Midkine drives cardiac inflammation by promoting neutrophil trafficking and NETosis in myocarditis

Neutrophil extracellular traps (NETs) and fibrotic diseases

Fibrosis, a common cause and serious outcome of organ failure that can affect any organ, is responsible for up to 45% of all deaths in various clinical settings. Both preclinical models and clinical trials investigating various organ systems have shown that fibrosis is a highly dynamic process. Although many studies have sought to gain understanding of the mechanism of fibrosis progression, their findings have been mixed. In recent years, increasing evidence indicates that neutrophil extracellular traps (NETs) are involved in many inflammatory and autoimmune disorders and participate in the regulation of fibrotic processes in various organs and systems. In this review, we summarize the current understanding of the role of NETs in fibrosis development and progression and their possibility as therapeutic targets.

Midkine promotes renal fibrosis by stabilizing C/EBPβ to facilitate endothelial-mesenchymal transition

Numerous myofibroblasts are arisen from endothelial cells (ECs) through endothelial to mesenchymal transition (EndMT) triggered by TGF-β. However, the mechanism of ECs transforms to a different subtype, or whether there exists an intermediate state of ECs remains unclear. In present study, we demonstrate Midkine (MDK) mainly expressed by CD31 + ACTA2+ECs going through partial EndMT contribute greatly to myofibroblasts by spatial and single-cell transcriptomics. MDK is induced in TGF-β treated ECs, which upregulates C/EBPβ and increases EndMT genes, and these effects could be reversed by siMDK. Mechanistically, MDK promotes the binding ability of C/EBPβ with ACTA2 promoter by stabilizing the C/EBPβ protein. In vivo, knockout of Mdk or conditional knockout of Mdk in ECs reduces EndMT markers and significantly reverses fibrogenesis. In conclusion, our study provides a mechanistic link between the induction of EndMT by TGF-β and MDK, which suggests that blocking MDK provides potential therapeutic strategies for renal fibrosis.

Peripheral priming induces plastic transcriptomic and proteomic responses in circulating neutrophils required for pathogen containment

Neutrophils rapidly respond to inflammation and infection, but to which degree their functional trajectories after mobilization from the bone marrow are shaped within the circulation remains vague. Experimental limitations have so far hampered neutrophil research in human disease. Here, using innovative fixation and single-cell-based toolsets, we profile human and murine neutrophil transcriptomes and proteomes during steady state and bacterial infection. We find that peripheral priming of circulating neutrophils leads to dynamic shifts dominated by conserved up-regulation of antimicrobial genes across neutrophil substates, facilitating pathogen containment. We show the TLR4/NF-κB signaling-dependent up-regulation of canonical neutrophil activation markers like CD177/NB-1 during acute inflammation, resulting in functional shifts in vivo. Blocking de novo RNA synthesis in circulating neutrophils abrogates these plastic shifts and prevents the adaptation of antibacterial neutrophil programs by up-regulation of distinct effector molecules upon infection. These data underline transcriptional plasticity as a relevant mechanism of functional neutrophil reprogramming during acute infection to foster bacterial containment within the circulation.

Identification of cuproptosis-related genes and immune infiltration in dilated cardiomyopathy

BACKGROUND

Dilated cardiomyopathy (DCM) is a leading cause of heart failure. Cuproptosis is involved in various diseases, although its role in DCM is still unclear. Here, this study aims to investigate the feasibility of using genes related to cuproptosis as diagnostic biomarkers for DCM and the association of their expression with immune infiltration and drug target in cardiac tissue.

METHODS

Gene expression data from nonfailure (NF) and DCM samples were retrieved from the GEO database. Cuproptosis scores were calculated using single-sample gene set enrichment analysis (ssGSEA). Weighted gene co-expression network analysis (WGCNA) was used to screen key modules associated with DCM and cuproptosis. Random forest and least absolute shrinkage and selection operator (LASSO) were applied to identify signature genes. Finally, immune cell infiltration was assessed using ssGSEA. mRNA-miRNA-lncRNA regulatory networks and chemical-drug regulatory networks based on signature genes were analyzed by Cytoscape.

RESULTS

8 modules were aggregated by WGCNA, among which MEblue was significantly associated with cuproptosis scores and DCM. A diagnostic model made up of six signature genes including SEPTIN1, CLEC11A, ISG15, P3H3, SDSL, and INKA1 was selected. Furthermore, immune infiltration studies showed significant differences between DCM and NF. Drugs networks and ceRNA regulatory network based on six signature genes were successfully constructed.

CONCLUSION

Six signature genes (SEPTIN1, CLEC11A, ISG15, P3H3, SDSL, and INKA1) were identified as novel diagnostic biomarkers in DCM. In addition, the expression of these genes was associated with immune cell infiltration, suggesting that cuproptosis may be involved in the immune regulation of DCM.

Neutrophil extracellular traps promote ΔNp63+ basal cell hyperplasia in chronic rhinosinusitis

BACKGROUND

Neutrophil extracellular traps (NETs) are observed in chronic rhinosinusitis (CRS), although their role remains unclear.

OBJECTIVES

This study aimed to investigate the influence of NETs on the CRS epithelium.

METHODS

Forty-five sinonasal biopsy specimens were immunofluorescence-stained to identify NETs and p63+ basal stem cells. Investigators treated human nasal epithelial cells with NETs and studied them with immunofluorescence staining, Western blotting, and quantitative real-time PCR. NET inhibitors were administered to a murine neutrophilic nasal polyp model.

RESULTS

NETs existed in tissues in patients with CRS with nasal polyps, especially in noneosinophilic nasal polyp tissues. p63+ basal cell expression had a positive correlation with the release of NETs. NETs induced the expansion of Ki-67+p63+ cells. We found that ΔNp63, an isoform of p63, was mainly expressed in the nasal epithelium and controlled by NETs. Treatment with deoxyribonuclease (DNase) I or Sivelestat (NET inhibitors) prevented the overexpression of ΔNp63+ epithelial stem cells and reduced polyp formation.

CONCLUSIONS

These results reveal that NETs are implicated in CRS pathogenesis via basal cell hyperplasia. This study suggests a novel possibility of treating CRS by targeting NETs.

Implications for neutrophils in cardiac arrhythmias

Cardiac arrhythmias commonly occur as a result of aberrant electrical impulse formation or conduction in the myocardium. Frequently discussed triggers include underlying heart diseases such as myocardial ischemia, electrolyte imbalances, or genetic anomalies of ion channels involved in the tightly regulated cardiac action potential. Recently, the role of innate immune cells in the onset of arrhythmic events has been highlighted in numerous studies, correlating leukocyte expansion in the myocardium to increased arrhythmic burden. Here, we aim to call attention to the role of neutrophils in the pathogenesis of cardiac arrhythmias and their expansion during myocardial ischemia and infectious disease manifestation. In addition, we will elucidate molecular mechanisms associated with neutrophil activation and discuss their involvement as direct mediators of arrhythmogenicity.

Immune cells and related cytokines in dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a non-ischemic cardiomyopathy involving one or more underlying etiologies. It is characterized by structural and functional dysfunction of the myocardium, potentially leading to fibrosis and ventricular remodeling, and an elevated risk of heart failure (HF). Although the pathogenesis of DCM remains unknown, compelling evidence suggests that DCM-triggered immune cells and inflammatory cascades play a crucial role in the occurrence and development of DCM. Various factors are linked to myocardial damage, inducing aberrant activation of the immune system and sustained inflammatory responses in DCM. The investigation of the immunopathogenesis of DCM also contributes to discovering new biomarkers and therapeutic targets. This review examines the roles of immune cells and related cytokines in DCM pathogenesis and explores immunotherapy strategies in DCM.

Role of immune cells in the pathogenesis of myocarditis

Myocarditis is an inflammatory heart disease that mostly affects young people. Myocarditis involves a complex immune network; however, its detailed pathogenesis is currently unclear. The diversity and plasticity of immune cells, either in the peripheral blood or in the heart, have been partially revealed in a number of previous studies involving patients and several kinds of animal models with myocarditis. It is the complexity of immune cells, rather than one cell type that is the culprit. Thus, recognizing the individual intricacies within immune cells in the context of myocarditis pathogenesis and finding the key intersection of the immune network may help in the diagnosis and treatment of this condition. With the vast amount of cell data gained on myocarditis and the recent application of single-cell sequencing, we summarize the multiple functions of currently recognized key immune cells in the pathogenesis of myocarditis to provide an immune background for subsequent investigations.

