Hypoxia Promotes Neutrophil Survival After Acute Myocardial Infarction

Multifaceted roles of neutrophils in cardiac disease

Neutrophils, the most abundant leukocytes in human blood, have long been recognized as critical first responders in the innate immune system's defense against pathogens. Some of the more notable innate antimicrobial properties of neutrophils include generation of superoxide free radicals like myeloperoxidase, production of proteases that reshape the extracellular matrix allowing for easier access to infected tissues, and release of neutrophil extracellular traps, extruded pieces of DNA that ensnare bacterial and fungi. These mechanisms developed to provide neutrophils with a vast array of specialized functions to provide the host defense against infection in an acute setting. However, emerging evidence over the past few decades has revealed a far more complex and nuanced role for these neutrophil-driven processes in various chronic conditions, particularly in cardiovascular diseases. The pathophysiology of cardiac diseases involves a complex interplay of hemodynamic, neurohumoral, and inflammatory factors. Neutrophils, as key mediators of inflammation, contribute significantly to this intricate network. Their involvement extends far beyond their classical role in pathogen clearance, encompassing diverse functions that can both exacerbate tissue damage and contribute to repair processes. Here, we consider the contributions of neutrophils to myocardial infarction, heart failure, cardiac arrhythmias, and nonischemic cardiomyopathies. Understanding these complex interactions is crucial for developing novel therapeutic strategies aimed at modulating neutrophil functions in these highly morbid cardiac diseases.

Correlation analysis of serum endothelial cell specific molecule-1, endothelial microparticles, hypoxia inducible factor-1α levels and acute myocardial infarction and their predictive value for major adverse cardiovascular events: a retrospective study

Objective

This study aimed to analyse the correlation of endothelial cell specific molecule-1 (ESM-1), endothelial microparticles (EMPs) and hypoxia inducible factor-1α (HIF-1α) serum levels with the occurrence of acute myocardial infarction (AMI) and determine their short-term predictive value for major adverse cardiovascular events (MACE) following AMI treatment.

Methods

Retrospective data analysis was performed on the medical records of 106 patients with AMI admitted to our hospital between October 2020 and October 2022. The control group consisted of 106 healthy volunteers that received a physical examination at our hospital's physical examination centre within the same time frame. ESM-1, EMP and HIF-1α serum levels were compared between the two groups. Independent risk variables for AMI were examined. Furthermore, these individuals were separated into the poor prognosis group (n = 41) and good prognosis group (n = 65) according to the presence or absence of MACE. Finally, the ESM-1, EMPs and HIF-1α serum levels were correlated with the development of MACE in patients with AMI, and the predictive value of serum ESM-1, EMPs and HIF-1α for MACE was evaluated. The serum HIF-1α, EMP and ESM-1 levels were significantly different between the two groups (P < 0.05). Multivariate logistic regression analysis revealed the elevated serum levels of HIF-1α (odds ratio (OR) = 1.819), EMPs (OR = 1.071) and ESM-1 (OR = 14.655) as AMI risk variables. A substantially significant (P < 0.05) correlation was found between the elevated levels of serum HIF-1α (OR = 18.716), EMPs (OR = 26.185) and ESM-1 (OR = 13.992) and the development of MACE in patients with AMI. According to receiver operating characteristic (ROC) curve analysis, the combined evaluation value of HIF-1α, EMPs and ESM-1 serum levels in predicting MACE was high with an area under the curve (AUC) of 0.931.

Conclusion

Patients with AMI have abnormally high ESM-1, EMP and HIF-1α levels in their serum, all of which have been linked to the development of MACE. Together, these parameters have high sensitivity and specificity for early MACE identification.

