Myeloperoxidase Stimulates Neutrophil Degranulation

A murine multiple-injury model for the study of thromboinflammation

INTRODUCTION

Neutrophil extracellular traps (NETs) contribute to trauma-induced coagulopathy. We aimed to develop a murine multiple-injury model that induces thrombo-inflammatory response, that is, NETosis and accelerated thrombin generation.

METHODS

Wild-type male mice (n = 10, aged 8-12 weeks) underwent multiple injuries (gastrocnemius crush, femur fracture, and laparotomy) and were compared with an uninjured control group (n = 10). Mice were euthanized by cardiac puncture performed 3 hours after injury. Whole blood samples were immediately processed to platelet poor plasma for thrombin generation kinetics (calibrated automated thrombogram), myeloperoxidase (MPO), and von Willebrand factor quantification. Immunohistochemistry of lung tissue was performed to assess for citrullinated histone 3 (CitH3) and MPO. A NETosis cluster was defined as 3+ neutrophils staining for CitH3 at 400× magnification (CitH3 cluster). Data were presented either as mean (SD) or median (interquartile range) with p < 0.05 significant. Sham and trauma treated animals were compared by the two-sample Wilcoxon rank-sum test.

RESULTS

Animals subjected to multiple injuries had accelerated thrombin generation compared with controls with greater peak height (61.3 [41.2-73.2] vs. 28.4 [19.5-37.5] nM, p = 0.035) and shorter time to peak (3.37 [2.81-3.81] vs. 4.5 [4.08-4.75] minutes, p = 0.046). Markers of neutrophil activation were greater following multiple injuries than in controls (MPO, 961.1 [858.1-1116.8] vs. 481.3 [438.0-648.9] ng/mL; p = 0.004). NETosis, as evidenced by the aforementioned defined number of CitH3 clusters in the lung, was greater in multiple-injury animals than in controls (mean [SD], 3 [2.9] vs. 0.2 [0.7]; p = 0.009).

CONCLUSION

This is the first study to demonstrate that NETosis and accelerated thrombin generation can be induced using a murine multiple-injury model, as early as 3 hours following injury.

Free Radical Lipid Peroxidation Induced by Reactive Halogen Species

The review is devoted to the mechanisms of free radical lipid peroxidation (LPO) initiated by reactive halogen species (RHS) produced in mammals, including humans, by heme peroxidase enzymes, primarily myeloperoxidase (MPO). It has been shown that RHS can participate in LPO both in the initiation and branching steps of the LPO chain reactions. The initiation step of RHS-induced LPO mainly involves formation of free radicals in the reactions of RHS with nitrite and/or with amino groups of phosphatidylethanolamine or Lys. The branching step of the oxidative chain is the reaction of RHS with lipid hydroperoxides, in which peroxyl and alkoxyl radicals are formed. The role of RHS-induced LPO in the development of human inflammatory diseases (cardiovascular and neurodegenerative diseases, cancer, diabetes, rheumatoid arthritis) is discussed in detail.

Suppression of neutrophils by sodium exacerbates oxidative stress and arthritis

Introduction

Typical Western diet, rich in salt, contributes to autoimmune disease development. However, conflicting reports exist about the effect of salt on neutrophil effector functions, also in the context of arthritis.

Methods

We investigated the effect of sodium chloride (NaCl) on neutrophil viability and functions in vitro, and in vivo employing the murine K/BxN-serum transfer arthritis (STA) model.

Results and discussion

The effects of NaCl and external reactive oxygen species (H2O2) were further examined on osteoclasts in vitro. Hypertonic sodium-rich media caused primary/secondary cell necrosis, altered the nuclear morphology, inhibited phagocytosis, degranulation, myeloperoxidase (MPO) peroxidation activity and neutrophil extracellular trap (NET) formation, while increasing total ROS production, mitochondrial ROS production, and neutrophil elastase (NE) activity. High salt diet (HSD) aggravated arthritis by increasing inflammation, bone erosion, and osteoclast differentiation, accompanied by increased NE expression and activity. Osteoclast differentiation was decreased with 25 mM NaCl or 100 nM H2O2 addition to isotonic media. In contrast to NaCl, external H2O2 had pro-resorptive effects in vitro. We postulate that in arthritis under HSD, increased bone erosion can be attributed to an enhanced oxidative milieu maintained by infiltrating neutrophils, rather than a direct effect of NaCl.

