More friend than foe: the emerging role of neutrophils in tissue repair

The role of interleukin-33 in organ fibrosis

Interleukin (IL)-33 is highly expressed in the nucleus of cells present at barrier sites and signals via the ST2 receptor. IL-33 signalling via ST2 is essential for return to tissue homeostasis after acute inflammation, promoting fibrinogenesis and wound healing at injury sites. However, this wound-healing response becomes aberrant during chronic or sustained inflammation, leading to transforming growth factor beta (TGF-β) release, excessive extracellular matrix deposition, and fibrosis. This review addresses the role of the IL-33 pathway in fibrotic diseases of the lung, liver, gastrointestinal tract, skin, kidney and heart. In the lung and liver, IL-33 release leads to the activation of pro-fibrotic TGF-β, and in these sites, IL-33 has clear pro-fibrotic roles. In the gastrointestinal tract, skin, and kidney, the role of IL-33 is more complex, being both pro-fibrotic and tissue protective. Finally, in the heart, IL-33 serves cardioprotective functions by favouring tissue healing and preventing cardiomyocyte death. Altogether, this review indicates the presence of an unclear and delicate balance between resolving and pro-fibrotic capabilities of IL-33, which has a central role in the modulation of type 2 inflammation and fibrosis in response to tissue injury.

Targeting Signaling Pathway Downstream of RIG-I/MAVS in the CNS Stimulates Production of Endogenous Type I IFN and Suppresses EAE

Type I interferons (IFN), including IFNβ, play a protective role in multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). Type I IFNs are induced by the stimulation of innate signaling, including via cytoplasmic RIG-I-like receptors. In the present study, we investigated the potential effect of a chimeric protein containing the key domain of RIG-I signaling in the production of CNS endogenous IFNβ and asked whether this would exert a therapeutic effect against EAE. We intrathecally administered an adeno-associated virus vector (AAV) encoding a fusion protein comprising RIG-I 2CARD domains (C) and the first 200 amino acids of mitochondrial antiviral-signaling protein (MAVS) (M) (AAV-CM). In vivo imaging in IFNβ/luciferase reporter mice revealed that a single intrathecal injection of AAV-CM resulted in dose-dependent and sustained IFNβ expression within the CNS. IFNβ expression was significantly increased for 7 days. Immunofluorescent staining in IFNβ-YFP reporter mice revealed extraparenchymal CD45+ cells, choroid plexus, and astrocytes as sources of IFNβ. Moreover, intrathecal administration of AAV-CM at the onset of EAE induced the suppression of EAE, which was IFN-I-dependent. These findings suggest that accessing the signaling pathway downstream of RIG-I represents a promising therapeutic strategy for inflammatory CNS diseases, such as MS.

Narrative Review: Glucocorticoids in Alcoholic Hepatitis—Benefits, Side Effects, and Mechanisms

Alcoholic hepatitis is a major health and economic burden worldwide. Glucocorticoids (GCs) are the only first-line drugs recommended to treat severe alcoholic hepatitis (sAH), with limited short-term efficacy and significant side effects. In this review, I summarize the major benefits and side effects of GC therapy in sAH and the potential underlying mechanisms. The review of the literature and data mining clearly indicate that the hepatic signaling of glucocorticoid receptor (GR) is markedly impaired in sAH patients. The impaired GR signaling causes hepatic down-regulation of genes essential for gluconeogenesis, lipid catabolism, cytoprotection, and anti-inflammation in sAH patients. The efficacy of GCs in sAH may be compromised by GC resistance and/or GC’s extrahepatic side effects, particularly the side effects of intestinal epithelial GR on gut permeability and inflammation in AH. Prednisolone, a major GC used for sAH, activates both the GR and mineralocorticoid receptor (MR). When GC non-responsiveness occurs in sAH patients, the activation of MR by prednisolone might increase the risk of alcohol abuse, liver fibrosis, and acute kidney injury. To improve the GC therapy of sAH, the effort should be focused on developing the biomarker(s) for GC responsiveness, liver-targeting GR agonists, and strategies to overcome GC non-responsiveness and prevent alcohol relapse in sAH patients.

Wound healing in aged skin exhibits systems-level alterations in cellular composition and cell-cell communication

Delayed and often impaired wound healing in the elderly presents major medical and socioeconomic challenges. A comprehensive understanding of the cellular/molecular changes that shape complex cell-cell communications in aged skin wounds is lacking. Here, we use single-cell RNA sequencing to define the epithelial, fibroblast, immune cell types, and encompassing heterogeneities in young and aged skin during homeostasis and identify major changes in cell compositions, kinetics, and molecular profiles during wound healing. Our comparative study uncovers a more pronounced inflammatory phenotype in aged skin wounds, featuring neutrophil persistence and higher abundance of an inflammatory/glycolytic Arg1^Hi macrophage subset that is more likely to signal to fibroblasts via interleukin (IL)-1 than in young counterparts. We predict systems-level differences in the number, strength, route, and signaling mediators of putative cell-cell communications in young and aged skin wounds. Our study exposes numerous cellular/molecular targets for functional interrogation and provides a hypothesis-generating resource for future wound healing studies.

Neutrophil and Eosinophil Responses Remain Abnormal for Several Months in Primary Care Patients With COVID-19 Disease

Introduction

Neutrophil and eosinophil activation and its relation to disease severity has been understudied in primary care patients with COVID-19. In this study, we investigated whether the neutrophil and eosinophil compartment were affected in primary care patients with COVID-19.

Methods

COVID-19 patients, aged ≥ 40 years with cardiovascular comorbidity presenting to the general practitioner with substantial symptoms, partaking in the COVIDSat@Home study between January and April 2021, were included. Blood was drawn during and 3 to 6 months after active COVID-19 disease and analyzed by automated flow cytometry, before and after stimulation with a formyl-peptide (fNLF). Mature neutrophil and eosinophil markers at both time points were compared to healthy controls. A questionnaire was conducted on disease symptoms during and 3 to 6 months after COVID-19 disease.

Results

The blood of 18 COVID-19 patients and 34 healthy controls was analyzed. During active COVID-19 disease, neutrophils showed reduced CD10 (p = 0.0360), increased CD11b (p = 0.0002) and decreased CD62L expression (p < 0.0001) compared to healthy controls. During active COVID-19 disease, fNLF stimulated neutrophils showed decreased CD10 levels (p < 0.0001). Three to six months after COVID-19 disease, unstimulated neutrophils showed lowered CD62L expression (p = 0.0003) and stimulated neutrophils had decreased CD10 expression (p = 0.0483) compared to healthy controls. Both (un)stimulated CD10 levels increased 3 to 6 months after active disease (p = 0.0120 and p < 0.0001, respectively) compared to during active disease. Eosinophil blood counts were reduced during active COVID-19 disease and increased 3 to 6 months after infection (p < 0.0001). During active COVID-19, eosinophils showed increased unstimulated CD11b (p = 0.0139) and decreased (un)stimulated CD62L expression (p = 0.0036 and p = 0.0156, respectively) compared to healthy controls. Three to six months after COVID-19 disease, (un)stimulated eosinophil CD62L expression was decreased (p = 0.0148 and p = 0.0063, respectively) and the percentage of CD11bbright cells was increased (p = 0.0083 and p = 0.0307, respectively) compared to healthy controls.

