokines, e.g., chemokines, to attract further immune cells, but also actively start to phagocytose and kill pathogens. In the case of sepsis, this tightly regulated host defense mechanism can become uncontrolled and hyperactive resulting in severe organ damage. Currently, no effective therapy is available to fight sepsis; therefore, novel treatment targets that could prevent excessive inflammatory responses are warranted. Src Family tyrosine Kinases (SFK), a group of tyrosine kinases, have been shown to play a major role in regulating immune cell recruitment and host defense. Leukocytes with SFK depletion display severe spreading and migration defects along with reduced cytokine production. Thus, we investigated the effects of dasatinib, a tyrosine kinase inhibitor, with a strong inhibitory capacity on SFKs during sterile inflammation and polymicrobial sepsis in mice. We found that dasatinib-treated mice displayed diminished leukocyte adhesion and extravasation in tumor necrosis factor-α-stimulated cremaster muscle venules in vivo. In polymicrobial sepsis, sepsis severity, organ damage, and clinical outcome improved in a dose-dependent fashion pointing toward an optimal therapeutic window for dasatinib dosage during polymicrobial sepsis. Dasatinib treatment may, therefore, provide a balanced immune response by preventing an overshooting inflammatory reaction on the one side and bacterial overgrowth on the other side.

Leukocyte Dynamics during the Evolution of Human Coronary Atherosclerosis: Conclusions from a Sevenfold, Chromogen-Based, Immunohistochemical Evaluation

Atherosclerosis is a complex process with strong inflammatory component. We developed a straightforward sevenfold staining protocol for simultaneous assessment of dominant leukocyte classes, vascularization, and expression of the putative foam cell maker CD36. The method was applied on human coronaries covering the full spectrum of atherosclerotic disease. Results confirm the progressive association of macrophages and T cells with the process and a global presence of mast cells. B cells are exclusively present in adventitial follicles that accompany the process plaque destabilization (thin cap and ruptured lesions) and are otherwise absent. Neutrophils are only present as part of the hemorrhage that accompanies plaque rupture. This study does not classify CD36 as a key factor in foam cell formation. Observed macrophage accumulation in the neointima of stabilized fibrous calcified plaques is consistent with a process of neoatherosclerosis. This study on human coronaries shows a progressive association of macrophage and T-cell abundance with plaque progression. Follicle-like structures are transiently present during the process of plaque destabilization. Plaque healing is accompanied by cessation of the inflammatory response but followed by a new cycle of atherosclerosis.

β2 -Adrenoceptors inhibit neutrophil extracellular traps in human polymorphonuclear leukocytes

This study tests the hypothesis that in isolated human polymorphonuclear leukocytes (PMN) adrenergic ligands can affect neutrophil extracellular trap (NET) formation. We have previously shown that, in PMN, adrenaline (A), through the activation of adrenergic receptors (AR), reduces stimulus-dependent cell activation; we have, therefore, planned to investigate if AR are involved in NET production. PMN were obtained from venous blood of healthy subject. The ability of adrenergic ligands to affect reactive oxygen species (ROS) production, NET production, and cell migration was investigated in cells cultured under resting conditions or after activation with N-formyl-methionyl-leucyl-phenylalanine (fMLP), LPS, or IL-8. Stimuli-induced NET production measured as ROS, microscopic evaluation, and elastase production was reverted by A and this effect was blocked by the selective β₂ -AR antagonist ICI-118,551. The stimulus-induced ROS generation and migration was prevented by A and by isoprenaline (ISO), and these effects were counteracted only by ICI-118,551 and not by the other two selective ligands for the β₁ and β₃ -AR. Finally, the presence of the β-ARs on PMN was confirmed, by means of microscopy and flow cytometry. The data of the present study suggest that adrenergic compounds, through the interaction of mainly β₂ -AR, are able to affect neutrophil functions. These data are suggestive of a possible therapeutic role of β₂ -AR ligands (in addition to their classical use), promoting the possible therapeutic relevance of adrenergic system in the modulation of innate immunity proposing their possible use as anti-inflammatory drugs.

The role of monocytosis and neutrophilia in atherosclerosis

Monocytosis and neutrophilia are frequent events in atherosclerosis. These phenomena arise from the increased proliferation of hematopoietic stem and multipotential progenitor cells (HSPCs) and HSPC mobilization from the bone marrow to other immune organs and circulation. High cholesterol and inflammatory signals promote HSPC proliferation and preferential differentiation to the myeloid precursors (i.e., myelopoiesis) that than give rise to pro-inflammatory immune cells. These cells accumulate in the plaques thereby enhancing vascular inflammation and contributing to further lesion progression. Studies in animal models of atherosclerosis showed that manipulation with HSPC proliferation and differentiation through the activation of LXR-dependent mechanisms and restoration of cholesterol efflux may have a significant therapeutic potential.

Neutrophil: A Cell with Many Roles in Inflammation or Several Cell Types?

Neutrophils are the most abundant leukocytes in the circulation, and have been regarded as first line of defense in the innate arm of the immune system. They capture and destroy invading microorganisms, through phagocytosis and intracellular degradation, release of granules, and formation of neutrophil extracellular traps after detecting pathogens. Neutrophils also participate as mediators of inflammation. The classical view for these leukocytes is that neutrophils constitute a homogenous population of terminally differentiated cells with a unique function. However, evidence accumulated in recent years, has revealed that neutrophils present a large phenotypic heterogeneity and functional versatility, which place neutrophils as important modulators of both inflammation and immune responses. Indeed, the roles played by neutrophils in homeostatic conditions as well as in pathological inflammation and immune processes are the focus of a renovated interest in neutrophil biology. In this review, I present the concept of neutrophil phenotypic and functional heterogeneity and describe several neutrophil subpopulations reported to date. I also discuss the role these subpopulations seem to play in homeostasis and disease.

