Age-related changes in the local milieu of inflamed tissues cause aberrant neutrophil trafficking and subsequent remote organ damage

MCTR1 ameliorates LPS-induced lung injury by inhibiting neutrophil reverse transendothelial migration

OBJECTIVES

Dysregulated inflammatory responses during sepsis often result in acute lung injury (ALI). Neutrophils activated at the primary site of injury can re-enter the circulation through reverse transendothelial migration (rTEM), subsequently infiltrating other organs and contributing to systemic inflammation and multi-organ damage. The specialized pro-resolving lipid mediator (SPM) maresin conjugate in tissue regeneration 1 (MCTR1) has been shown to mitigate organ injury in sepsis. This study investigated the role of neutrophil rTEM in ALI and examined whether MCTR1 can alleviate ALI by modulating neutrophil rTEM.

METHODS

Lung injury was induced in mice by administrating lipopolysaccharide (LPS). Lung damage was assessed using H&E staining, lung wet-to-dry ratio, inflammatory mediator levels, and protein content in the bronchoalveolar lavage fluid. Neutrophil infiltration in lung tissue was evaluated by immunofluorescence, and flow cytometry was used to quantify rTEM neutrophils. Protein expression of neutrophil elastase (NE) and junctional adhesion molecule-C (JAM-C) was analyzed to assess rTEM activity. The role of CXCR4 in neutrophil rTEM was investigated using the CXCR4 inhibitor AMD3100. Additionally, bone marrow-derived neutrophils were isolated to evaluate the effects of MCTR1 on CXCR4 and GRK2 expression.

RESULTS

MCTR1 alleviated lung injury and inhibited neutrophils rTEM in LPS-induced lung injury. MCTR1 also decreased NE expression and increased JAM-C expression. The CXCR4 inhibitor AMD3100 effectively suppressed neutrophil rTEM and alleviated lung injury. Furthermore, MCTR1 inhibited CXCR4 expression and enhanced GRK2 expression.

CONCLUSIONS

MCTR1 reduces lung damage by upregulating GRK2 to inhibit CXCR4 expression, thereby suppressing neutrophil rTEM in LPS-induced lung injury.

A single-cell spatial chart of the airway wall reveals proinflammatory cellular ecosystems and their interactions in health and asthma

Determining spatial location of cells within tissues gives vital insight into the interactions between resident and inflammatory cells and is a critical factor for uncoupling the mechanisms driving disease. Here, we apply single-cell spatial transcriptomics to reveal the airway wall landscape in health and during asthma. We identified proinflammatory cellular ecosystems that exist within discrete spatial niches in healthy and asthma samples. These cellular hubs are characterized by a high level of chemokine and alarmin expression, along with unique combinations of stromal cells. Mechanistically, we demonstrated that receptors, such as ACKR1, retain immune mediators locally, while amphiregulin-expressing mast cells are prominent within these proinflammatory hubs. Despite anti-inflammatory treatments, the asthma airway mucosa exhibited a distinct remodeling program within these cellular ecosystems, marked by increased proximity between key cell types. This study provides an unprecedented view of the topography of the airway wall, revealing distinct, specific ecosystems within spatial niches to target for therapeutic intervention.

Unraveling immunosenescence in sepsis: from cellular mechanisms to therapeutics

Sepsis is a life-threatening multiple organ dysfunction resulting from a dysregulated host response to infection, and patients with sepsis always exhibit a state of immune disorder characterized by both overwhelming inflammation and immunosuppression. The aging of immune system, namely "immunosenescence", has been reported to be correlated with high morbidity and mortality in elderly patients with sepsis. Initially, immunosenescence was considered as a range of age-related alterations in the immune system. However, increasing evidence has proven that persistent inflammation or even a short-term inflammatory challenge during sepsis could trigger accelerated aging of immune cells, which might further exacerbate inflammatory cytokine storm and promote the shift towards immunosuppression. Thus, premature immunosenescence is found in young sepsis individuals, which further aggravates immune disorders and induces the progression of sepsis. Furthermore, in old sepsis patients, the synergistic effects of both sepsis and aging may cause immunosenescence-associated alterations more significantly, resulting in more severe immune dysfunction and a worse prognosis. Therefore, it is necessary to explore the potential therapeutic strategies targeting immunosenescence during sepsis.

Immunological biomarkers of aging

The immune system has long been recognized for its critical role in the elimination of pathogens and the development of autoimmune diseases, but recent evidence demonstrates that it also contributes to noncommunicable diseases associated with biological aging processes, such as cancer, cardiovascular disease, neurodegeneration, and frailty. This review examines immunological biomarkers of aging, focusing on how the immune system evolves with age and its impact on health and disease. It discusses the historical development of immunological assessments, technological advancements, and the creation of novel biomarkers and models to study immune aging. We also explore the clinical implications of immune aging, such as increased susceptibility to infectious diseases, poor vaccine responses, and a higher incidence of noncommunicable diseases. In summary, we provide a comprehensive overview of current research, highlight the clinical relevance of immune aging, and identify gaps in knowledge that require further investigation.

Adenosine accumulation in the blood of newborn mice weakens antimicrobial host defenses

Pediatric intensive care patients are particularly susceptible to severe bacterial infections because of ineffective neutrophil responses. The reasons why neutrophils of newborns are less responsive than those of adults are not clear. Because adenosine triphosphate and adenosine tightly regulate neutrophils, we studied whether the adenosine triphosphate and adenosine levels in the blood of newborn mice could impair the function of their neutrophils. We observed significant changes in plasma adenosine triphosphate and adenosine levels throughout the lifespan of mice. Adenosine levels in newborns were significantly higher than in older mice, while adenosine triphosphate levels were significantly lower. These changes were particularly striking in newborn and juvenile mice with adenosine triphosphate and adenosine levels of about 80 and 600 nM in newborns vs 130 and 190 nM in juveniles, respectively. The ratios of the adenosine triphosphate vs adenosine levels of newborns were (with 0.2) significantly lower than those of juveniles (1.4) and adults (0.5). These low adenosine triphosphate/adenosine ratios correlated with significantly weakened neutrophil activation responses following in vitro stimulation with a formyl peptide receptor agonist and a markedly higher morbidity and mortality rate of newborns following bacterial infection. We found that enhanced adenosine monophosphate hydrolysis via CD73, a lack of adenosine breakdown by adenosine deaminase, and reduced adenosine uptake by nucleoside transporters are responsible for the low adenosine triphosphate/adenosine ratios in blood of newborn mice. We conclude that the extracellular adenosine accumulation in newborn mice impairs inflammatory responses and reduces the ability of neutrophils to mount effective antimicrobial defenses against bacterial infections.

β-hydroxybutyrylation and O-GlcNAc modifications of STAT1 modulate antiviral defense in aging

Aging changes the protein activity status to affect the body's functions. However, how aging regulates protein posttranslational modifications (PTMs) to modulate the antiviral defense ability of the body remains unclear. Here, we found that aging promotes STAT1 β-hydroxybutyrylation (Kbhb) at Lys592, which inhibits the interaction between STAT1 and type-I interferon (IFN-I) receptor 2 (IFNAR2), thereby attenuating IFN-I-mediated antiviral defense activity. Additionally, we discovered that a small molecule from a plant source, hydroxy camptothecine, can effectively reduce the level of STAT1 Kbhb, thus increasing antiviral defense ability in vivo. Further studies revealed that STAT1 O-GlcNAc modifications at Thr699 block CBP-induced STAT1 Kbhb. Importantly, fructose can improve IFN-I antiviral defense activity by orchestrating STAT1 O-GlcNAc and Kbhb modifications. This study reveals the significance of the switch between STAT1 Kbhb and O-GlcNAc modifications in regulating IFN-I antiviral immunity during aging and provides potential strategies to improve the body's antiviral defense ability in elderly individuals.