Conclusion

Automated flow cytometry analysis reveals specific mature neutrophil and eosinophil activation patterns in primary care patients with COVID-19 disease, during and 3 to 6 months after active disease. This suggests that the neutrophil and eosinophil compartment are long-term affected by COVID-19 in primary care patients. This indicates that these compartments may be involved in the pathogenesis of long COVID.

Immunomodulation Effect of Biomaterials on Bone Formation

Traditional bone replacement materials have been developed with the goal of directing the osteogenesis of osteoblastic cell lines toward differentiation and therefore achieving biomaterial-mediated osteogenesis, but the osteogenic effect has been disappointing. With advances in bone biology, it has been revealed that the local immune microenvironment has an important role in regulating the bone formation process. According to the bone immunology hypothesis, the immune system and the skeletal system are inextricably linked, with many cytokines and regulatory factors in common, and immune cells play an essential role in bone-related physiopathological processes. This review combines advances in bone immunology with biomaterial immunomodulatory properties to provide an overview of biomaterials-mediated immune responses to regulate bone regeneration, as well as methods to assess the bone immunomodulatory properties of bone biomaterials and how these strategies can be used for future bone tissue engineering applications.

Chronic wounds

Chronic wounds are characterized by their inability to heal within an expected time frame and have emerged as an increasingly important clinical problem over the past several decades, owing to their increasing incidence and greater recognition of associated morbidity and socio-economic burden. Even up to a few years ago, the management of chronic wounds relied on standards of care that were outdated. However, the approach to these chronic conditions has improved, with better prevention, diagnosis and treatment. Such improvements are due to major advances in understanding of cellular and molecular aspects of basic science, in innovative and technological breakthroughs in treatment modalities from biomedical engineering, and in our ability to conduct well-controlled and reliable clinical research. The evidence-based approaches resulting from these advances have become the new standard of care. At the same time, these improvements are tempered by the recognition that persistent gaps exist in scientific knowledge of impaired healing and the ability of clinicians to reduce morbidity, loss of limb and mortality. Therefore, taking stock of what is known and what is needed to improve understanding of chronic wounds and their associated failure to heal is crucial to ensuring better treatments and outcomes.

The changing landscape of immune cells in the fetal mouse testis

Fetal testis growth involves cell influx and extensive remodeling. Immediately after sex determination in mouse, macrophages enable normal cord formation and removal of inappropriately positioned cells. This study provides new information about macrophages and other immune cells after cord formation in fetal testes, including their density, distribution, and close cellular contacts. C57BL6J mouse testes from embryonic day (E) 13.5 to birth (post-natal day 0; PND0), were examined using immunofluorescence, immunohistochemistry, and RT-qPCR to identify macrophages (F4/80, CD206, MHCII), T cells (CD3), granulocytes/neutrophils (Ly6G), and germ cells (DDX4). F4/80⁺ cells were the most abundant, comprising 90% of CD45⁺ cells at E13.5 and declining to 65% at PND0. Changes in size, shape, and markers (CD206 and MHCII) documented during this interval align with the understanding that F4/80⁺ cells have different origins during embryonic life. CD3⁺ cells and F4/80⁻/MHCII⁺ were absent to rare until PND0. Ly6G⁺ cells were scarce at E13.5 but increased robustly by PND0 to represent half of the CD45⁺ cells. These immunofluorescence data were in accord with transcript analysis, which showed that immune marker mRNAs increased with testis age. F4/80⁺ and Ly6G⁺ cells were frequently inside cords adjacent to germ cells at E13.5 and E15.5. F4/80⁺ cells were often in clusters next to other immune cells. Macrophages inside cords at E13.5 and E15.5 (F4/80^Hi/CD206⁺) were different from macrophages at PND0 (F4/80^Dim/CD206⁻), indicating that they have distinct origins. This histological quantification coupled with transcript information identifies new cellular interactions for immune cells in fetal testis morphogenesis, and highlights new avenues for studies of their functional significance.

Opportunities presented by zebrafish larval models to study neutrophil function in tissues

Appropriate neutrophil function is essential for innate immune defence and to avoid inflammatory pathology. Neutrophils can adapt their responses according to their environment and recently, the existence of multiple distinct neutrophil populations has been confirmed in both health and disease. However, the study of neutrophil functions in their tissue environment has remained challenging, and for instance, the relationship between neutrophil maturity and function is not fully understood. Many neutrophil morphological and functional features are highly conserved between mammals and non-mammalian vertebrates. This enables the use of the transparent and genetically tractable zebrafish larvae to study neutrophil biology. We review data on the development and function of zebrafish larval neutrophils and advances zebrafish have brought to studies of neutrophil biology. In addition, we discuss opportunities and aspects to be considered when using the larval zebrafish model to further enhance our understanding of neutrophil function in health and disease.

Hybrid Biomaterial Initiates Refractory Wound Healing via Inducing Transiently Heightened Inflammatory Responses

Inflammation plays a crucial role in triggering regeneration, while inadequate or chronic inflammation hinders the regenerative process, resulting in refractory wounds. Inspired by the ideal regeneration mode in lower vertebrates and the human oral mucosa, realigning dysregulated inflammation to a heightened and acute response provides a promising option for refractory wound therapy. Neutrophils play important roles in inflammation initiation and resolution. Here, a hybrid biomaterial is used to stimulate transiently heightened inflammatory responses by precise tempospatial regulation of neutrophil recruitment and apoptosis. The hybrid biomaterial (Gel@fMLP/SiO₂ -FasL) is constructed by loading of formyl-met-leu-phe (fMLP) and FasL-conjugated silica nanoparticles (SiO₂ -FasL) into a pH-responsive hydrogel matrix. This composition enables burst release of fMLP to rapidly recruit neutrophils for heightened inflammation initiation. After neutrophils act to produce acids, the pH-responsive hydrogel degrades to expose SiO₂ -FasL, which induces activated neutrophils apoptosis via FasL-Fas signaling triggering timely inflammation resolution. Apoptotic neutrophils are subsequently cleared by macrophages, and this efferocytosis activates key signalings to promote macrophage anti-inflammatory phenotypic transformation to drive regeneration. Ultimately, Gel@fMLP/SiO₂ -FasL successfully promotes tissue regeneration by manipulating inflammation in critical-sized calvarial bone defects and diabetic cutaneous wound models. This work provides a new strategy for refractory wound therapy via inducing transiently heightened inflammatory responses.

