Cathepsin G Controls Arterial But Not Venular Myeloid Cell Recruitment

Differential effects of angiotensin II and aldosterone on human neutrophil adhesion and concomitant secretion of proteins, free amino acids and reactive oxygen and nitrogen species

Invasion and adhesion of neutrophils into tissues and their concomitant secretion play an important role in the development of vascular pathologies, including abdominal aortic aneurysm (AAA). Chronic administration of angiotensin II is used to initiate AAA formation in mice. The role of aldosterone in this process is being studied. We conducted for the first time a complex comparative study of the effects of angiotensin II and aldosterone on the adhesion of human neutrophils to fibronectin and the concomitant secretion of proteins, free amino acids as well as reactive oxygen (ROS) and nitrogen (NO) species. Neither angiotensin II nor aldosterone affected the attachment of neutrophils to fibronectin and the concomitant production of ROS. We showed for the first time that aldosterone stimulated the release of amino acid hydroxylysine, a product of lysyl hydroxylase, the activity of which is positively correlated with cell invasiveness. Aldosterone also initiates the secretion of matrix metalloproteinase 9 (MMP-9) and cathepsin G, which may reorganize the extracellular matrix and stimulate the recruitment and adhesion of neutrophils to the aortic walls. Angiotensin II did not affect protein secretion. It may contribute to neutrophil-induced vascular injury by inhibiting the production of NO or by increasing the secretion of isoleucine. Our results suggest that it is aldosterone-induced neutrophil secretion that may play a significant role in neutrophil-induced vascular wall destruction in angiotensin II-induced AAA or other vascular complications.

Novel strategies for targeting neutrophil against myocardial infarction

Inflammation is a crucial factor in cardiac remodeling after acute myocardial infarction (MI). Neutrophils, as the first wave of leukocytes to infiltrate the injured myocardium, exacerbate inflammation and cardiac injury. However, therapies that deplete neutrophils to manage cardiac remodeling after MI have not consistently produced promising outcomes. Recent studies have revealed that neutrophils at different time points and locations may have distinct functions. Thus, transferring neutrophil phenotypes, rather than simply blocking their activities, potentially meet the needs of cardiac repair. In this review, we focus on discussing the fate, heterogeneity, functions of neutrophils, and attempt to provide a more comprehensive understanding of their roles and targeting strategies in MI. We highlight the strategies and translational potential of targeting neutrophils to limit cardiac injury to reduce morbidity and mortality from MI.

Regulation of vascular remodeling by immune microenvironment after the establishment of autologous arteriovenous fistula in ESRD patients

Autogenous arteriovenous fistula (AVF) is the preferred dialysis access for receiving hemodialysis treatment in end-stage renal disease patients. After AVF is established, vascular remodeling occurs in order to adapt to hemodynamic changes. Uremia toxins, surgical injury, blood flow changes and other factors can induce inflammatory response, immune microenvironment changes, and play an important role in the maintenance of AVF vascular remodeling. This process involves the infiltration of pro-inflammatory and anti-inflammatory immune cells and the secretion of cytokines. Pro-inflammatory and anti-inflammatory immune cells include neutrophil (NEUT), dendritic cell (DC), T lymphocyte, macrophage (Mφ), etc. This article reviews the latest research progress and focuses on the role of immune microenvironment changes in vascular remodeling of AVF, in order to provide a new theoretical basis for the prevention and treatment of AVF failure.

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.

Inflammation Resolution in the Cardiovascular System: Arterial Hypertension, Atherosclerosis, and Ischemic Heart Disease

Significance: Chronic inflammation has emerged as a major underlying cause of many prevalent conditions in the Western world, including cardiovascular diseases. Although targeting inflammation has emerged as a promising avenue by which to treat cardiovascular disease, it is also associated with increased risk of infection. Recent Advances: Though previously assumed to be passive, resolution has now been identified as an active process, mediated by unique immunoresolving mediators and mechanisms designed to terminate acute inflammation and promote tissue repair. Recent work has determined that failures of resolution contribute to chronic inflammation and the progression of human disease. Specifically, failure to produce pro-resolving mediators and the impaired clearance of dead cells from inflamed tissue have been identified as major mechanisms by which resolution fails in disease. Critical Issues: Drawing from a rapidly expanding body of experimental and clinical studies, we review here what is known about the role of inflammation resolution in arterial hypertension, atherosclerosis, myocardial infarction, and ischemic heart disease. For each, we discuss the involvement of specialized pro-resolving mediators and pro-reparative cell types, including T regulatory cells, myeloid-derived suppressor cells, and macrophages. Future Directions: Pro-resolving therapies offer the promise of limiting chronic inflammation without impairing host defense. Therefore, it is imperative to better understand the mechanisms underlying resolution to identify therapeutic targets. Antioxid. Redox Signal. 40, 292-316.

Neutrophils in Physiology and Pathology

Infections, cardiovascular disease, and cancer are major causes of disease and death worldwide. Neutrophils are inescapably associated with each of these health concerns, by either protecting from, instigating, or aggravating their impact on the host. However, each of these disorders has a very different etiology, and understanding how neutrophils contribute to each of them requires understanding the intricacies of this immune cell type, including their immune and nonimmune contributions to physiology and pathology. Here, we review some of these intricacies, from basic concepts in neutrophil biology, such as their production and acquisition of functional diversity, to the variety of mechanisms by which they contribute to preventing or aggravating infections, cardiovascular events, and cancer. We also review poorly explored aspects of how neutrophils promote health by favoring tissue repair and discuss how discoveries about their basic biology inform the development of new therapeutic strategies.

Impact of Immunity on Coronary Artery Disease: An Updated Pathogenic Interplay and Potential Therapeutic Strategies

Coronary artery disease (CAD) is the leading cause of death worldwide. It is a result of the buildup of atherosclerosis within the coronary arteries. The role of the immune system in CAD is complex and multifaceted. The immune system responds to damage or injury to the arterial walls by initiating an inflammatory response. However, this inflammatory response can become chronic and lead to plaque formation. Neutrophiles, macrophages, B lymphocytes, T lymphocytes, and NKT cells play a key role in immunity response, both with proatherogenic and antiatherogenic signaling pathways. Recent findings provide new roles and activities referring to endothelial cells and vascular smooth muscle cells, which help to clarify the intricate signaling crosstalk between the involved actors. Research is ongoing to explore immunomodulatory therapies that target the immune system to reduce inflammation and its contribution to atherosclerosis. This review aims to summarize the pathogenic interplay between immunity and CAD and the potential therapeutic strategies, and explore immunomodulatory therapies that target the immune system to reduce inflammation and its contribution to atherosclerosis.

Role of neutrophils in different stages of atherosclerosis

Neutrophils constitute the first line of defense in human immunity and can be attracted to inflamed and infected sites by various chemokines. As essential players in immune processes, neutrophils theoretically play integral roles in the course of chronic inflammation-induced atherosclerosis. However, because neutrophils are rarely found in atherosclerotic lesions, their involvement in the pathophysiological progression of atherosclerosis has been largely underestimated or ignored. Recent research has revealed convincing evidence showing the presence of neutrophils in atherosclerotic lesions and has revealed neutrophil contributions to different atherosclerosis stages in mice and humans. This review describes the underlying mechanisms of neutrophils in different stages of atherosclerosis and highlights potential neutrophil-targeted therapeutic strategies relevant to atherosclerosis. An in-depth understanding of neutrophils' roles in atherosclerosis pathology will promote exploration of new methods for the prevention and treatment of atherogenesis and atherothrombosis.