Single-cell RNA sequencing in donor and end-stage heart failure patients identifies NLRP3 as a therapeutic target for arrhythmogenic right ventricular cardiomyopathy

BACKGROUND

Dilation may be the first right ventricular change and accelerates the progression of threatening ventricular tachyarrhythmias and heart failure for patients with arrhythmogenic right ventricular cardiomyopathy (ARVC), but the treatment for right ventricular dilation remains limited.

METHODS

Single-cell RNA sequencing (scRNA-seq) of blood and biventricular myocardium from 8 study participants was performed, including 6 end-stage heart failure patients with ARVC and 2 normal controls. ScRNA-seq data was then deeply analyzed, including cluster annotation, cellular proportion calculation, and characterization of cellular developmental trajectories and interactions. An integrative analysis of our single-cell data and published genome-wide association study-based data provided insights into the cell-specific contributions to the cardiac arrhythmia phenotype of ARVC. Desmoglein 2 (Dsg2)mut/mut mice were used as the ARVC model to verify the therapeutic effects of pharmacological intervention on identified cellular cluster.

RESULTS

Right ventricle of ARVC was enriched of CCL3+ proinflammatory macrophages and TNMD+ fibroblasts. Fibroblasts were preferentially affected in ARVC and perturbations associated with ARVC overlap with those reside in genetic variants associated with cardiac arrhythmia. Proinflammatory macrophages strongly interact with fibroblast. Pharmacological inhibition of Nod-like receptor protein 3 (NLRP3), a transcriptional factor predominantly expressed by the CCL3+ proinflammatory macrophages and several other myeloid subclusters, could significantly alleviate right ventricular dilation and dysfunction in Dsg2mut/mut mice (an ARVC mouse model).

CONCLUSIONS

This study provided a comprehensive analysis of the lineage-specific changes in the blood and myocardium from ARVC patients at a single-cell resolution. Pharmacological inhibition of NLRP3 could prevent right ventricular dilation and dysfunction of mice with ARVC.

Pyroptotic Macrophage-Derived Microvesicles Accelerate Formation of Neutrophil Extracellular Traps via GSDMD-N-expressing Mitochondrial Transfer during Sepsis

Macrophage pyroptosis and neutrophil extracellular traps (NETs) play a critical role in sepsis pathophysiology; however, the role of macrophage pyroptosis in the regulation of NETs formation during sepsis is unknown. Here, we showed that macrophages transfer mitochondria to neutrophils through microvesicles following pyroptosis; this process induces mitochondrial dysfunction and triggers the induction of NETs formation through mitochondrial reactive oxygen species (mtROS)/Gasdermin D (GSDMD) axis. These pyroptotic macrophage-derived microvesicles can induce tissues damage, coagulation, and NETs formation in vivo. Disulfiram partly inhibits these effects in a mouse model of sepsis. Pyroptotic macrophage-derived microvesicles induce NETs formation through mitochondrial transfer, both in vitro and in vivo. Microvesicles-mediated NETs formation depends on the presence of GSDMD-N-expressing mitochondria in the microvesicles. This study elucidates a microvesicles-based pathway for NETs formation during sepsis and proposes a microvesicles-based intervention measure for sepsis management.

Elevated Midkine Serum Levels Are Associated with Long-Term Survival in Critically Ill Patients

Midkine (Mdk) is a multifunctional protein involved in inflammatory processes. Hence, circulating Mdk is increased in sepsis and has been previously suggested as a potential biomarker in these patients. The aim of this study was to elucidate the role of Mdk serum concentrations in critical illness and sepsis and to verify its value as a prognostic biomarker. Thus, we analyzed the Mdk serum concentrations of 192 critically ill patients on admission to the medical intensive care unit (ICU). While the serum levels of Mdk at admission were similar in septic and nonseptic critical illness (362 vs. 337 ng/L, p = 0.727), we found several interesting correlations of Mdk to laboratory and clinical markers associated with ischemia or hypoxia, e.g., to renal failure and hepatic injury. Mdk serum concentrations at admission did not differ between various causes of sepsis or other critical illness. Most noticeable, we observed upregulated Mdk serum concentrations at admission in patients surviving in the long-term, which was only seen in nonseptic critical illness but not in sepsis. Our study suggests a relevant role of Mdk in critically ill patients in general and highlights the possible protective features of Mdk in critical illness.

Delineating the early dissemination mechanisms of acral melanoma by integrating single-cell and spatial transcriptomic analyses

Acral melanoma (AM) is a rare subtype of melanoma characterized by a high incidence of lymph node (LN) metastasis, a critical factor in tumor dissemination and therapeutic decision-making. Here, we employ single-cell and spatial transcriptomic analyses to investigate the dynamic evolution of early AM dissemination. Our findings reveal substantial inter- and intra-tumor heterogeneity in AM, alongside a highly immunosuppressive tumor microenvironment and complex intercellular communication networks, particularly in patients with LN metastasis. Notably, we identify a strong association between MYC+ Melanoma (MYC+MEL) and FGFBP2+NKT cells with LN metastasis. Furthermore, we demonstrate that LN metastasis requires a metabolic shift towards fatty acid oxidation (FAO) induced by MITF in MYC+MEL cells. Etomoxir, a clinically approved FAO inhibitor, can effectively suppress MITF-mediated LN metastasis. This comprehensive dataset enhances our understanding of LN metastasis in AM, and provides insights into the potential therapeutic targeting for the management of early AM dissemination.

Aβ Amyloid Scaffolds the Accumulation of Matrisome and Additional Proteins in Alzheimer's Disease

We report a highly significant correlation in brain proteome changes between Alzheimers disease (AD) and CRND8 APP695NL/F transgenic mice. However, integrating protein changes observed in the CRND8 mice with co-expression networks derived from human AD, reveals both conserved and divergent module changes. For the most highly conserved module (M42, matrisome) we find many proteins accumulate in plaques, cerebrovascular amyloid (CAA), dystrophic processes, or a combination thereof. Overexpression of two M42 proteins, midkine (Mdk) and pleiotrophin (PTN), in CRND8 mice brains leads to increased accumulation of A β ; in plaques and in CAA; further, recombinant MDK and PTN enhance A β ; aggregation into amyloid. Multiple M42 proteins, annotated as heparan sulfate binding proteins, bind to fibrillar A β 42 and a non-human amyloid fibril in vitro. Supporting this binding data, MDK and PTN co-accumulate with transthyretin (TTR) amyloid in the heart and islet amyloid polypeptide (IAPP) amyloid in the pancreas. Our findings establish several critical insights. Proteomic changes in modules observed in human AD brains define an A β ; amyloid responsome that is well conserved from mouse model to human. Further, distinct amyloid structures may serve as scaffolds, facilitating the co-accumulation of proteins with signaling functions. We hypothesize that this co-accumulation may contribute to downstream pathological sequalae. Overall, this contextualized understanding of proteomic changes and their interplay with amyloid deposition provides valuable insights into the complexity of AD pathogenesis and potential biomarkers and therapeutic targets.

Crosstalk between neutrophil extracellular traps and immune regulation: insights into pathobiology and therapeutic implications of transfusion-related acute lung injury

Transfusion-related acute lung injury (TRALI) is the leading cause of transfusion-associated death, occurring during or within 6 hours after transfusion. Reports indicate that TRALI can be categorized as having or lacking acute respiratory distress syndrome (ARDS) risk factors. There are two types of TRALI in terms of its pathogenesis: antibody-mediated and non-antibody-mediated. The key initiation steps involve the priming and activation of neutrophils, with neutrophil extracellular traps (NETs) being established as effector molecules formed by activated neutrophils in response to various stimuli. These NETs contribute to the production and release of reactive oxygen species (ROS) and participate in the destruction of pulmonary vascular endothelial cells. The significant role of NETs in TRALI is well recognized, offering a potential pathway for TRALI treatment. Moreover, platelets, macrophages, endothelial cells, and complements have been identified as promoters of NET formation. Concurrently, studies have demonstrated that the storage of platelets and concentrated red blood cells (RBC) can induce TRALI through bioactive lipids. In this article, recent clinical and pre-clinical studies on the pathophysiology and pathogenesis of TRALI are reviewed to further illuminate the mechanism through which NETs induce TRALI. This review aims to propose new therapeutic strategies for TRALI, with the hope of effectively improving its poor prognosis.