Indole metabolites and colorectal cancer: Gut microbial tryptophan metabolism, host gut microbiome biomarkers, and potential intervention mechanisms

Tryptophan (Trp) functions in host-disease interactions. Its metabolism is a multi-pathway process. Indole and its derivatives are Trp metabolites unique to the human gut microbiota. Changes in Trp metabolism have also been detected in colorectal cancer (CRC). Here, combined with the existing CRC biomarkers, we ascribed it to the altered bacteria having the indole-producing ability by making a genomic prediction. We also reviewed the anti-inflammatory and possible anti-cancer mechanisms of indoles, including their effects on tumor cells, the ability to repair the gut barrier, regulation of the host immune system, and provide resistance against oxidative stress. Indole and its derivatives, along with related bacteria, could be targeted as auxiliary strategies to restrain cancer development in the future.

Non-Canonical Functions of Myeloperoxidase in Immune Regulation, Tissue Inflammation and Cancer

Myeloperoxidase (MPO) is one of the most abundantly expressed proteins in neutrophils. It serves as a critical component of the antimicrobial defense system, facilitating microbial killing via generation of reactive oxygen species (ROS). Interestingly, emerging evidence indicates that in addition to the well-recognized canonical antimicrobial function of MPO, it can directly or indirectly impact immune cells and tissue responses in homeostatic and disease states. Here, we highlight the emerging non-canonical functions of MPO, including its impact on neutrophil longevity, activation and trafficking in inflammation, its interactions with other immune cells, and how these interactions shape disease outcomes. We further discuss MPO interactions with barrier forming endothelial and epithelial cells, specialized cells of the central nervous system (CNS) and its involvement in cancer progression. Such diverse function and the MPO association with numerous inflammatory disorders make it an attractive target for therapies aimed at resolving inflammation and limiting inflammation-associated tissue damage. However, while considering MPO inhibition as a potential therapy, one must account for the diverse impact of MPO activity on various cellular compartments both in health and disease.

Dissecting the process of human neutrophil lineage determination by using alpha-lipoic acid inducing neutrophil deficiency model

Granulocyte-monocyte progenitors (GMPs) differentiate into both neutrophils and monocytes. Recently, uni-potential neutrophil progenitors have been identified both in mice and humans using an array of surface markers. However, how human GMPs commit to neutrophil progenitors and the regulatory mechanisms of fate determination remain incompletely understood. In the present study, we established a human neutrophil deficiency model using the small molecule alpha-lipoic acid. Using this neutrophil deficiency model, we determined that the neutrophil progenitor commitment process from CD371⁺ CD115^– GMPs defined by CD34 and CD15 and discovered that critical signals generated by RNA splicing and rRNA biogenesis regulate the process of early commitment for human early neutrophil progenitors derived from CD371⁺ CD115^– GMPs. These processes were elucidated by single-cell RNA sequencing both in vitro and in vivo derived cells. Sequentially, we identified that the transcription factor ELK1 is essential for human neutrophil lineage commitment using the alpha-lipoic acid (ALA)-inducing neutrophil deficiency model. Finally, we also revealed differential roles for long-ELK1 and short-ELK1, balanced by SF3B1, in the commitment process of neutrophil progenitors. Taken together, we discovered a novel function of ALA in regulating neutrophil lineage specification and identified that the SF3B1-ELK axis regulates the commitment of human neutrophil progenitors from CD371⁺ CD115^– GMPs.

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ALA completely blocks the differentiation of human neutrophils derived from CD34⁺ stem cells in ex-vivo culture.

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CD34 and CD15 could be used to define the early differentiation stages of human neutrophil lineage determination.

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SF3B1-ELK1 signal axis regulates human neutrophil lineage determination.

Ex vivo observation of granulocyte activity during thrombus formation

Background

The process of thrombus formation is thought to involve interactions between platelets and leukocytes. Leukocyte incorporation into growing thrombi has been well established in vivo, and a number of properties of platelet-leukocyte interactions critical for thrombus formation have been characterized in vitro in thromboinflammatory settings and have clinical relevance. Leukocyte activity can be impaired in distinct hereditary and acquired disorders of immunological nature, among which is Wiskott-Aldrich Syndrome (WAS). However, a more quantitative characterization of leukocyte behavior in thromboinflammatory conditions has been hampered by lack of approaches for its study ex vivo. Here, we aimed to develop an ex vivo model of thromboinflammation, and compared granulocyte behavior of WAS patients and healthy donors.

Results

Thrombus formation in anticoagulated whole blood from healthy volunteers and patients was visualized by fluorescent microscopy in parallel-plate flow chambers with fibrillar collagen type I coverslips. Moving granulocytes were observed in hirudinated or sodium citrate-recalcified blood under low wall shear rate conditions (100 s⁻¹). These cells crawled around thrombi in a step-wise manner with an average velocity of 90–120 nm/s. Pre-incubation of blood with granulocyte priming agents lead to a significant decrease in mean-velocity of the cells and increase in the number of adherent cells. The leukocytes from patients with WAS demonstrated a 1.5-fold lower mean velocity, in line with their impaired actin polymerization. It is noteworthy that in an experimental setting where patients’ platelets were replaced with healthy donor’s platelets the granulocytes’ crawling velocity did not change, thus proving that WASP (WAS protein) deficiency causes disruption of granulocytes’ behavior. Thereby, the observed features of granulocytes crawling are consistent with the neutrophil chemotaxis phenomenon. As most of the crawling granulocytes carried procoagulant platelets teared from thrombi, we propose that the role of granulocytes in thrombus formation is that of platelet scavengers.