Navarixin alleviates cardiac remodeling after myocardial infarction by decreasing neutrophil infiltration and the inflammatory response

Coronary atherosclerotic heart disease is an important, worldwide burden on human health. Central muscle infarction is the most dangerous condition, has the highest mortality and disability rates, and is gradually becoming more common among young people. After myocardial infarction, neutrophils recruited to the infarcted area promote the myocardial inflammatory response by releasing proinflammatory factors and chemokines and release matrix metalloproteinases and myeloperoxidases that degrade the extracellular matrix and produce reactive oxygen species, resulting in irreversible myocardial damage and thereby promoting ventricular remodeling. In this study, we constructed a mouse model of myocardial infarction and utilized the CXCR2 receptor inhibitor navarixin (Nav) to reduce neutrophil recruitment after MI. We observed that Nav improved cardiac function, reduced myocardial damage, reduced neutrophil infiltration, reduced inflammatory factor expression and improved cardiac fibrosis in mice. Through transcriptomic analysis, we found that Nav affects signaling pathways such as the innate immune response and the chemokine signaling pathway, thereby decreasing the inflammatory response by reducing neutrophil chemotaxis. This study provides new insights for the use of CXCR2 inhibitors as new therapeutic options for myocardial infarction in the future.

How oxygenation shapes immune responses: emerging roles for physioxia and pathological hypoxia

Most eukaryotes require oxygen for their survival and, with increasing multicellular complexity, oxygen availability and delivery rates vary across the tissues of complex organisms. In humans, healthy tissues have markedly different oxygen gradients, ranging from the hypoxic environment of the bone marrow (where our haematopoietic stem cells reside) to the lungs and their alveoli, which are among the most oxygenated areas of the body. Immune cells are therefore required to adapt to varying oxygen availability as they move from the bone marrow to peripheral organs to mediate their effector functions. These changing oxygen gradients are exaggerated during inflammation, where oxygenation is often depleted owing to alterations in tissue perfusion and increased cellular activity. As such, it is important to consider the effects of oxygenation on shaping the immune response during tissue homeostasis and disease conditions. In this Review, we address the relevance of both physiological oxygenation (physioxia) and disease-associated hypoxia (where cellular oxygen demand outstrips supply) for immune cell functions, discussing the relevance of hypoxia for immune responses in the settings of tissue homeostasis, inflammation, infection, cancer and disease immunotherapy.

Regulated cell death in acute myocardial infarction: Molecular mechanisms and therapeutic implications

Acute myocardial infarction (AMI), primarily caused by coronary atherosclerosis, initiates a series of events that culminate in the obstruction of coronary arteries, resulting in severe myocardial ischemia and hypoxia. The subsequent myocardial ischemia/reperfusion (I/R) injury further aggravates cardiac damage, leading to a decline in heart function and the risk of life-threatening complications. The complex interplay of multiple regulated cell death (RCD) pathways plays a pivotal role in the pathogenesis of AMI. Each RCD pathway is orchestrated by a symphony of molecular regulatory mechanisms, highlighting the dynamic changes and critical roles of key effector molecules. Strategic disruption or inhibition of these molecular targets offers a tantalizing prospect for mitigating or even averting the onset of RCD, thereby limiting the extensive loss of cardiomyocytes and the progression of detrimental myocardial fibrosis. This review systematically summarizes the mechanisms underlying various forms of RCD, provides an in-depth exploration of the pathogenesis of AMI through the lens of RCD, and highlights a range of promising therapeutic targets that hold the potential to revolutionize the management of AMI.

Preliminary evidence of immune infiltration and neutrophil degranulation in peripheral blood of non-obese OSA patients related to cognitive decline

