Cholesterol-Induced M4-Like Macrophages Recruit Neutrophils and Induce NETosis

Reprogram to heal: Macrophage phenotypes as living therapeutics

Macrophages represent a crucial cell type within the immune system, exhibiting significant adaptability that allows for the transformation into various phenotypes in response to their surrounding environment. This review investigates the characteristics of various macrophage phenotypes and their functional roles in disease pathogenesis and resolution. The M1 phenotype, recognized for its inflammatory attributes, plays a pivotal role in combating infections and tumors; however, it may also contribute to tissue injury, persistent inflammation, and the pathogenesis of autoimmune and inflammatory diseases. Conversely, the M2 phenotype is associated with anti-inflammatory activities and tissue repair processes. But this is not the end of the story and researches illustrated novel phenotypes that may provide new approaches and therapeutic opportunities. Recent progress in characterizing distinct macrophage phenotypes has enabled the development of innovative therapeutic strategies for chronic inflammatory conditions, autoimmune disorders, and cancers. This review underscores the critical role of macrophage polarization, illustrating how various stimuli can influence macrophage fate and modify their responses. Additionally, it explores the implications of macrophage plasticity on disease progression and treatment efficacy. A comprehensive understanding of these dynamics is essential for the advancement of targeted immunotherapies, which possess the potential to transform treatment strategies for a variety of medical conditions.

Advancements in the study of short-chain fatty acids and their therapeutic effects on atherosclerosis

Atherosclerosis (AS) remains a leading cause of cardiovascular disease and mortality globally. This chronic condition is characterized by inflammation, lipid accumulation, and the deposition of cellular components within arterial walls. Emerging evidence has highlighted the multifaceted therapeutic potential of short-chain fatty acids (SCFAs) in mitigating AS progression. SCFAs have demonstrated anti-inflammatory properties and the ability to regulate immune responses, metabolic pathways, vascular integrity, and intestinal barrier function in animal models of AS. Consequently, SCFAs have garnered significant attention as a promising approach for the prevention and treatment of AS. However, further clinical trials and studies are necessary to fully elucidate the underlying mechanisms and effects of SCFAs. Additionally, different types of SCFAs may exert distinct impacts, necessitating more in-depth investigation into their specific roles and mechanisms. This review provides an overview of the diverse cellular mechanisms contributing to AS formation, as well as a discussion of the significance of SCFAs in AS pathogenesis and their multifaceted therapeutic potential. Nonetheless, additional research is warranted to comprehensively understand and harness the potential of various SCFAs in the context of AS.

The Role of Neutrophil Extracellular Traps in Atherosclerosis: From the Molecular to the Clinical Level

Atherosclerosis is a chronic inflammatory condition that is typified by the deposition of lipids and the subsequent inflammation of medium and large arteries. Neutrophil extracellular traps (NETs) are fibrous meshworks of DNA, histones, and granzymes expelled by activated neutrophils in response to a variety of pathogenic conditions. In addition to their role in pathogen eradication, NETs have been demonstrated to play a pivotal role in the development of atherosclerosis. This article presents a review of the bidirectional interactions in which atherosclerosis-related risk factors stimulate the formation of NETs, which in turn support disease progression. This article emphasizes the involvement of NETs in the various stages of atherogenesis and development, influencing multiple factors such as the vascular endothelium, platelets, the inflammatory milieu, and lipid metabolism. The findings of this study offer new insights and avenues for further investigation into the processes underlying the formation and regulation of the vascular inflammatory microenvironment in atherosclerosis. Finally, potential targeted therapeutic strategies for NETs are discussed to facilitate their progression to clinical practice (Graphical Abstract).