Advances in sepsis research: Insights into signaling pathways, organ failure, and emerging intervention strategies

Sepsis is a complex syndrome resulting from an aberrant host response to infection. A hallmark of sepsis is the failure of the immune system to restore balance, characterized by hyperinflammation or immunosuppression. However, the net effect of immune system imbalance and the clinical manifestations are highly heterogeneous among patients. In recent years, research interest has shifted from focusing on the pathogenicity of microorganisms to the molecular mechanisms of host responses which is also associated with biomarkers that can help early diagnose sepsis and guide treatment decisions. Despite significant advancements in medical science, sepsis remains a major challenge in healthcare, contributing to substantial morbidity and mortality worldwide. Further research is needed to improve our understanding of this condition and develop novel therapies to improve outcomes for patients with sepsis. This review explores the related signal pathways of sepsis and underscores recent advancements in understanding its mechanisms. Exploration of diverse biomarkers and the emerging concept of sepsis endotypes offer promising avenues for precision therapy in the future.

New insights on extramedullary granulopoiesis and neutrophil heterogeneity in the spleen and its importance in disease

Neutrophils are traditionally viewed as uncomplicated exterminators that arrive quickly at sites of infection, kill pathogens, and then expire. However, recent studies employing modern transcriptomics coupled with novel imaging modalities have discovered that neutrophils exhibit significant heterogeneity within organs and have complex functional roles ranging from tissue homeostasis to cancer and chronic pathologies. This has revised the view that neutrophils are simplistic butchers, and there has been a resurgent interest in neutrophils. The spleen was described as a granulopoietic organ more than 4 decades ago, and studies indicate that neutrophils are briefly retained in the spleen before returning to circulation after proliferation. Transcriptomic studies have discovered that splenic neutrophils are heterogeneous and distinct compared with those in blood. This suggests that a unique hematopoietic niche exists in the splenic microenvironment, i.e., capable of programming neutrophils in the spleen. During severe systemic inflammation with an increased need of neutrophils, the spleen can adapt by producing neutrophils through emergency granulopoiesis. In this review, we describe the structure and microanatomy of the spleen and examine how cells within the splenic microenvironment help to regulate splenic granulopoiesis. A focus is placed on exploring the increase in splenic granulopoiesis to meet host needs during infection and inflammation. Emerging technologies such as single-cell RNA sequencing, which provide valuable insight into splenic neutrophil development and heterogeneity, are also discussed. Finally, we examine how tumors subvert this natural pathway in the spleen to generate granulocytic suppressor cells to promote tumor growth.

Dysregulation of neutrophil in sepsis: recent insights and advances

Sepsis remains the leading cause of death in intensive care units. Despite newer antimicrobial and supportive therapies, specific treatments are still lacking. Neutrophils are pivotal components of the effector phase of the host immune defense against pathogens and play a crucial role in the control of infections under normal circumstances. In addition to its anti-infective effects, the dysregulation and overactivation of neutrophils may lead to severe inflammation or tissue damage and are potential mechanisms for poor prognosis in sepsis. This review focuses on recent advancements in the understanding of the functional status of neutrophils across various pathological stages of sepsis to explore the mechanisms by which neutrophils participate in sepsis progression and provide insights for the treatment of sepsis by targeting neutrophils.

The 129 strain-derived passenger mutations in ACKR1-deficient mice alter the expression of PYHIN and Fc-gamma receptor genes

Most genetically modified mice have been produced using 129 strain-derived embryonic stem cells. Despite ample backcrosses with other strains, these may retain characteristics for 129 passenger mutations, leading to confounding phenotypes unrelated to targeted genes. Here we show that widely used Ackr1-/-129ES mice have approximately 6 Mb of the 129-derived genome retained adjacently to the Ackr1 locus on chromosome 1, including several characteristic polymorphisms. These most notably affect the expression of PYHIN and Fc-gamma receptor genes in myeloid cells, resulting in the overproduction of IL-1β by activated macrophages and the loss of Fc-gamma receptors on myeloid progenitor cells. Therefore, caution is warranted when interpreting Ackr1-/-129ES mouse phenotypes as being solely due to the ACKR1 deficiency. Our findings call for a careful reevaluation of data from previous studies using Ackr1-/-129ES mice and underscore the limitations and pitfalls inherent to mouse models produced using traditional genetic engineering techniques involving 129 embryonic stem cells.

Neutrophil heterogeneity and plasticity: unveiling the multifaceted roles in health and disease

Neutrophils, the most abundant circulating leukocytes, have long been recognized as key players in innate immunity and inflammation. However, recent discoveries unveil their remarkable heterogeneity and plasticity, challenging the traditional view of neutrophils as a homogeneous population with a limited functional repertoire. Advances in single-cell technologies and functional assays have revealed distinct neutrophil subsets with diverse phenotypes and functions and their ability to adapt to microenvironmental cues. This review provides a comprehensive overview of the multidimensional landscape of neutrophil heterogeneity, discussing the various axes along which diversity manifests, including maturation state, density, surface marker expression, and functional polarization. We highlight the molecular mechanisms underpinning neutrophil plasticity, focusing on the complex interplay of signaling pathways, transcriptional regulators, and epigenetic modifications that shape neutrophil responses. Furthermore, we explore the implications of neutrophil heterogeneity and plasticity in physiological processes and pathological conditions, including host defense, inflammation, tissue repair, and cancer. By integrating insights from cutting-edge research, this review aims to provide a framework for understanding the multifaceted roles of neutrophils and their potential as therapeutic targets in a wide range of diseases.

Immune aging and infectious diseases

ABSTRACT

The rise in global life expectancy has led to an increase in the older population, presenting significant challenges in managing infectious diseases. Aging affects the innate and adaptive immune systems, resulting in chronic low-grade inflammation (inflammaging) and immune function decline (immunosenescence). These changes would impair defense mechanisms, increase susceptibility to infections and reduce vaccine efficacy in older adults. Cellular senescence exacerbates these issues by releasing pro-inflammatory factors, further perpetuating chronic inflammation. Moreover, comorbidities, such as cardiovascular disease and diabetes, which are common in older adults, amplify immune dysfunction, while immunosuppressive medications further complicate responses to infections. This review explores the molecular and cellular mechanisms driving inflammaging and immunosenescence, focusing on genomic instability, telomere attrition, and mitochondrial dysfunction. Additionally, we discussed how aging-associated immune alterations influence responses to bacterial, viral, and parasitic infections and evaluated emerging antiaging strategies, aimed at mitigating these effects to improve health outcomes in the aging population.

Cancer-induced systemic pre-conditioning of distant organs: building a niche for metastatic cells

From their early genesis, tumour cells integrate with the surrounding normal cells to form an abnormal structure that is tightly integrated with the host organism via blood and lymphatic vessels and even neural associations. Using these connections, emerging cancers send a plethora of mediators that efficiently perturb the entire organism and induce changes in distant tissues. These perturbations serendipitously favour early metastatic establishment by promoting a more favourable tissue environment (niche) that supports the persistence of disseminated tumour cells within a foreign tissue. Because the establishment of early metastatic niches represents a key limiting step for metastasis, the creation of a more suitable pre-conditioned tissue strongly enhances metastatic success. In this Review, we provide an updated view of the mechanisms and mediators of primary tumours described so far that induce a pro-metastatic conditioning of distant organs, which favours early metastatic niche formation. We reflect on the nature of cancer-induced systemic conditioning, considering that non-cancer-dependent perturbations of tissue homeostasis are also able to trigger pro-metastatic conditioning. We argue that a more holistic view of the processes catalysing metastatic progression is needed to identify preventive or therapeutic opportunities.

Immunosenescence: Aging and Immune System Decline

Immunosenescence, a systematic reduction in the immune system connected with age, profoundly affects the health and well-being of elderly individuals. This review outlines the hallmark features of immunosenescence, including thymic involution, inflammaging, cellular metabolic adaptations, and hematopoietic changes, and their impact on immune cells such as macrophages, neutrophils, T cells, dendritic cells, B cells, and natural killer (NK) cells. Thymic involution impairs the immune system's capacity to react to novel antigens by reducing thymopoiesis and shifting toward memory T cells. Inflammaging, characterized by chronic systemic inflammation, further impairs immune function. Cellular metabolic adaptations and hematopoietic changes alter immune cell function, contributing to a diminished immune response. Developing ways to reduce immunosenescence and enhance immunological function in the elderly population requires an understanding of these mechanisms.