Obstructive sleep apnea (OSA) patients have varying degrees of cognitive impairment, but the specific pathogenic mechanism is still unclear. Meanwhile, poor compliance with continuous positive airway pressure (CPAP) in OSA prompts better solutions. This study aimed to identify differentially expressed genes between the non-obese OSA patients and healthy controls, and to explore potential biomarkers associated with cognitive impairment. Cohorts of healthy control (n = 20) and non-obese, treatment-naïve OSA patients (n = 20) were recruited. We collected their peripheral blood mononuclear cells and neutrophils, and their cognitive performances were evaluated by the Montreal Cognitive Assessment (MoCA). The differentially expressed genes were identified by bioinformatic analysis and confirmed by PCR. Imbalanced immune cell proportions were assessed by Cibersort. Biomarkers related to enriched cellular pathways were measured by ELISA. OSA patients showed a significant decline in overall cognitive function and were associated with higher daytime sleepiness scores. Multiple signaling pathways were enriched in the non-obese OSA cohort, including upregulation of neutrophil-degranulation. Increased monocyte proportion and decreased NK cell proportion were figured out. The relevant genes, including upregulated defensin alpha 4 (DEFA4), haptoglobin (HP), survivin (BIRC5), and suppressed interferon gamma (IFNG) expression were detected. The relative expression of DEFA4 was significantly correlated with the MoCA score and sleep parameters. Biomarkers such as myeloperoxidase (MPO), H2O2, and lipocalin-2, as representatives of neutrophils' activation, elevated significantly in the OSA group. The data demonstrated a positive correlation between MPO and oxygen desaturation index (ODI) and a negative correlation between MPO and lowest oxygen saturation (LSaO2). The level of Lipocalin-2 was positively correlated with apnea-hypopnea index (AHI) and ODI and negatively correlated with LSaO2 and MoCA score. We also observed a negative correlation between H2O2 and mean oxygen saturation (MSaO2). Degranulation of neutrophils was activated in non-obese OSA patients without other complications. The process is related to OSA severity and cognitive impairment, implying its role in pathogenesis.

Von Willebrand factor exacerbates heart failure through formation of neutrophil extracellular traps

BACKGROUND AND AIMS

Heart failure (HF) is a leading cause of mortality worldwide and characterized by significant co-morbidities and dismal prognosis. Neutrophil extracellular traps (NETs) aggravate inflammation in various cardiovascular diseases; however, their function and mechanism of action in HF pathogenesis remain underexplored. This study aimed to investigate the involvement of a novel VWF-SLC44A2-NET axis in HF progression.

METHODS

NET levels were examined in patients with HF and mouse models of transverse aortic constriction (TAC) HF. PAD4 knockout mice and NET inhibitors (GSK-484, DNase I, NEi) were used to evaluate the role of NETs in HF. RNA sequencing was used to investigate the downstream mechanisms. Recombinant human ADAMTS13 (rhADAMTS13), ADAMTS13, and SLC44A2 knockouts were used to identify novel upstream factors of NETs.

RESULTS

Elevated NET levels were observed in patients with HF and TAC mouse models of HF. PAD4 knockout and NET inhibitors improved the cardiac function. Mechanistically, NETs induced mitochondrial dysfunction in cardiomyocytes, inhibiting mitochondrial biogenesis via the NE-TLR4-mediated suppression of PGC-1α. Furthermore, VWF/ADAMTS13 regulated NET formation via SLC44A2. Additionally, sacubitril/valsartan amplifies the cardioprotective effects of the VWF-SLC44A2-NET axis blockade.

CONCLUSIONS

This study established the role of a novel VWF-SLC44A2-NET axis in regulating mitochondrial homeostasis and function, leading to cardiac apoptosis and contributing to HF pathogenesis. Targeting this axis may offer a potential therapeutic approach for HF treatment.

The new insights of hyperbaric oxygen therapy: focus on inflammatory bowel disease

Inflammatory bowel diseases (IBD), with an increasing incidence, pose a significant health burden. Although there have been significant advances in the treatment of IBD, more progress is still needed. Hyperbaric oxygen therapy (HBOT) has been shown to treat a host of conditions such as carbon monoxide poisoning, decompression sickness, and gas gangrene. In the last few years, there has been an increase in research into the use of HBOT as an adjunct to conventional treatment for IBD. Related research has shown that HBOT may exert its therapeutic effects by decreasing oxidative stress, inhibiting mucosal inflammation, promoting ulcer healing, influencing gut microbes, and reducing the incidence of IBD complications. This paper aims to provide a comprehensive review of experimental and clinical trials exploring HBOT as a supplement to IBD treatment strategies.