Changes Within H3K4me3-Marked Histone Reveal Molecular Background of Neutrophil Functional Plasticity

Neutrophils are a heterogenous population capable of both antimicrobial functions and suppressor ones, however, no specific pattern of transcription factors controlling this plasticity has been identified. We observed rapid changes in the neutrophil status after stimulation with LPS, pre-activating concentration of TNF-α, or IL-10. Chromatin immunoprecipitation sequencing (ChIP-Seq) analysis of histone H3K4me3 allowed us to identify various transcriptional start sites (TSSs) associated with plasticity and heterogeneity of human neutrophils. Gene Ontology analysis demonstrated great variation within target genes responsible for neutrophil activation, cytokine production, apoptosis, histone remodelling as well as NF-κB transcription factor pathways. These data allowed us to assign specific target genes positioned by H3K4me3-marked histone with a different pattern of gene expression related to NF-κB pathways, apoptosis, and a specific profile of cytokines/chemokines/growth factors realised by neutrophils stimulated by LPS, IL-10, or TNF-α. We discovered IL-10-induced apoptotic neutrophils being transcriptionally active cells capable of switching the profile of cytokines/chemokines/growth factors desired in resolving inflammation via non-canonical NF-κB pathway with simultaneous inhibition of canonical NF-κB pathway. As apoptotic/suppressive neutrophils induced by IL-10 via positioning genes within H3K4me3-marked histone were transcriptionally active, newly described DNA binding sites can be considered as potential targets for immunotherapy.

Are Alterations in DNA Methylation Related to CKD Development?

The modifications in genomic DNA methylation are involved in the regulation of normal and pathological cellular processes. The epigenetic regulation stimulates biological plasticity as an adaptive response to variations in environmental factors. The role of epigenetic changes is vital for the development of some diseases, including atherogenesis, cancers, and chronic kidney disease (CKD). The results of studies presented in this review have suggested that altered DNA methylation can modulate the expression of pro-inflammatory and pro-fibrotic genes, as well those essential for kidney development and function, thus stimulating renal disease progression. Abnormally increased homocysteine, hypoxia, and inflammation have been suggested to alter epigenetic regulation of gene expression in CKD. Studies of renal samples have demonstrated the relationship between variations in DNA methylation and fibrosis and variations in estimated glomerular filtration rate (eGFR) in human CKD. The unravelling of the genetic–epigenetic profile would enhance our understanding of processes underlying the development of CKD. The understanding of multifaceted relationship between DNA methylation, genes expression, and disease development and progression could improve the ability to identify individuals at risk of CKD and enable the choice of appropriate disease management.

Atherosclerosis is a side effect of cellular senescence

Atherosclerosis is a systemic autoimmune disease of the arterial wall characterized by chronic inflammation, high blood pressure, oxidative stress, and progressive loss of cell and organ function with aging. An imbalance of macrophage polarization is associated with many aging diseases, including atherosclerosis. The polarization toward the pro-inflammatory M1 macrophage is a major promoter of the atheroma formation. It is known that efferocytosis, or ingestion of apoptotic cells, is stimulated by M2 macrophage polarization. A failure of efferocytosis leads to the prolongation of chronic pathology in tissue. In addition, fat-laden macrophages contribute to the plague progression by transforming into foam cells in response to excess lipid deposition in arteries. In spite of the generally accepted theory that macrophages capture oxidized low-density lipoprotein by phagocytosis and become foam cells, we postulate that the main source of lipid accumulation in foam cells are senescent erythrocytes. Senescent erythrocytes lose their plasticity, which affects the rheological blood properties. It is known that their membrane contains high levels of cholesterol. There is evidence that senescent erythrocytes play a pathogenic role in the atheroma formation after breaking down during flowing through an artery bifurcation. Here we review the current knowledge on the impact of age-associated immune cells and red blood cells modifications on atherogenesis.

Graphical abstract:

From infection to repair: Understanding the workings of our innate immune cells

In a world filled with microbes, some posing a threat to our body, our immune system is key to living a healthy life. The innate immune system is made of various cell types that act to guard our bodies. Unlike the adaptive immune system that has a specific response, our innate immune system encompasses cells that elicit unspecific immune responses, triggered whenever the right signals are detected. Our understanding of immunity started with the concept of our immune system only responding to "nonself" like the pathogens that invade our body. However, over the past few decades, we have learned that the immune system is more than an on/off switch that recognizes nonself. The innate immune system regularly patrols our bodies for pathogens and tissue damage. Our innate immune system not only seeks to resolve infection but also repair tissue injury, through phagocytosing debris and initiating the release of growth factors. Recently, we are starting to see that it is not just recognizing danger, our innate immune system plays a crucial role in repair. Innate immune cells phenotypically change during repair. In the context of severe injury or trauma, our innate immune system is modified quite drastically to help repair, resulting in reduced infection control. Moreover, these changes in immune cell function can be modified by sex as a biological variable. From past to present, in this overview, we provide a summary of the innate immune cells and pathways in infection and tissue repair. This article is categorized under: Immune System Diseases > Molecular and Cellular Physiology.

Neutrophil phenotypes and functions in cancer: A consensus statement

Neutrophils are the first responders to infection and inflammation and are thus a critical component of innate immune defense. Understanding the behavior of neutrophils as they act within various inflammatory contexts has provided insights into their role in sterile and infectious diseases; however, the field of neutrophils in cancer is comparatively young. Here, we summarize key concepts and current knowledge gaps related to the diverse roles of neutrophils throughout cancer progression. We discuss sources of neutrophil heterogeneity in cancer and provide recommendations on nomenclature for neutrophil states that are distinct in maturation and activation. We address discrepancies in the literature that highlight a need for technical standards that ought to be considered between laboratories. Finally, we review emerging questions in neutrophil biology and innate immunity in cancer. Overall, we emphasize that neutrophils are a more diverse population than previously appreciated and that their role in cancer may present novel unexplored opportunities to treat cancer.

Context-dependent effects of inflammation on retina regeneration

Inflammation is required for the proliferation of Müller glia (MG) into multipotent progenitors (MGPCs) in the injured fish and avian retinas. However, its function in retina regeneration has not been fully understood. Here we investigated the role of inflammation in three different retinal regeneration paradigms in zebrafish (stab-injury, NMDA-injury and insulin treatment). We first show that different types of immune cells and levels of inflammatory cytokines were found in the retinas of these paradigms. Though zymosan injection alone was insufficient to induce MG proliferation in the uninjured retina, immune suppression significantly inhibited MGPC formation in all three paradigms. Enhancing inflammation promoted MGPC formation after stab-injury, while exhibiting a context-dependent role in the NMDA or insulin models. We further show that proper levels of inflammation promoted MG reprogramming and cell cycle re-entry after stab- or NMDA-injury, but excessive inflammation also suppressed MG proliferation in the latter model. Finally, inflammation differentially affected neuronal regeneration in various injury paradigms. Our study reveals the complex and context-dependent role of inflammation during retinal repair in fish and suggests accurate inflammation management may be crucial for successful retina regeneration in mammals.