Single-cell and bulk RNA sequencing-based screening and identification of extracellular trap network-related genes in neutrophils in acute myocardial infarction

BACKGROUND

The neutrophil-mediated generation of neutrophil extracellular traps (NETs) results in an augmented inflammatory response and cellular tissue injury during acute myocardial infarction (AMI). Through the analysis of public database information, we discovered and confirmed putative critical genes involved in NETs-mediated AMI.

METHODS

The AMI dataset GSE66360 and the single-cell dataset GSE163465 were downloaded from the Gene Expression Omnibus database. Key genes were screened by bioinformatics. Quantitative real-time PCR (qRT-PCR) was used to verify the key genes, and then a Mendelian randomization (MR) study was conducted on the basis of the genome-wide association study to determine the causal relationship between key genes and AMI. Dimensionality reduction clustering, pseudo-time series, and cell communication were performed on the single-cell dataset to analyze the key genes screened by bulk RNA sequencing and the dynamic evolution of NETs in the AMI process. Immunohistochemistry and Western blot were used to verify the key genes.

RESULTS

Six key genes, IL1β, S100A12, TLR2, CXCL1, CXCL2, and CCL4, were screened out through bioinformatics. qRT-PCR results showed that compared with the control group, the expression of 5 key genes was upregulated in the AMI group. In the MR study, CXCL1 and CCL4 were observed to have a causal relationship with AMI. Single-cell analysis showed that NETs-related genes CCL4, CXCL2, and IL1β were highly expressed. Combining single cells, qRT-PCR and MR, gene CCL4 was selected as the focus of the study. H9c2 cardiomyocytes simulated myocardial infarction under hypoxia, and the results showed that the expression of gene CCL4 was increased. The immunohistochemical results of gene CCL4 showed that the expression was upregulated in the AMI group.

CONCLUSIONS

We found 6 key genes related to NETs-mediated cell damage during AMI. The results of MR showed that CXCL1 and CCL4 were causally related to AMI. Combining single cells, qRT-PCR and MR, gene CCL4 may play an important role in the AMI process. Our results may provide some insights into neutrophil-mediated cell damage during AMI.

Immune Alterations with Aging: Mechanisms and Intervention Strategies

Aging is the result of a complex interplay of physical, environmental, and social factors, leading to an increased prevalence of chronic age-related diseases that burden health and social care systems. As the global population ages, it is crucial to understand the aged immune system, which undergoes declines in both innate and adaptive immunity. This immune decline exacerbates the aging process, creating a feedback loop that accelerates the onset of diseases, including infectious diseases, autoimmune disorders, and cancer. Intervention strategies, including dietary adjustments, pharmacological treatments, and immunomodulatory therapies, represent promising approaches to counteract immunosenescence. These interventions aim to enhance immune function by improving the activity and interactions of aging-affected immune cells, or by modulating inflammatory responses through the suppression of excessive cytokine secretion and inflammatory pathway activation. Such strategies have the potential to restore immune homeostasis and mitigate age-related inflammation, thus reducing the risk of chronic diseases linked to aging. In summary, this review provides insights into the effects and underlying mechanisms of immunosenescence, as well as its potential interventions, with particular emphasis on the relationship between aging, immunity, and nutritional factors.

Intravital Microscopy With an Airy Beam Light Sheet Microscope Improves Temporal Resolution and Reduces Surgical Trauma

Intravital microscopy has emerged as a powerful imaging tool, which allows the visualization and precise understanding of rapid physiological processes at sites of inflammation in vivo, such as vascular permeability and leukocyte migration. Leukocyte interactions with the vascular endothelium can be characterized in the living organism in the murine cremaster muscle. Here, we present a microscopy technique using an Airy Beam Light Sheet microscope that has significant advantages over our previously used confocal microscopy systems. In comparison, the light sheet microscope offers near isotropic optical resolution and faster acquisition speed, while imaging a larger field of view. With less invasive surgery we can significantly reduce side effects such as bleeding, muscle twitching, and surgical inflammation. However, the increased acquisition speed requires exceptional tissue stability to avoid imaging artefacts. Since respiratory motion is transmitted to the tissue under investigation, we have developed a relocation algorithm that removes motion artefacts from our intravital microscopy images. Using these techniques, we are now able to obtain more detailed 3D time-lapse images of the cremaster vascular microcirculation, which allow us to observe the process of leukocyte emigration into the surrounding tissue with increased temporal resolution in comparison to our previous confocal approach.

Mast cells contribute to T-cell accumulation in the bronchoalveolar space in mice with IL-33-induced airway inflammation

Interleukin (IL)-33 released from airway epithelial cells plays a vital role in shaping type 2 immune responses by binding to the ST2 receptor present in many immune cells, including mast cells (MCs). Intranasal administration of IL-33 in mice induces type 2 lung inflammation, an increase in lung MC progenitors, and transepithelial migration of leukocytes to the bronchoalveolar space. The aim of this study was to determine the contribution of MCs in IL-33-induced lung pathology. Four daily intranasal administrations of IL-33 reduced spirometry-like lung function parameters, induced airway hyperresponsiveness, and increased leukocytes in bronchoalveolar lavage fluid (BAL) in an ST2-dependent manner. MC-deficient (Cpa3cre/+) mice, which lack MCs, had intact spirometry-like lung function but slightly reduced airway hyperresponsiveness, possibly related to reduced IL-33 or serotonin. Strikingly, Cpa3cre/+ mice exposed to IL-33 had 50% reduction in BAL T-cells, and CXCL1 and IL-33 were reduced in the lung. Intranasal IL-33 induced CXCR2 expression in T-cells in a MC-independent fashion. Furthermore, IL-33-induced lung MCs were immunopositive for CXCL1 and localized in the epithelium of wild-type mice. These results suggest that MCs are required to sustain intact lung IL-33 and CXCL1 levels in mice with IL-33-induced airway inflammation, thereby facilitating T-cell accumulation in the bronchoalveolar space.

Light-activated nanoclusters with tunable ROS for wound infection treatment

Infected wounds pose a significant clinical challenge due to bacterial resistance, recurrent infections, and impaired healing. Reactive oxygen species (ROS)-based strategies have shown promise in eradicating bacterial infections. However, the excess ROS in the infection site after treatments may cause irreversible damage to healthy tissues. To address this issue, we developed bovine serum albumin-iridium oxide nanoclusters (BSA-IrOx NCs) which enable photo-regulated ROS generation and scavenging using near infrared (NIR) laser. Upon NIR laser irradiation, BSA-IrOx NCs exhibit enhanced photodynamic therapy, destroying biofilms and killing bacteria. When the NIR laser is off, the nanoclusters' antioxidant enzyme-like activities prevent inflammation and repair damaged tissue through ROS clearance. Transcriptomic and metabolomic analyses revealed that BSA-IrOx NCs inhibit bacterial nitric oxide synthase, blocking bacterial growth and biofilm formation. Furthermore, the nanoclusters repair impaired skin by strengthening cell junctions and reducing mitochondrial damage in a fibroblast model. In vivo studies using rat infected wound models confirmed the efficacy of BSA-IrOx NCs. This study presents a promising strategy for treating biofilm-induced infected wounds by regulating the ROS microenvironment, addressing the challenges associated with current ROS-based antibacterial approaches.

DAMPs in immunosenescence and cancer

Damage-associated molecular patterns (DAMPs) are endogenous molecules released by cells in response to injury or stress, recognized by host pattern recognition receptors that assess the immunological significance of cellular damage. The interaction between DAMPs and innate immune receptors triggers sterile inflammation, which serves a dual purpose: promoting tissue repair and contributing to pathological conditions, including age-related diseases. Chronic inflammation mediated by DAMPs accelerates immunosenescence and influences both tumor progression and anti-tumor immunity, underscoring the critical role of DAMPs in the nexus between aging and cancer. This review explores the characteristics of immunosenescence and its impact on age-related cancers, investigates the various types of DAMPs, their release mechanisms during cell death, and the immune activation pathways they initiate. Additionally, we examine the therapeutic potential of targeting DAMPs in age-related diseases. A detailed understanding of DAMP-induced signal transduction could provide critical insights into immune regulation and support the development of innovative therapeutic strategies.