Low-intensity pulsed ultrasound of different intensities differently affects myocardial ischemia/reperfusion injury by modulating cardiac oxidative stress and inflammatory reaction

Introduction

The prevalence of ischemic heart disease has reached pandemic levels worldwide. Early revascularization is currently the most effective therapy for ischemic heart diseases but paradoxically induces myocardial ischemia/reperfusion (MI/R) injury. Cardiac inflammatory reaction and oxidative stress are primarily involved in the pathology of MI/R injury. Low-intensity pulsed ultrasound (LIPUS) has been demonstrated to reduce cell injury by protecting against inflammatory reaction and oxidative stress in many diseases, including cardiovascular diseases, but rarely on MI/R injury.

Methods

This study was designed to clarify whether LIPUS alleviates MI/R injury by alleviating inflammatory reaction and oxidative stress. Simultaneously, we have also tried to confirm which intensity of the LIPUS might be more suitable to ameliorate the MI/R injury, as well as to clarify the signaling mechanisms. MI/R and simulated ischemia/reperfusion (SI/R) were respectively induced in Sprague Dawley rats and human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs). LIPUS treatment, biochemical measurements, cell death assay, estimation of cardiac oxidative stress and inflammatory reaction, and protein detections by western blotting were performed according to the protocol.

Results

In our study, both in vivo and in vitro, LIPUS of 0.1 W/cm2 (LIPUS0.1) and 0.5 W/cm2 (LIPUS0.5) make no significant difference in the cardiomyocytes under normoxic condition. Under the hypoxic condition, MI/R injury, inflammatory reaction, and oxidative stress were partially ameliorated by LIPUS0.5 but were significantly aggravated by LIPUS of 2.5 W/cm2 (LIPUS2.5) both in vivo and in vitro. The activation of the apoptosis signal-regulating kinase 1 (ASK1)/c-Jun N-terminal kinase (JNK) pathway in cardiomyocytes with MI/R injury was partly rectified LIPUS0.5 both in vivo and in vitro.

Conclusion

Our study firstly demonstrated that LIPUS of different intensities differently affects MI/R injury by regulating cardiac inflammatory reaction and oxidative stress. Modulations on the ASK1/JNK pathway are the signaling mechanism by which LIPUS0.5 exerts cardioprotective effects. LIPUS0.5 is promising for clinical translation in protecting against MI/R injury. This will be great welfare for patients suffering from MI/R injury.

Hypoxia-inducible factor-1α is a biomarker for predicting patients with sepsis

OBJECTIVE

This study aimed to investigate the potential value of serum hypoxia-inducible factor-1α (HIF-1α) concentrations as a biomarker in patients with sepsis.

METHODS

The enrolled patients were divided into the following four groups: the intensive care unit (ICU) control group (n = 33), infection group (n = 29), septic nonshock group (n = 40), and septic shock group (n = 94). An enzyme-linked immunosorbent assay was used to measure serum HIF-1α concentrations on ICU admission. Clinical parameters and laboratory test results were also collected.

RESULTS

Serum HIF-1α concentrations were significantly higher in the infection group, septic nonshock group, and septic shock group than in the ICU control group. Moreover, HIF-1α concentrations were associated with a better predictive ability for diagnosing sepsis than the Acute Physiology and Chronic Health Evaluation II score, procalcitonin concentrations, and lactate concentrations. Patients with sepsis and HIF-1α concentrations >161.14 pg/mL had a poor prognosis.

CONCLUSIONS

Serum HIF-1α concentrations are a useful biomarker for the diagnosis of sepsis and predicting the prognosis of patients.

The Efficacy of Nanoparticle Delivery to Hypoxic Solid Tumors by ciRGD Co-Administration Depends on Neuropilin-1 and Neutrophil Levels

The ability to improve nanoparticle delivery to solid tumors is an actively studied domain, where various mechanisms are looked into. In previous work, the authors have looked into nanoparticle size, tumor vessel normalization, and disintegration, and here it is aimed to continue this work by performing an in-depth mechanistic study on the use of ciRGD peptide co-administration. Using a multiparametric approach, it is observed that ciRGD can improve nanoparticle delivery to the tumor itself, but also to tumor cells specifically better than vessel normalization strategies. The effect depends on the level of tumor perfusion, hypoxia, neutrophil levels, and vessel permeability. This work shows that upon characterizing tumors for these parameters, conditions can be selected that can optimally benefit from ciRGD co-administration as a means to improve NP delivery to solid tumors.