Neutrophil extracellular traps in homeostasis and disease

Neutrophil extracellular traps (NETs), crucial in immune defense mechanisms, are renowned for their propensity to expel decondensed chromatin embedded with inflammatory proteins. Our comprehension of NETs in pathogen clearance, immune regulation and disease pathogenesis, has grown significantly in recent years. NETs are not only pivotal in the context of infections but also exhibit significant involvement in sterile inflammation. Evidence suggests that excessive accumulation of NETs can result in vessel occlusion, tissue damage, and prolonged inflammatory responses, thereby contributing to the progression and exacerbation of various pathological states. Nevertheless, NETs exhibit dual functionalities in certain pathological contexts. While NETs may act as autoantigens, aggregated NET complexes can function as inflammatory mediators by degrading proinflammatory cytokines and chemokines. The delineation of molecules and signaling pathways governing NET formation aids in refining our appreciation of NETs' role in immune homeostasis, inflammation, autoimmune diseases, metabolic dysregulation, and cancer. In this comprehensive review, we delve into the multifaceted roles of NETs in both homeostasis and disease, whilst discussing their potential as therapeutic targets. Our aim is to enhance the understanding of the intricate functions of NETs across the spectrum from physiology to pathology.

A Review of Advances in Molecular Imaging of Rheumatoid Arthritis: From In Vitro to Clinic Applications Using Radiolabeled Targeting Vectors with Technetium-99m

Rheumatoid arthritis (RA) is a systemic autoimmune disorder caused by inflammation of cartilaginous diarthrodial joints that destroys joints and cartilage, resulting in synovitis and pannus formation. Timely detection and effective management of RA are pivotal for mitigating inflammatory arthritis consequences, potentially influencing disease progression. Nuclear medicine using radiolabeled targeted vectors presents a promising avenue for RA diagnosis and response to treatment assessment. Radiopharmaceutical such as technetium-99m (99mTc), combined with single photon emission computed tomography (SPECT) combined with CT (SPECT/CT), introduces a more refined diagnostic approach, enhancing accuracy through precise anatomical localization, representing a notable advancement in hybrid molecular imaging for RA evaluation. This comprehensive review discusses existing research, encompassing in vitro, in vivo, and clinical studies to explore the application of 99mTc radiolabeled targeting vectors with SPECT imaging for RA diagnosis. The purpose of this review is to highlight the potential of this strategy to enhance patient outcomes by improving the early detection and management of RA.

The PD-1/PD-L1 Axis in the Biology of MASLD

Metabolic Dysfunction-Associated Steatotic Liver (MASL), previously named nonalcoholic fatty liver (NAFL), is a multifactorial disease in which metabolic, genetic, and environmental risk factors play a predominant role. Obesity and type 2 diabetes act as triggers of the inflammatory response, which contributes to the progression of MASL to Metabolic Dysfunction-Associated Steatohepatitis and the development of hepatocellular carcinoma. In the liver, several parenchymal, nonparenchymal, and immune cells maintain immunological homeostasis, and different regulatory pathways balance the activation of the innate and adaptative immune system. PD-1/PD-L1 signaling acts, in the maintenance of the balance between the immune responses and the tissue immune homeostasis, promoting self-tolerance through the modulation of activated T cells. Recently, PD-1 has received much attention for its roles in inducing an exhausted T cells phenotype, promoting the tumor escape from immune responses. Indeed, in MASLD, the excessive fat accumulation dysregulates the immune system, increasing cytotoxic lymphocytes and decreasing their cytolytic activity. In this context, T cells exacerbate liver damage and promote tumor progression. The aim of this review is to illustrate the main pathogenetic mechanisms by which the immune system promotes the progression of MASLD and the transition to HCC, as well as to discuss the possible therapeutic applications of PD-1/PD-L1 target therapy to activate T cells and reinvigorate immune surveillance against cancer.

Cholinergic Polarization of Human Macrophages

Macrophages serve as vital defenders, protecting the body by exhibiting remarkable cellular adaptability in response to invading pathogens and various stimuli. These cells express nicotinic acetylcholine receptors, with the α7-nAChR being extensively studied due to its involvement in activating the cholinergic anti-inflammatory pathway. Activation of this pathway plays a crucial role in suppressing macrophages' production of proinflammatory cytokines, thus mitigating excessive inflammation and maintaining host homeostasis. Macrophage polarization, which occurs in response to specific pathogens or insults, is a process that has received limited attention concerning the activation of the cholinergic anti-inflammatory pathway and the contributions of the α7-nAChR in this context. This review aims to present evidence highlighting how the cholinergic constituents in macrophages, led by the α7-nAChR, facilitate the polarization of macrophages towards anti-inflammatory phenotypes. Additionally, we explore the influence of viral infections on macrophage inflammatory phenotypes, taking into account cholinergic mechanisms. We also review the current understanding of macrophage polarization in response to these infections. Finally, we provide insights into the relatively unexplored partial duplication of the α7-nAChR, known as dup α7, which is emerging as a significant factor in macrophage polarization and inflammation scenarios.