Radiation Exposure Perturbs IL-17RA-Mediated Immunity Leading to Changes in Neutrophil Responses That Increase Susceptibility to Oropharyngeal Candidiasis

Fungal infections caused by Candida albicans are a serious problem for immunocompromised individuals, including those undergoing radiotherapy for head and neck cancers. Targeted irradiation causes inflammatory dysregulation and damage to the oral mucosa that can be exacerbated by candidiasis. Post-irradiation the cytokine interleukin-17 (IL-17) protects the oral mucosae by promoting oral epithelial regeneration and balancing the oral immune cell populations, which leads to the eventual healing of the tissue. IL-17 signaling is also critical for the antifungal response during oropharyngeal candidiasis (OPC). Yet, the benefit of IL-17 during other forms of candidiasis, such as vulvovaginal candidiasis, is not straightforward. Therefore, it was important to determine the role of IL-17 during OPC associated with radiation-induced inflammatory damage. To answer this question, we exposed Il17ra^−/− and wild-type mice to head-neck irradiation (HNI) and OPC to determine if the IL-17 signaling pathway was still protective against C. albicans. HNI increased susceptibility to OPC, and in Il17ra^−/− mice, the mucosal damage and fungal burden were elevated compared to control mice. Intriguingly, neutrophil influx was increased in Il17ra^−/− mice, yet these cells had reduced capacity to phagocytose C. albicans and failed to clear OPC compared to immunocompetent mice. These findings suggest that radiotherapy not only causes physical damage to the oral cavity but also skews immune mediators, leading to increased susceptibility to oropharyngeal candidiasis.

Endothelial Cell Adhesion Molecules- (un)Attainable Targets for Nanomedicines

Endothelial cell adhesion molecules have long been proposed as promising targets in many pathologies. Despite promising preclinical data, several efforts to develop small molecule inhibitors or monoclonal antibodies (mAbs) against cell adhesion molecules (CAMs) ended in clinical-stage failure. In parallel, many well-validated approaches for targeting CAMs with nanomedicine (NM) were reported over the years. A wide range of potential applications has been demonstrated in various preclinical studies, from drug delivery to the tumor vasculature, imaging of the inflamed endothelium, or blocking immune cells infiltration. However, no NM drug candidate emerged further into clinical development. In this review, we will summarize the most advanced examples of CAM-targeted NMs and juxtapose them with known traditional drugs against CAMs, in an attempt to identify important translational hurdles. Most importantly, we will summarize the proposed strategies to enhance endothelial CAM targeting by NMs, in an attempt to offer a catalog of tools for further development.

Targeting Neutrophils for Promoting the Resolution of Inflammation

Acute inflammation is a localized and self-limited innate host-defense mechanism against invading pathogens and tissue injury. Neutrophils, the most abundant immune cells in humans, play pivotal roles in host defense by eradicating invading pathogens and debris. Ideally, elimination of the offending insult prompts repair and return to homeostasis. However, the neutrophils` powerful weaponry to combat microbes can also cause tissue damage and neutrophil-driven inflammation is a unifying mechanism for many diseases. For timely resolution of inflammation, in addition to stopping neutrophil recruitment, emigrated neutrophils need to be disarmed and removed from the affected site. Accumulating evidence documents the phenotypic and functional versatility of neutrophils far beyond their antimicrobial functions. Hence, understanding the receptors that integrate opposing cues and checkpoints that determine the fate of neutrophils in inflamed tissues provides insight into the mechanisms that distinguish protective and dysregulated, excessive inflammation and govern resolution. This review aims to provide a brief overview and update with key points from recent advances on neutrophil heterogeneity, functional versatility and signaling, and discusses challenges and emerging therapeutic approaches that target neutrophils to enhance the resolution of inflammation.

Generation of resolving memory neutrophils through pharmacological training with 4-PBA or genetic deletion of TRAM

Neutrophils are the dominant leukocytes in circulation and the first responders to infection and inflammatory cues. While the roles of neutrophils in driving inflammation have been widely recognized, the contribution of neutrophils in facilitating inflammation resolution is under-studied. Here, through single-cell RNA sequencing analysis, we identified a subpopulation of neutrophils exhibiting pro-resolving characteristics with greater Cd200r and Cd86 expression at the resting state. We further discovered that 4-PBA, a peroxisomal stress-reducing agent, can potently train neutrophils into the resolving state with enhanced expression of CD200R, CD86, as well as soluble pro-resolving mediators Resolvin D1 and SerpinB1. Resolving neutrophils trained by 4-PBA manifest enhanced phagocytosis and bacterial-killing functions. Mechanistically, the generation of resolving neutrophils is mediated by the PPARγ/LMO4/STAT3 signaling circuit modulated by TLR4 adaptor molecule TRAM. We further demonstrated that genetic deletion of TRAM renders the constitutive expansion of resolving neutrophils, with an enhanced signaling circuitry of PPARγ/LMO4/STAT3. These findings may have profound implications for the effective training of resolving neutrophils with therapeutic potential in the treatment of both acute infection as well as chronic inflammatory diseases.

Vaccine Adjuvants Induce Formation of Intraperitoneal Extracellular Traps in Flounder (Paralichthys olivaceus)

Adjuvants are used to increase the strength, quality, and duration of the immune response of vaccines. Neutrophils are the first immune cells that arrive at the injection site and can release DNA fibers together with granular proteins, so-called neutrophil extracellular traps (NETs), to entrap microbes in a sticky matrix of extracellular chromatin and microbicidal agents. Similar extracellular structures were also released by macrophages, mast cells, and eosinophils and are now generalized as “ETs.” Here we demonstrated that Alum adjuvant stimulation led to peritoneal cells swarming and ET release in vitro. Moreover, compared to antigen stimulation alone, ET release was significantly increased after stimulation with antigen-mixed adjuvants and in a time- and dose-dependent manner. In vivo, we were able to monitor and quantify the continuous changes of the ET release in the same fish by using the small animal in vivo imaging instrument at different times during the early stages after intraperitoneal immunization. The results showed that the fluorescence signal of ETs in the peritoneum increased from 0 to 12 h after injection and then gradually decreased. The fluorescence signals came from extracellular DNA fibers, which are sensitive to DNase I and confirmed by microscopy of peritoneal fluid ex vivo. In summary, this study introduced a new method for detecting ETs in the peritoneum of fish in vivo and indicated that ET formation is involved in the immune response at the early stage after intraperitoneal immunization to vaccines.

Low Level Of Neutrophil Gelatinase-Associated Lipocalin (NGAL) In Patients With Chronic Heart Failure And Multivessel Coronary Atherosclerosis

Rationale — Several biomarkers are used to determine the prognosis of patients with heart failure (HF), including neutrophil gelatinase-associated lipocalin (NGAL, Lipocalin-2). We investigated NGAL serum levels in patients with HF and coronary artery disease (CAD). Methods — Fifty-three patients with chronic HF and stable multivessel CAD were included in the study. Patients were grouped on the basis of the NGAL level: low NGAL group (NGAL<37 ng/mL, n=19) and normal NGAL group (NGAL ≥37 ng/mL, n=34). Results and Discussion — The main findings from our study of patients with HF and multivessel CAD were: 1) Plasma NGAL levels were below reference values in 35.8% of cases. 2) We detected a strong positive correlation between neutrophil count and NGAL level (0.573, р<0.001). 3) Neutropenia was present in 15.8% of patients in the low NGAL group and in none in the group with a normal NGAL level (p=0.041). 4) Postinfarction left ventricular aneurysms were more often diagnosed in patients of the first group (15.8%) and in none of patients in the second group (p=0.041). Conclusion — Low NGAL has been associated with neutropenia in patients with heart failure and multivessel atherosclerotic CAD. Left ventricular aneurysms were diagnosed in 15.8% (n=3) patients with low NGAL and in none with normal NGAL levels. These changes may be due to maladaptive remodeling of the heart after myocardial infarction, but further research is needed.