Conclusions

We have developed an ex vivo experimental model applicable for observation of granulocyte activity in thrombus formation. Using the proposed setting, we observed a reduction of motility of granulocytes of patients with WAS. We suggest that our ex vivo approach should be useful both for basic and for clinical research.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-022-01238-x.

Free fatty acids promote degranulation of azurophil granules in neutrophils by inducing production of NADPH oxidase-derived reactive oxygen species in cows with subclinical ketosis

Subclinical ketosis (SCK) in dairy cows, a common metabolic disorder during the peripartal period, is accompanied by systemic inflammation. Excessive release of azurophil granule (AG) contents during degranulation of polymorphonuclear neutrophils (PMN) could contribute to systemic inflammation in SCK cows. Although the increase in blood free fatty acids (FFA) in SCK cows may promote AG degranulation from PMN, the underlying mechanisms are unclear. Thirty multiparous cows (within 3 wk postpartum) with similar lactation numbers (median = 3, range = 2-4) and days in milk (median = 6, range = 3-15) were classified based on serum β-hydroxybutyrate (BHB) level as control (n = 15, BHB < 0.6 mM) or SCK (n = 15, 1.2 mM < BHB < 3.0 mM). Cows with SCK had greater levels of serum haptoglobin, serum amyloid A, IL-1β, IL-6, IL-8 and tumor necrosis factor-α. These proinflammatory factors had strong positive correlations with myeloperoxidase (MPO), a marker protein of PMN AG, whose content was greater in the serum of SCK cows. Both the number of AG and the protein abundance of MPO were lower in PMN isolated from SCK cows. Additionally, we found a greater ratio of blood CH138A⁺/CD63^high cells and greater mean fluorescence intensity of CD63 on the PMN membrane, further confirming the greater degree of AG degranulation in cows with SCK. In vitro FFA dose response (0, 0.3, 0.6, 1.2, and 2.4 mM for 4 h) and time course (0, 0.5, 1, 2, and 4 h with 0.6 mM) experiments were performed on PMN isolated from control cows. The increase in MPO content in extracellular supernatant resulting from those experiments led to the selection of 0.6 mM FFA for 1 h duration as conditions for subsequent studies. After FFA treatment, release of intracellular MPO was increased along with increased levels of CD63 mean fluorescence intensity on the PMN membrane, confirming that FFA promoted degranulation of AG. In addition, FFA treatment increased reactive oxygen species (ROS) production by PMN, an effect that was attenuated by incubation with diphenyleneiodonium chloride (DPI), a NADPH oxidase-derived ROS inhibitor. The mitochondrial-derived ROS inhibitor carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP) did not affect ROS in response to FFA treatment. Treatment with FFA increased p47 phosphorylation and mRNA abundance of NCF1, NCF2, and CYBB in PMN. Furthermore, DPI, but not FCCP, dampened the degranulation of PMN AG induced by FFA in vitro. These data suggested that the degranulation of AG in PMN induced by FFA was mediated by NADPH oxidase-derived ROS. As verified ex vivo, PMN from SCK cows had greater levels of ROS, phosphorylation of p47, and mRNA abundance of NCF1, NCF2, and CYBB. Overall, the present study revealed that high blood concentrations of FFA in SCK cows induce the production of NADPH oxidase-derived ROS, thereby promoting degranulation of AG in PMN. The stimulatory effect of FFA on the release of AG content during degranulation, especially MPO, provides a new insight into the systemic inflammation experienced by peripartal cows with SCK.

D-Mannose Slows Glioma Growth by Modulating Myeloperoxidase Activity

Simple Summary

Inflammation and oxidative stress are important host defense responses. However, while the host response can be cytotoxic and kill tumor cells, tumor cells can also alter and exploit the host immune environment to further their survival. Thus, the host response can impact both tumor suppression and progression. Modulating the tumor–host response interaction to favor tumor suppression would be highly desirable. D-mannose has been found to have anti-inflammatory properties and can block signaling related to myeloperoxidase (MPO), a highly oxidizing pro-inflammatory enzyme secreted in host defense. However, the effect of D-mannose on host immune response in the glioma microenvironment has not been explored. We found that D-mannose slowed glioma growth by increasing MPO activity and oxidative stress in the glioma microenvironment. Our findings revealed that D-mannose may be able to shift the host immune response toward tumor suppression and could be a potential new therapeutic direction for these difficult-to-treat tumors.