The role of midkine in health and disease

Midkine (MDK) is a neurotrophic growth factor highly expressed during embryogenesis with important functions related to growth, proliferation, survival, migration, angiogenesis, reproduction, and repair. Recent research has indicated that MDK functions as a key player in autoimmune disorders of the central nervous system (CNS), such as Multiple Sclerosis (MS) and is a promising therapeutic target for the treatment of brain tumors, acute injuries, and other CNS disorders. This review summarizes the modes of action and immunological functions of MDK both in the peripheral immune compartment and in the CNS, particularly in the context of traumatic brain injury, brain tumors, neuroinflammation, and neurodegeneration. Moreover, we discuss the role of MDK as a central mediator of neuro-immune crosstalk, focusing on the interactions between CNS-infiltrating and -resident cells such as astrocytes, microglia, and oligodendrocytes. Finally, we highlight the therapeutic potential of MDK and discuss potential therapeutic approaches for the treatment of neurological disorders.

Rethinking neutrophil extracellular traps

Neutrophils are a major subset of leukocytes in human circulating blood. In some circumstances, neutrophils release neutrophil extracellular traps (NETs). lnitially, NETs were considered to have a strong antibacterial capacity. However, currently, NETs have been shown to have a pivotal impact on various diseases. Different stimulators induce the production of different types of NETs, and their biological functions and modes of clearance do not appear to be the same. In this review, we will discuss several important issues related to NETs in order to better understand the relationship between NETs and diseases, as well as how to utilize the characteristics of NETs for disease treatment.

Nasopharynx Battlefield: Cellular Immune Responses Mediated by Midkine in Nasopharyngeal Carcinoma and COVID-19

Clinical evidence suggests that the severe respiratory illness coronavirus disease 2019 (COVID-19) is often associated with a cytokine storm that results in dysregulated immune responses. Prolonged COVID-19 positivity is thought to disproportionately affect cancer patients. With COVID-19 disrupting the delivery of cancer care, it is crucial to gain momentum and awareness of the mechanistic intersection between these two diseases. This review discusses the role of the cytokine midkine (MK) as an immunomodulator in patients with COVID-19 and nasopharyngeal carcinoma (NPC), both of which affect the nasal cavity. We conducted a review and analysis of immunocellular similarities and differences based on clinical studies, research articles, and published transcriptomic datasets. We specifically focused on ligand-receptor pairs that could be used to infer intercellular communication, as well as the current medications used for each disease, including NPC patients who have contracted COVID-19. Based on our findings, we recommend close monitoring of the MK axis to maintain the desirable effects of therapeutic regimens in fighting both NPC and COVID-19 infections.

Management of autofluorescence in formaldehyde-fixed myocardium: choosing the right treatment

Autofluorescence (AF) poses challenges for detecting proteins of interest in situ when employing immunofluorescence (IF) microscopy. This interference is particularly pronounced in strongly autofluorescent tissues such as myocardium, where tissue AF can be comparable to IF. Although various histochemical methods have been developed to achieve effective AF suppression in different types of tissue, their applications on myocardial  samples have not been well validated. Due to inconsistency across different autofluorescent structures in sometypes of tissue, it is unclear if these methods can effectively suppress AF across all autofluorescent structures within the myocardium. Here, we quantitatively evaluated the performance of several commonly used quenching treatments on formaldehyde-fixed myocardial samples, including 0.3 M glycine, 0.3% Sudan Black B (SBB), 0.1% and 1% sodium borohydride (NaBH4), TrueVIEW® and TrueBlack®. We further assessed their quenching performance by employing the pre-treatment and post-treatment protocols, designed to cover two common IF staining scenarios where buffers contained detergents or not. The results suggest that SBB and TrueBlack® outperform other reagents in AF suppression on formaldehyde-fixed myocardial samples in both protocols. Furthermore, we inspected the quenching performance of SBB and TrueBlack® on major autofluorescent myocardial structures and evaluated their influence on IF imaging. The results suggest that SBB outperforms TrueBlack® in quenching major autofluorescent structures, while TrueBlack® excels in preserving IF labeling signal. Surprisingly, we found the treatment of NaBH4 increased AF signal and enhanced the AF contrast of major autofluorescent structures. This finding suggests that NaBH4 has the potential to act as an AF enhancer and may facilitate the interpretation of myocardial structures without the need for counterstaining.

Neutrophil extracellular traps and long COVID

Post-acute COVID-19 sequelae, commonly known as long COVID, encompasses a range of systemic symptoms experienced by a significant number of COVID-19 survivors. The underlying pathophysiology of long COVID has become a topic of intense research discussion. While chronic inflammation in long COVID has received considerable attention, the role of neutrophils, which are the most abundant of all immune cells and primary responders to inflammation, has been unfortunately overlooked, perhaps due to their short lifespan. In this review, we discuss the emerging role of neutrophil extracellular traps (NETs) in the persistent inflammatory response observed in long COVID patients. We present early evidence linking the persistence of NETs to pulmonary fibrosis, cardiovascular abnormalities, and neurological dysfunction in long COVID. Several uncertainties require investigation in future studies. These include the mechanisms by which SARS-CoV-2 brings about sustained neutrophil activation phenotypes after infection resolution; whether the heterogeneity of neutrophils seen in acute SARS-CoV-2 infection persists into the chronic phase; whether the presence of autoantibodies in long COVID can induce NETs and protect them from degradation; whether NETs exert differential, organ-specific effects; specifically which NET components contribute to organ-specific pathologies, such as pulmonary fibrosis; and whether senescent cells can drive NET formation through their pro-inflammatory secretome in long COVID. Answering these questions may pave the way for the development of clinically applicable strategies targeting NETs, providing relief for this emerging health crisis.

Overexpression and potential roles of midkine via regulation of vascular endothelial growth factor A in psoriasis

Midkine plays a critical role in angiogenesis by regulating the vascular endothelial growth factor (VEGF) signalling pathway, which is known to be associated with psoriasis pathogenesis. However, research on midkine-psoriasis relationship remains limited. The objective of this study was to detect midkine expression in psoriasis and investigate its potential role in the disease. Midkine expression was measured using immunohistochemistry and ELISA. Effects of midkine on HaCaT cell proliferation, VEGF-A production and signalling pathways were assessed using CCK8, RT-PCR and WB. Scratch and in vitro tube formation tests were used to evaluate the effects of HaCaT-cell-activated midkine on the migration and tube formation of human dermal microvascular endothelial cells. Murine psoriasiform models were injected with midkine recombinant protein and midkine monoclonal antibody to investigate skin lesions, tissue sections and dermal microvessel density. Levels of midkine significantly increased in both lesions and serum of patients with psoriasis. Serum expression of midkine decreased after treatment and a positive correlation was found between midkine and disease severity. Midkine promoted HaCaT cell proliferation and VEGF-A production. The Notch2/HES1/JAK2-STAT5A pathway expression increased after midkine treatment of HaCaT cells. The supernatant of HaCaT cells treated with midkine promoted HMEC-1 migration and angiogenesis in vitro. Recombinant midkine protein exacerbated psoriasiform lesions with increased expressions of VEGF-A and microvessel density, while midkine monoclonal antibody alleviated psoriasis lesions. Midkine may have a significant impact on psoriasis angiogenesis by regulating VEGF-A expression through the Notch2/HES1/JAK2-STAT5A pathway, highlighting a potential therapeutic target for psoriasis treatment.