Study of the immunologic response of marine-derived collagen and gelatin extracts for tissue engineering applications

The host immunologic response to a specific material is a critical aspect when considering it for clinical implementation. Collagen and gelatin extracted from marine sources have been proposed as biomaterials for tissue engineering applications, but there is a lack of information in the literature about their immunogenicity. In this work, we evaluated the immune response to collagen and/or gelatin from blue shark and codfish, previously extracted and characterized. After endotoxin evaluation, bone marrow-derived macrophages were exposed to the materials and a panel of pro- and anti-inflammatory cytokines were evaluated both for protein quantification and gene expression. Then, the impact of those materials in the host was evaluated through peritoneal injection in C57BL/6 mice. The results suggested shark collagen as the less immunogenic material, inducing low expression of pro-inflammatory cytokines as well as inducible nitric oxide synthase (encoded by Nos2) and high expression of Arginase 1 (encoded by Arg1). Although shark gelatin appeared to be the material with higher pro-inflammatory expression, it also presents a high expression of IL-10 (anti-inflammatory cytokine) and Arginase (both markers for M2-like macrophages). When injected in the peritoneal cavity of mice, our materials demonstrated a transient recruitment of neutrophil, being almost non-existent after 24 hours of injection. Based on these findings, the studied collagenous materials can be considered interesting biomaterial candidates for regenerative medicine as they may induce an activation of the M2-like macrophage population, which is involved in suppressing the inflammatory processes promoting tissue remodeling. STATEMENT OF SIGNIFICANCE: Marine-origin biomaterials are emerging in the biomedical arena, namely the ones based in marine-derived collagen/gelatin proposed as cell templates for tissue regeneration. Nevertheless, although the major cause of implant rejection in clinical practice is the host's negative immune response, there is a lack of information in the literature about the immunological impact of these marine collagenous materials. This work aims to contribute with knowledge about the immunologic response to collagen/gelatin extracted from blue shark and codfish skins. The results demonstrated that despite some differences observed, all the materials can induce a macrophage phenotype related with anti-inflammation resolution and then act as immuno-modulators and anti-inflammatory inducible materials.

Rora Regulates Neutrophil Migration and Activation in Zebrafish

Neutrophil migration and activation are essential for defense against pathogens. However, this process may also lead to collateral tissue injury. We used microRNA overexpression as a platform and discovered protein-coding genes that regulate neutrophil migration. Here we show that miR-99 decreased the chemotaxis of zebrafish neutrophils and human neutrophil-like cells. In zebrafish neutrophils, miR-99 directly targets the transcriptional factor RAR-related orphan receptor alpha (roraa). Inhibiting RORα, but not the closely related RORγ, reduced chemotaxis of zebrafish and primary human neutrophils without causing cell death, and increased susceptibility of zebrafish to bacterial infection. Expressing a dominant-negative form of Rorα or disrupting the roraa locus specifically in zebrafish neutrophils reduced cell migration. At the transcriptional level, RORα regulates transmembrane signaling receptor activity and protein phosphorylation pathways. Our results, therefore, reveal previously unknown functions of miR-99 and RORα in regulating neutrophil migration and anti-microbial defense.

Neutrophil Migratory Patterns: Implications for Cardiovascular Disease

The body's inflammatory response involves a series of processes that are necessary for the immune system to mitigate threats from invading pathogens. Leukocyte migration is a crucial process in both homeostatic and inflammatory states. The mechanisms involved in immune cell recruitment to the site of inflammation are numerous and require several cascades and cues of activation. Immune cells have multiple origins and can be recruited from primary and secondary lymphoid, as well as reservoir organs within the body to generate an immune response to certain stimuli. However, no matter the origin, an important aspect of any inflammatory response is the web of networks that facilitates immune cell trafficking. The vasculature is an important organ for this trafficking, especially during an inflammatory response, mainly because it allows cells to migrate towards the source of insult/injury and serves as a reservoir for leukocytes and granulocytes under steady state conditions. One of the most active and vital leukocytes in the immune system's arsenal are neutrophils. Neutrophils exist under two forms in the vasculature: a marginated pool that is attached to the vessel walls, and a demarginated pool that freely circulates within the blood stream. In this review, we seek to present the current consensus on the mechanisms involved in leukocyte margination and demargination, with a focus on the role of neutrophil migration patterns during physio-pathological conditions, in particular diabetes and cardiovascular disease.

Neutrophil Extracellular Traps in ANCA-Associated Vasculitis and Interstitial Lung Disease: A Scoping Review

Background: Deregulated neutrophil extracellular traps (NETs) formation is implicated in various diseases, including ANCA-associated vasculitis and pulmonary fibrosis (PF). Lung involvement is frequent in AAV, and interstitial lung diseases (ILDs) are strongly related to MPO-ANCA positivity and mainly reported in microscopic polyangiitis. The association between AAV and ILD is a strong indicator of poor prognosis and limited survival. Neutrophils, ANCA and NET interplay in PF development in AAV. This study aimed to review the literature concerning the implications of NET in lung fibrogenesis specifically focused on AAV associated with ILD, and the potential of NET as a theranostic marker. Methods: Through scoping review methodology, we used a descriptive thematic analysis to understand the pathogenic role of NETs in patients with AAV and pulmonary fibrosis and their further role as a theranostic marker of this disease. Results: The implications of NET in the pathogenesis of AAV and ILD, as well as an association between these two diseases, have been identified, but the underlying pathophysiological mechanisms are still unknown. The pharmacological or genetic inhibition of NET release reduces disease severity in multiple inflammatory disease models, indicating that NETs are potential therapeutic targets. In this regard, despite the lack of clinical data, we may hypothesise that an optimal management of AAV-ILD patients would require not only B-cells targeted therapy, but also NETs inhibition. Conclusion: Preliminary findings seem to display a lack of efficacy of traditional immunosuppressants, such as Rituximab, in this subset of patients, while to date no patients suffering from a definite ILD have been enrolled in clinical trials. Further insights would be provided by their employment, as a combination treatment, in common clinical practice. Although we can imagine that the inhibition of NETs in patients with AAV-ILD could reduce severity and mortality, we still lack the scientific basis that could improve our understanding of the disease from a molecular point of view.

Neutrophils-From Bone Marrow to First-Line Defense of the Innate Immune System

Neutrophils (polymorphonuclear cells; PMNs) form a first line of defense against pathogens and are therefore an important component of the innate immune response. As a result of poorly controlled activation, however, PMNs can also mediate tissue damage in numerous diseases, often by increasing tissue inflammation and injury. According to current knowledge, PMNs are not only part of the pathogenesis of infectious and autoimmune diseases but also of conditions with disturbed tissue homeostasis such as trauma and shock. Scientific advances in the past two decades have changed the role of neutrophils from that of solely immune defense cells to cells that are responsible for the general integrity of the body, even in the absence of pathogens. To better understand PMN function in the human organism, our review outlines the role of PMNs within the innate immune system. This review provides an overview of the migration of PMNs from the vascular compartment to the target tissue as well as their chemotactic processes and illuminates crucial neutrophil immune properties at the site of the lesion. The review is focused on the formation of chemotactic gradients in interaction with the extracellular matrix (ECM) and the influence of the ECM on PMN function. In addition, our review summarizes current knowledge about the phenomenon of bidirectional and reverse PMN migration, neutrophil microtubules, and the microtubule organizing center in PMN migration. As a conclusive feature, we review and discuss new findings about neutrophil behavior in cancer environment and tumor tissue.