The RNA editor ADAR2 promotes immune cell trafficking by enhancing endothelial responses to interleukin-6 during sterile inflammation

Immune cell trafficking constitutes a fundamental component of immunological response to tissue injury, but the contribution of intrinsic RNA nucleotide modifications to this response remains elusive. We report that RNA editor ADAR2 exerts a tissue- and stress-specific regulation of endothelial responses to interleukin-6 (IL-6), which tightly controls leukocyte trafficking in IL-6-inflamed and ischemic tissues. Genetic ablation of ADAR2 from vascular endothelial cells diminished myeloid cell rolling and adhesion on vascular walls and reduced immune cell infiltration within ischemic tissues. ADAR2 was required in the endothelium for the expression of the IL-6 receptor subunit, IL-6 signal transducer (IL6ST; gp130), and subsequently, for IL-6 trans-signaling responses. ADAR2-induced adenosine-to-inosine RNA editing suppressed the Drosha-dependent primary microRNA processing, thereby overwriting the default endothelial transcriptional program to safeguard gp130 expression. This work demonstrates a role for ADAR2 epitranscriptional activity as a checkpoint in IL-6 trans-signaling and immune cell trafficking to sites of tissue injury.

Association of admission neutrophil serine proteinases levels with the outcomes of acute ischemic stroke: a prospective cohort study

BACKGROUND

Neutrophil serine proteinases (NSPs), released by activated neutrophils, are key proteins involved in the pathophysiologic processes of stroke. NSPs are also implicated in the process and response of thrombolysis. This study aimed to analyze three NSPs (neutrophil elastase, cathepsin G, and proteinase 3) in relation to acute ischemic stroke (AIS) outcomes and in relation to the outcomes of patients treated with intravenous recombinant tissue plasminogen activator (IV-rtPA).

METHODS

Among 736 patients prospectively recruited at the stroke center from 2018 to 2019, 342 patients diagnosed with confirmed AIS were included. Plasma neutrophil elastase (NE), cathepsin G (CTSG), and proteinase 3 (PR3) concentrations were measured on admission. The primary endpoint was unfavorable outcome defined as modified Rankin Scale score 3-6 at 3 months, and the secondary endpoints were symptomatic intracerebral hemorrhage (sICH) within 48 h, and mortality within 3 months. In the subgroup of patients who received IV-rtPA, post-thrombolysis early neurological improvement (ENI) (defined as National Institutes of Health Stroke Scale score = 0 or decrease of ≥ 4 within 24 h after thrombolysis) was also included as the secondary endpoint. Univariate and multivariate logistic regression analyses were performed to evaluate the association between NSPs levels and AIS outcomes.

RESULTS

Higher NE and PR3 plasma levels were associated with the 3-month mortality and 3-month unfavorable outcome. Higher NE plasma levels were also associated with the risk of sICH after AIS. After adjusting for potential confounders, plasma NE level > 229.56 ng/mL (odds ratio [OR] = 4.478 [2.344-8.554]) and PR3 > 388.77 ng/mL (OR = 2.805 [1.504-5.231]) independently predicted the 3-month unfavorable outcome. Regarding rtPA treatment, patients with NE plasma concentration > 177.22 ng/mL (OR = 8.931 [2.330-34.238]) or PR3 > 388.77 ng/mL (OR = 4.275 [1.045-17.491]) were over 4 times more likely to suffer unfavorable outcomes after rtPA treatment. The addition of NE and PR3 to clinical predictors of unfavorable functional outcome after AIS and the outcome after rtPA treatment improved discrimination as well as reclassification (integrated discrimination improvement = 8.2% and 18.1%, continuous net reclassification improvement = 100.0% and 91.8%, respectively).

CONCLUSIONS

Plasma NE and PR3 are novel and independent predictors of 3-month functional outcomes after AIS. Plasma NE and PR3 also possess predictive value to identify patients with unfavorable outcomes after rtPA treatment. NE is probably an important mediator of the effects of neutrophils on stroke outcomes, which worth further investigation.

The Role of Neutrophils in Lower Limb Peripheral Artery Disease: State of the Art and Future Perspectives

In recent years, increasing attention has been paid to the role of neutrophils in cardiovascular (CV) disease (CVD) with evidence supporting their role in the initiation, progression, and rupture of atherosclerotic plaque. Although these cells have long been considered as terminally differentiated cells with a relatively limited spectrum of action, recent research has revealed intriguing novel cellular functions, including neutrophil extracellular trap (NET) generation and inflammasome activation, which have been linked to several human diseases, including CVD. While most research to date has focused on the role of neutrophils in coronary artery and cerebrovascular diseases, much less information is available on lower limb peripheral artery disease (PAD). PAD is a widespread condition associated with great morbidity and mortality, though physician and patient awareness of the disease remains low. To date, several studies have produced some evidence on the role of certain biomarkers of neutrophil activation in this clinical setting. However, the etiopathogenetic role of neutrophils, and in particular of some of the newly discovered mechanisms, has yet to be fully elucidated. In the future, complementary assessment of neutrophil activity should improve CV risk stratification and provide personalized treatments to patients with PAD. This review aims to summarize the basic principles and recent advances in the understanding of neutrophil biology, current knowledge about the role of neutrophils in atherosclerosis, as well as available evidence on their role of PAD.

Recent Insights into Neutrophil Extracellular Traps in Cardiovascular Diseases

Neutrophils are primary effector cells of the innate immune system. Emerging evidence has consistently shown that activated neutrophils produce and release neutrophil extracellular traps (NETs) that play roles in immunity and non-infectious diseases. NETs are composed of DNA and proteins and serve as a structural platform for pathogen sequestration and degradation. In contrast to their protective role during pathogenic infection, NETs are pathologically involved in cardiovascular disease (CVD). In this review, we introduce the formation, release, and clearance of NETs and the regulatory mechanisms of NETs formation, followed by an overview of the clinical evidence for the involvement of NETs in CVD. Because atherosclerosis is a fundamental part of the pathogenesis of CVD, we chose to focus on the mechanisms by which NETs promote endothelial cell damage and collaborate with macrophages and platelets to accelerate plaque progression and thrombosis. Finally, we present options for clinical intervention to inhibit NETs production and release in the treatment of CVD. In conclusion, this review integrates the latest findings and provides new insights into NETs, which represent a novel biomarker and therapeutic target in clinical practice.

Neutrophil Count as Atrioventricular Block (AVB) Predictor following Pediatric Heart Surgery

Neutrophils play a significant role in immune and inflammatory reactions. The preoperative inflammatory activation may have a detrimental effect on postoperative outcomes. The aim of the study was to investigate the relation between preoperative hematological indices on postoperative complications’ risk in pediatric cardiac congenital surgery. The retrospective single center analysis included 93 pediatric patients (48 (65%) males and 45 (35%) females), mean age of 7 (3−30) months referred for cardiac surgery in cardiopulmonary bypass due to functional single ventricle disease (26 procedures), shunts lesions (40 procedures) and cyanotic disease (27 procedures). Among simple hematological indices, the receiver-operating-characteristic curve showed that a neutrophil count below 2.59 K/uL was found as an optimal cut-off point for predicting postoperative atrioventricular block following pediatric cardiac surgery (AUC = 0.845, p < 0.0001) yielding a sensitivity of 100% and a specificity of 65.62%. Preoperative values of neutrophil count below 2.59 K/uL in whole blood analysis can be regarded as a predictive factor (AUC = 0.845, p < 0.0001) for postoperative atrioventricular block in pediatric cardiac surgery.