Abstract

Host immune response in the tumor microenvironment plays key roles in tumorigenesis. We hypothesized that D-mannose, a simple sugar with anti-inflammatory properties, could decrease oxidative stress and slow glioma progression. Using a glioma stem cell model in immunocompetent mice, we induced gliomas in the brain and tracked MPO activity in vivo with and without D-mannose treatment. As expected, we found that D-mannose treatment decreased the number of MPO⁺ cells and slowed glioma progression compared to PBS-treated control animals with gliomas. Unexpectedly, instead of decreasing MPO activity, D-mannose increased MPO activity in vivo, revealing that D-mannose boosted the MPO activity per MPO⁺ cell. On the other hand, D-glucose had no effect on MPO activity. To better understand this effect, we examined the effect of D-mannose on bone marrow-derived myeloid cells. We found that D-mannose modulated MPO activity via two mechanisms: directly via N-glycosylation of MPO, which boosted the MPO activity of each molecule, and indirectly by increasing H₂O₂ production, the main substrate for MPO. This increased host immune response acted to reduce tumor size, suggesting that increasing MPO activity such as through D-mannose administration may be a potential new therapeutic direction for glioma treatment.

Microbial-derived indoles inhibit neutrophil myeloperoxidase to diminish bystander tissue damage

During episodes of acute inflammation, polymorphonuclear leukocytes (PMNs) are actively recruited to sites of inflammation or injury where they provide anti-microbial and wound-healing functions. One enzyme crucial for fulfilling these functions is myeloperoxidase (MPO), which generates hypochlorous acid from Cl^- and hydrogen peroxide. The potential exists, however, that uncontrolled the extracellular generation of hypochlorous acid by MPO can cause bystander tissue damage and inhibit the healing response. Previous work suggests that the microbiota-derived tryptophan metabolites 1H-indole and related molecules ("indoles") are protective during intestinal inflammation, although their precise mechanism of action is unclear. In the present work, we serendipitously discovered that indoles are potent and selective inhibitors of MPO. Using both primary human PMNs and recombinant human MPO in a cell-free system, we revealed that indoles inhibit MPO at physiologic concentrations. Particularly, indoles block the chlorinating activity of MPO, a reliable marker for MPO-associated tissue damage, as measured by coulometric-coupled HPLC. Further, we observed direct interaction between indoles and MPO using the established biochemical techniques microscale thermophoresis and STD-NMR. Utilizing a murine colitis model, we demonstrate that indoles inhibit bystander tissue damage, reflected in decreased colon 3-chlorotyrosine and pro-inflammatory chemokine expression in vivo. Taken together, these results identify microbiota-derived indoles that acts as endogenous immunomodulatory compounds through their actions on MPO, suggesting a symbiotic association between the gut microbiota and host innate immune system. Such findings offer exciting new targets for future pharmacological intervention.

The downregulation of NCXs is positively correlated with the prognosis of stage II-IV colon cancer

Purpose

Colon cancer (CC) is a very common gastrointestinal tumor that is prone to invasion and metastasis in the late stage. This study aims to observe the expression of Na⁺/Ca²⁺ exchangers (NCXs) and analyze the correlation between NCXs and the prognosis of CC.

Methods

Specimens of 111 stage II–IV CC patients were collected. We used western blotting, qPCR, and immunohistochemical staining to observe the distributions and expression levels of NCX isoforms (NCX1, NCX2, and NCX3) in CC and distal normal tissues. Cox proportional hazards models were used to assess prognostic factors for patients.

Results

The expression of NCXs in most tumor specimens was lower than that in normal tissues. The NCX expression levels in tumor tissues from the primary tumor, local lymph node metastasis sites, and distant liver metastasis sites were increasingly significantly lower than those in normal tissues. The results of the Kaplan-Meier survival curves showed that the downregulation of any NCX isoform was closely related to the worse prognosis of advanced CC.

Conclusion

NCXs can be used as independent prognostic factors for CC. Our research results are expected to provide new targets for the treatment of CC.

Toxicity in hematopoietic stem cells from bone marrow and peripheral blood in mice after benzene exposure: Single-cell transcriptome sequencing analysis