The Immune-Centric Revolution in the Diabetic Foot: Monocytes and Lymphocytes Role in Wound Healing and Tissue Regeneration-A Narrative Review

Monocytes and lymphocytes play a key role in physiologic wound healing and might be involved in the impaired mechanisms observed in diabetes. Skin wound macrophages are represented by tissue resident macrophages and infiltrating peripheral blood recruited monocytes which play a leading role during the inflammatory phase of wound repair. The impaired transition of diabetic wound macrophages from pro-inflammatory M1 phenotypes to anti-inflammatory pro-regenerative M2 phenotypes might represent a key issue for impaired diabetic wound healing. This review will focus on the role of immune system cells in normal skin and diabetic wound repair. Furthermore, it will give an insight into therapy able to immuno-modulate wound healing processes toward to a regenerative anti-inflammatory fashion. Different approaches, such as cell therapy, exosome, and dermal substitute able to promote the M1 to M2 switch and able to positively influence healing processes in chronic wounds will be discussed.

ADAM8 signaling drives neutrophil migration and ARDS severity

Acute respiratory distress syndrome (ARDS) results in catastrophic lung failure and has an urgent, unmet need for improved early recognition and therapeutic development. Neutrophil influx is a hallmark of ARDS and is associated with the release of tissue-destructive immune effectors, such as matrix metalloproteinases (MMPs) and membrane-anchored metalloproteinase disintegrins (ADAMs). Here, we observed using intravital microscopy that Adam8-/- mice had impaired neutrophil transmigration. In mouse pneumonia models, both genetic deletion and pharmacologic inhibition of ADAM8 attenuated neutrophil infiltration and lung injury while improving bacterial containment. Unexpectedly, the alterations of neutrophil function were not attributable to impaired proteolysis but resulted from reduced intracellular interactions of ADAM8 with the actin-based motor molecule Myosin1f that suppressed neutrophil motility. In 2 ARDS cohorts, we analyzed lung fluid proteolytic signatures and identified that ADAM8 activity was positively correlated with disease severity. We propose that in acute inflammatory lung diseases such as pneumonia and ARDS, ADAM8 inhibition might allow fine-tuning of neutrophil responses for therapeutic gain.

Tumour cell apoptosis modulates the colorectal cancer immune microenvironment via interleukin-8-dependent neutrophil recruitment

Sporadic apoptosis of tumour cells is a commonly observed feature of colorectal cancer (CRC) and strongly correlates with adverse patient prognosis. The uptake of apoptotic cell debris by neutrophils induces a non-inflammatory, pro-regenerative, and hence potentially pro-tumorigenic phenotype. In this study, we therefore sought to investigate the impact of apoptotic CRC cells on neutrophils and its consequence on other immune cells of the tumour microenvironment. Apoptosis induced by combined TNFα-treatment and UV-C irradiation, as well as various chemotherapeutic agents, led to a substantial release of neutrophil-attracting chemokines, most importantly interleukin-8 (IL-8), in both primary patient-derived and established CRC cells. Accordingly, conditioned media of apoptotic tumour cells selectively stimulated chemotaxis of neutrophils, but not T cells or monocytes. Notably, caspase-inhibition partially reduced IL-8 secretion, suggesting that caspase activity might be required for apoptosis-induced IL-8 release. Moreover, apoptotic tumour cell-conditioned media considerably prolonged neutrophil lifespan and induced an activated CD66b^highCD11b^highCD62L^low phenotype, comparable to that of tumour-associated neutrophils in CRC patients, as assessed by flow cytometry of dissociated CRC tissues. Immunohistochemical analyses of 35 CRC patients further revealed a preferential accumulation of neutrophils at sites of apoptotic tumour cells defined by the expression of epithelial cell-specific caspase-cleaved cytokeratin-18. The same areas were also highly infiltrated by macrophages, while T cells were virtually absent. Notably, neutrophils induced an M2-like CD86^lowCD163⁺CD206⁺ phenotype in co-cultured monocyte-derived macrophages and suppressed LPS-induced pro-inflammatory cytokine release. In an in vitro transwell model, IL-8 blockade efficiently prevented neutrophil-induced anti-inflammatory macrophage polarisation by inhibiting neutrophil migration towards IL-8 gradients generated by apoptotic CRC cells. To conclude, our data suggest that apoptotic cancer cells release chemotactic factors that attract neutrophils into the tumour, where their interaction with neighbouring macrophages might promote an immunologically unfavourable tumour microenvironment. This effect may contribute to tumour recurrence after chemotherapy-induced apoptosis.

Neutrophils in chronic inflammatory diseases

Chronic inflammation is a component of many disease conditions that affect a large group of individuals worldwide. Chronic inflammation is characterized by persistent, low-grade inflammation and is increased in the aging population. Neutrophils are normally the first responders to acute inflammation and contribute to the resolution of inflammation. However, in chronic inflammation, the role of neutrophils is less well understood and has been described as either beneficial or detrimental, causing tissue damage and enhancing the immune response. Emerging evidence suggests that neutrophils are important players in several chronic diseases, such as atherosclerosis, diabetes mellitus, nonalcoholic fatty liver disease and autoimmune disorders. This review will highlight the interaction of neutrophils with other cells in the context of chronic inflammation, the contribution of neutrophils to selected chronic inflammatory diseases, and possible future therapeutic strategies.

Genetically inducible and reversible zebrafish model of systemic inflammation

The inflammatory response is a vital defense mechanism against trauma and pathogen induced damage, but equally important is its appropriate resolution. In some instances of severe trauma or sustained infection, inappropriate and persistent activation of the immune response can occur resulting in a dangerous systemic inflammatory response. Untreated, this systemic inflammatory response can lead to tissue damage, organ shutdown, and death. Replicating this condition in tractable model organisms can provide insight into the mechanisms involved in the induction, maintenance, and resolution of inflammation. To that end, we developed a non-invasive, inducible, and reversible model of systemic inflammation in zebrafish. Using the Gal4-EcR/UAS system activated by the ecdysone analog tebufenozide, we generated transgenic zebrafish that allow for chemically-induced, ubiquitous secretion of the mature form of zebrafish interleukin-1β (Il-1βmat) in both larval and adult developmental stages. To ensure a robust immune response, we attached a strong signal peptide from the Gaussia princeps luciferase enzyme to promote active secretion of the cytokine. We observe a dose-dependent inflammatory response involving neutrophil expansion accompanied by tissue damage and reduced survival. Washout of tebufenozide permits inflammation resolution. We also establish the utility of this model for the identification of small molecule anti-inflammatory compounds by treatment with the immunosuppressant rapamycin. Taken together, these features make this model a valuable new tool that can aid in identifying potential new therapies while broadening our understanding of systemic inflammation, its impact on the immune system and its resolution.