The Roles of Neutrophils Linking Periodontitis and Atherosclerotic Cardiovascular Diseases

Inflammation plays a crucial role in the onset and development of atherosclerosis. Periodontitis is a common chronic disease linked to other chronic inflammatory diseases such as atherosclerotic cardiovascular disease (ASCVD). The mechanistic pathways underlying this association are yet to be fully understood. This critical review aims at discuss the role of neutrophils in mediating the relationship between periodontitis and ASCVD. Systemic inflammation triggered by periodontitis could lead to adaptations in hematopoietic stem and progenitor cells (HSPCs) resulting in trained granulopoiesis in the bone marrow, thereby increasing the production of neutrophils and driving the hyper-responsiveness of these abundant innate-immune cells. These alterations may contribute to the onset, progression, and complications of atherosclerosis. Despite the emerging evidence suggesting that the treatment of periodontitis improves surrogate markers of cardiovascular disease, the resolution of periodontitis may not necessarily reverse neutrophil hyper-responsiveness since the hyper-inflammatory re-programming of granulopoiesis can persist long after the inflammatory inducers are removed. Novel and targeted approaches to manipulate neutrophil numbers and functions are warranted within the context of the treatment of periodontitis and also to mitigate its potential impact on ASCVD.

Neutrophil-Platelet Interactions as Novel Treatment Targets in Cardiovascular Disease

Neutrophils and platelets are among the most abundant cell types in peripheral blood and characterized by high plasticity and a readily available reservoir of surface proteins and secretable granule contents. Receptor-mediated activation and granule release predispose both cell types for rapid responses to various stimuli. While neutrophils provide the first line of defense to microbial infections and platelets are known for their aggregatory functions in hemostasis and thrombosis, research of the past decade has highlighted that both cell types jointly shape local and systemic immune responses and clot formation alike. Concomitant activation of neutrophils and platelets has been observed in a variety of cardiovascular diseases, including arterial and venous thrombosis, atherosclerosis as well as myocardial infarction and ischemia-reperfusion injury. In this review, we describe the mechanisms by which neutrophils and platelets interact physically, how release of granule contents and soluble molecules by either cell type affects the other and how this mutual activation supports the efficacy of immune responses. We go on to describe how activated platelets contribute to host defense by triggering neutrophil extracellular trap (NET) formation in a process termed immunothrombosis, which in turn promotes local platelet activation and coagulation. Further, we review current evidence of hazardous overactivation of either cell type and their respective role in cardiovascular disease, with a focus on thrombosis, myocardial infarction and ischemia-reperfusion injury, and describe how neutrophils and platelets shape thromboinflammation in COVID-19. Finally, we provide an overview of therapeutic approaches targeting neutrophil-platelet interactions as novel treatment strategy in cardiovascular disease.

Where the Action Is-Leukocyte Recruitment in Atherosclerosis

Atherosclerosis is the leading cause of death worldwide and leukocyte recruitment is a key element of this phenomenon, thus allowing immune cells to enter the arterial wall. There, in concert with accumulating lipids, the invading leukocytes trigger a plethora of inflammatory responses which promote the influx of additional leukocytes and lead to the continued growth of atherosclerotic plaques. The recruitment process follows a precise scheme of tethering, rolling, firm arrest, crawling and transmigration and involves multiple cellular and subcellular players. This review aims to provide a comprehensive up-to-date insight into the process of leukocyte recruitment relevant to atherosclerosis, each from the perspective of endothelial cells, monocytes and macrophages, neutrophils, T lymphocytes and platelets. In addition, therapeutic options targeting leukocyte recruitment into atherosclerotic lesions-or potentially arising from the growing body of insights into its precise mechanisms-are highlighted.

Circulating proteomic panels for risk stratification of intracranial aneurysm and its rupture

The prevalence of intracranial aneurysm (IA) is increasing, and the consequences of its rupture are severe. This study aimed to reveal specific, sensitive, and non-invasive biomarkers for diagnosis and classification of ruptured and unruptured IA, to benefit the development of novel treatment strategies and therapeutics altering the course of the disease. We first assembled an extensive candidate biomarker bank of IA, comprising up to 717 proteins, based on altered proteins discovered in the current tissue and serum proteomic analysis, as well as from previous studies. Mass spectrometry assays for hundreds of biomarkers were efficiently designed using our proposed deep learning-based method, termed DeepPRM. A total of 113 potential markers were further quantitated in serum cohort I (n = 212) & II (n = 32). Combined with a machine-learning-based pipeline, we built two sets of biomarker combinations (P6 & P8) to accurately distinguish IA from healthy controls (accuracy: 87.50%) or classify IA rupture patients (accuracy: 91.67%) upon evaluation in the external validation set (n = 32). This extensive circulating biomarker development study provides valuable knowledge about IA biomarkers.

Hindrance of the Proteolytic Activity of Neutrophil-Derived Serine Proteases by Serine Protease Inhibitors as a Management of Cardiovascular Diseases and Chronic Inflammation

During inflammation neutrophils become activated and segregate neutrophil serine proteases (NSPs) to the surrounding environment in order to support a natural immune defense. However, an excess of proteolytic activity of NSPs can cause many complications, such as cardiovascular diseases and chronic inflammatory disorders, which will be elucidated on a biochemical and immunological level. The application of selective serine protease inhibitors is the logical consequence in the management of the indicated comorbidities and will be summarized in this briefing.

Vitronectin stabilizes intravascular adhesion of neutrophils by coordinating β2 integrin clustering

The recruitment of neutrophils from the microvasculature to the site of injury or infection represents a key event in the inflammatory response. Vitronectin (VN) is a multifunctional macromolecule abundantly present in blood and extracellular matrix. The role of this glycoprotein in the extravasation process of circulating neutrophils remains elusive. Employing advanced in vivo/ex vivo imaging techniques in different mouse models as well as in vitro methods, we uncovered a previously unrecognized function of VN in the transition of dynamic to static intravascular interactions of neutrophils with microvascular endothelial cells. These distinct properties of VN require the heteromerization of this glycoprotein with plasminogen activator inhibitor-1 (PAI- 1) on the activated venular endothelium and subsequent interactions of this protein complex with the scavenger receptor low-density lipoprotein receptor-related protein-1 on intravascularly adhering neutrophils. This induces p38 mitogen-activated protein kinases-dependent intracellular signaling events which, in turn, regulates the proper clustering of the b2 integrin lymphocyte function associated antigen-1 on the surface of these immune cells. As a consequence of this molecular interplay, neutrophils become able to stabilize their adhesion to the microvascular endothelium and, subsequently, to extravasate to the perivascular tissue. Hence, endothelial-bound VN-PAI-1 heteromers stabilize intravascular adhesion of neutrophils by coordinating b2 integrin clustering on the surface of these immune cells, thereby effectively controlling neutrophil trafficking to inflamed tissue. Targeting this protein complex might be beneficial for the prevention and treatment of inflammatory pathologies.