Primed polymorphonuclear leukocytes from hemodialysis patients enhance monocyte transendothelial migration

Increased counts and priming of peripheral polymorphonuclear leukocytes (PMNLs) are associated with future or ongoing atherosclerosis; however, the role of PMNLs in enhancing monocyte transendothelial migration is still unclear. Our aims were to examine endothelial and monocyte activation, transmigration, and posttransmigration activation induced ex vivo by in vivo primed PMNLs and the effect of antioxidants on the activation. A unique ex vivo coculture system of three cell types was developed in this study, enabling interactions among the following: primary human umbilical vein endothelial cells (HUVECs), monocytes (THP-1 cell line), and in vivo primed PMNLs from hemodialysis (HD) patients and healthy control (HC) subjects. The interactions among these cells were examined, and an intervention with superoxide dismutase and catalase was performed. Preexposed HUVECs to HD/HC PMNLs showed a significant monocyte transmigration yield, 120–170% above HCs. Monocyte exposure to HD PMNLs induced pre- and posttransmigration activation. When the three cell types were cocultivated at the same time, monocyte chemoattractant protein-1 protein levels released from HUVECs, and activation markers on HUVECs [CD54 and chemokine (C-X3-C motif) ligand 1] and monocytes [chemokine (C-X3-C) receptor 1 and chemokine (C-C motif) receptor 2] were increased. Monocyte transmigration yield decreased to 70% (compared with HC subjects) due to adherence and accumulation of monocytes to HUVECs. When superoxide dismutase and catalase were used, reduced HUVEC and monocyte activation markers brought the transmigration yields to control levels and abolished accumulation of monocytes, emphasizing the role of superoxide in this process. We conclude that peripheral primed PMNLs play a pivotal role in enhancing monocyte transendotelial migration, the hallmark of the atherosclerotic process. Primed PMNLs can be used as a mediator and a biomarker of atherosclerosis even before plaque formation.

NEW & NOTEWORTHY Primed polymorphonuclear leukocytes are key mediators in monocyte transendothelial migration, a new understanding of the initiation of endothelial dysfunction and monocyte activation, transmigration, and accumulation in the subendothelial layer.

Regenerative immunology: the immunological reaction to biomaterials

Regenerative medicine promises to meet two of the most urgent needs of modern organ transplantation, namely immunosuppression-free transplantation and an inexhaustible source of organs. Ideally, bioengineered organs would be manufactured from a patient's own biomaterials-both cells and the supporting scaffolding materials in which cells would be embedded and allowed to mature to eventually regenerate the organ in question. While some groups are focusing on the feasibility of this approach, few are focusing on the immunogenicity of the scaffolds that are being developed for organ bioengineering purposes. This review will succinctly discuss progress in the understanding of immunological characteristics and behavior of different scaffolds currently under development, with emphasis on the extracellular matrix scaffolds obtained decellularized animal or human organs which seem to provide the ideal template for bioengineering purposes.

Neutrophil Extracellular Traps and Endothelial Dysfunction in Atherosclerosis and Thrombosis

Cardiovascular diseases are a leading cause of mortality and morbidity worldwide. Neutrophils are a component of the innate immune system which protect against pathogen invasion; however, the contribution of neutrophils to cardiovascular disease has been underestimated, despite infiltration of leukocyte subsets being a known driving force of atherosclerosis and thrombosis. In addition to their function as phagocytes, neutrophils can release their extracellular chromatin, nuclear protein, and serine proteases to form net-like fiber structures, termed neutrophil extracellular traps (NETs). NETs can entrap pathogens, induce endothelial activation, and trigger coagulation, and have been detected in atherosclerotic and thrombotic lesions in both humans and mice. Moreover, NETs can induce endothelial dysfunction and trigger proinflammatory immune responses. Overall, current data indicate that NETs are not only present in plaques and thrombi but also have causative roles in triggering formation of atherosclerotic plaques and venous thrombi. This review is focused on published findings regarding NET-associated endothelial dysfunction during atherosclerosis, atherothrombosis, and venous thrombosis pathogenesis. The NET structure is a novel discovery that will find its appropriate place in our new understanding of cardiovascular disease. In addition, NETs have high potential to be further explored toward much better treatment of atherosclerosis and venous thromboembolism in clinic.

An overview of the role of neutrophils in innate immunity, inflammation and host-biomaterial integration

Despite considerable recent progress in defining neutrophil functions and behaviors in tissue repair, much remains to be determined with regards to its overall role in the tissue integration of biomaterials. This article provides an overview of the neutrophil’s numerous, important roles in both inflammation and resolution, and subsequently, their role in biomaterial integration. Neutrophils function in three primary capacities: generation of oxidative bursts, release of granules and formation of neutrophil extracellular traps (NETs); these combined functions enable neutrophil involvement in inflammation, macrophage recruitment, M2 macrophage differentiation, resolution of inflammation, angiogenesis, tumor formation and immune system activation. Neutrophils exhibit great flexibility to adjust to the prevalent microenvironmental conditions in the tissue; thus, the biomaterial composition and fabrication will potentially influence neutrophil behavior following confrontation. This review serves to highlight the neutrophil’s plasticity, reiterating that neutrophils are not just simple suicidal killers, but the true maestros of resolution and regeneration.