An Emerging Role of TIM3 Expression on T Cells in Chronic Kidney Inflammation

T cell immunoglobulin domain and mucin domain 3 (TIM3) was initially identified as an inhibitory molecule on IFNγ-producing T cells. Further research discovered the broad expression of TIM3 on different immune cells binding to multiple ligands. Apart from its suppressive effects on the Th1 cells, recent compelling experiments highlighted the indispensable role of TIM3 in the myeloid cell-mediated inflammatory response, supporting that TIM3 exerts pleiotropic effects on both adaptive and innate immune cells in a context-dependent manner. A large number of studies have been conducted on TIM3 biology in the disease settings of infection, cancer, and autoimmunity. However, there is a lack of clinical evidence to closely evaluate the role of T cell-expressing TIM3 in the pathogenesis of chronic kidney disease (CKD). Here, we reported an intriguing case of Mycobacterium tuberculosis (Mtb) infection that was characterized by persistent overexpression of TIM3 on circulating T cells and ongoing kidney tubulointerstitial inflammation for a period of 12 months. In this case, multiple histopathological biopsies revealed a massive accumulation of recruited T cells and macrophages in the enlarged kidney and liver. After standard anti-Mtb treatment, repeated renal biopsy identified a dramatic remission of the infiltrated immune cells in the tubulointerstitial compartment. This is the first clinical report to reveal a time-course expression of TIM3 on the T cells, which is pathologically associated with the progression of severe kidney inflammation in a non-autoimmunity setting. Based on this case, we summarize the recent findings on TIM3 biology and propose a novel model of CKD progression due to the aberrant crosstalk among immune cells.

Neutrophil subsets and their differential roles in viral respiratory diseases

Neutrophils play significant roles in immune homeostasis and as neutralizers of microbial infections. Recent evidence further suggests heterogeneity of neutrophil developmental and activation states that exert specialized effector functions during inflammatory disease conditions. Neutrophils can play multiple roles during viral infections, secreting inflammatory mediators and cytokines that contribute significantly to host defense and pathogenicity. However, their roles in viral immunity are not well understood. In this review, we present an overview of neutrophil heterogeneity and its impact on the course and severity of viral respiratory infectious diseases. We focus on the evidence demonstrating the crucial roles neutrophils play in the immune response toward respiratory infections, using influenza as a model. We further extend the understanding of neutrophil function with the studies pertaining to COVID‐19 disease and its neutrophil‐associated pathologies. Finally, we discuss the relevance of these results for future therapeutic options through targeting and regulating neutrophil‐specific responses.

Immune response after central nervous system injury

Traumatic injuries of the central nervous system (CNS) affect millions of people worldwide, and they can lead to severely damaging consequences such as permanent disability and paralysis. Multiple factors can obstruct recovery after CNS injury. One of the most significant is the progressive neuronal death that follows the initial mechanical impact, leading to the loss of undamaged cells via a process termed secondary neurodegeneration. Efforts to define treatments that limit the spread of damage, while important, have been largely ineffectual owing to gaps in the mechanistic understanding that underlies the persisting neuronal cell death. Inflammation, with its influx of immune cells that occurs shortly after injury, has been associated with secondary neurodegeneration. However, the role of the immune system after CNS injury is far more complex. Studies have indicated that the immune response after CNS injury is detrimental, owing to immune cell-produced factors (e.g., pro-inflammatory cytokines, free radicals, neurotoxic glutamate) that worsen tissue damage. Our lab and others have also demonstrated the beneficial immune response that occurs after CNS injury, with the release of growth factors such as brain-derived growth factor (BDNF) and interleukin (IL-10) and the clearance of apoptotic and myelin debris by immune cells^1-4. In this review, we first discuss the multifaceted roles of the immune system after CNS injury. We then speculate on how advancements in single-cell RNA technologies can dramatically change our understanding of the immune response, how the spinal cord meninges serve as an important site for hosting immunological processes critical for recovery, and how the origin of peripherally recruited immune cells impacts their function in the injured CNS.

High fat diet induced gut dysbiosis alters corneal epithelial injury response in mice

PURPOSE

Commensal microbiome secretes various metabolites that can exert important effects on the host immunity and inflammation and can alter cellular functions. However, little is known regarding the effect of microbiome on corneal immunity and genetic expression. The purpose of this study is to describe the effect of diet-induced gut dysbiosis on corneal immunity and corneal gene expression after wounding.

METHODS

This study is approved by the Animal Care and Use of the University of Illinois. Six-week-old female C57BL6 mice were fed on a normal chow diet (ND), isocaloric low-fat control diet (LFD), or a 21% milk high-fat diet (HFD) for six weeks. 2 mm corneal epithelial debridement was performed (n = 10). Fecal samples from mice were used for microbial diversity analysis (n > 3). Immunofluorescence staining of corneal wholemount tissue post-debridement was used to visualize immune cell distribution. RNA Seq was performed on tissue samples from corneas following debridement.

RESULTS

Mice fed differing diets had significant alterations in gut microbial diversities. After corneal debridement, HFD mice experienced delayed wound healing in comparison to LFD mice and ND mice groups. However, fecal transplantation led to normalization of wound closure rates. Increased γδTCR staining was observed in the LFD group, and decreased LY6G was observed in HFD group (p < 0.05). Gene Ontology terms of differentially expressed genes included response to external stimulus, cell proliferation, migration, adhesion, defense response and leukocyte migration. Top over-represented pathways included ECM-receptor interaction, Cytokine-cytokine receptor interaction, Focal adhesion and Leukocyte trans-endothelial migration.

CONCLUSIONS

Gut microbial dysbiosis alters corneal immune cell distribution, corneal response to injury, and genes related to epithelial function and corneal immunity.

Peripheral immune cells and perinatal brain injury: a double-edged sword?

Perinatal brain injury is the leading cause of neurological mortality and morbidity in childhood ranging from motor and cognitive impairment to behavioural and neuropsychiatric disorders. Various noxious stimuli, including perinatal inflammation, chronic and acute hypoxia, hyperoxia, stress and drug exposure contribute to the pathogenesis. Among a variety of pathological phenomena, the unique developing immune system plays an important role in the understanding of mechanisms of injury to the immature brain. Neuroinflammation following a perinatal insult largely contributes to evolution of damage to resident brain cells, but may also be beneficial for repair activities. The present review will focus on the role of peripheral immune cells and discuss processes involved in neuroinflammation under two frequent perinatal conditions, systemic infection/inflammation associated with encephalopathy of prematurity (EoP) and hypoxia/ischaemia in the context of neonatal encephalopathy (NE) and stroke at term. Different immune cell subsets in perinatal brain injury including their infiltration routes will be reviewed and critical aspects such as sex differences and maturational stage will be discussed. Interactions with existing regenerative therapies such as stem cells and also potentials to develop novel immunomodulatory targets are considered. IMPACT: Comprehensive summary of current knowledge on the role of different immune cell subsets in perinatal brain injury including discussion of critical aspects to be considered for development of immunomodulatory therapies.