Leveling Up the Controversial Role of Neutrophils in Cancer: When the Complexity Becomes Entangled

Neutrophils are the most abundant immune cell in the circulation of human and act as gatekeepers to discard foreign elements that have entered the body. They are essential in initiating immune responses for eliminating invaders, such as microorganisms and alien particles, as well as to act as immune surveyors of cancer cells, especially during the initial stages of carcinogenesis and for eliminating single metastatic cells in the circulation and in the premetastatic organs. Since neutrophils can secrete a whole range of factors stored in their many granules as well as produce reactive oxygen and nitrogen species upon stimulation, neutrophils may directly or indirectly affect carcinogenesis in both the positive and negative directions. An intricate crosstalk between tumor cells, neutrophils, other immune cells and stromal cells in the microenvironment modulates neutrophil function resulting in both anti- and pro-tumor activities. Both the anti-tumor and pro-tumor activities require chemoattraction towards the tumor cells, neutrophil activation and ROS production. Divergence is seen in other neutrophil properties, including differential secretory repertoire and membrane receptor display. Many of the direct effects of neutrophils on tumor growth and metastases are dependent on tight neutrophil–tumor cell interactions. Among them, the neutrophil Mac-1 interaction with tumor ICAM-1 and the neutrophil L-selectin interaction with tumor-cell sialomucins were found to be involved in the neutrophil-mediated capturing of circulating tumor cells resulting in increased metastatic seeding. On the other hand, the anti-tumor function of neutrophils was found to rely on the interaction between tumor-surface-expressed receptor for advanced glycation end products (RAGE) and Cathepsin G expressed on the neutrophil surface. Intriguingly, these two molecules are also involved in the promotion of tumor growth and metastases. RAGE is upregulated during early inflammation-induced carcinogenesis and was found to be important for sustaining tumor growth and homing at metastatic sites. Cathepsin G was found to be essential for neutrophil-supported lung colonization of cancer cells. These data level up the complexity of the dual role of neutrophils in cancer.

Neutrophils in cardiovascular disease: warmongers, peacemakers, or both?

Neutrophils, the most abundant of all leucocytes and the first cells to arrive at the sites of sterile inflammation/injury act as a double-edged sword. On one hand, they inflict a significant collateral damage to the tissues and on the other hand, they help facilitate wound healing by a number of mechanisms. Recent studies have drastically changed the perception of neutrophils from being simple one-dimensional cells with an unrestrained mode of action to a cell type that display maturity and complex behaviour. It is now recognized that neutrophils are transcriptionally active and respond to plethora of signals by deploying a wide variety of cargo to influence the activity of other cells in the vicinity. Neutrophils can regulate macrophage behaviour, display innate immune memory, and play a major role in the resolution of inflammation in a context-dependent manner. In this review, we provide an update on the factors that regulate neutrophil production and the emerging dichotomous role of neutrophils in the context of cardiovascular diseases, particularly in atherosclerosis and the ensuing complications, myocardial infarction, and heart failure. Deciphering the complex behaviour of neutrophils during inflammation and resolution may provide novel insights and in turn facilitate the development of potential therapeutic strategies to manage cardiovascular disease.

Contemporary Lifestyle and Neutrophil Extracellular Traps: An Emerging Link in Atherosclerosis Disease

Neutrophil extracellular traps (NETs) are networks of extracellular genetic material decorated with proteins of nuclear, granular and cytosolic origin that activated neutrophils expel under pathogenic inflammatory conditions. NETs are part of the host's innate immune defense system against invading pathogens. Interestingly, these extracellular structures can also be released in response to sterile inflammatory stimuli (e.g., shear stress, lipidic molecules, pro-thrombotic factors, aggregated platelets, or pro-inflammatory cytokines), as in atherosclerosis disease. Indeed, NETs have been identified in the intimal surface of diseased arteries under cardiovascular disease conditions, where they sustain inflammation via NET-mediated cell-adhesion mechanisms and promote cellular dysfunction and tissue damage via NET-associated cytotoxicity. This review will focus on (1) the active role of neutrophils and NETs as underestimated players of the inflammatory process during atherogenesis and lesion progression; (2) how these extracellular structures communicate with the main cell types present in the atherosclerotic lesion in the arterial wall; and (3) how these neutrophil effector functions interplay with lifestyle-derived risk factors such as an unbalanced diet, physical inactivity, smoking or lack of sleep quality, which represent major elements in the development of cardiovascular disease.

New Insight Into Neutrophils: A Potential Therapeutic Target for Cerebral Ischemia

Ischemic stroke is one of the main issues threatening human health worldwide, and it is also the main cause of permanent disability in adults. Energy consumption and hypoxia after ischemic stroke leads to the death of nerve cells, activate resident glial cells, and promote the infiltration of peripheral immune cells into the brain, resulting in various immune-mediated effects and even contradictory effects. Immune cell infiltration can mediate neuronal apoptosis and aggravate ischemic injury, but it can also promote neuronal repair, differentiation and regeneration. The central nervous system (CNS), which is one of the most important immune privileged parts of the human body, is separated from the peripheral immune system by the blood-brain barrier (BBB). Under physiological conditions, the infiltration of peripheral immune cells into the CNS is controlled by the BBB and regulated by the interaction between immune cells and vascular endothelial cells. As the immune response plays a key role in regulating the development of ischemic injury, neutrophils have been proven to be involved in many inflammatory diseases, especially acute ischemic stroke (AIS). However, neutrophils may play a dual role in the CNS. Neutrophils are the first group of immune cells to enter the brain from the periphery after ischemic stroke, and their exact role in cerebral ischemia remains to be further explored. Elucidating the characteristics of immune cells and their role in the regulation of the inflammatory response may lead to the identification of new potential therapeutic strategies. Thus, this review will specifically discuss the role of neutrophils in ischemic stroke from production to functional differentiation, emphasizing promising targeted interventions, which may promote the development of ischemic stroke treatments in the future.

uPA-PAI-1 heteromerization promotes breast cancer progression by attracting tumorigenic neutrophils

High intratumoral levels of urokinase-type plasminogen activator (uPA)-plasminogen activator inhibitor-1 (PAI-1) heteromers predict impaired survival and treatment response in early breast cancer. The pathogenetic role of this protein complex remains obscure. Here, we demonstrate that heteromerization of uPA and PAI-1 multiplies the potential of the single proteins to attract pro-tumorigenic neutrophils. To this end, tumor-released uPA-PAI-1 utilizes very low-density lipoprotein receptor and mitogen-activated protein kinases to initiate a pro-inflammatory program in perivascular macrophages. This enforces neutrophil trafficking to cancerous lesions and skews these immune cells toward a pro-tumorigenic phenotype, thus supporting tumor growth and metastasis. Blockade of uPA-PAI-1 heteromerization by a novel small-molecule inhibitor interfered with these events and effectively prevented tumor progression. Our findings identify a therapeutically targetable, hitherto unknown interplay between hemostasis and innate immunity that drives breast cancer progression. As a personalized immunotherapeutic strategy, blockade of uPA-PAI-1 heteromerization might be particularly beneficial for patients with highly aggressive uPA-PAI-1high tumors.

Roles of neutrophil granule proteins in orchestrating inflammation and immunity

Neutrophil granulocytes form the first line of host defense against invading pathogens and tissue injury. They are rapidly recruited from the blood to the affected sites, where they deploy an impressive arsenal of effectors to eliminate invading microbes and damaged cells. This capacity is endowed in part by readily mobilizable proteins acquired during granulopoiesis and stored in multiple types of cytosolic granules with each granule type containing a unique cargo. Once released, granule proteins contribute to killing bacteria within the phagosome or the extracellular milieu, but are also capable of inflicting collateral tissue damage. Neutrophil-driven inflammation underlies many common diseases. Research over the last decade has documented neutrophil heterogeneity and functional versatility far beyond their antimicrobial function. Emerging evidence indicates that neutrophils utilize granule proteins to interact with innate and adaptive immune cells and orchestrate the inflammatory response. Granule proteins have been identified as important modulators of neutrophil trafficking, reverse transendothelial migration, phagocytosis, neutrophil life span, neutrophil extracellular trap formation, efferocytosis, cytokine activity, and autoimmunity. Hence, defining their roles within the inflammatory locus is critical for minimizing damage to the neighboring tissue and return to homeostasis. Here, we provide an overview of recent advances in the regulation of degranulation, granule protein functions, and signaling in modulating neutrophil-mediated immunity. We also discuss how targeting granule proteins and/or signaling could be harnessed for therapeutic benefits.