Atypical chemokine receptors in the immune system

Leukocyte migration is a fundamental component of innate and adaptive immune responses as it governs the recruitment and localization of these motile cells, which is crucial for immune cell priming, effector functions, memory responses and immune regulation. This complex cellular trafficking system is controlled to a large extent via highly regulated production of secreted chemokines and the restricted expression of their membrane-tethered G-protein-coupled receptors. The activity of chemokines and their receptors is also regulated by a subfamily of molecules known as atypical chemokine receptors (ACKRs), which are chemokine receptor-like molecules that do not couple to the classical signalling pathways that promote cell migration in response to chemokine ligation. There has been a great deal of progress in understanding the biology of these receptors and their functions in the immune system in the past decade. Here, we describe the contribution of the various ACKRs to innate and adaptive immune responses, focussing specifically on recent progress. This includes recent findings that have defined the role for ACKRs in sculpting extracellular chemokine gradients, findings that broaden the spectrum of chemokine ligands recognized by these receptors, candidate new additions to ACKR family, and our increasing understanding of the role of these receptors in shaping the migration of innate and adaptive immune cells.

Endothelial Cell-Derived Extracellular Vesicles Promote Aberrant Neutrophil Trafficking and Subsequent Remote Lung Injury

The development of acute respiratory distress syndrome (ARDS) in sepsis is associated with substantial morbidity and mortality. However, the molecular pathogenesis underlying sepsis-induced ARDS remains elusive. Neutrophil heterogeneity and dysfunction contribute to uncontrolled inflammation in patients with ARDS. A specific subset of neutrophils undergoing reverse transendothelial migration (rTEM), which is characterized by an activated phenotype, is implicated in the systemic dissemination of inflammation. Using single-cell RNA sequencing (scRNA-seq), it identified functionally activated neutrophils exhibiting the rTEM phenotype in the lung of a sepsis mouse model using cecal ligation and puncture. The prevalence of neutrophils with the rTEM phenotype is elevated in the blood of patients with sepsis-associated ARDS and is positively correlated with disease severity. Mechanically, scRNA-seq and proteomic analys revealed that inflamed endothelial cell (EC) released extracellular vesicles (EVs) enriched in karyopherin subunit beta-1 (KPNB1), promoting abluminal-to-luminal neutrophil rTEM. Additionally, EC-derived EVs are elevated and positively correlated with the proportion of rTEM neutrophils in clinical sepsis. Collectively, EC-derived EV is identified as a critical regulator of neutrophil rTEM, providing insights into the contribution of rTEM neutrophils to sepsis-associated lung injury.

Macrophage-Expressed Coagulation Factor VII Promotes Adverse Cardiac Remodeling

BACKGROUND

Excess fibrotic remodeling causes cardiac dysfunction in ischemic heart disease, driven by MAP (mitogen-activated protein) kinase-dependent TGF-ß1 (transforming growth factor-ß1) activation by coagulation signaling of myeloid cells. How coagulation-inflammatory circuits can be specifically targeted to achieve beneficial macrophage reprogramming after myocardial infarction (MI) is not completely understood.

METHODS

Mice with permanent ligation of the left anterior descending artery were used to model nonreperfused MI and analyzed by single-cell RNA sequencing, protein expression changes, confocal microscopy, and longitudinal monitoring of recovery. We probed the role of the tissue factor (TF)-FVIIa (activated factor VII)-integrin ß1-PAR2 (protease-activated receptor 2) signaling complex by utilizing genetic mouse models and pharmacological intervention.

RESULTS

Cleavage-insensitive PAR2R38E and myeloid cell integrin ß1-deficient mice had improved cardiac function after MI compared with controls. Proximity ligation assays of monocytic cells demonstrated that colocalization of FVIIa with integrin ß1 was diminished in monocyte/macrophage FVII-deficient mice after MI. Compared with controls, F7fl/fl CX3CR1 (CX3C motif chemokine receptor 1)Cre mice showed reduced TGF-ß1 and MAP kinase activation, as well as cardiac dysfunction after MI, despite unaltered overall recruitment of myeloid cells. Single-cell mRNA sequencing of CD45 (cluster of differentiation 45)+ cells 3 and 7 days after MI uncovered a trajectory from recruited monocytes to inflammatory TF+/TREM (triggered receptor expressed on myeloid cells) 1+ macrophages requiring F7. As early as 7 days after MI, macrophage F7 deletion led to an expansion of reparative Olfml 3 (olfactomedin-like protein 3)+ macrophages and, conversely, to a reduction of TF+/TREM1+ macrophages, which were also reduced in PAR2R38E mice. Short-term treatment from days 1 to 5 after nonreperfused MI with a monoclonal antibody inhibiting the macrophage TF-FVIIa-PAR2 signaling complex without anticoagulant activity improved cardiac dysfunction, decreased excess fibrosis, attenuated vascular endothelial dysfunction, and increased survival 28 days after MI.

CONCLUSIONS

Extravascular TF-FVIIa-PAR2 complex signaling drives inflammatory macrophage polarization in ischemic heart disease. Targeting this signaling complex for specific therapeutic macrophage reprogramming following MI attenuates cardiac fibrosis and improves cardiovascular function.

Neutrophils-biology and diversity

Neutrophils, the most abundant white blood cells in the human circulation, play crucial roles in various diseases, including kidney disease. Traditionally viewed as short-lived pro-inflammatory phagocytes that release reactive oxygen species, cytokines and neutrophil extracellular traps, recent studies have revealed their complexity and heterogeneity, thereby challenging this perception. Neutrophils are now recognized as transcriptionally active cells capable of proliferation and reverse migration, displaying phenotypic and functional heterogeneity. They respond to a wide range of signals and deploy various cargo to influence the activity of other cells in the circulation and in tissues. They can regulate the behavior of multiple immune cell types, exhibit innate immune memory, and contribute to both acute and chronic inflammatory responses while also promoting inflammation resolution in a context-dependent manner. Here, we explore the origin and heterogeneity of neutrophils, their functional diversity, and the cues that regulate their effector functions. We also examine their emerging role in infectious and non-infectious diseases with a particular emphasis on kidney disease. Understanding the complex behavior of neutrophils during tissue injury and inflammation may provide novel insights, thereby paving the way for potential therapeutic strategies to manage acute and chronic conditions. By deciphering their multifaceted role, targeted interventions can be developed to address the intricacies of neutrophil-mediated immune responses and improve disease outcomes.

Age-associated changes in innate and adaptive immunity: role of the gut microbiota

Aging is generally regarded as an irreversible process, and its intricate relationship with the immune system has garnered significant attention due to its profound implications for the health and well-being of the aging population. As people age, a multitude of alterations occur within the immune system, affecting both innate and adaptive immunity. In the realm of innate immunity, aging brings about changes in the number and function of various immune cells, including neutrophils, monocytes, and macrophages. Additionally, certain immune pathways, like the cGAS-STING, become activated. These alterations can potentially result in telomere damage, the disruption of cytokine signaling, and impaired recognition of pathogens. The adaptive immune system, too, undergoes a myriad of changes as age advances. These include shifts in the number, frequency, subtype, and function of T cells and B cells. Furthermore, the human gut microbiota undergoes dynamic changes as a part of the aging process. Notably, the interplay between immune changes and gut microbiota highlights the gut's role in modulating immune responses and maintaining immune homeostasis. The gut microbiota of centenarians exhibits characteristics akin to those found in young individuals, setting it apart from the microbiota observed in typical elderly individuals. This review delves into the current understanding of how aging impacts the immune system and suggests potential strategies for reversing aging through interventions in immune factors.