Prospects and Applications of Natural Blood-Derived Products in Regenerative Medicine

Currently, there are a number of therapeutic schemes used for the treatment of various types of musculoskeletal disorders. However, despite the use of new treatment options, therapeutic failure remains common due to impaired and delayed healing, or implant rejection. Faced with this challenge, in recent years regenerative medicine started looking for alternative solutions that could additionally support tissue regeneration. This review aims to outline the functions and possible clinical applications of, and future hopes associated with, using autologous or heterologous products such as antimicrobial peptides (AMPs), microvesicles (MVs), and neutrophil degranulation products (DGP) obtained from circulating neutrophils. Moreover, different interactions between neutrophils and platelets are described. Certain products released from neutrophils are critical for interactions between different immune cells to ensure adequate tissue repair. By acting directly and indirectly on host cells, these neutrophil-derived products can modulate the body’s inflammatory responses in various ways. The development of new formulations based on these products and their clinically proven success would give hope for significant progress in regenerative therapy in human and veterinary medicine.

Zearalenone interferes with the sperm-triggered inflammation in the bovine uterus in vitro: Negative impact on sperm motility and survival

Zearalenone (ZEN)-contaminated diets induce detrimental effects on the bovine reproduction. Recently, we reported that active sperm induce pro-inflammatory responses in bovine endometrial epithelial cells (BEECs) in vitro. This study aimed to investigate the impact of presence of ZEN on the sperm-uterine crosstalk in vitro. BEECs monolayers were stimulated by ZEN (10, 100, and 1000 ng/mL) for 0, 3, 6, 12, or 24 h and gene expressions were analyzed by real-time PCR. Moreover, BEECs were pre-exposed to ZEN (10, 100, and 1000 ng/mL) for 24 h then, co-incubated with sperm for 6 h. Conditioned media (CM) from a sperm-BEECs co-culture, after pre-exposure to ZEN, were harvested and exploited to challenge either polymorphonuclear cells (PMNs) or sperm. Both PMNs phagocytic activity toward sperm and sperm motility parameters were then assessed. Results showed that ZEN alone induced pro-inflammatory responses in BEECs through the induction of mRNA expressions of pro-inflammatory cytokines (TNFA and IL1B) and PGES1 at different time points. Pre-exposure of BEECs to ZEN, amplified the sperm-triggered upregulation of pro-inflammatory cytokines (TNFA and IL1B) and chemokine IL8 mRNA abundance in BEECs. Sperm-BEECs conditioned media, primed by ZEN, stimulated the PMNs phagocytosis for sperm whereas suppressed sperm motility parameters. Taken together, these findings indicate that the presence of ZEN augments the pro-inflammatory cascade triggered by sperm in BEECs, provokes PMNs phagocytosis for sperm, and reduces sperm motility parameters. Such immunological reactions may create a hostile environment for sperm competence and survival in the bovine uterus, thus impair fertility.

Imaging reveals novel innate immune responses in lung, liver, and beyond

Highly dynamic immune responses are generated toward pathogens or injuries, in vivo. Multiple immune cell types participate in various facets of the response which leads to a concerted effort in the removal and clearance of pathogens or injured tissue and a return to homeostasis. Intravital microscopy (IVM) has been extensively utilized to unravel the dynamics of immune responses, visualizing immune cell behavior in intact living tissues, within a living organism. For instance, the phenomenon of leukocyte recruitment cascade. Importantly, IVM has led to a deep appreciation that immune cell behavior and responses in individual organs are distinct, but also can influence one another. In this review, we discuss how IVM as a tool has been used to study the innate immune responses in various tissues during homeostasis, injury, and infection.

Immunosuppression Affects Neutrophil Functions: Does Calcineurin-NFAT Signaling Matter?

Neutrophils are innate immune cells with important roles in antimicrobial defense. However, impaired or dysregulated neutrophil function can result in host tissue damage, loss of homeostasis, hyperinflammation or pathological immunosuppression. A central link between neutrophil activation and immune outcomes is emerging to be the calcineurin-nuclear factor of activated T cells (NFAT) signaling pathway, which is activated by neutrophil detection of a microbial threat via pattern recognition receptors and results in inflammatory cytokine production. This potent pro-inflammatory pathway is also the target of several immunosuppressive drugs used for the treatment of autoimmune disorders, during solid organ and hematopoietic cell transplantations, and as a part of anti-cancer therapy: but what effects these drugs have on neutrophil function, and their broader consequences for immune homeostasis and microbial defense are not yet known. Here, we bring together the emerging literature describing pathology- and drug- induced neutrophil impairment, with particular focus on their effects on calcineurin-NFAT signaling in the innate immune compartment.

Neutrophil accumulation within tissues: A damage x healing dichotomy

The abundance of neutrophils in human circulation, their fast mobilization from blood to tissues, along with their alleged short life-span led to the image of neutrophils as a homogeneous cell type designed to fight infections and die in the process. Additionally, their granule content and capacity to produce molecules with considerable cytotoxic potential, lead to the general belief that neutrophil activation inexorably results in side effect of extensive tissue injury. Neutrophil activation in fact causes tissue injury as an adverse effect, but it seems that this is restricted to particular pathological situations and more of an "exception to the rule". Here we review evidences arising especially from intravital microscopy studies that demonstrate neutrophils as cells endowed with sophisticated mechanisms and able to engage in complex interactions as to minimize damage and optimize their effector functions. Moreover, neutrophil infiltration may even contribute to tissue healing and repair which may altogether demand a reexamination of current anti-inflammatory therapies that have neutrophil migration and activation as a target.

IL-17E, iNOS and Arginase1 as new biomarkers in the identification of neutrophilic dermatoses

Background

Neutrophilic dermatoses (ND) are a heterogeneous group of diseases, but can often have a relatively similar histological appearance.

Aim

To identify a combination of biomarkers allowing a better differentiation of ND types.

Methods

Biopsies were obtained from normal human skin (NS; n = 4), chronic plaque‐type psoriasis (PsO; n = 7), paradoxical psoriasis (PP; n = 8), generalized pustular psoriasis (GPP; n = 9), subcorneal pustular dermatosis of Sneddon–Wilkinson (SPD; n = 3), acute generalized exanthematous pustulosis (AGEP; n = 3), hidradenitis suppurativa (HS; n = 7), Sweet syndrome (SS; n = 8) and pyoderma gangrenosum (PG; n = 8). Samples were analysed by immunofluorescence using three biomarkers, interleukin (IL)‐17E, inducible nitric oxide synthase (iNOS) and arginase1, each one in combination with two cell markers, myeloperoxidase (MPO) and CD68, which allow the identification of neutrophils and macrophages, respectively.

Results

We found that SS is characterized by high expression of IL‐17E and iNOS in the epidermis, while PG exhibits low expression. The density of the neutrophil infiltrate helps to differentiate PP (high‐density infiltrate) from PsO (low‐density infiltrate). High expression of arginase1 in the granular layer of the epidermis is a hallmark of SPD. Finally, mature neutrophils and proinflammatory macrophages are readily detectable in PP, SPD and PG, whereas immature neutrophils and anti‐inflammatory macrophages are more frequent in GPP, AGEP, HS and SS.

Conclusions

The analysis of ND by immunofluorescence using IL‐17E, iNOS and arginase1 in combination with MPO and CD68 allows for characterization of differential expression patterns in the epidermis as well as the determination of the polarization status of the dermal neutrophils and macrophages. The appropriate markers may help in the differentiation of ND in clinical practice.