Benzene is a ubiquitous, occupational, and environmental hematotoxic and leukemogen. Damage to hematopoietic stem cells (HSCs) induced by benzene and its metabolites is a key event in bone marrow (BM) depression and leukemogenesis. There are no reports on transcriptome profiles of HSCs following benzene exposure. Here, Smart-seq2 single-cell transcriptome sequencing was used to detect transcriptomic alternations in BM HSCs and peripheral blood HSCs (PBSCs) in male C57B/6 mice exposed to benzene. We found that benzene caused hematotoxicity which was confirmed by routine blood test, pathological examination, and HSCs percentage analysis. A total of 1514 differentially expressed genes (DEGs) in BM HSCs and 1703 DEGs in PBSCs were screened after treatment with benzene. Weighted gene correlation network analysis revealed that pathways in cancer, transcriptional misregulation in cancer, and hematopoietic cell lineage are vital pathways involved in benzene-induced toxicity in BM HSCs, whereas hematopoietic cell lineage and leukocyte transendothelial migration are critical pathways in PBSCs. Of note, there were 164 common DEGs in both HSCs, out of which 53 genes were co-regulated in both types of HSCs. Subsequent pathway analysis of these 53 genes indicated that the most relevant pathways involved neutrophil degranulation and CD93 localized in the core of the network of the 53 genes, which are known to regulate leukemia stem cell self-renewal and quiescence. Our results could enhance our understanding of HSC responses to benzene, facilitate the identification of potential molecular biomarkers and future studies on its mechanism of toxicity toward HSCs.

Neutrophil signaling during myocardial infarction wound repair

Neutrophils are key effector cells of the innate immune system, serving as a first line of defense in the response to injury and playing essential roles in the wound healing process. Following myocardial infarction (MI), neutrophils infiltrate into the infarct region to propagate inflammation and begin the initial phase of cardiac wound repair. Pro-inflammatory neutrophils release proteases to degrade extracellular matrix (ECM), a necessary step for the removal of necrotic myocytes as a prelude for scar formation. Neutrophils transition their phenotype over time to regulate MI inflammation resolution and stabilize scar formation. Neutrophils contribute to the evolution from inflammation to resolution and scar formation by serving anti-inflammatory and repair functions. As anti-inflammatory cells, neutrophils contribute ECM proteins during scar formation, in particular fibronectin, galectin-3, and vimentin. The diverse and polarizing functions that contribute to MI wound repair make this innate immune cell a viable target to improve MI outcomes. Thus, understanding the signaling involved in neutrophil physiology in the context of MI may help to identify novel therapeutic targets.

Neutrophil-to-Lymphocyte Ratio: A Biomarker to Monitor the Immune Status of Astronauts

A comprehensive understanding of spaceflight factors involved in immune dysfunction and the evaluation of biomarkers to assess in-flight astronaut health are essential goals for NASA. An elevated neutrophil-to-lymphocyte ratio (NLR) is a potential biomarker candidate, as leukocyte differentials are altered during spaceflight. In the reduced gravity environment of space, rodents and astronauts displayed elevated NLR and granulocyte-to-lymphocyte ratios (GLR), respectively. To simulate microgravity using two well-established ground-based models, we cultured human whole blood-leukocytes in high-aspect rotating wall vessels (HARV-RWV) and used hindlimb unloaded (HU) mice. Both HARV-RWV simulation of leukocytes and HU-exposed mice showed elevated NLR profiles comparable to spaceflight exposed samples. To assess mechanisms involved, we found the simulated microgravity HARV-RWV model resulted in an imbalance of redox processes and activation of myeloperoxidase-producing inflammatory neutrophils, while antioxidant treatment reversed these effects. In the simulated microgravity HU model, mitochondrial catalase-transgenic mice that have reduced oxidative stress responses showed reduced neutrophil counts, NLR, and a dampened release of selective inflammatory cytokines compared to wildtype HU mice, suggesting simulated microgravity induced oxidative stress responses that triggered inflammation. In brief, both spaceflight and simulated microgravity models caused elevated NLR, indicating this as a potential biomarker for future in-flight immune health monitoring.

Anti-neutrophil antibodies (anti-MPO-ANCAs) are associated with poor prognosis in breast cancer patients

Anti-neutrophil antibodies are capable of activating neutrophils in sterile environments, releasing extracellular traps containing myeloperoxidase (MPO) and anti-MPO antibodies (MPO-ANCAs or anti-MPO-ANCAs), which have been implicated in the pathogenesis of several diseases. The present study evaluated systemic and tumor tissue levels of anti-MPO-ANCAs breast cancer patients, and its relation to clinicopathological characteristics. Anti-MPO-ANCAs were measured in serum and tissue samples of 150 patients by enzyme-linked immunoassay. Samples were pooled according to clinicopathological characteristics of patients. Higher anti-MPO-ANCAs levels were detected in groups presenting negative clinicopathological characteristics, such as high histological grade tumors and risk factors such as body mass index, menopausal status and early onset at diagnosis. The present data highlights anti-MPO-ANCAs as associated to poor prognosis in breast cancer, a role beyond its actually discussed role in autoimmunity and vasculitis.