Senescent endothelial cells promote pathogenic neutrophil trafficking in inflamed tissues

Cellular senescence is a hallmark of advanced age and a major instigator of numerous inflammatory pathologies. While endothelial cell (EC) senescence is aligned with defective vascular functionality, its impact on fundamental inflammatory responses in vivo at single-cell level remain unclear. To directly investigate the role of EC senescence on dynamics of neutrophil-venular wall interactions, we applied high resolution confocal intravital microscopy to inflamed tissues of an EC-specific progeroid mouse model, characterized by profound indicators of EC senescence. Progerin-expressing ECs supported prolonged neutrophil adhesion and crawling in a cell autonomous manner that additionally mediated neutrophil-dependent microvascular leakage. Transcriptomic and immunofluorescence analysis of inflamed tissues identified elevated levels of EC CXCL1 on progerin-expressing ECs and functional blockade of CXCL1 suppressed the dysregulated neutrophil responses elicited by senescent ECs. Similarly, cultured progerin-expressing human ECs exhibited a senescent phenotype, were pro-inflammatory and prompted increased neutrophil attachment and activation. Collectively, our findings support the concept that senescent ECs drive excessive inflammation and provide new insights into the mode, dynamics, and mechanisms of this response at single-cell level.

Understanding the Complex Dynamics of Immunosenescence in Multiple Sclerosis: From Pathogenesis to Treatment

Immunosenescence, the gradual deterioration of immune function with age, holds profound implications for our understanding and management of multiple sclerosis (MS), a chronic autoimmune disease affecting the central nervous system. Traditionally diagnosed in young adults, advancements in disease-modifying therapies and increased life expectancy have led to a growing number of older individuals with MS. This demographic shift underscores the need for a deeper investigation into how age-related alterations in immune function shape the course of MS, influencing disease progression, treatment effectiveness, and overall patient outcomes. Age-related immunosenescence involves changes such as shifts in cytokine profiles, the accumulation of senescent immune cells, and compromised immune surveillance, collectively contributing to a state known as "inflammaging". In the context of MS, these immunological changes disturb the intricate balance between inflammatory and regulatory responses, thereby impacting mechanisms of central immune tolerance and peripheral regulation. This paper stands out by combining the most recent advancements in immunosenescence with both pathophysiological and treatment perspectives on multiple sclerosis, offering a cohesive and accessible discussion that bridges theory and practice, while also introducing novel insights into underexplored concepts such as therapy discontinuation and the latest senolytic, neuroprotective, and remyelination therapies. Enhancing our understanding of these complexities will guide tailored approaches to MS management, ultimately improving clinical outcomes for affected individuals.

Ageing-related bone and immunity changes: insights into the complex interplay between the skeleton and the immune system

Ageing as a natural irreversible process inherently results in the functional deterioration of numerous organ systems and tissues, including the skeletal and immune systems. Recent studies have elucidated the intricate bidirectional interactions between these two systems. In this review, we provide a comprehensive synthesis of molecular mechanisms of cell ageing. We further discuss how age-related skeletal changes influence the immune system and the consequent impact of immune system alterations on the skeletal system. Finally, we highlight the clinical implications of these findings and propose potential strategies to promote healthy ageing and reduce pathologic deterioration of both the skeletal and immune systems.

A mild increase in nutrient signaling to mTORC1 in mice leads to parenchymal damage, myeloid inflammation and shortened lifespan

The mechanistic target of rapamycin complex 1 controls cellular anabolism in response to growth factor signaling and to nutrient sufficiency signaled through the Rag GTPases. Inhibition of mTOR reproducibly extends longevity across eukaryotes. Here we report that mice that endogenously express active mutant variants of RagC exhibit multiple features of parenchymal damage that include senescence, expression of inflammatory molecules, increased myeloid inflammation with extensive features of inflammaging and a ~30% reduction in lifespan. Through bone marrow transplantation experiments, we show that myeloid cells are abnormally activated by signals emanating from dysfunctional RagC-mutant parenchyma, causing neutrophil extravasation that inflicts additional inflammatory damage. Therapeutic suppression of myeloid inflammation in aged RagC-mutant mice attenuates parenchymal damage and extends survival. Together, our findings link mildly increased nutrient signaling to limited lifespan in mammals, and support a two-component process of parenchymal damage and myeloid inflammation that together precipitate a time-dependent organ deterioration that limits longevity.

Age-related dysregulation of CXCL9/10 in monocytes is linked to impaired innate immune responses in a mouse model of Staphylococcus aureus osteomyelitis

BACKGROUND

Age-associated impairments in innate immunity are believed to be a causative factor responsible for severe pathogenesis of Staphylococcus aureus (S. aureus) infection in the bone tissue. However, the basis for age-associated decline in innate immune response upon S. aureus infection remains poorly understood.

RESULTS

Our transcriptional data (GEO: GSE166522) from a mouse model of S. aureus osteomyelitis show up-regulated CXCL9 and CXCL10 (CXCL9/10), which is further confirmed in vitro and in vivo by the present study. Notably, monocytes are a main source for CXCL9/10 production in bone marrow upon S. aureus challenge, but this response declines in middle-aged mice. Interestingly, conditional medium of bone marrow monocytes from middle-aged mice has a strikingly decreased effect on bactericidal functions of neutrophils and macrophages compares with that from young mice. We further show that activation of CXCL9/10-CXCR3 axis between monocytes and macrophages/neutrophils promotes the bactericidal function of the cells, whereas blocking the axis impairs such function. Importantly, treatment with either exogenous CXCL9 or CXCL10 in a middle-aged mice model enhances, while pharmacological inhibition of CXCR3 in young mice model impairs, bacterial clearance and bone marrow structure.

CONCLUSIONS

These findings demonstrate that bone marrow monocytes act as a critical promotor of innate immune response via the CXLCL9/10-CXCR3 axis upon S. aureus infection, and that the increased susceptibility to S. aureus infection in skeleton in an aged host may be largely attributable to the declined induction of CXCR9/10 in monocytes.

Impaired ATP hydrolysis in blood plasma contributes to age-related neutrophil dysfunction

BACKGROUND

The function of polymorphonuclear neutrophils (PMNs) decreases with age, which results in infectious and inflammatory complications in older individuals. The underlying causes are not fully understood. ATP release and autocrine stimulation of purinergic receptors help PMNs combat microbial invaders. Excessive extracellular ATP interferes with these mechanisms and promotes inflammatory PMN responses. Here, we studied whether dysregulated purinergic signaling in PMNs contributes to their dysfunction in older individuals.

RESULTS

Bacterial infection of C57BL/6 mice resulted in exaggerated PMN activation that was significantly greater in old mice (64 weeks) than in young animals (10 weeks). In contrast to young animals, old mice were unable to prevent the systemic spread of bacteria, resulting in lethal sepsis and significantly greater mortality in old mice than in their younger counterparts. We found that the ATP levels in the plasma of mice increased with age and that, along with the extracellular accumulation of ATP, the PMNs of old mice became increasingly primed. Stimulation of the formyl peptide receptors of those primed PMNs triggered inflammatory responses that were significantly more pronounced in old mice than in young animals. However, bacterial phagocytosis and killing by PMNs of old mice were significantly lower than that of young mice. These age-dependent PMN dysfunctions correlated with a decrease in the enzymatic activity of plasma ATPases that convert extracellular ATP to adenosine. ATPases depend on divalent metal ions, including Ca2+, Mg2+, and Zn2+, and we found that depletion of these ions blocked the hydrolysis of ATP and the formation of adenosine in human blood, resulting in ATP accumulation and dysregulation of PMN functions equivalent to those observed in response to aging.

CONCLUSIONS

Our findings suggest that impaired hydrolysis of plasma ATP dysregulates PMN function in older individuals. We conclude that strategies aimed at restoring plasma ATPase activity may offer novel therapeutic opportunities to reduce immune dysfunction, inflammation, and infectious complications in older patients.