Neutrophil subsets in noncancer liver diseases: Cellular crosstalk and therapeutic targets

Neutrophils are the most abundant circulating granulocytes, linking innate and adaptive immunity. Neutrophils can regulate inflammatory and immune responses through degranulation, reactive oxygen species generation, the production of cytokines and chemokines, and NETosis. Emerging evidence has indicated that neutrophils contribute to the pathogenesis of various noncancer liver diseases, including nonalcoholic fatty liver disease, alcohol-associated liver disease, hepatic ischemia-reperfusion injury, and liver fibrosis. Cellular interactions among neutrophils, other immune cells, and nonimmune cells constitute a complex network that regulates the immune microenvironment of the liver. This review summarizes novel neutrophil subtypes, including CD177+ neutrophils and low-density neutrophils. Moreover, we provide an overview of the cellular cros stalk of neutrophils in noncancer liver diseases, aiming to shed new light on mechanistic studies of novel neutrophil subtypes. In addition, we discuss the potential of neutrophils as therapeutic targets in noncancer liver diseases, including inhibitors targeting NETosis, granule proteins, and chemokines.

Oxidized low-density lipoprotein regulates macrophage polarization in atherosclerosis

Atherosclerosis is the pathological basis of acute cardiovascular and cerebrovascular diseases. Oxidized LDL has been recognized as a major atherogenic factor in the vessel wall for decades. A growing body of evidence suggests that oxidized LDL modulates macrophage phenotypes in atherosclerosis. This article reviews the research progress on the regulation of macrophage polarization by oxidized LDL. Mechanistically, oxidized LDL induces macrophage polarization via cell signaling, metabolic reprogramming, epigenetic regulation, and intercellular regulation. This review is expected to provide new targets for the treatment of atherosclerosis.

Targeting macrophages in atherosclerosis using nanocarriers loaded with liver X receptor agonists: A narrow review

Macrophages are involved in the whole process of atherosclerosis, which is characterized by accumulation of lipid and inflammation. Presently, clinically used lipid-lowering drugs cannot completely retard the progress of atherosclerosis. Liver X receptor (LXR) plays a key role in regulation of lipid metabolism and inflammation. Accumulating evidence have demonstrated that synthetic LXR agonists can significantly retard the development of atherosclerosis. However, these agonists induce sever hypertriglyceridemia and liver steatosis. These side effects have greatly limited their potential application for therapy of atherosclerosis. The rapid development of drug delivery system makes it possible to delivery interested drugs to special organs or cells using nanocarriers. Macrophages express various receptors which can recognize and ingest specially modified nanocarriers loaded with LXR agonists. In the past decades, a great progress has been made in this field. These macrophage-targeted nanocarriers loaded with LXR agonists are found to decrease atherosclerosis by reducing cholesterol accumulation and inflammatory reactions. Of important, these nanocarriers can alleviate side effects of LXR agonists. In this article, we briefly review the roles of macrophages in atherosclerosis, mechanisms of action of LXR agonists, and focus on the advances of macrophage-targeted nanocarriers loaded with LXR agonists. This work may promote the potential clinical application of these nanocarriers.

Lack of SIRP-alpha reduces lung cancer growth in mice by promoting anti-tumour ability of macrophages and neutrophils

OBJECTIVES

Signal regulatory protein-alpha (SIRPα) is a transmembrane glycoprotein specifically expressed on myeloid cells. Blockade of SIRPα/CD47 interaction is effective in combinational therapy of some cancers. This study aimed to explore into the role and underlying molecular mechanisms of SIRPα in lung cancer growth.