Development and Validation of a Diagnostic Model Based on Hypoxia-Related Genes in Myocardial Infarction

Purpose

Myocardial infarction (MI) is a common cardiovascular disease, and its underlying pathological mechanism remains unclear. We aimed to develop a diagnostic model to distinguish different subtypes of MI.

Patients and Methods

The gene expression profiles of MI from the GEO database and hypoxia-related genes (HRGs) from MSigDB were downloaded. Then, the different MI subtypes based on HRGs were identified with unsupervised clustering. The difference of expression patterns and hypoxic-immune status among different subtypes of MI were investigated. The diagnostic model to distinguish the different subtypes of MI was developed and validated.

Results

Based on HRGs, MI samples were divided into two subtypes, cluster A and cluster B. A total of 211 genes showed significant changes in expression between the two subtypes. Cluster A was characterized by high hypoxia status and low immunity status. Based on weighted gene co-expression network analysis, ROC analysis and LASSO regression algorithm, 5 genes were identified as potential diagnostic markers. Finally, a diagnostic model based on these 5 genes was established, which can distinguish the two subtypes well.

Conclusion

The five hub genes, including ANKRD36, HLTF, KIF3A, OXCT1 and VPS13A, may be associated with the different subtypes of MI.

Inflammation and immunity in the pathogenesis of hypoxic pulmonary hypertension

Hypoxic pulmonary hypertension (HPH) is a complicated vascular disorder characterized by diverse mechanisms that lead to elevated blood pressure in pulmonary circulation. Recent evidence indicates that HPH is not simply a pathological syndrome but is instead a complex lesion of cellular metabolism, inflammation, and proliferation driven by the reprogramming of gene expression patterns. One of the key mechanisms underlying HPH is hypoxia, which drives immune/inflammation to mediate complex vascular homeostasis that collaboratively controls vascular remodeling in the lungs. This is caused by the prolonged infiltration of immune cells and an increase in several pro-inflammatory factors, which ultimately leads to immune dysregulation. Hypoxia has been associated with metabolic reprogramming, immunological dysregulation, and adverse pulmonary vascular remodeling in preclinical studies. Many animal models have been developed to mimic HPH; however, many of them do not accurately represent the human disease state and may not be suitable for testing new therapeutic strategies. The scientific understanding of HPH is rapidly evolving, and recent efforts have focused on understanding the complex interplay among hypoxia, inflammation, and cellular metabolism in the development of this disease. Through continued research and the development of more sophisticated animal models, it is hoped that we will be able to gain a deeper understanding of the underlying mechanisms of HPH and implement more effective therapies for this debilitating disease.

Glutathione peroxidase 3 is a novel clinical diagnostic biomarker and potential therapeutic target for neutrophils in rheumatoid arthritis

BACKGROUND

Neutrophils have a critical role in the pathogenesis of rheumatoid arthritis (RA) with immune system dysfunction. However, the molecular mechanisms of this process mediated by neutrophils still remain elusive. The purpose of the present study is to identify hub genes in neutrophils for diagnosis and treatment of RA utilizing publicly available datasets.

METHODS

Gene expression profiles were downloaded from the Gene Expression Omnibus, and batch-corrected and normalized expression data were obtained using the ComBat package. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis were used to conduct significantly functional analysis and crucial pathways. The resulting co-expression genes modules and hub genes were generated based on the weighted gene co-expression network analysis and visualization by Cytoscape. Flow cytometry was conducted to detect reactive oxygen species (ROS) levels in neutrophils.

RESULTS

Neutrophils underwent transcriptional changes in synovial fluid (SF) of RA patients, different from peripheral blood of healthy controls or patients with RA. Especially, glycolysis, HIF-1 signaling, NADH metabolism, and oxidative stress were affected. These hub genes were strongly linked with classical glycolysis-related genes (ENO1, GAPDH, and PKM) responsible for ROS production. The antioxidant enzyme glutathione peroxidase 3 (GPX3), a ROS scavenger, was first identified as a hub gene in RA neutrophils. Neutrophils from patients with autoinflammatory and autoimmune diseases had markedly enhanced ROS levels, most notably in RA SF.