Endogenous Retroviruses Unveiled: A Comprehensive Review of Inflammatory Signaling/Senescence-Related Pathways and Therapeutic Strategies

Endogenous retroviruses (ERVs), a subset of genomic transposable elements (TEs) in a broader sense, have remained latent within mammalian genomes for tens of millions of years. These genetic elements are typically in a silenced state due to stringent regulatory mechanisms. However, under specific conditions, they can become activated, triggering inflammatory responses through diverse mechanisms. This activation has been shown to play a potential role in various neurological disorders, tumors, and cellular senescence. Consequently, the regulation of ERV expression through various methods holds promise for clinical applications in disease treatment. ERVs also engage in interactions with a variety of exogenous viruses, thereby influencing the outcomes of viral infectious diseases. This article comprehensively reviews the pathogenic cascade of ERVs, encompassing activation, inflammation, associated diseases, senescence, and interplay with viruses. Additionally, it outlines therapeutic strategies targeting ERVs with the aim of offering novel research directions for understanding the relationship between ERVs and diseases, along with corresponding treatment modalities.

Predictive Value of Combined HbA1c and Neutrophil-to-Lymphocyte Ratio for Diabetic Peripheral Neuropathy in Type 2 Diabetes

BACKGROUND Diabetic peripheral neuropathy (DPN) is a prevalent complication affecting over 60% of type 2 diabetes patients. Early diagnosis is challenging, leading to irreversible impacts on quality of life. This study explores the predictive value of combining HbA1c and Neutrophil-to-Lymphocyte Ratio (NLR) for early DPN detection. MATERIAL AND METHODS An observational study was conducted at the First People's Hospital of Linping District, Hangzhou spanning from May 2019 to July 2020. Data on sex, age, biochemical measurements were collected from electronic medical records and analyzed. Employing multivariate logistic regression analysis, we sought to comprehend the factors influencing the development of DPN. To assess the predictive value of individual and combined testing for DPN, a receiver operating characteristic (ROC) curve was plotted. The data analysis was executed using R software (Version: 4.1.0). RESULTS The univariate and multivariate logistic regression analysis identified the level of glycated hemoglobin (HbA1C) (OR=1.94, 95% CI: 1.27-3.14) and neutrophil-to-lymphocyte ratio (NLR) (OR=4.60, 95% CI: 1.15-22.62, P=0.04) as significant risk factors for the development of DPN. Receiver operating characteristic (ROC) curve analysis demonstrated that HbA1c, NLR, and their combined detection exhibited high sensitivity in predicting the development of DPN (71.60%, 90.00%, and 97.2%, respectively), with moderate specificity (63.8%, 45.00%, and 50.00%, respectively). The area under the curve (AUC) for these predictors was 0.703, 0.661, and 0.733, respectively. CONCLUSIONS HbA1c and NLR emerge as noteworthy risk indicators associated with the manifestation of DPN in patients with type 2 diabetes. The combined detection of HbA1c and NLR exhibits a heightened predictive value for the development of DPN.

Harnessing anti-inflammatory pathways and macrophage nano delivery to treat inflammatory and fibrotic disorders

Targeting specific organs and cell types using nanotechnology and sophisticated delivery methods has been at the forefront of applicative biomedical sciences lately. Macrophages are an appealing target for immunomodulation by nanodelivery as they are heavily involved in various aspects of many diseases and are highly plastic in their nature. Their continuum of functional "polarization" states has been a research focus for many years yielding a profound understanding of various aspects of these cells. The ability of monocyte-derived macrophages to metamorphose from pro-inflammatory to reparative and consequently to pro-resolving effectors has raised significant interest in its therapeutic potential. Here, we briefly survey macrophages' ontogeny and various polarization phenotypes, highlighting their function in the inflammation-resolution shift. We review their inducing mediators, signaling pathways, and biological programs with emphasis on the nucleic acid sensing-IFN-I axis. We also portray the polarization spectrum of macrophages and the characteristics of their transition between different subtypes. Finally, we highlighted different current drug delivery methods for targeting macrophages with emphasis on nanotargeting that might lead to breakthroughs in the treatment of wound healing, bone regeneration, autoimmune, and fibrotic diseases.

The Dual Role of Neutrophil Extracellular Traps (NETs) in Sepsis and Ischemia-Reperfusion Injury: Comparative Analysis across Murine Models

A better understanding of the function of neutrophil extracellular traps (NETs) may facilitate the development of interventions for sepsis. The study aims to investigate the formation and degradation of NETs in three murine sepsis models and to analyze the production of reactive oxygen species (ROS) during NET formation. Murine sepsis was induced by midgut volvulus (720° for 15 min), cecal ligation and puncture (CLP), or the application of lipopolysaccharide (LPS) (10 mg/kg body weight i.p.). NET formation and degradation was modulated using mice that were genetically deficient for peptidyl arginine deiminase-4 (PAD4-KO) or DNase1 and 1L3 (DNase1/1L3-DKO). After 48 h, mice were killed. Plasma levels of circulating free DNA (cfDNA) and neutrophil elastase (NE) were quantified to assess NET formation and degradation. Plasma deoxyribonuclease1 (DNase1) protein levels, as well as tissue malondialdehyde (MDA) activity and glutathione peroxidase (GPx) activity, were quantified. DNase1 and DNase1L3 in liver, intestine, spleen, and lung tissues were assessed. The applied sepsis models resulted in a simultaneous increase in NET formation and oxidative stress. NET formation and survival differed in the three models. In contrast to LPS and Volvulus, CLP-induced sepsis showed a decreased and increased 48 h survival in PAD4-KO and DNase1/1L3-DKO mice, when compared to WT mice, respectively. PAD4-KO mice showed decreased formation of NETs and ROS, while DNase1/1L3-DKO mice with impaired NET degradation accumulated ROS and chronicled the septic state. The findings indicate a dual role for NET formation and degradation in sepsis and ischemia-reperfusion (I/R) injury: NETs seem to exhibit a protective capacity in certain sepsis paradigms (CLP model), whereas, collectively, they seem to contribute adversely to scenarios where sepsis is combined with ischemia-reperfusion (volvulus).

Age-related bone diseases: Role of inflammaging

Bone aging is characterized by an imbalance in the physiological and pathological processes of osteogenesis, osteoclastogenesis, adipogenesis, and chondrogenesis, resulting in exacerbated bone loss and the development of age-related bone diseases, including osteoporosis, osteoarthritis, rheumatoid arthritis, and periodontitis. Inflammaging, a novel concept in the field of aging research, pertains to the persistent and gradual escalation of pro-inflammatory reactions during the aging process. This phenomenon is distinguished by its low intensity, systemic nature, absence of symptoms, and potential for management. The mechanisms by which inflammaging contribute to age-related chronic diseases, particularly in the context of age-related bone diseases, remain unclear. The precise manner in which systemic inflammation induces bone aging and consequently contributes to the development of age-related bone diseases has yet to be fully elucidated. This article primarily examines the mechanisms underlying inflammaging and its association with age-related bone diseases, to elucidate the potential mechanisms of inflammaging in age-related bone diseases and offer insights for developing preventive and therapeutic strategies for such conditions.

Neutrophils in Physiology and Pathology

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

Dynamic Multiplex Tissue Imaging in Inflammation Research

Inflammation is a highly dynamic process with immune cells that continuously interact with each other and parenchymal components as they migrate through tissue. The dynamic cellular responses and interaction patterns are a function of the complex tissue environment that cannot be fully reconstructed ex vivo, making it necessary to assess cell dynamics and changing spatial patterning in vivo. These dynamics often play out deep within tissues, requiring the optical focus to be placed far below the surface of an opaque organ. With the emergence of commercially available two-photon excitation lasers that can be combined with existing imaging systems, new avenues for imaging deep tissues over long periods of time have become available. We discuss a selected subset of studies illustrating how two-photon microscopy (2PM) has helped to relate the dynamics of immune cells to their in situ function and to understand the molecular patterns that govern their behavior in vivo. We also review some key practical aspects of 2PM methods and point out issues that can confound the results, so that readers can better evaluate the reliability of conclusions drawn using this technology.

Age-related exacerbation of lung damage after trauma is associated with increased expression of inflammasome components

Background

Trauma, a significant global cause of mortality and disability, often leads to fractures and hemorrhagic shock, initiating an exaggerated inflammatory response, which harms distant organs, particularly the lungs. Elderly individuals are more vulnerable to immune dysregulation post-trauma, leading to heightened organ damage, infections, and poor health outcomes. This study investigates the role of NF-κB and inflammasomes in lung damage among aged mice post-trauma.