The Role of Halogenative Stress in Atherogenic Modification of Low-Density Lipoproteins

This review discusses formation of reactive halogen species (RHS) catalyzed by myeloperoxidase (MPO), an enzyme mostly present in leukocytes. An imbalance between the RHS production and body's ability to remove or neutralize them leads to the development of halogenative stress. RHS reactions with proteins, lipids, carbohydrates, and antioxidants in the content of low-density lipoproteins (LDLs) of the human blood are described. MPO binds site-specifically to the LDL surface and modifies LDL properties and structural organization, which leads to the LDL conversion into proatherogenic forms captured by monocytes/macrophages, which causes accumulation of cholesterol and its esters in these cells and their transformation into foam cells, the basis of atherosclerotic plaques. The review describes the biomarkers of MPO enzymatic activity and halogenative stress, as well as the involvement of the latter in the development of atherosclerosis.

Neutrophil traps, anti-myeloperoxidase antibodies and cancer: Are they linked?

Myeloperoxidase is an enzyme present in neutrophils and has been demonstrated to be an important molecule for neutrophil extracellular traps (NETs) formation and function. Yet, it is also a source of autoantigens for anti-neutrophil or anti-myeloperoxidase antibodies (ANCAs), which are capable of activating these immune cells and provoke tissue damage in a sterile microenvironment. The presence of these antibodies in cancer has been related by case reports, but a few studies addressed the significance of this finding beyond autoimmunity context. In this review, we discuss the evidences regarding ANCAs and cancer and its putative clinical meaning in the context of tumor immunology.

The color of skin: yellow diseases of the skin, nails, and mucosa

The colors reflected from the skin are important indicators of dermatologic and systemic disorders. Incident light is subject to absorption by chromophores in the skin and scattering. Chromophores associated with yellow light reflection include the carotenoids and bilirubin. Various pathophysiologic mechanisms associated with these and other chromophores manifest with a yellow hue on examination. This review describes these mechanisms and the clinical features of yellow skin disorders by morphology. A brief summary of the differential diagnosis, laboratory investigations, and treatments are presented. Yellow skin disorders are a heterogenous group composed of abnormalities in keratin, elastic and connective tissue, lipid metabolism, and other states of metabolic, inflammatory, or organ dysfunction. Patients will present through different routes, and skin disease may precede or follow systemic disease. Dermatologists have an essential role in identifying those with malignant or systemic associations to ensure early diagnosis and treatment.

Neutrophil pyroptosis: new perspectives on sepsis

Pyroptosis is a caspase-1 or caspase-4/5/11-dependent programmed cell death associated with inflammation, which is initiated by inflammasomes or cytosolic LPS in innate immunity. Sepsis is a life-threatening organ dysfunction caused by an imbalance in the body's response to infection. It is a complex interaction between the pathogen and the host's immune system. Neutrophils play the role of a double-edged sword in sepsis, and a number of studies have previously shown that regulation of neutrophils is the most crucial part of sepsis treatment. Pyroptosis is one of the important forms for neutrophils to function, which is increasingly understood as a host active immune response. There is ample evidence that neutrophil pyroptosis may play an important role in sepsis. In recent years, a breakthrough in pyroptosis research has revealed the main mechanism of pyroptosis. However, the potential value of neutrophil pyroptosis in the treatment of sepsis did not draw enough attention. A literature review was performed on the main mechanism of pyroptosis in sepsis and the potential value of neutrophils pyroptosis in sepsis, which may be suitable targets for sepsis treatment in future.

Immunonutritional consequences of different serine-type protease inhibitors in a C57BL/6 hepatocarcinoma model

Imbalances in innate immunity and the activity of innate immune cells are implicated in the development of hepatocellular carcinoma (HCC). Plant seeds are good sources of protease inhibitors, which can have a significant influence on human health disorders, especially in the field of cancer prevention. To elucidate the impact and preventive effects of immunonutritional serine-type protease inhibitors (STPIs) on HCC, it was used an established model of chemically induced liver injury. Injured livers induced Akt as well as hepatic infiltration of NKG2D⁺ and CD74⁺ cells. Feeding STPIs reduced size and number of intrahepatic nodes of mononuclear. These animals showed an inverse association of the severity of HCC with bioactive hepcidin levels, which was significantly correlated with the hepatic myeloperoxidase activity. According to their origin, administration of STPIs significantly induce increased numbers of F4/80⁺ cells in injured livers that can be responsible for the biological effects detected on the parenchyma and inflammatory markers under DEN/TAA treatment. These findings can have direct implications in HCC immunotherapy where enhanced response(s) in inflammation-driven cancer patients could help promoting inflammation-driven processes and favor tumor growth. Altogether, this study demonstrates that oral administration of STPIs modulate innate immunity response influencing HCC aggressiveness and progression. These results represent a path forward to develop durable, long-lasting response against hepatocarcinoma and open a future research path in the development of coadjutant intervention strategies to pharmacological therapies.