Targeting inflammation in atherosclerosis - from experimental insights to the clinic

Atherosclerosis, a dominant and growing cause of death and disability worldwide, involves inflammation from its inception to the emergence of complications. Targeting inflammatory pathways could therefore provide a promising new avenue to prevent and treat atherosclerosis. Indeed, clinical studies have now demonstrated unequivocally that modulation of inflammation can forestall the clinical complications of atherosclerosis. This progress pinpoints the need for preclinical investigations to refine strategies for combatting inflammation in the human disease. In this Review, we consider a gamut of attractive possibilities for modifying inflammation in atherosclerosis, including targeting pivotal inflammatory pathways such as the inflammasomes, inhibiting cytokines, manipulating adaptive immunity and promoting pro-resolution mechanisms. Along with lifestyle measures, pharmacological interventions to mute inflammation could complement traditional targets, such as lipids and hypertension, to make new inroads into the management of atherosclerotic risk.

Interplay between inflammation and thrombosis in cardiovascular pathology

Thrombosis is the most feared complication of cardiovascular diseases and a main cause of death worldwide, making it a major health-care challenge. Platelets and the coagulation cascade are effectively targeted by antithrombotic approaches, which carry an inherent risk of bleeding. Moreover, antithrombotics cannot completely prevent thrombotic events, implicating a therapeutic gap due to a third, not yet adequately addressed mechanism, namely inflammation. In this Review, we discuss how the synergy between inflammation and thrombosis drives thrombotic diseases. We focus on the huge potential of anti-inflammatory strategies to target cardiovascular pathologies. Findings in the past decade have uncovered a sophisticated connection between innate immunity, platelet activation and coagulation, termed immunothrombosis. Immunothrombosis is an important host defence mechanism to limit systemic spreading of pathogens through the bloodstream. However, the aberrant activation of immunothrombosis in cardiovascular diseases causes myocardial infarction, stroke and venous thromboembolism. The clinical relevance of aberrant immunothrombosis, referred to as thromboinflammation, is supported by the increased risk of cardiovascular events in patients with inflammatory diseases but also during infections, including in COVID-19. Clinical trials in the past 4 years have confirmed the anti-ischaemic effects of anti-inflammatory strategies, backing the concept of a prothrombotic function of inflammation. Targeting inflammation to prevent thrombosis leaves haemostasis mainly unaffected, circumventing the risk of bleeding associated with current approaches. Considering the growing number of anti-inflammatory therapies, it is crucial to appreciate their potential in covering therapeutic gaps in cardiovascular diseases.

Endotoxinemia Accelerates Atherosclerosis Through Electrostatic Charge-Mediated Monocyte Adhesion

BACKGROUND

Acute infection is a well-established risk factor of cardiovascular inflammation increasing the risk for a cardiovascular complication within the first weeks after infection. However, the nature of the processes underlying such aggravation remains unclear. Lipopolysaccharide derived from Gram-negative bacteria is a potent activator of circulating immune cells including neutrophils, which foster inflammation through discharge of neutrophil extracellular traps (NETs). Here, we use a model of endotoxinemia to link acute infection and subsequent neutrophil activation with acceleration of vascular inflammation Methods: Acute infection was mimicked by injection of a single dose of lipopolysaccharide into hypercholesterolemic mice. Atherosclerosis burden was studied by histomorphometric analysis of the aortic root. Arterial myeloid cell adhesion was quantified by intravital microscopy.

RESULTS

Lipopolysaccharide treatment rapidly enhanced atherosclerotic lesion size by expansion of the lesional myeloid cell accumulation. Lipopolysaccharide treatment led to the deposition of NETs along the arterial lumen, and inhibition of NET release annulled lesion expansion during endotoxinemia, thus suggesting that NETs regulate myeloid cell recruitment. To study the mechanism of monocyte adhesion to NETs, we used in vitro adhesion assays and biophysical approaches. In these experiments, NET-resident histone H2a attracted monocytes in a receptor-independent, surface charge-dependent fashion. Therapeutic neutralization of histone H2a by antibodies or by in silico designed cyclic peptides enables us to reduce luminal monocyte adhesion and lesion expansion during endotoxinemia.

CONCLUSIONS

Our study shows that NET-associated histone H2a mediates charge-dependent monocyte adhesion to NETs and accelerates atherosclerosis during endotoxinemia.

Evidence of macrophage modulation in the mouse pubic symphysis remodeling during the end of first pregnancy and postpartum

In mouse pregnancy, pubic symphysis (PS) remodels into an elastic interpubic ligament (IpL) in a temporally regulated process to provide safe delivery. It restores at postpartum to assure reproductive tract homeostasis. Recently, macrophage localization in the IpL and dynamic changes in the expression of inflammatory mediators observed from the end of pregnancy (D18, D19) to early days postpartum (1dpp, 3dpp) highlighted the necessity of the identification of the key molecules involved in innate immune processes in PS remodeling. Therefore, this study uses morphological and high-sensitivity molecular techniques to identify both macrophage association with extracellular matrix (ECM) remodeling and the immunological processes involved in PS changes from D18 to 3dpp. Results showed macrophage association with active gelatinases and ECM components and 25 differentially expressed genes (DEGs) related to macrophage activities in interpubic tissues from D18 to 3dpp. Additionally, microarray and proteomic analysis showed a significant association of interpubic tissue DEGs with complement system activation and differentially expressed proteins (DEPs) with phagocytosis, highlighting the involvement of macrophage-related activities in mouse PS remodeling. Therefore, the findings suggest that PS ECM remodeling is associated with evidence of macrophage modulation that ensures both IpL relaxation and fast PS recovery postpartum for first labor.

Depletion of NK Cells Improves Cognitive Function in the Alzheimer Disease Mouse Model

Despite mounting evidence suggesting the involvement of the immune system in regulating brain function, the specific role of immune and inflammatory cells in neurodegenerative diseases remain poorly understood. In this study, we report that depletion of NK cells, a type of innate lymphocytes, alleviates neuroinflammation, stimulates neurogenesis, and improves cognitive function in a triple-transgenic Alzheimer disease (AD) mouse model. NK cells in the brains of triple-transgenic AD mouse model (3xTg-AD) mice exhibited an enhanced proinflammatory profile. Depletion of NK cells by anti-NK1.1 Abs drastically improved cognitive function of 3xTg-AD mice. NK cell depletion did not affect amyloid β concentrations but enhanced neurogenesis and reduced neuroinflammation. Notably, in 3xTg-AD mice depleted of NK cells, microglia demonstrated a homeostatic-like morphology, decreased proliferative response and reduced expression of neurodestructive proinflammatory cytokines. Together, our results suggest a proinflammatory role for NK cells in 3xTg-AD mice and indicate that targeting NK cells might unlock novel strategies to combat AD.

Hematopoiesis and Cardiovascular Disease

A central feature of atherosclerosis, the most prevalent chronic vascular disease and root cause of myocardial infarction and stroke, is leukocyte accumulation in the arterial wall. These crucial immune cells are produced in specialized niches in the bone marrow, where a complex cell network orchestrates their production and release. A growing body of clinical studies has documented a correlation between leukocyte numbers and cardiovascular disease risk. Understanding how leukocytes are produced and how they contribute to atherosclerosis and its complications is, therefore, critical to understanding and treating the disease. In this review, we focus on the key cells and products that regulate hematopoiesis under homeostatic conditions, during atherosclerosis and after myocardial infarction.