Methods

Twelve male C57BL/6J mice underwent hemorrhagic shock and a femoral fracture (osteotomy) with external fixation (Fx) (trauma/hemorrhage, THFx), while another 12 underwent sham procedures. Mice from young (17-26 weeks) and aged (64-72 weeks) groups (n=6) were included. After 24h, lung injury was assessed by hematoxylin-eosin staining, prosurfactant protein C (SPC) levels, HMGB1, and Muc5ac qRT-PCR. Gene expression of Nlrp3 and Il-1β, and protein levels of IL-6 and IL-1β in lung tissue and bronchoalveolar lavage fluid were determined. Levels of lung-infiltrating polymorphonuclear leukocytes (PMNL) and activated caspase-3 expression to assess apoptosis, as well as NLRP3, ASC, and Gasdermin D (GSDMD) to assess the expression of inflammasome components were analyzed via immunostaining. To investigate the role of NF-κB signaling, protein expression of phosphorylated and non-phosphorylated p50 were determined by western blot.

Results

Muc5ac, and SPC as lung protective proteins, significantly declined in THFx versus sham. THFx-aged exhibited significantly lower SPC and higher HMGB1 levels versus THFx-young. THFx significantly increased activated caspase-3 versus both sham groups, and THFx-aged had significantly more caspase-3 positive cells versus THFx-young. IL-6 significantly increased in both sham and THFx-aged groups versus corresponding young groups. THFx significantly enhanced PMNL in both groups versus corresponding sham groups. This increase was further heightened in THFx-aged versus THFx-young. Expression of p50 and phosphorylated p50 increased in all aged groups, and THFx-induced p50 phosphorylation significantly increased in THFx-aged versus THFx-young. THFx increased the expression of inflammasome markers IL-1β, NLRP3, ASC and GSDMD versus sham, and aging further amplified these changes significantly.

Conclusion

This study's findings suggest that the aging process exacerbates the excessive inflammatory response and damage to the lung following trauma. The underlying mechanisms are associated with enhanced activation of NF-κB and increased expression of inflammasome components.

A metabolic perspective of the neutrophil life cycle: new avenues in immunometabolism

Neutrophils are the most abundant innate immune cells. Multiple mechanisms allow them to engage a wide range of metabolic pathways for biosynthesis and bioenergetics for mediating biological processes such as development in the bone marrow and antimicrobial activity such as ROS production and NET formation, inflammation and tissue repair. We first discuss recent work on neutrophil development and functions and the metabolic processes to regulate granulopoiesis, neutrophil migration and trafficking as well as effector functions. We then discuss metabolic syndromes with impaired neutrophil functions that are influenced by genetic and environmental factors of nutrient availability and usage. Here, we particularly focus on the role of specific macronutrients, such as glucose, fatty acids, and protein, as well as micronutrients such as vitamin B3, in regulating neutrophil biology and how this regulation impacts host health. A special section of this review primarily discusses that the ways nutrient deficiencies could impact neutrophil biology and increase infection susceptibility. We emphasize biochemical approaches to explore neutrophil metabolism in relation to development and functions. Lastly, we discuss opportunities and challenges to neutrophil-centered therapeutic approaches in immune-driven diseases and highlight unanswered questions to guide future discoveries.

Neutrophil heterogeneity and aging: implications for COVID-19 and wound healing

Neutrophils play a critical role in the immune response to infection and tissue injury. However, recent studies have shown that neutrophils are a heterogeneous population with distinct subtypes that differ in their functional properties. Moreover, aging can alter neutrophil function and exacerbate immune dysregulation. In this review, we discuss the concept of neutrophil heterogeneity and how it may be affected by aging. We then examine the implications of neutrophil heterogeneity and aging for COVID-19 pathogenesis and wound healing. Specifically, we summarize the evidence for neutrophil involvement in COVID-19 and the potential mechanisms underlying neutrophil recruitment and activation in this disease. We also review the literature on the role of neutrophils in the wound healing process and how aging and neutrophil heterogeneity may impact wound healing outcomes. Finally, we discuss the potential for neutrophil-targeted therapies to improve clinical outcomes in COVID-19 and wound healing.

A genomic perspective of the aging human and mouse lung with a focus on immune response and cellular senescence

BACKGROUND

The aging lung is a complex process and influenced by various stressors, especially airborne pathogens and xenobiotics. Additionally, a lifetime exposure to antigens results in structural and functional changes of the lung; yet an understanding of the cell type specific responses remains elusive. To gain insight into age-related changes in lung function and inflammaging, we evaluated 89 mouse and 414 individual human lung genomic data sets with a focus on genes mechanistically linked to extracellular matrix (ECM), cellular senescence, immune response and pulmonary surfactant, and we interrogated single cell RNAseq data to fingerprint cell type specific changes.

RESULTS

We identified 117 and 68 mouse and human genes linked to ECM remodeling which accounted for 46% and 27%, respectively of all ECM coding genes. Furthermore, we identified 73 and 31 mouse and human genes linked to cellular senescence, and the majority code for the senescence associated secretory phenotype. These cytokines, chemokines and growth factors are primarily secreted by macrophages and fibroblasts. Single-cell RNAseq data confirmed age-related induced expression of marker genes of macrophages, neutrophil, eosinophil, dendritic, NK-, CD4+, CD8+-T and B cells in the lung of aged mice. This included the highly significant regulation of 20 genes coding for the CD3-T-cell receptor complex. Conversely, for the human lung we primarily observed macrophage and CD4+ and CD8+ marker genes as changed with age. Additionally, we noted an age-related induced expression of marker genes for mouse basal, ciliated, club and goblet cells, while for the human lung, fibroblasts and myofibroblasts marker genes increased with age. Therefore, we infer a change in cellular activity of these cell types with age. Furthermore, we identified predominantly repressed expression of surfactant coding genes, especially the surfactant transporter Abca3, thus highlighting remodeling of surfactant lipids with implications for the production of inflammatory lipids and immune response.

CONCLUSION

We report the genomic landscape of the aging lung and provide a rationale for its growing stiffness and age-related inflammation. By comparing the mouse and human pulmonary genome, we identified important differences between the two species and highlight the complex interplay of inflammaging, senescence and the link to ECM remodeling in healthy but aged individuals.

Association between neutrophil-to-albumin ratio and long-term mortality of aneurysmal subarachnoid hemorrhage

OBJECTIVE

The prognosis of aneurysmal subarachnoid hemorrhage (aSAH) survivors is concerning. The goal of this study was to investigate and demonstrate the relationship between the neutrophil-to-albumin ratio (NAR) and long-term mortality of aSAH survivors.

METHODS

A retrospective observational cohort study was conducted at Sichuan University West China Hospital between January 2009 and June 2019. The investigation of relationship between NAR and long-term mortality was conducted using univariable and multivariable Cox regression models. To demonstrate the predictive performance of different biomarkers over time, time-dependent receiver operating characteristic curve (ROC) analysis and decision curve analysis (DCA) were created.

RESULTS

In total, 3173 aSAH patients were included in this study. There was a strong and continuous relationship between NAR levels and long-term mortality (HR 3.23 95% CI 2.75-3.79, p < 0.001). After adjustment, the result was still significant (adjusted HR 1.78 95% CI 1.49-2.12). Compared with patients with the lowest quartile (< 0.15) of NAR levels, the risk of long-term mortality in the other groups was higher (0.15-0.20: adjusted HR 1.30 95% CI 0.97-1.73; 0.20-0.28: adjusted HR 1.37 95% CI 1.03-1.82; >0.28: adjusted HR 1.74 95% CI 1.30-2.32). Results in survivors were found to be still robust. Moreover, out of all the inflammatory markers studied, NAR demonstrated the highest correlation with long-term mortality.

CONCLUSIONS

A high level of NAR was associated with increased long-term mortality among patients with aSAH. NAR was a promising inflammatory marker for long-term mortality of aSAH.