Endotracheal intubation results in acute tracheal damage induced by mtDNA/TLR9/NF-κB activity

Tracheitis secondary to placement of an endotracheal tube (ETT) is characterized by neutrophil accumulation in the tracheal lumen, which is generally associated with epithelial damage. Mitochondrial DNA (mtDNA), has been implicated in systemic inflammation and organ dysfunction following trauma; however, less is known about the effects of a foreign body on local trauma and tissue damage. We hypothesized that tracheal damage secondary to the ETT will result in local release of mtDNA at sufficient levels to induce TLR9 and NF‐κB activation. In a swine model we compared the differences between uncoated, and chloroquine (CQ) and N‐acetylcysteine (NAC) coated ETTs as measured by tracheal lavage fluids (TLF) over a period of 6 h. The swine model allowed us to recreate human conditions. ETT presence was characterized by neutrophil activation, necrosis, and release of proinflammatory cytokines mediated by TLR9/NF‐κB induction. Amelioration of the tracheal damage was observed in the CQ and NAC coated ETT group as shown in tracheal tissue specimens and TLF. The role of TLR9/NF‐κB dependent activity was confirmed by HEK‐Blue hTLR9 reporter cell line analysis after coincubation with TLF specimens with predetermined concentrations of NAC or CQ alone or TLR9 inhibitory oligodeoxynucleotide (iODN). These findings indicate that therapeutic interventions aimed at preventing mtDNA/TLR9/NF‐κB activity may have benefits in prevention of acute tracheal damage.

Neutrophil activation in response to monomeric myeloperoxidase

Myeloperoxidase (MPO) is an oxidant-producing enzyme that can also regulate cellular functions via its nonenzymatic effects. Mature active MPO isolated from normal human neutrophils is a 145 kDa homodimer, which consists of 2 identical protomers, connected by a single disulfide bond. By binding to CD11b/CD18 integrin, dimeric MPO induces neutrophil activation and adhesion augmenting leukocyte accumulation at sites of inflammation. This study was performed to compare the potency of dimeric and monomeric MPO to elicit selected neutrophil responses. Monomeric MPO (hemi-MPO) was obtained by treating the dimeric MPO by reductive alkylation. Analysis of the crucial signal transducer, intracellular Ca2+, showed that dimeric MPO induces Ca2+ mobilization from the intracellular calcium stores of neutrophils and influx of extracellular Ca2+ whereas the effect of monomeric MPO on Ca2+ increase in neutrophils was less. It was also shown that monomeric MPO was less efficient than dimeric MPO at inducing actin cytoskeleton reorganization, cell survival, and neutrophil degranulation. Furthermore, we have detected monomeric MPO in the blood plasma of patients with acute inflammation. Our data suggest that the decomposition of dimeric MPO into monomers can serve as a regulatory mechanism that controls MPO-dependent activation of neutrophils and reduces the proinflammatory effects of MPO.

Differential genomics and transcriptomics between tyrosine kinase inhibitor-sensitive and -resistant BCR-ABL-dependent chronic myeloid leukemia

Previously, it has been stated that the BCR-ABL fusion-protein is sufficient to induce Chronic Myeloid Leukemia (CML), but additional genomic-changes are required for disease progression. Hence, we profiled control and tyrosine kinase inhibitors (TKI) alone or in combination with other drug-treated CML-samples in different phases, categorized as drug-sensitive and drug-resistant on the basis of BCR-ABL transcripts, the marker of major molecular-response. Molecular-profiling was done using the molecular-inversion probe-based-array, Human Transcriptomics-Array2.0, and Axiom-Biobank genotyping-arrays. At the transcript-level, clusters of control, TKI-resistant and TKI-sensitive cases were correlated with BCR-ABL transcript-levels. Both at the gene- and exon-levels, up-regulation of MPO, TPX2, and TYMS and down-regulation of STAT6, FOS, TGFBR2, and ITK lead up-regulation of the cell-cycle, DNA-replication, DNA-repair pathways and down-regulation of the immune-system, chemokine- and interleukin-signaling, TCR, TGF beta and MAPK signaling pathways. A comparison between TKI-sensitive and TKI-resistant cases revealed up-regulation of LAPTM4B, HLTF, PIEZO2, CFH, CD109, ANGPT1 in CML-resistant cases, leading to up-regulation of autophagy-, protein-ubiquitination-, stem-cell-, complement-, TGFβ- and homeostasis-pathways with specific involvement of the Tie2 and Basigin signaling-pathway. Dysregulated pathways were accompanied with low CNVs in CP-new and CP-UT-TKI-sensitive-cases with undetectable BCR-ABL-copies. High CNVs (previously reported gain of 9q34) were observed in BCR-ABL-independent and -dependent TKI, non-sensitive-CP-UT/AP-UT/B-UT and B-new samples. Further, genotyping CML-CP-UT cases with BCR-ABL 0-to-77.02%-copies, the identified, rsID239798 and rsID9475077, were associated with FAM83B, a candidate for therapeutic resistance. The presence of BCR-ABL, additional genetic-events, dysregulated-signaling-pathways and rsIDs associated with FAM83B in TKI-resistant-cases can be used to develop a signature-profile that may help in monitoring therapy.