Inflammation and aging: signaling pathways and intervention therapies

Aging is characterized by systemic chronic inflammation, which is accompanied by cellular senescence, immunosenescence, organ dysfunction, and age-related diseases. Given the multidimensional complexity of aging, there is an urgent need for a systematic organization of inflammaging through dimensionality reduction. Factors secreted by senescent cells, known as the senescence-associated secretory phenotype (SASP), promote chronic inflammation and can induce senescence in normal cells. At the same time, chronic inflammation accelerates the senescence of immune cells, resulting in weakened immune function and an inability to clear senescent cells and inflammatory factors, which creates a vicious cycle of inflammation and senescence. Persistently elevated inflammation levels in organs such as the bone marrow, liver, and lungs cannot be eliminated in time, leading to organ damage and aging-related diseases. Therefore, inflammation has been recognized as an endogenous factor in aging, and the elimination of inflammation could be a potential strategy for anti-aging. Here we discuss inflammaging at the molecular, cellular, organ, and disease levels, and review current aging models, the implications of cutting-edge single cell technologies, as well as anti-aging strategies. Since preventing and alleviating aging-related diseases and improving the overall quality of life are the ultimate goals of aging research, our review highlights the critical features and potential mechanisms of inflammation and aging, along with the latest developments and future directions in aging research, providing a theoretical foundation for novel and practical anti-aging strategies.

Neutrophil extracellular traps in acute coronary syndrome

Acute coronary syndrome (ACS) is a group of clinical syndromes caused by acute myocardial ischemia, which can cause heart failure, arrhythmia and even sudden death. It is the major cause of disability and death worldwide. Neutrophil extracellular traps (NETs) are reticular structures released by neutrophils activation and have various biological functions. NETs are closely related to the occurrence and development of ACS and also the subsequent damage after myocardial infarction. The mechanisms are complex and interdependent on various pathways, which require further exploration. This article reviewed the role and mechanism of NETs in ACS, thereby providing a valuable reference for the diagnosis and clinical treatment of ACS.

Characterizing and Quenching Autofluorescence in Fixed Mouse Adrenal Cortex Tissue

Tissue autofluorescence of fixed tissue sections is a major concern of fluorescence microscopy. The adrenal cortex emits intense intrinsic fluorescence that interferes with signals from fluorescent labels, resulting in poor-quality images and complicating data analysis. We used confocal scanning laser microscopy imaging and lambda scanning to characterize the mouse adrenal cortex autofluorescence. We evaluated the efficacy of tissue treatment methods in reducing the intensity of the observed autofluorescence, such as trypan blue, copper sulfate, ammonia/ethanol, Sudan Black B, TrueVIEW^TM Autofluorescence Quenching Kit, MaxBlock^TM Autofluorescence Reducing Reagent Kit, and TrueBlack^TM Lipofuscin Autofluorescence Quencher. Quantitative analysis demonstrated autofluorescence reduction by 12-95%, depending on the tissue treatment method and excitation wavelength. TrueBlack^TM Lipofuscin Autofluorescence Quencher and MaxBlock^TM Autofluorescence Reducing Reagent Kit were the most effective treatments, reducing the autofluorescence intensity by 89-93% and 90-95%, respectively. The treatment with TrueBlack^TM Lipofuscin Autofluorescence Quencher preserved the specific fluorescence signals and tissue integrity, allowing reliable detection of fluorescent labels in the adrenal cortex tissue. This study demonstrates a feasible, easy-to-perform, and cost-effective method to quench tissue autofluorescence and improve the signal-to-noise ratio in adrenal tissue sections for fluorescence microscopy.

Neutrophil profiles of pediatric COVID-19 and multisystem inflammatory syndrome in children

Multisystem inflammatory syndrome in children (MIS-C) is a delayed-onset, COVID-19-related hyperinflammatory illness characterized by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigenemia, cytokine storm, and immune dysregulation. In severe COVID-19, neutrophil activation is central to hyperinflammatory complications, yet the role of neutrophils in MIS-C is undefined. Here, we collect blood from 152 children: 31 cases of MIS-C, 43 cases of acute pediatric COVID-19, and 78 pediatric controls. We find that MIS-C neutrophils display a granulocytic myeloid-derived suppressor cell (G-MDSC) signature with highly altered metabolism that is distinct from the neutrophil interferon-stimulated gene (ISG) response we observe in pediatric COVID-19. Moreover, we observe extensive spontaneous neutrophil extracellular trap (NET) formation in MIS-C, and we identify neutrophil activation and degranulation signatures. Mechanistically, we determine that SARS-CoV-2 immune complexes are sufficient to trigger NETosis. Our findings suggest that hyperinflammatory presentation during MIS-C could be mechanistically linked to persistent SARS-CoV-2 antigenemia, driven by uncontrolled neutrophil activation and NET release in the vasculature.

Role of neutrophil extracellular traps in inflammatory evolution in severe acute pancreatitis

ABSTRACT

Severe acute pancreatitis (SAP) is a life-threatening acute abdominal disease with two peaks of death: the first in the early stage, characterized by systemic inflammatory response-associated organ failure; and the second in the late stage, characterized by infectious complications. Neutrophils are the main immune cells participating in the whole process of SAP. In addition to the traditional recognition of neutrophils as the origination of chemokine and cytokine cascades or phagocytosis and degranulation of pathogens, neutrophil extracellular traps (NETs) also play an important roles in inflammatory reactions. We reviewed the role of NETs in the occurrence and development of SAP and its fatal complications, including multiple organs injury, infected pancreatic necrosis, and thrombosis. This review provides novel insights into the involvement of NETs throughout the entire process of SAP, showing that targeting NETs might be a promising strategy in SAP treatment. However, precision therapeutic options targeting NETs in different situations require further investigation.

Epigallocatechin-3-gallate reduces neutrophil extracellular trap formation and tissue injury in severe acute pancreatitis

Neutrophil extracellular traps (NETs) promote intra-acinar trypsin activation and tissue damage. Therefore, reducing NET formation can reduce tissue damage in severe acute pancreatitis (SAP). However, NET formation pathways may differ among disease models. In this study, we evaluated the role of the myeloperoxidase-neutrophil elastase (NE) pathway in NET formation in SAP. SAP was induced by intraperitoneal injection of cerulein and LPSs in mice, and NE activity was inhibited by GW311616. Pancreatic tissues were collected for multiplex immunofluorescence, scanning electron microscopy, and western blotting to detect NET formation and the effect of NE on citrullinated histone H3, followed by analyses of serum amylase and cytokine levels. Pretreatment with GW311616 significantly reduced NET formation, pancreatic tissue damage, and systemic inflammatory responses in SAP. Network pharmacology analyses using NE as the target revealed the monomeric compound epigallocatechin-3-gallate (EGCG). Binding between EGCG and NE was validated using molecular docking, and the ability of EGCG to inhibit NE activity was verified experimentally. NET formation by PMA-stimulated neutrophils was significantly reduced in vitro when the cells were pretreated with 40 μM EGCG. Pretreatment with EGCG significantly reduced NET formation, pancreatic tissue damage, and systemic inflammatory responses in vivo. These results reveal that NET formation requires the myeloperoxidase-NE pathway, and citrullination of histone H3 is affected by NE activity in SAP. EGCG shows therapeutic potential for affecting NE activity, NET formation, and systemic inflammation in SAP.

Combination of tolvaptan and valsartan improves cardiac and renal functions in doxorubicin-induced heart failure in mice

Heart failure (HF) is often complicated by renal dysfunction. Tolvaptan and valsartan are two well-known agents for the treatment of HF. However, the role of tolvaptan/valsartan combination on HF with renal dysfunction remains unclear. To establish a mice model with HF with renal dysfunction, mice were intraperitoneally injected with doxorubicin (Dox). Echocardiogram was applied to assess the left ventricular function. Additionally, serum aldosterone (ALD) and angiotensin II (Ang II) level in mice were determined by ELISA. Meanwhile, western blot assay was used to evaluate the expressions of B cell lymphoma-2 (Bcl-2), Bcl-2 associated X (Bax) and cleaved caspase 3 in the heart and kidney tissues of mice. In this study, we found that compared to tolvaptan or valsartan alone treatment group, tolvaptan/valsartan combination obviously improved the left ventricular ejection fraction (LVEF) and the left ventricular fractional shortening (LVFS), and reduced serum ALD and Ang II level in Dox-treated mice. Additionally, tolvaptan/valsartan combination significantly prevented the inflammation and fibrosis of heart and kidney tissues in Dox-treated mice. Meanwhile, tolvaptan/valsartan combination notably inhibited the myocardial and renal cell apoptosis in Dox-treated mice via upregulation of Bcl-2 and downregulation of Bax and cleaved caspase 3, compared to the single drug treatment. Collectively, tolvaptan/valsartan combination could improve cardiac and renal functions, as well as prevent the fibrosis, inflammation and apoptosis of heart and kidney tissues in Dox-treated mice. Taken together, combining tolvaptan with valsartan might be a promising approach to achieve enhanced therapeutic effect for treatment of HF with renal dysfunction.