Neutrophils as regulators of cardiovascular inflammation

Neutrophils have traditionally been viewed as bystanders or biomarkers of cardiovascular disease. However, studies in the past decade have demonstrated the important functions of neutrophils during cardiovascular inflammation and repair. In this Review, we discuss the influence of traditional and novel cardiovascular risk factors on neutrophil production and function. We then appraise the current knowledge of the contribution of neutrophils to the different stages of atherosclerosis, including atherogenesis, plaque destabilization and plaque erosion. In the context of cardiovascular complications of atherosclerosis, we highlight the dichotomous role of neutrophils in pathogenic and repair processes in stroke, heart failure, myocardial infarction and neointima formation. Finally, we emphasize how detailed knowledge of neutrophil functions in cardiovascular homeostasis and disease can be used to generate therapeutic strategies to target neutrophil numbers, functional status and effector mechanisms.

Neutrophil Cathepsin G and Tumor Cell RAGE Facilitate Neutrophil Anti-Tumor Cytotoxicity

Neutrophils are a heterogeneous population of myeloid cells which may either promote or hinder tumor growth and progression. Anti-tumor neutrophils have the capacity to kill tumor cells in a contact-dependent manner. However, the molecular mechanisms underlying tumor cell recognition by neutrophils remained unexplored. Tumor cells were shown to express aberrant glycosylation patterns and neutrophils are equipped with receptors capable of recognizing such glycosylations. Accordingly, we hypothesized that the receptor for advanced glycation end products (RAGE) may facilitate neutrophil recognition of tumor cells. Indeed, RAGE decoy receptors and RAGE-specific blocking antibodies dramatically reduce tumor cell susceptibility to neutrophil cytotoxicity. Unexpectedly, we found that tumor cell RAGE rather than neutrophil RAGE is important for the killing process. We further identified neutrophil Cathepsin G as the neutrophil component interacting with tumor cell RAGE. Cathepsin G-deficient neutrophils show impaired ability to kill tumor cells, suggesting that RAGE-Cathepsin G interaction is required for neutrophil cytotoxicity. These data unravel new aspects of neutrophil anti-tumor activity and identify a novel role for RAGE and Cathepsin G in neutrophil-mediated cytotoxicity.

Biological Roles of Neutrophil-Derived Granule Proteins and Cytokines

Neutrophils, the most abundant white blood cells in human circulation, entertain intense interactions with other leukocyte subsets, platelets, and stromal cells. Molecularly, such interactions are typically communicated through proteins generated during granulopoiesis, stored in granules, or produced on demand. Here, we provide an overview of the mammalian regulation of granule protein production in the bone marrow and the de novo synthesis of cytokines by neutrophils recruited to tissues. In addition, we discuss some of the known biological roles of these protein messengers, and how neutrophil-borne granule proteins and cytokines can synergize to modulate inflammation and tumor development. Decoding the neutrophil interactome is important for therapeutically neutralizing individual proteins to putatively dampen inflammation, or for delivering modified neutrophil-borne proteins to boost host defense.

G-Protein Coupled Receptor Targeting on Myeloid Cells in Atherosclerosis

Atherosclerosis, the underlying cause of the majority of cardiovascular diseases (CVDs), is a lipid-driven, inflammatory disease of the large arteries. Gold standard therapy with statins and the more recently developed proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors have improved health conditions among CVD patients by lowering low density lipoprotein (LDL) cholesterol. Nevertheless, a substantial part of these patients is still suffering and it seems that 'just' lipid lowering is insufficient. The results of the Canakinumab Anti-inflammatory Thrombosis Outcome Study (CANTOS) have now proven that inflammation is a key driver of atherosclerosis and that targeting inflammation improves CVD outcomes. Therefore, the identification of novel drug targets and development of novel therapeutics that block atherosclerosis-specific inflammatory pathways have to be promoted. The inflammatory processes in atherosclerosis are facilitated by a network of immune cells and their subsequent responses. Cell networking is orchestrated by various (inflammatory) mediators which interact, bind and induce signaling. Over the last years, G-protein coupled receptors (GPCRs) emerged as important players in recognizing these mediators, because of their diverse functions in steady state but also and specifically during chronic inflammatory processes - such as atherosclerosis. In this review, we will therefore highlight a selection of these receptors or receptor sub-families mainly expressed on myeloid cells and their role in atherosclerosis. More specifically, we will focus on chemokine receptors, both classical and atypical, formyl-peptide receptors, the chemerin receptor 23 and the calcium-sensing receptor. When information is available, we will also describe the consequences of their targeting which may hold promising options for future treatment of CVD.

[Atherothrombosis : Novel therapeutic strategies]

Despite intensive scientific research over the past decades, atherosclerosis and atherothrombosis are the leading cause of mortality worldwide. During the recent past it has become clear that atherosclerosis is not merely a lipid-driven disease but a multifactorial process involving chronic inflammation of large arteries. This review article briefly outlines the mechanistic nature of atherosclerosis, presents a synopsis of the current state of the art treatment strategies and finally outlines several therapeutic options, which are in clinical and experimental testing.

Factor XII in inflammation and wound healing

PURPOSE OF REVIEW

This review describes the contribution of coagulation factor XII (FXII) in sterile inflammation and wound healing, focusing on recently identified roles for zymogen FXII in neutrophil functions.

RECENT FINDINGS

Recent studies have identified an important role for FXII in neutrophil trafficking. In particular, following neutrophil activation, autocrine FXII signals through the urokinase plasminogen activator receptor (uPAR) on the neutrophil surface to upregulate neutrophil functions. The sum of these activities leads to neutrophil adhesion, chemotaxis, and neutrophil extracellular (NET) formation. Downregulating FXII-mediated signaling in neutrophils is associated with improved wound healing.

SUMMARY

These recent findings show the sophisticated role of FXII in vivo and create new opportunities for research on the treatment of chronic inflammatory diseases.

Endothelial NOD1 directs myeloid cell recruitment in atherosclerosis through VCAM-1

Atherosclerosis is a chronic disease characterized by vascular lipid retention and inflammation, and pattern recognition receptors (PRRs) are important contributors in early stages of the disease. Given the implication of the intracellular PRR nucleotide-binding oligomerization domain 1 (NOD1) in cardiovascular diseases, we investigated its contribution to early atherosclerosis. We evidenced NOD1 induction in atherosclerotic human and mouse tissues, predominantly in vascular endothelial cells. Accordingly, NOD1 genetic inactivation in Apoe^-/- mice reduced not only atherosclerosis burden, but also monocyte and neutrophil accumulation in atheromata. Of note, in the presence of either peptidoglycan or oxidized LDLs, endothelial NOD1 triggered VCAM-1 up-regulation through the RIP2-NF-κB axis in an autocrine manner, enhancing firm adhesion of both sets of myeloid cells to the inflamed micro- and macrovasculature in vivo. Our data define a major proatherogenic role for endothelial NOD1 in early leukocyte recruitment to the athero-prone vasculature, thus introducing NOD1 as an innovative therapeutic target and potential prognostic molecule.-González-Ramos, S., Paz-García, M., Rius, C., del Monte-Monge, A., Rodríguez, C., Fernández-García, V., Andrés, V., Martínez-González, J., Lasunción, M. A., Martín-Sanz, P., Soehnlein, O., Boscá, L. Endothelial NOD1 directs myeloid cell recruitment in atherosclerosis through VCAM-1.