Metabolic reprogramming in inflammaging and aging in T cells

Aging represents an emerging challenge for public health due to the declined immune responses against pathogens, weakened vaccination efficacy, and disturbed tissue homeostasis. Metabolic alterations in cellular and systemic levels are also known to be cardinal features of aging. Moreover, cellular metabolism has emerged to provide regulations to guide immune cell behavior via modulations on signaling cascades and epigenetic landscape, and the aberrant aging process in immune cells can lead to inflammaging, a chronic and low-grade inflammation that facilitates aging by perturbing homeostasis in tissues and organs. Here, we review how the metabolic program in T cells is influenced by the aging process and how aged T cells modulate inflammaging. In addition, we discuss the potential approaches to reverse or ameliorate aging by rewiring the metabolic programming of immune cells.

Neutrophil diversity and plasticity: Implications for organ transplantation

Neutrophils, as the first defenders against external microbes and stimuli, are highly active and finely regulated innate immune cells. Emerging evidence has challenged the conventional dogma that neutrophils are a homogeneous population with a short lifespan that promotes tissue damage. Recent findings on neutrophil diversity and plasticity in homeostatic and disease states have centered on neutrophils in the circulation. In contrast, a comprehensive understanding of tissue-specialized neutrophils in health and disease is still lacking. This article will first discuss how multiomics advances have contributed to our understanding of neutrophil heterogeneity and diversification in resting and pathological settings. This discussion will be followed by a focus on the heterogeneity and role of neutrophils in solid organ transplantation and how neutrophils may contribute to transplant-related complications. The goal of this article is to provide an overview of the research on the involvement of neutrophils in transplantation, with the aim that this may draw attention to an underappreciated area of neutrophil research.

Impact of age on liver damage, inflammation, and molecular signaling pathways in response to femoral fracture and hemorrhage

Background

Trauma causes disability and mortality globally, leading to fractures and hemorrhagic shock. This can trigger an irregular inflammatory response that damages remote organs, including liver. Aging increases the susceptibility to dysregulated immune responses following trauma, raising the risk of organ damage, infections, and higher morbidity and mortality in elderly patients. This study investigates how aging affects liver inflammation and damage post-trauma.

Methods

24 male C57BL/6J mice were randomly divided into four groups. Twelve young (17-26 weeks) and 12 aged (64-72 weeks) mice were included. Mice further underwent either hemorrhagic shock (trauma/hemorrhage, TH), and femoral fracture (osteotomy) with external fixation (Fx) (THFx, n=6) or sham procedures (n=6). After 24 hours, mice were sacrificed. Liver injury and apoptosis were evaluated using hematoxylin-eosin staining and activated caspase-3 immunostaining. CXCL1 and infiltrating polymorphonuclear leukocytes (PMNL) in the liver were assessed by immunostaining, and concentrations of CXCL1, TNF, IL-1β, and IL-10 in the liver tissue were determined by ELISA. Gene expression of Tnf, Cxcl1, Il-1β, and Cxcl2 in the liver tissue was determined by qRT-PCR. Finally, western blot was used to determine protein expression levels of IκBα, Akt, and their phosphorylated forms.

Results

THFx caused liver damage and increased presence of active caspase-3-positive cells compared to the corresponding sham group. THFx aged group had more severe liver injury than the young group. CXCL1 and PMNL levels were significantly higher in both aged groups, and THFx caused a greater increase in CXCL and PMNL levels in aged compared to the young group. Pro-inflammatory TNF and IL-1β levels were elevated in aged groups, further intensified by THFx. Anti-inflammatory IL-10 levels were lower in aged groups. Tnf and Cxcl1 gene expression was enhanced in the aged sham group. Phosphorylation ratio of IκBα was significantly increased in the aged sham group versus young sham group. THFx-induced IκBα phosphorylation in the young group was significantly reduced in the aged THFx group. Akt phosphorylation was significantly reduced in the THFx aged group compared to the THFx young group.

Conclusion

The findings indicate that aging may lead to increased vulnerability to liver injury and inflammation following trauma due to dysregulated immune responses.

Microbial-Immune Crosstalk in Elderly-Onset Inflammatory Bowel Disease: Unchartered Territory

Elderly-onset inflammatory bowel disease [IBD] patients exhibit a distinct natural history compared to younger IBD patients, with unique disease phenotypes, differential responses to therapy, and increased surgical morbidity and mortality. Despite the foreseeable high demand for personalized medicine and specialized IBD care in the elderly, current paradigms of IBD management fail to capture the required nuances of care for elderly-onset IBD patients. Our review postulates the roles of systemic and mucosal immunosenescence, inflammageing and a dysbiotic microbial ecosystem in the pathophysiology of elderly-onset IBD. Ultimately, a better understanding of elderly-onset IBD can lead to improved patient outcomes and the tailoring of future preventative and treatment strategies.

The double-edged role of neutrophil heterogeneity in inflammatory diseases and cancers

Neutrophils are important immune cells act as the body's first line of defense against infection and respond to diverse inflammatory cues. Many studies have demonstrated that neutrophils display plasticity in inflammatory diseases and cancers. Clarifying the role of neutrophil heterogeneity in inflammatory diseases and cancers will contribute to the development of novel treatment strategies. In this review, we have presented a review on the development of the understanding on neutrophil heterogeneity from the traditional perspective and a high-resolution viewpoint. A growing body of evidence has confirmed the double-edged role of neutrophils in inflammatory diseases and tumors. This may be due to a lack of precise understanding of the role of specific neutrophil subsets in the disease. Thus, elucidating specific neutrophil subsets involved in diseases would benefit the development of precision medicine. Thusly, we have summarized the relevance and actions of neutrophil heterogeneity in inflammatory diseases and cancers comprehensively. Meanwhile, we also discussed the potential intervention strategy for neutrophils. This review is intended to deepen our understanding of neutrophil heterogeneity in inflammatory diseases and cancers, while hold promise for precise treatment of neutrophil-related diseases.

GPR35 and mediators from platelets and mast cells in neutrophil migration and inflammation

Neutrophil recruitment from circulation to sites of inflammation is guided by multiple chemoattractant cues emanating from tissue cells, immune cells, and platelets. Here, we focus on the function of one G-protein coupled receptor, GPR35, in neutrophil recruitment. GPR35 has been challenging to study due the description of multiple ligands and G-protein couplings. Recently, we found that GPR35-expressing hematopoietic cells respond to the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA). We discuss distinct response profiles of GPR35 to 5-HIAA compared to other ligands. To place the functions of 5-HIAA in context, we summarize the actions of serotonin in vascular biology and leukocyte recruitment. Important sources of serotonin and 5-HIAA are platelets and mast cells. We discuss the dynamics of cell migration into inflamed tissues and how multiple platelet and mast cell-derived mediators, including 5-HIAA, cooperate to promote neutrophil recruitment. Additional actions of GPR35 in tissue physiology are reviewed. Finally, we discuss how clinically approved drugs that modulate serotonin uptake and metabolism may influence 5-HIAA-GPR35 function, and we speculate about broader influences of the GPR35 ligand-receptor system in immunity and disease.

Granulocyte development, tissue recruitment, and function during allergic inflammation

Granulocytes provide a fast innate response to pathogens and allergens. In allergy and anti-helminth immunity, epithelial cells of damaged barriers release alarmins like IL-25, IL-33, and thymic stromal lymphopoietin (TSLP) but also chemokines like CXCL1 or CCL11 to promote cell recruitment and inflammation. In addition, mast cells positioned at barrier tissue sites also quickly release mediators upon specifically sensing antigens through IgE bound to FcεR1 on their surface. Released mediators induce the recruitment of different granulocytes in a timely ordered manner. First, neutrophils extravasate from the blood vasculature to the side of alarmin release and promote a potent inflammatory response. Alarmins and activated mast cells further promote activation of ILC2s and recruitment of basophils and eosinophils, which inhibit neutrophil recruitment and enhance tissue type 2 immunity. In addition to their potent pro-inflammatory effector functions, granulocytes can also contribute to termination and resolution of inflammation. Here, we summarize the development and tissue recruitment of granulocyte subsets, and describe general effector functions and aspects of their increasingly appreciated role in limiting tissue damage. We further discuss targeting approaches for therapeutic interventions in allergic disorders.