MATERIALS AND METHODS

A mouse model with lung cancer in wild-type (WT) and SIRPα-knockout mouse (KO) mice was established by subcutaneous injection of Lewis murine lung cancer cells (LLC). Circulating monocytes and neutrophils were depleted in mice by intraperitoneal administration of clodronate liposomes and anti-Ly6G antibody, respectively. Phenotypes and phagocytosis of macrophages and neutrophils were analysed by flow cytometry. Transwell assay was used to analyse LLC cells migration and invasion.

RESULTS

Lack of SIRPα inhibited LLC cells growth in KO mice, associated with reduced infiltrating PD-1⁺ CD8⁺ T cells and production of IL-6 from infiltrating macrophages and neutrophils in tumour tissues. Depletion of circulating monocytes and neutrophils reduced LLC cells growth in WT mice, which was abolished in KO mice. Studies in vitro showed that lack of SIRPα increased M1/M2 ratio, and reduced LLC cell migration and invasion via attenuated IL-6 secretion. Lack of SIRPα expression in neutrophils effectively increased the cytotoxic activity to LLC cells in vitro.

CONCLUSIONS

Lack of SIRPα suppressed lung cancer cell growth in mice, dependent on circulating macrophages and neutrophils, in association with improved phagocytosis and reduced IL-6 expression.

Polystyrene nanoparticle exposure supports ROS-NLRP3 axis-dependent DNA-NET to promote liver inflammation

The widespread use of plastics and the rapid development of nanotechnology bring convenience to our lives while also increasing the environmental burden and increasing the risk of exposure of organisms to nanoparticles (NPs). While recent studies have revealed an association between nanoparticles and liver injury, the intrinsic mechanism of NP exposure-induced liver damage remains to be explored. Here, we found that polystyrene nanoparticle (PSNP) exposure resulted in a significant increase in local neutrophil infiltration and neutrophil extracellular trap (NET) formation in the liver. Analysis of a coculture system of PBNs and AML12 cells revealed that PSNP-induced NET formation positively correlates with the reactive oxygen species (ROS)-NLRP3 axis. Inhibition of ROS and genetic and pharmacological inhibition of NLRP3 in AML12 can both alleviate PSNP-induced NET formation. In turn, exposure of mice to deoxyribonuclease I (DNase Ⅰ)-coated PSNPs disassembled NET in vivo, neutrophil infiltration in the liver was reduced, the ROS-NLRP3 axis was inhibited, and the expression of cytokines was markedly decreased. Collectively, our work reveals a mechanism of NET formation in PSNP exposure-induced liver inflammation and highlights the possible role of DNase Ⅰ as a key enzyme in degrading NET and alleviating liver inflammation.

Neutrophil extracellular traps enriched with IL-1β and IL-17A participate in the hepatic inflammatory process of patients with non-alcoholic steatohepatitis

Neutrophil extracellular traps (NETs) are implicated in the pathogenesis of various non-infectious inflammatory and thrombotic diseases. We investigated the presence and possible associations of NETs with various histopathologic parameters in patients with non-alcoholic steatohepatitis (NASH). We retrospectively assessed 20 liver biopsy specimens from patients with non-alcoholic fatty liver disease (NAFLD), including 17 specimens with NASH, and 14 control specimens. NETs were identified with confocal microscopy as extracellular structures with co-localization of neutrophil elastase (NE) and citrullinated histone-3. Interleukin-1β (IL-1β) and IL-17A were assessed with the same methodology. Histologic features of NAFLD were semi-quantitatively evaluated, and correlated with presence of NETs, neutrophil density, and platelet density/aggregates (assessed by immunohistochemistry for NE and CD42b, respectively). NETs were identified in 94.1% (16/17) of the NASH biopsy specimens; they were absent from all other NAFLD and control specimens. The presence of NETs was strongly correlated with steatosis (p = 0.003), ballooning degeneration (p < 0.001), lobular inflammation (p < 0.001), portal inflammation (p < 0.001), NAS score (p = 0.001), stage (p = 0.001), and diagnosis of NASH (p < 0.001). NETs were decorated with IL-1β and IL-17A. Platelet aggregates were much larger in NASH specimens, as compared to controls. In conclusion, NETs are implicated in the pathogenesis of NASH. Their associations with inflammation, ballooning degeneration (a hallmark of NASH), and stage emphasize their role in the disease process. In this setting, NETs provide a vehicle for IL-1β and IL-17A. In addition, platelet aggregation in hepatic sinusoids implies a role for thromboinflammation in NASH, and may explain the low peripheral blood platelet counts reported in patients with NASH.