Organ-Specific Mechanisms of Transendothelial Neutrophil Migration in the Lung, Liver, Kidney, and Aorta

Immune responses are dependent on the recruitment of leukocytes to the site of inflammation. The classical leukocyte recruitment cascade, consisting of capture, rolling, arrest, adhesion, crawling, and transendothelial migration, is thoroughly studied but mostly in model systems, such as the cremasteric microcirculation. This cascade paradigm, which is widely accepted, might be applicable to many tissues, however recruitment mechanisms might substantially vary in different organs. Over the last decade, several studies shed light on organ-specific mechanisms of leukocyte recruitment. An improved awareness of this matter opens new therapeutic windows and allows targeting inflammation in a tissue-specific manner. The aim of this review is to summarize the current understanding of the leukocyte recruitment in general and how this varies in different organs. In particular we focus on neutrophils, as these are the first circulating leukocytes to reach the site of inflammation. Specifically, the recruitment mechanism in large arteries, as well as vessels in the lungs, liver, and kidney will be addressed.

Nuclear Deformation During Neutrophil Migration at Sites of Inflammation

Cell migration is indispensable for various biological processes including angiogenesis, wound healing, and immunity. In general, there are two different migration modes described, the mesenchymal migration mode and the amoeboid migration mode. Neutrophils rapidly migrate toward the sites of injury, infection, and inflammation using the amoeboid migration mode which is characterized by cell polarization and a high migration velocity. During site-directed trafficking of neutrophils from the blood stream into the inflamed tissue, neutrophils must first withstand shear stress while migrating on the 2-dimensional endothelial surface. Subsequently, they have to cross different physical barriers during the extravasation process including the squeezing through the compact endothelial monolayer that comprises the blood vessel, the underlining basement membrane and then the 3-dimensional meshwork of extracellular matrix (ECM) proteins in the tissue. Therefore, neutrophils have to rapidly switch between distinct migration modes such as intraluminal crawling, transmigration, and interstitial migration to pass these different confinements and mechanical barriers. The nucleus is the largest and stiffest organelle in every cell and is therefore the key cellular element involved in cellular migration through variable confinements. This review highlights the importance of nuclear deformation during neutrophil crossing of such confinements, with a focus on transendothelial migration and interstitial migration. We discuss the key molecular components involved in the nuclear shape changes that underlie neutrophil motility and squeezing through cellular and ECM barriers. Understanding the precise molecular mechanisms that orchestrate these distinct neutrophil migration modes introduces an opportunity to develop new therapeutic concepts for controlling pathological neutrophil-driven inflammation.

Chrono-pharmacological Targeting of the CCL2-CCR2 Axis Ameliorates Atherosclerosis

Onset of cardiovascular complications as a consequence of atherosclerosis exhibits a circadian incidence with a peak in the morning hours. Although development of atherosclerosis extends for long periods of time through arterial leukocyte recruitment, we hypothesized that discrete diurnal invasion of the arterial wall could sustain atherogenic growth. Here, we show that myeloid cell recruitment to atherosclerotic lesions oscillates with a peak during the transition from the activity to the resting phase. This diurnal phenotype is regulated by rhythmic release of myeloid cell-derived CCL2, and blockade of its signaling abolished oscillatory leukocyte adhesion. In contrast, we show that myeloid cell adhesion to microvascular beds peaks during the early activity phase. Consequently, timed pharmacological CCR2 neutralization during the activity phase caused inhibition of atherosclerosis without disturbing microvascular recruitment. These findings demonstrate that chronic inflammation of large vessels feeds on rhythmic myeloid cell recruitment, and lay the foundation for chrono-pharmacology-based therapy.

Chronic Intake of the Selective Serotonin Reuptake Inhibitor Fluoxetine Enhances Atherosclerosis

Objective—

Cardiovascular diseases and depression are the leading causes of disability in Western countries. Clinical data on potential cardiovascular effects of serotonin reuptake inhibitors (SSRIs), the most commonly used antidepressant drugs, are controversial. In addition to blocking serotonin reuptake transporter in the brain, SSRIs deplete the major peripheral serotonin (5-hydroxytryptamine [5-HT]) storage by inhibiting serotonin reuptake transporter–mediated uptake in platelets. In this study, we aimed to investigate the effect of chronic SSRI intake on the development of atherosclerosis.

Approach and Results—

Treatment of apolipoprotein E–deficient mice with the SSRI fluoxetine for 2, 4, or 16 weeks increased atherosclerotic lesion formation, with most pronounced effect during early plaque development. Intravital microscopy of carotid arteries revealed enhanced myeloid cell adhesion on fluoxetine treatment. Mechanistically, we found that fluoxetine augmented vascular permeability and increased chemokine-induced integrin-binding activity of circulating leukocytes. In vitro stimulation of murine blood demonstrated that fluoxetine, but not 5-HT, could directly promote β1 and β2 integrin activation provided C-C motif chemokine ligand 5 was also present. Similar effects were observed with the SSRI escitalopram. Enhanced C-C motif chemokine ligand 5–induced integrin activation by fluoxetine was also confirmed in a human neutrophil-like cell line. In contrast to the proatherogenic properties of fluoxetine, pharmacological inhibition of the peripheral 5-HT synthesizing enzyme tryptophan hydroxylase 1 did not promote atherosclerosis, suggesting that the proatherogenic effect of fluoxetine occurs independent of peripheral 5-HT depletion.

Conclusions—

SSRI intake may promote atherosclerosis and therefore potentially increase the risk for acute cardiovascular events by a mechanism that is independent of 5-HT depletion.

The Ins and Outs of Myeloid Cells in Atherosclerosis

Atherosclerosis is a chronic inflammation of the arterial vessel wall that arises from an imbalanced lipid metabolism. A growing body of literature describes leukocyte recruitment as a critical step in the initiation and progression of lesion development. By contrast, the role of leukocytes during plaque regression has been described in less detail. Leukocyte egress might be an important step to resolving chronic inflammation and therefore it may be a promising target for limiting advanced lesion development. This review aims to summarize our current knowledge of leukocyte recruitment to the arterial vessel wall. We will discuss mechanisms of leukocyte egress from the lesion site, as well as potential therapeutic strategies to promote atherosclerotic regression.

Human mast cell neutral proteases generate modified LDL particles with increased proteoglycan binding

BACKGROUND AND AIMS

Subendothelial interaction of LDL with extracellular matrix drives atherogenesis. This interaction can be strengthened by proteolytic modification of LDL. Mast cells (MCs) are present in atherosclerotic lesions, and upon activation, they degranulate and release a variety of neutral proteases. Here we studied the ability of MC proteases to cleave apoB-100 of LDL and affect the binding of LDL to proteoglycans.

METHODS

Mature human MCs were differentiated from human peripheral blood-derived CD34⁺ progenitors in vitro and activated with calcium ionophore to generate MC-conditioned medium. LDL was incubated in the MC-conditioned medium or with individual MC proteases, and the binding of native and modified LDL to isolated human aortic proteoglycans or to human atherosclerotic plaques ex vivo was determined. MC proteases in atherosclerotic human coronary artery lesions were detected by immunofluorescence and qPCR.