Hox-driven conditional immortalization of myeloid and lymphoid progenitors: Uses, advantages, and future potential

Those who study macrophage biology struggle with the decision whether to utilize primary macrophages derived directly from mice or opt for the convenience and genetic tractability of immortalized macrophage-like cell lines in in vitro studies. Particularly when it comes to studying phagocytosis and phagosomal maturation-a signature cellular process of the macrophage-many commonly used cell lines are not representative of what occurs in primary macrophages. A system developed by Mark Kamps' group, that utilizes conditionally constitutive activity of Hox transcription factors (Hoxb8 and Hoxa9) to immortalize differentiation-competent myeloid cell progenitors of mice, offers an alternative to the macrophage/macrophage-like dichotomy. In this resource, we will review the use of Hoxb8 and Hoxa9 as hematopoietic regulators to conditionally immortalize murine hematopoietic progenitor cells which retain their ability to differentiate into many functional immune cell types including macrophages, neutrophils, basophils, osteoclasts, eosinophils, dendritic cells, as well as limited potential for the generation of lymphocytes. We further demonstrate that the use of macrophages derived from Hoxb8/Hoxa9 immortalized progenitors and their similarities to bone marrow-derived macrophages. To supplement the existing data, mass spectrometry-based proteomics, flow cytometry, cytology, and in vitro phagosomal assays were conducted on macrophages derived from Hoxb8 immortalized progenitors and compared to bone marrow-derived macrophages and the macrophage-like cell line J774. We additionally propose the use of a standardized nomenclature to describe cells derived from the Hoxb8/Hoxa9 system in anticipation of their expanded use in the study of leukocyte cell biology.

A model-informed approach to assess the risk of immune checkpoint inhibitor-induced autoimmune myocarditis

Immune checkpoint inhibitors (ICIs), as a novel immunotherapy, are designed to modulate the immune system to attack malignancies. Despite their promising benefits, immune-related adverse events (IRAEs) may occur, and incidences are bound to increase with surging demand of this class of drugs in treating cancer. Myocarditis, although rare compared to other IRAEs, has a significantly higher fatal frequency. Due to the overwhelming complexity of the immune system, this condition is not well understood, despite the significant research efforts devoted to it. To better understand the development and progression of autoimmune myocarditis and the roles of ICIs therein, we suggest a new approach: mathematical modelling. Mathematical modelling of myocarditis has enormous potential to determine which parts of the immune system are critical to the development and progression of the disease, and therefore warrant further investigation. We provide the immunological background needed to develop a mathematical model of this disease and review relevant existing models of immunology that serve as the mathematical inspiration needed to develop this field.

Midkine—A novel player in cardiovascular diseases

Midkine (MK) is a 13-kDa heparin-binding cytokine and growth factor with anti-apoptotic, pro-angiogenic, pro-inflammatory and anti-infective functions, that enable it to partake in a series of physiological and pathophysiological processes. In the past, research revolving around MK has concentrated on its roles in reproduction and development, tissue protection and repair as well as inflammatory and malignant processes. In the recent few years, MK's implication in a wide scope of cardiovascular diseases has been rigorously investigated. Nonetheless, there is still no broadly accepted consensus on whether MK exerts generally detrimental or favorable effects in cardiovascular diseases. The truth probably resides somewhere in-between and depends on the underlying physiological or pathophysiological condition. It is therefore crucial to thoroughly examine and appraise MK's participation in cardiovascular diseases. In this review, we introduce the MK gene and protein, its multiple receptors and signaling pathways along with its expression in the vascular system and its most substantial functions in cardiovascular biology. Further, we recapitulate the current evidence of MK's expression in cardiovascular diseases, addressing the various sources and modes of MK expression. Moreover, we summarize the most significant implications of MK in cardiovascular diseases with particular emphasis on MK's advantageous and injurious functions, highlighting its ample diagnostic and therapeutic potential. Also, we focus on conflicting roles of MK in a number of cardiovascular diseases and try to provide some clarity and guidance to MK's multifaceted roles. In summary, we aim to pave the way for MK-based diagnostics and therapies that could present promising tools in the diagnosis and treatment of cardiovascular diseases.

Elevated serum midkine levels in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infected patients

BACKGROUND

The coronavirus disease-2019 (COVID-19) pandemic has caused important health, economic, social, and cultural problems worldwide. Recent findings demonstrate an excessive cytokine release during the disease development, especially in the seriously life-threatening form of COVID-19. Among other chemokines and cytokines that are released in high amounts at the infection site of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), midkine (MK), which is a potent pro-inflammatory growth factor/ cytokine, can be also overexpressed and contribute to the pathophysiological process in patients infected with SARS-CoV-2.

MATERIALS AND METHOD

Serum was collected from 87 intensive care unit (ICU) patients that are COVID-19 positive and 50 healthy volunteers in the control group with a negative PCR test and without disease symptoms. Circulating MK concentration was measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

COVID-19 patients had a significantly higher serum MK concentration compared to non-COVID-19 control subjects (1892.8 ± 1615.8 pg/mL versus 680.7 ± 907.6 pg/mL, respectively; P < 0.001). The cut-off MK concentration was 716.7 pg/ mL, with the sensitivity and specificity of 75.9 % and 76.0 %, respectively. The area under the receiver operating characteristic (ROC) curve of MK was = 0.827. Our findings showed that circulating MK levels are significantly increased in SARS-CoV-2 infected patients.

CONCLUSION

We suggest that MK is involved in the pathogenesis of COVID-19 and may be a part of hypercytokinaemia. Therefore, MK may serve as a supporting biomarker in the diagnosis of COVID-19, and blocking MK actions or its targets may attenuate the inflammatory process and the severity of the disease.

Roles, detection, and visualization of neutrophil extracellular traps in acute pancreatitis

Neutrophil extracellular traps (NETs) are produced in large quantities at the site of inflammation, and they locally capture and eliminate various pathogens. Thus, NETs quickly control the infection of pathogens in the body and play vital roles in immunity and antibacterial effects. However, evidence is accumulating that NET formation can exacerbate pancreatic tissue damage during acute pancreatitis (AP). In this review, we describe the research progress on NETs in AP and discuss the possibility of NETs as potential therapeutic targets. In addition, since the current detection and visualization methods of NET formation are not uniform and the selection of markers is still controversial, a synopsis of these issues is provided in this review.

Neutrophils and Neutrophil Extracellular Traps in Cardiovascular Disease: An Overview and Potential Therapeutic Approaches

Recent advances in pharmacotherapy have markedly improved the prognosis of cardiovascular disease (CVD) but have not completely conquered it. Therapies targeting the NOD-like receptor family pyrin domain containing 3 inflammasome and its downstream cytokines have proven effective in the secondary prevention of cardiovascular events, suggesting that inflammation is a target for treating residual risk in CVD. Neutrophil-induced inflammation has long been recognized as important in the pathogenesis of CVD. Circadian rhythm-related and disease-specific microenvironment changes give rise to neutrophil diversity. Neutrophils are primed by various stimuli, such as chemokines, cytokines, and damage-related molecular patterns, and the activated neutrophils contribute to the inflammatory response in CVD through degranulation, phagocytosis, reactive oxygen species generation, and the release of neutrophil extracellular traps (NETs). In particular, NETs promote immunothrombosis through the interaction with vascular endothelial cells and platelets and are implicated in the development of various types of CVD, such as acute coronary syndrome, deep vein thrombosis, and heart failure. NETs are promising candidates for anti-inflammatory therapy in CVD, and their efficacy has already been demonstrated in various animal models of the disease; however, they have yet to be clinically applied in humans. This narrative review discusses the diversity and complexity of neutrophils in the trajectory of CVD, the therapeutic potential of targeting NETs, and the related clinical issues.