CONCLUSION

This research recognized hub genes and explored the characteristics of neutrophils in RA. Our findings suggest that the novel hub gene GPX3 is involved in the neutrophil-driven oxidative stress-mediated pathogenesis of RA. It has the potency to be a target for neutrophil-directed RA therapy.

Moonlighting chromatin: when DNA escapes nuclear control

Extracellular chromatin, for example in the form of neutrophil extracellular traps (NETs), is an important element that propels the pathological progression of a plethora of diseases. DNA drives the interferon system, serves as autoantigen, and forms the extracellular scaffold for proteins of the innate immune system. An insufficient clearance of extruded chromatin after the release of DNA from the nucleus into the extracellular milieu can perform a secret task of moonlighting in immune-inflammatory and occlusive disorders. Here, we discuss (I) the cellular events involved in the extracellular release of chromatin and NET formation, (II) the devastating consequence of a dysregulated NET formation, and (III) the imbalance between NET formation and clearance. We include the role of NET formation in the occlusion of vessels and ducts, in lung disease, in autoimmune diseases, in chronic oral disorders, in cancer, in the formation of adhesions, and in traumatic spinal cord injury. To develop effective therapies, it is of utmost importance to target pathways that cause decondensation of chromatin during exaggerated NET formation and aggregation. Alternatively, therapies that support the clearance of extracellular chromatin are conceivable.

Neutrophil intrinsic and extrinsic regulation of NETosis in health and disease

Neutrophil extracellular traps (NETs) evolved to protect the host against microbial infections and are formed by a web-like structure of DNA that is decorated with antimicrobial effectors. Due to their potent inflammatory functions, NETs also cause tissue damage and can favor and/or aggravate inflammatory diseases. This multipronged activity of NETs requires that the induction, release, and degradation of NETs are tightly regulated. Here we describe the key pathways that are intrinsic to neutrophils and regulate NETosis, and we review the most recent findings on how neutrophil extrinsic factors participate in the formation of NETs. In particular, we emphasize how bystander cells contribute to modifying the capacity of neutrophils to undergo NETosis. Finally, we discuss how these neutrophil extrinsic processes can be harnessed to protect the host against the excessive inflammation elicited by uncontrolled NET release.

Insights into the Role of Neutrophils and Neutrophil Extracellular Traps in Causing Cardiovascular Complications in Patients with COVID-19: A Systematic Review

BACKGROUND

The coronavirus disease 2019 (COVID-19) pandemic caused by the SARS-CoV-2 virus has resulted in significant mortality and burdening of healthcare resources. While initially noted as a pulmonary pathology, subsequent studies later identified cardiovascular involvement with high mortalities reported in specific cohorts of patients. While cardiovascular comorbidities were identified early on, the exact manifestation and etiopathology of the infection remained elusive. This systematic review aims to investigate the role of inflammatory pathways, highlighting several culprits including neutrophil extracellular traps (NETs) which have since been extensively investigated.

METHOD

A search was conducted using three databases (MEDLINE; MEDLINE In-Process & Other Non-Indexed Citations and EMBASE). Data from randomized controlled trials (RCT), prospective series, meta-analyses, and unmatched observational studies were considered for the processing of the algorithm and treatment of inflammatory response during SARS-CoV-2 infection. Studies without the SARS-CoV-2 Infection period and case reports were excluded.

RESULTS

A total of 47 studies were included in this study. The role of the acute inflammatory response in the propagation of the systemic inflammatory sequelae of the disease plays a major part in determining outcomes. Some of the mechanisms of activation of these pathways have been highlighted in previous studies and are highlighted.

CONCLUSION

NETs play a pivotal role in the pathogenesis of the inflammatory response. Despite moving into the endemic phase of the disease in most countries, COVID-19 remains an entity that has not been fully understood with long-term effects remaining uncertain and requiring ongoing monitoring and research.