RESULTS

Activated human MCs released the neutral proteases tryptase, chymase, carboxypeptidase A3, cathepsin G, and granzyme B. Of these, cathepsin G degraded most efficiently apoB-100, induced LDL fusion, and enhanced binding of LDL to isolated human aortic proteoglycans and human atherosclerotic lesions ex vivo. Double immunofluoresence staining of human atherosclerotic coronary arteries for tryptase and cathepsin G indicated that lesional MCs contain cathepsin G. In the lesions, expression of cathepsin G correlated with the expression of tryptase and chymase, but not with that of neutrophil proteinase 3.

CONCLUSIONS

The present study suggests that cathepsin G in human atherosclerotic lesions is largely derived from MCs and that activated MCs may contribute to atherogenesis by enhancing LDL retention.

Extended cleavage specificity of human neutrophil cathepsin G: A low activity protease with dual chymase and tryptase-type specificities

Human neutrophils express at least four active serine proteases, cathepsin G, N-elastase, proteinase 3 and neutrophil serine protease 4 (NSP4). They have all been extensively studied due to their importance in neutrophil biology and immunity. However, their extended cleavage specificities have never been determined in detail. Here we present a detailed cleavage specificity analysis of human cathepsin G (hCG). The specificity was determined by phage display analysis and the importance of individual amino acids in and around the cleavage site was then validated using novel recombinant substrates. To provide a broader context to this serine protease, a comparison was made to the related mast cell protease, human chymase (HC). hCG showed similar characteristics to HC including both the primary and extended specificities. As expected, Phe, Tyr, Trp and Leu were preferred in the P1 position. In addition, both proteases showed a preference for negatively charged amino acids in the P2´ position of substrates and a preference for aliphatic amino acids both upstream and downstream of the cleavage site. However, overall the catalytic activity of hCG was ~10-fold lower than HC. hCG has previously been reported to have a dual specificity consisting of chymase and tryptase-type activities. In our analysis, tryptase activity against substrates with Lys in P1 cleavage position was indeed only 2-fold less efficient as compared to optimal chymase substrates supporting strong dual-type specificity. We hope the information presented here on extended cleavage specificities of hCG and HC will assist in the search for novel in vivo substrates for these proteases as well as aid in the efforts to better understand the role of hCG in immunity and bacterial defence.

Myosin 1f is specifically required for neutrophil migration in 3D environments during acute inflammation

Neutrophil extravasation and interstitial migration are important steps during the recruitment of neutrophils to sites of inflammation. In the present study, we addressed the functional importance of the unconventional class I myosin 1f (Myo1f) for neutrophil trafficking during acute inflammation. In contrast to leukocyte rolling and adhesion, the genetic absence of Myo1f severely compromised neutrophil extravasation into the inflamed mouse cremaster tissue when compared with Myo1f^+/+ mice as studied by intravital microscopy. Similar results were obtained in experimental models of acute peritonitis and acute lung injury. In contrast to 2-dimensional migration, which occurred independently of Myo1f, Myo1f was indispensable for neutrophil migration in 3-dimensional (3D) environments, that is, transmigration and migration in collagen networks as it regulated squeezing and dynamic deformation of the neutrophil nucleus during migration through physical barriers. Thus, we provide evidence for an important role of Myo1f in neutrophil trafficking during inflammation by specifically regulating neutrophil extravasation and migration in 3D environments.

Decision shaping neutrophil-platelet interplay in inflammation: From physiology to intervention

Inflammation is a well-coordinated process in response to tissue injury or infection aimed at restoration of tissue homoeostasis. Platelets and neutrophils are typically viewed important in the context of haemostasis and bacterial killing, respectively. However, as these cells are equipped with readily available armoury, both have received much attention for their importance in shaping the early inflammatory reaction in recent years. While some of these activities are executed individually, both cells join forces during much of their pro-inflammatory activities. This brief review summarizes recently identified mechanisms of neutrophil-platelet interaction and describes functional consequences on neutrophil trafficking and the release of neutrophil extracellular traps. Moreover, the synergy of neutrophils and platelets during the recruitment of monocytes is reviewed. Finally, this review discusses how knowledge on the intimate neutrophil-platelet partnership can be employed to design interventional strategies.

How neutrophils resist shear stress at blood vessel walls: molecular mechanisms, subcellular structures, and cell-cell interactions

Neutrophils are the first cells arriving at sites of tissue injury or infection to combat invading pathogens. Successful neutrophil recruitment to sites of inflammation highly depends on specific molecular mechanisms, fine-tuning the received information into signaling pathways and converting them into well-described recruitment steps. This review highlights the impact of vascular flow conditions on neutrophil recruitment and the multitude of mechanisms developed to enable this sophisticated process under wall shear stress conditions. The recruitment process underlies a complex interplay between adhesion and signaling molecules, as well as chemokines, in which neutrophils developed specific mechanisms to travel to sites of lesion in low and high shear stress conditions. Rolling, as the first step in the recruitment process, highly depends on endothelial selectins and their ligands on neutrophils, inducting of intracellular signaling and subsequently activating β₂ integrins, enabling adhesion and postadhesion events. In addition, subcellular structures, such as microvilli, tethers, and slings allow the cell to arrest, even under high wall shear stress. Thereby, microvilli that are pulled out from the cell body form tethers that develop into slings upon their detachment from the substrate. In addition to the above-described primary capture, secondary capture of neutrophils via neutrophil-neutrophil or neutrophil-platelet interaction promotes the process of neutrophil recruitment to sites of lesion. Thus, precise mechanisms based on a complex molecular interplay, subcellular structures, and cell-cell interactions turn the delicate process of neutrophil trafficking during flow into a robust response allowing effective neutrophil accumulation at sites of injury.

Extracellular matrix proteomics identifies molecular signature of symptomatic carotid plaques

BACKGROUND. The identification of patients with high-risk atherosclerotic plaques prior to the manifestation of clinical events remains challenging. Recent findings question histology- and imaging-based definitions of the “vulnerable plaque,” necessitating an improved approach for predicting onset of symptoms.

METHODS. We performed a proteomics comparison of the vascular extracellular matrix and associated molecules in human carotid endarterectomy specimens from 6 symptomatic versus 6 asymptomatic patients to identify a protein signature for high-risk atherosclerotic plaques. Proteomics data were integrated with gene expression profiling of 121 carotid endarterectomies and an analysis of protein secretion by lipid-loaded human vascular smooth muscle cells. Finally, epidemiological validation of candidate biomarkers was performed in two community-based studies.

RESULTS. Proteomics and at least one of the other two approaches identified a molecular signature of plaques from symptomatic patients that comprised matrix metalloproteinase 9, chitinase 3-like-1, S100 calcium binding protein A8 (S100A8), S100A9, cathepsin B, fibronectin, and galectin-3-binding protein. Biomarker candidates measured in 685 subjects in the Bruneck study were associated with progression to advanced atherosclerosis and incidence of cardiovascular disease over a 10-year follow-up period. A 4-biomarker signature (matrix metalloproteinase 9, S100A8/S100A9, cathepsin D, and galectin-3-binding protein) improved risk prediction and was successfully replicated in an independent cohort, the SAPHIR study.

CONCLUSION. The identified 4-biomarker signature may improve risk prediction and diagnostics for the management of cardiovascular disease. Further, our study highlights the strength of tissue-based proteomics for biomarker discovery.

FUNDING. UK: British Heart Foundation (BHF); King’s BHF Center; and the National Institute for Health Research Biomedical Research Center based at Guy’s and St Thomas’ NHS Foundation Trust and King’s College London in partnership with King’s College Hospital. Austria: Federal Ministry for Transport, Innovation and Technology (BMVIT); Federal Ministry of Science, Research and Economy (BMWFW); Wirtschaftsagentur Wien; and Standortagentur Tirol.