Inflammation and atherosclerosis: signaling pathways and therapeutic intervention

Atherosclerosis is a chronic inflammatory vascular disease driven by traditional and nontraditional risk factors. Genome-wide association combined with clonal lineage tracing and clinical trials have demonstrated that innate and adaptive immune responses can promote or quell atherosclerosis. Several signaling pathways, that are associated with the inflammatory response, have been implicated within atherosclerosis such as NLRP3 inflammasome, toll-like receptors, proprotein convertase subtilisin/kexin type 9, Notch and Wnt signaling pathways, which are of importance for atherosclerosis development and regression. Targeting inflammatory pathways, especially the NLRP3 inflammasome pathway and its regulated inflammatory cytokine interleukin-1β, could represent an attractive new route for the treatment of atherosclerotic diseases. Herein, we summarize the knowledge on cellular participants and key inflammatory signaling pathways in atherosclerosis, and discuss the preclinical studies targeting these key pathways for atherosclerosis, the clinical trials that are going to target some of these processes, and the effects of quelling inflammation and atherosclerosis in the clinic.

Diverse Epigenetic Regulations of Macrophages in Atherosclerosis

Emerging research on epigenetics has resulted in many novel discoveries in atherosclerosis (AS), an inflammaging-associated disease characterized by chronic inflammation primarily driven by macrophages. The bulk of evidence has demonstrated the central role of epigenetic machinery in macrophage polarization to pro- (M1-like) or anti-inflammatory (M2-like) phenotype. An increasing number of epigenetic alterations and their modifiers involved in reprogramming macrophages by regulating DNA methylation or histone modifications (e.g., methylation, acetylation, and recently lactylation) have been identified. They may act to determine or skew the direction of macrophage polarization in AS lesions, thereby representing a promising target. Here we describe the current understanding of the epigenetic machinery involving macrophage polarization, to shed light on chronic inflammation-driving onset and progression of inflammaging-associated diseases, using AS as a prototypic example, and discuss the challenge for developing effective therapies targeting the epigenetic modifiers against these diseases, particularly highlighting a potential strategy based on epigenetically-governed repolarization from M1-like to M2-like phenotype.

Pathological Significance of Macrophages in Erectile Dysfunction Including Peyronie's Disease

Erectile function is regulated by complex mechanisms centered on vascular- and nerve-related systems. Hence, dysregulation of these systems leads to erectile dysfunction (ED), which causes mental distress and decreases the quality of life of patients and their partners. At the molecular level, many factors, such as fibrosis, lipid metabolism abnormalities, the immune system, and stem cells, play crucial roles in the etiology and development of ED. Although phosphodiesterase type 5 (PDE5) inhibitors are currently the standard treatment agents for patients with ED, they are effective only in a subgroup of patients. Therefore, further insight into the pathological mechanism underlying ED is needed to discuss ED treatment strategies. In this review, we focused on the biological and pathological significance of macrophages in ED because the interaction of macrophages with ED-related mechanisms have not been well explored, despite their important roles in vasculogenic and neurogenic diseases. Furthermore, we examined the pathological significance of macrophages in Peyronie’s disease (PD), a cause of ED characterized by penile deformation (visible curvature) during erection and pain. Although microinjury and the subsequent abnormal healing process of the tunica albuginea are known to be important processes in this disease, the detailed etiology and pathophysiology of PD are not fully understood. This is the first review on the pathological role of macrophages in PD.