Targeting Myocardial Fibrosis—A Magic Pill in Cardiovascular Medicine?

Fibrosis, characterized by an excessive accumulation of extracellular matrix, has long been seen as an adaptive process that contributes to tissue healing and regeneration. More recently, however, cardiac fibrosis has been shown to be a central element in many cardiovascular diseases (CVDs), contributing to the alteration of cardiac electrical and mechanical functions in a wide range of clinical settings. This paper aims to provide a comprehensive review of cardiac fibrosis, with a focus on the main pathophysiological pathways involved in its onset and progression, its role in various cardiovascular conditions, and on the potential of currently available and emerging therapeutic strategies to counteract the development and/or progression of fibrosis in CVDs. We also emphasize a number of questions that remain to be answered, and we identify hotspots for future research.

The Scientific Rationale for the Introduction of Renalase in the Concept of Cardiac Fibrosis

Cardiac fibrosis represents a redundant accumulation of extracellular matrix proteins, resulting from a cascade of pathophysiological events involved in an ineffective healing response, that eventually leads to heart failure. The pathophysiology of cardiac fibrosis involves various cellular effectors (neutrophils, macrophages, cardiomyocytes, fibroblasts), up-regulation of profibrotic mediators (cytokines, chemokines, and growth factors), and processes where epithelial and endothelial cells undergo mesenchymal transition. Activated fibroblasts and myofibroblasts are the central cellular effectors in cardiac fibrosis, serving as the main source of matrix proteins. The most effective anti-fibrotic strategy will have to incorporate the specific targeting of the diverse cells, pathways, and their cross-talk in the pathogenesis of cardiac fibroproliferation. Additionally, renalase, a novel protein secreted by the kidneys, is identified. Evidence demonstrates its cytoprotective properties, establishing it as a survival element in various organ injuries (heart, kidney, liver, intestines), and as a significant anti-fibrotic factor, owing to its, in vitro and in vivo demonstrated pleiotropy to alleviate inflammation, oxidative stress, apoptosis, necrosis, and fibrotic responses. Effective anti-fibrotic therapy may seek to exploit renalase’s compound effects such as: lessening of the inflammatory cell infiltrate (neutrophils and macrophages), and macrophage polarization (M1 to M2), a decrease in the proinflammatory cytokines/chemokines/reactive species/growth factor release (TNF-α, IL-6, MCP-1, MIP-2, ROS, TGF-β1), an increase in anti-apoptotic factors (Bcl2), and prevention of caspase activation, inflammasome silencing, sirtuins (1 and 3) activation, and mitochondrial protection, suppression of epithelial to mesenchymal transition, a decrease in the pro-fibrotic markers expression (’α-SMA, collagen I, and III, TIMP-1, and fibronectin), and interference with MAPKs signaling network, most likely as a coordinator of pro-fibrotic signals. This review provides the scientific rationale for renalase’s scrutiny regarding cardiac fibrosis, and there is great anticipation that these newly identified pathways are set to progress one step further. Although substantial progress has been made, indicating renalase’s therapeutic promise, more profound experimental work is required to resolve the accurate underlying mechanisms of renalase, concerning cardiac fibrosis, before any potential translation to clinical investigation.

Midkine promotes kidney injury in diabetic kidney disease by increasing neutrophil extracellular traps formation

Background

We sought to investigate the role of midkine (MK) on neutrophil extracellular trap formation (NETosis) and diabetic kidney disease (DKD) progression.

Methods

The expression of MK and NETosis in the renal tissue of DKD patients was examined by immunohistochemistry and immunofluorescence, respectively. Neutrophils extracted from mouse bone marrow by gradient centrifugation were treated with MK for this in-vitro study. A mouse diabetes model was induced by a high-fat diet combined with an intraperitoneal injection of streptozocin (STZ). Antisense oligodeoxynucleotide (ODN) for MK inhibition was administered via tail vein injection.

Results

We found that the expression of MK was increased in the kidney tissue of DKD patients. Additionally, a greater number of neutrophils were primed toward NETosis in the kidney tissue of DKD patients, which was manifested by the increased expression of NETosis biomarkers citrullinated histone H3 (H3Cit) and myeloperoxidase (MPO). In vitro, MK treatment concentration-dependently increased neutrophil proliferation (cell counting kit-8). Further, western blot and enzyme-linked immunosorbent assays showed that MK (100 ng/mL) significantly promoted NETosis and the expression of inflammatory factors interleukin (IL)-1 and IL-6 secretion in high-glucose treated neutrophils. In the mouse diabetes model, MK promoted the pathological damage and fibrosis of kidney tissue, as demonstrated by the reversion of the pathological damage and fibrosis by the MK antisense ODN [diabetes mellitus (DM) + MK – ODN] treatment. Additionally, the inhibition of MK reduced the formation of NETs.

Conclusions

MK promotes DKD progression by increasing NETosis.

Neutrophil inhibition improves acute inflammation in a murine model of viral myocarditis

AIMS

Viral myocarditis (VM) is an inflammatory pathology of the myocardium triggered by a viral infection that may cause sudden death or heart failure (HF), especially in the younger population. Current treatments only stabilize and improve cardiac function without resolving the underlying inflammatory cause. The factors that induce VM to progress to HF are still uncertain, but neutrophils have been increasingly associated with the negative evolution of cardiac pathologies. The present study investigates the contribution of neutrophils to VM disease progression in different ways.

METHODS AND RESULTS

In a coxsackievirus B3- (CVB3) induced mouse model of VM, neutrophils and neutrophil extracellular traps (NETs) were prominent in the acute phase of VM as revealed by enzyme-linked immunosorbent assay analysis and immunostaining. Anti-Ly6G-mediated neutrophil blockade starting at model induction decreased cardiac necrosis and leucocyte infiltration, preventing monocyte and Ly6CHigh pro-inflammatory macrophage recruitment. Furthermore, genetic peptidylarginine deiminase 4-dependent NET blockade reduced cardiac damage and leucocyte recruitment, significantly decreasing cardiac monocyte and macrophage presence. Depleting neutrophils with anti-Ly6G antibodies at 7 days post-infection, after the acute phase, did not decrease cardiac inflammation.

CONCLUSION

Collectively, these results indicate that the repression of neutrophils and the related NET response in the acute phase of VM improves the pathological phenotype by reducing cardiac inflammation.

Midkine promotes breast cancer cell proliferation and migration by upregulating NR3C1 expression and activating the NF-κB pathway

BACKGROUND

Breast cancer (BC) is the most common malignancy in females and is the second leading cause of cancer-related death among women worldwide. Midkine (MDK) is a heparin-binding growth factor that is abnormally expressed at high levels in various human malignancies. We aimed to uncover the biological function and molecular mechanism of MDK in BC cells.

METHODS AND RESULTS

MDA-MB-231-shMDK and T47D-shMDK BC cells were established. The in vitro biological functions of MDK were demonstrated by CCK-8 assays, Transwell assays and Western blotting, whereas qPCR pathway arrays were implemented to explore the mechanism of MDK in BC cells. Functionally, we verified that silencing MDK significantly suppressed BC cell proliferation and migration by inhibiting the activation of the nuclear factor kappa B (NF-κB) pathway and the nuclear distribution of NF-κB. Meanwhile, Ingenuity Pathway Analysis (IPA) and a qPCR pathway array revealed that silencing MDK decreased the expression of NR3C1, a potential downstream target of the NF-κB pathway. We also confirmed that treatment with an NF-κB inhibitor suppressed NR3C1 expression in BC cells. Finally, we demonstrated that silencing NR3C1 repressed BC cell proliferation and migration.

CONCLUSIONS

Our findings highlight a novel mechanism by which MDK influences BC progression via regulation of the NF-κB-NR3C1 pathway.

Mathematical modelling of autoimmune myocarditis and the effects of immune checkpoint inhibitors

Autoimmune myocarditis is a rare, but frequently fatal, side effect of immune checkpoint inhibitors (ICIs), a class of cancer therapies. Despite extensive experimental work on the causes, development and progression of this disease, much still remains unknown about the importance of the different immunological pathways involved. We present a mathematical model of autoimmune myocarditis and the effects of ICIs on its development and progression to either resolution or chronic inflammation. From this, we gain a better understanding of the role of immune cells, cytokines and other components of the immune system in driving the cardiotoxicity of ICIs. We parameterise the model using existing data from the literature, and show that qualitative model behaviour is consistent with disease characteristics seen in patients in an ICI-free context. The bifurcation structures of the model show how the presence of ICIs increases the risk of developing autoimmune myocarditis. This predictive modelling approach is a first step towards determining treatment regimens that balance the benefits of treating cancer with the risk of developing autoimmune myocarditis.

Mast Cells Trigger Disturbed Bone Healing in Osteoporotic Mice

Mast cells are important tissue-resident sensor and effector immune cells but also play a major role in osteoporosis development. Mast cells are increased in numbers in the bone marrow of postmenopausal osteoporotic patients, and mast cell-deficient mice are protected from ovariectomy (OVX)-induced bone loss. In this study, we showed that mast cell-deficient Mcpt5-Cre R-DTA mice were protected from OVX-induced disturbed fracture healing, indicating a critical role for mast cells in the pathomechanisms of impaired bone repair under estrogen-deficient conditions. We revealed that mast cells trigger the fracture-induced inflammatory response by releasing inflammatory mediators, including interleukin-6, midkine (Mdk), and C-X-C motif chemokine ligand 10 (CXCL10), and promote neutrophil infiltration into the fracture site in OVX mice. Furthermore, mast cells were responsible for reduced osteoblast and increased osteoclast activities in OVX mice callus, as well as increased receptor activator of NF-κB ligand serum levels in OVX mice. Additional in vitro studies with human cells showed that mast cells stimulate osteoclastogenesis by releasing the osteoclastogenic mediators Mdk and CXCL10 in an estrogen-dependent manner, which was mediated via the estrogen receptor alpha on mast cells. In conclusion, mast cells negatively affect the healing of bone fractures under estrogen-deficient conditions. Hence, targeting mast cells might provide a therapeutic strategy to improve disturbed bone repair in postmenopausal osteoporosis. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Neutrophil Profiles of Pediatric COVID-19 and Multisystem Inflammatory Syndrome in Children

Multisystem Inflammatory Syndrome in Children (MIS-C) is a delayed-onset, COVID-19-related hyperinflammatory systemic illness characterized by SARS-CoV-2 antigenemia, cytokine storm and immune dysregulation; however, the role of the neutrophil has yet to be defined. In adults with severe COVID-19, neutrophil activation has been shown to be central to overactive inflammatory responses and complications. Thus, we sought to define neutrophil activation in children with MIS-C and acute COVID-19. We collected samples from 141 children: 31 cases of MIS-C, 43 cases of acute pediatric COVID-19, and 67 pediatric controls. We found that MIS-C neutrophils display a granulocytic myeloid-derived suppressor cell (G-MDSC) signature with highly altered metabolism, which is markedly different than the neutrophil interferon-stimulated gene (ISG) response observed in pediatric patients during acute SARS-CoV-2 infection. Moreover, we identified signatures of neutrophil activation and degranulation with high levels of spontaneous neutrophil extracellular trap (NET) formation in neutrophils isolated from fresh whole blood of MIS-C patients. Mechanistically, we determined that SARS-CoV-2 immune complexes are sufficient to trigger NETosis. Overall, our findings suggest that the hyperinflammatory presentation of MIS-C could be mechanistically linked to persistent SARS-CoV-2 antigenemia through uncontrolled neutrophil activation and NET release in the vasculature.

ONE SENTENCE SUMMARY

Circulating SARS-CoV-2 antigen:antibody immune complexes in Multisystem Inflammatory Syndrome in Children (MIS-C) drive hyperinflammatory and coagulopathic neutrophil extracellular trap (NET) formation and neutrophil activation pathways, providing insight into disease pathology and establishing a divergence from neutrophil signaling seen in acute pediatric COVID-19.

Live imaging of neolymphangiogenesis identifies acute antimetastatic roles of dsRNA mimics

Long-range communication between tumor cells and the lymphatic vasculature defines competency for metastasis in different cancer types, particularly in melanoma. Nevertheless, the discovery of selective blockers of lymphovascular niches has been compromised by the paucity of experimental systems for whole-body analyses of tumor progression. Here, we exploit immunocompetent and immunodeficient mouse models for live imaging of Vegfr3-driven neolymphangiogenesis, as a versatile platform for drug screening in vivo. Spatiotemporal analyses of autochthonous melanomas and patient-derived xenografts identified double-stranded RNA mimics (dsRNA nanoplexes) as potent inhibitors of neolymphangiogenesis, metastasis, and post-surgical disease relapse. Mechanistically, dsRNA nanoplexes were found to exert a rapid dual action in tumor cells and in their associated lymphatic vasculature, involving the transcriptional repression of the lymphatic drivers Midkine and Vegfr3, respectively. This suppressive function was mediated by a cell-autonomous type I interferon signaling and was not shared by FDA-approved antimelanoma treatments. These results reveal an alternative strategy for targeting the tumor cell-lymphatic crosstalk and underscore the power of Vegfr3-lymphoreporters for pharmacological testing in otherwise aggressive cancers.

Protein tyrosine phosphatase receptor zeta 1 deletion triggers defective heart morphogenesis in mice and zebrafish

Protein tyrosine phosphatase receptor-ζ1 (PTPRZ1) is a transmembrane tyrosine phosphatase receptor highly expressed in embryonic stem cells. In the present work, gene expression analyses of Ptprz1^−/− and Ptprz1^+/+ mice endothelial cells and hearts pointed to an unidentified role of PTPRZ1 in heart development through the regulation of heart-specific transcription factor genes. Echocardiography analysis in mice identified that both systolic and diastolic functions are affected in Ptprz1^−/− compared with Ptprz1^+/+ hearts, based on a dilated left ventricular (LV) cavity, decreased ejection fraction and fraction shortening, and increased angiogenesis in Ptprz1^−/− hearts, with no signs of cardiac hypertrophy. A zebrafish ptprz1^−/− knockout was also generated and exhibited misregulated expression of developmental cardiac markers, bradycardia, and defective heart morphogenesis characterized by enlarged ventricles and defected contractility. A selective PTPRZ1 tyrosine phosphatase inhibitor affected zebrafish heart development and function in a way like what is observed in the ptprz1^−/− zebrafish. The same inhibitor had no effect in the function of the adult zebrafish heart, suggesting that PTPRZ1 is not important for the adult heart function, in line with data from the human cell atlas showing very low to negligible PTPRZ1 expression in the adult human heart. However, in line with the animal models, Ptprz1 was expressed in many different cell types in the human fetal heart, such as valvar, fibroblast-like, cardiomyocytes, and endothelial cells. Collectively, these data suggest that PTPRZ1 regulates cardiac morphogenesis in a way that subsequently affects heart function and warrant further studies for the involvement of PTPRZ1 in idiopathic congenital cardiac pathologies.

NEW & NOTEWORTHY Protein tyrosine phosphatase receptor ζ1 (PTPRZ1) is expressed in fetal but not adult heart and seems to affect heart development. In both mouse and zebrafish animal models, loss of PTPRZ1 results in dilated left ventricle cavity, decreased ejection fraction, and fraction shortening, with no signs of cardiac hypertrophy. PTPRZ1 also seems to be involved in atrioventricular canal specification, outflow tract morphogenesis, and heart angiogenesis. These results suggest that PTPRZ1 plays a role in heart development and support the hypothesis that it may be involved in congenital cardiac pathologies.

Neutrophil extracellular traps: from physiology to pathology

At the frontline of the host defense response, neutrophil antimicrobial functions have adapted to combat infections and injuries of different origins and magnitude. The release of web-like DNA structures named neutrophil extracellular traps (NETs) constitutes an important mechanism by which neutrophils prevent pathogen dissemination or deal with microorganisms of a bigger size. At the same time, nuclear and granule proteins with microbicidal activity bind to these DNA structures promoting the elimination of entrapped pathogens. However, these toxic properties may produce unwanted effects in the host, when neutrophils uncontrollably release NETs upon persistent inflammation. As a consequence, NET accumulation can produce vessel occlusion, tissue damage, and prolonged inflammation associating with the progression and exacerbation of multiple pathologic conditions. This review outlines recent advances in understanding the mechanisms of NET release and functions in sterile disease. We also discuss mechanisms of physiological regulation and the importance of neutrophil heterogeneity in NET formation and composition.

Midkine and chronic kidney disease-associated multisystem organ dysfunctions

Chronic kidney disease (CKD) is a progressive multisystem condition with yet undefined mechanistic drivers and multiple implicated soluble factors. If identified, these factors could be targeted for therapeutic intervention for a disease that currently lacks specific treatment. There is increasing preclinical evidence that the heparin/endothelial glycocalyx-binding molecule midkine (MK) has a pathological role in multiple CKD-related, organ-specific disease processes, including CKD progression, hypertension, vascular and cardiac disease, bone disease and CKD-related cancers. Concurrent with this are studies documenting increases in circulating and urine MK proportional to glomerular filtration rate (GFR) loss in CKD patients and evidence that administering soluble MK reverses the protective effects of MK deficiency in experimental kidney disease. This review summarizes the growing body of evidence supporting MK's potential role in driving CKD-related multisystem disease, including MK's relationship with the endothelial glycocalyx, the deranged MK levels and glycocalyx profile in CKD patients and a proposed model of MK organ interplay in CKD disease processes and highlights the importance of ongoing research into MK's potential as a therapeutic target.

EDIL3 deficiency ameliorates adverse cardiac remodeling by neutrophil extracellular traps (NET)-mediated macrophage polarization

AIMS

After myocardial infarction (MI), injured cardiomyocytes recruit neutrophils and monocytes/macrophages to myocardium, which in turn initiates inflammatory and reparative cascades, respectively. Either insufficient or excessive inflammation impairs cardiac healing. As an endogenous inhibitor of neutrophil adhesion, EDIL3 plays a crucial role in inflammatory regulation. However, the role of EDIL3 in MI remains obscure. We aimed to define the role of EDIL3 in cardiac remodeling after MI.

METHODS AND RESULTS

Serum EDIL3 levels in MI patients were negatively associated with MI biomarkers. Consistently, WT mice after MI showed low levels of cardiac EDIL3. Compared with WT mice, Edil3-/- mice showed improvement of post-MI adverse remodeling, as they exhibited lower mortality, better cardiac function, shorter scar length and smaller LV cavity. Accordingly, infarcted hearts of Edil3-/- mice contained fewer cellular debris and lower amounts of fibrosis content, with decreased collagen I/III expression and the percentage of α-smooth muscle actin (α-SMA) myofibroblasts. Mechanistically, EDIL3 deficiency did not affect the recruitment of monocytes or T cells, but enhanced neutrophil recruitment and following expansion of pro-inflammatory Mertk-MHC-IIlo-int (myeloid-epithelial-reproductive tyrosine kinase/major histocompatibility complex II) macrophages. The injection of neutrophil-specific C-X-C motif chemokine receptor 2 (CXCR2) antagonist eliminated the differences in macrophage polarization and cardiac function between WT and Edil3-/- mice after MI. Neutrophil extracellular traps (NETs), which were more abundant in the hearts of Edil3-/- mice, contributed to Mertk-MHC-IIlo-int polarization via toll-like receptor 9 pathway. The inhibition of NET formation by treatment of neutrophil elastase inhibitor or DNase I impaired macrophage polarization, increased cellular debris and aggravated cardiac adverse remodeling, thus removed the differences of cardiac function between WT and Edil3-/- mice. Totally, EDIL3 plays an important role in NET-primed macrophage polarization and cardiac remodeling during MI.

CONCLUSION

We not only reveal that EDIL3 deficiency ameliorates adverse cardiac healing via NET-mediated pro-inflammatory macrophage polarization but also discover a new crosstalk between neutrophil and macrophage after MI.

TRANSLATIONAL PERSPECTIVE

We established EDIL3 as a critical regulator of neutrophil recruitment and macrophage polarization during post-MI cardiac remodeling. EDIL3 may be a candidate prognostic biomarker and drug target for cardiovascular diseases. The novel pathways and mechanisms revealed in this study has renewed our understanding of the role of leukocyte adhesion inhibitors in cardiovascular disease. Meanwhile, our study reaffirmed the indispensable role of inflammation in the healing process, thereby prompting the reevaluation of post-MI anti-inflammatory treatments.

Midkine: A multifaceted driver of atherosclerosis

Atherosclerosis constitutes the pathological basis of life-threatening events, including heart attack and stroke. Midkine is a heparin-binding growth factor and forms a small protein family with pleiotrophin. Under inflammatory or hypoxic conditions, midkine expression is up-regulated. Upon binding to its receptors, midkine can activate multiple signal pathways to regulate cell survival and migration, epithelial-to-mesenchymal transition, and oncogenesis. Circulating midkine levels are significantly increased in patients with essential hypertension, obesity or severe peripheral artery disease. Importantly, midkine exerts a proatherogenic effect by altering multiple pathophysiological processes involving atherogenesis, including macrophage lipid accumulation, vascular inflammation, neointima formation, insulin resistance and macrophage apoptosis. Midkine represents a potential therapeutic target for atherosclerosis-associated diseases. This review described the structure characteristics, expression patterns and signal transduction pathways of midkine with an emphasis on its role in atherosclerosis.

Sitagliptin Modulates Oxidative, Nitrative and Halogenative Stress and Inflammatory Response in Rat Model of Hepatic Ischemia-Reperfusion

A possibility of repurposing sitagliptin, a well-established antidiabetic drug, for alleviating injury caused by ischemia-reperfusion (IR) is being researched. The aim of this study was to shed some light on the molecular background of the protective activity of sitagliptin during hepatic IR. The expression and/or concentration of inflammation and oxidative stress-involved factors have been determined in rat liver homogenates using quantitative RT-PCR and Luminex^® xMAP^® technology and markers of nitrative and halogenative stress were quantified using targeted metabolomics (LC-MS/MS). Animals (n = 36) divided into four groups were treated with sitagliptin (5 mg/kg) (S and SIR) or saline solution (C and IR), and the livers from IR and SIR were subjected to ischemia (60 min) and reperfusion (24 h). The midkine expression (by 2.2-fold) and the free 3-nitrotyrosine (by 2.5-fold) and IL-10 (by 2-fold) concentration were significantly higher and the Nox4 expression was lower (by 9.4-fold) in the IR than the C animals. As compared to IR, the SIR animals had a lower expression of interleukin-6 (by 4.2-fold) and midkine (by 2-fold), a lower concentration of 3-nitrotyrosine (by 2.5-fold) and a higher Nox4 (by 2.9-fold) and 3-bromotyrosine (by 1.4-fold). In conclusion, IR disturbs the oxidative, nitrative and halogenative balance and aggravates the inflammatory response in the liver, which can be attenuated by low doses of sitagliptin.

Neutrophil extracellular traps in cancer

Beyond their well-known functions in the acute phases of the immune response, neutrophils play important roles in the various phases of tumor initiation and progression, through the release of their stored or newly synthesized mediators. In addition to reactive oxygen species, cytokines, chemokines, granule proteins and lipid mediators, neutrophil extracellular traps (NETs) can also be released upon neutrophil activation. NET formation can be achieved through a cell-death process or in association with the release of mitochondrial DNA from viable neutrophils. NETs are described as extracellular fibers of DNA and decorating proteins responsible for trapping and killing extracellular pathogens, playing a protective role in the antimicrobial defense. There is increasing evidence, however, that NETs play multiple roles in the scenario of cancer-related inflammation. For instance, NETs directly or indirectly promote tumor growth and progression, fostering tumor spread at distant sites and shielding cancer cells thus preventing the effects of cytotoxic lymphocytes. NETs can also promote tumor angiogenesis and cancer-associated thrombosis. On the other hand, there is some evidence that NETs may play anti-inflammatory and anti-tumorigenic roles. In this review, we focus on the main mechanisms underlying the emerging effects of NETs in cancer initiation and progression.