The Ontogeny of a Neutrophil: Mechanisms of Granulopoiesis and Homeostasis

Comprising the majority of leukocytes in humans, neutrophils are the first immune cells to respond to inflammatory or infectious etiologies and are crucial participants in the proper functioning of both innate and adaptive immune responses. From their initial appearance in the liver, thymus, and spleen at around the eighth week of human gestation to their generation in large numbers in the bone marrow at the end of term gestation, the differentiation of the pluripotent hematopoietic stem cell into a mature, segmented neutrophil is a highly controlled process where the transcriptional regulators C/EBP-α and C/EBP-ε play a vital role. Recent advances in neutrophil biology have clarified the life cycle of these cells and revealed striking differences between neonatal and adult neutrophils based on fetal maturation and environmental factors. Here we detail neutrophil ontogeny, granulopoiesis, and neutrophil homeostasis and highlight important differences between neonatal and adult neutrophil populations.

Fine Regulation of Neutrophil Oxidative Status and Apoptosis by Ceruloplasmin and Its Derivatives

Timely neutrophil apoptosis is an essential part of the resolution phase of acute inflammation. Ceruloplasmin, an acute-phase protein, which is the predominant copper-carrying protein in the blood, has been suggested to have a marked effect on neutrophil life span. The present work is a comparative study on the effects of intact holo-ceruloplasmin, its copper-free (apo-) and partially proteolyzed forms, and synthetic free peptides RPYLKVFNPR (883-892) and RRPYLKVFNPRR (882-893) on polymorphonuclear leukocyte (PMNL, neutrophil) oxidant status and apoptosis. The most pronounced effect on both investigated parameters was found with copper-containing samples, namely, intact and proteolyzed proteins. Both effectively reduced spontaneous and tumor necrosis factor-α (TNF-α)-induced extracellular and intracellular accumulation of superoxide radicals, but induced a sharp increase in the oxidation of intracellular 2',7'-dichlorofluorescein upon short exposure. Therefore, intact and proteolyzed ceruloplasmin have both anti- and pro-oxidant effects on PMNLs wherein the latter effect is diminished by TNF-α and lactoferrin. Additionally, all compounds investigated were determined to be inhibitors of delayed spontaneous apoptosis. Intact enzyme retained its pro-survival activity, whereas proteolytic degradation converts ceruloplasmin from a mild inhibitor to a potent activator of TNF-α-induced neutrophil apoptosis.

Paucimannose-Rich N-glycosylation of Spatiotemporally Regulated Human Neutrophil Elastase Modulates Its Immune Functions

Human neutrophil elastase (HNE) is an important N-glycosylated serine protease in the innate immune system, but the structure and immune-modulating functions of HNE N-glycosylation remain undescribed. Herein, LC-MS/MS-based glycan, glycopeptide and glycoprotein profiling were utilized to first determine the heterogeneous N-glycosylation of HNE purified from neutrophil lysates and then from isolated neutrophil granules of healthy individuals. The spatiotemporal expression of HNE during neutrophil activation and the biological importance of its N-glycosylation were also investigated using immunoblotting, cell surface capture, native MS, receptor interaction, protease inhibition, and bacteria growth assays. Site-specific HNE glycoprofiling demonstrated that unusual paucimannosidic N-glycans, particularly Manα1,6Manβ1,4GlcNAcβ1,4(Fucα1,6)GlcNAcβ, predominantly occupied Asn124 and Asn173. The equally unusual core fucosylated monoantenna complex-type N-sialoglycans also decorated these two fully occupied sites. In contrast, the mostly unoccupied Asn88 carried nonfucosylated paucimannosidic N-glycans probably resulting from low glycosylation site solvent accessibility. Asn185 was not glycosylated. Subcellular- and site-specific glycoprofiling showed highly uniform N-glycosylation of HNE residing in distinct neutrophil compartments. Stimulation-induced cell surface mobilization demonstrated a spatiotemporal regulation, but not cell surface-specific glycosylation signatures, of HNE in activated human neutrophils. The three glycosylation sites of HNE were located distal to the active site indicating glycan functions other than interference with HNE enzyme activity. Functionally, the paucimannosidic HNE glycoforms displayed preferential binding to human mannose binding lectin compared with the HNE sialoglycoforms, suggesting a glycoform-dependent involvement of HNE in complement activation. The heavily N-glycosylated HNE protease inhibitor, α1-antitrypsin, displayed concentration-dependent complex formation and preferred glycoform-glycoform interactions with HNE. Finally, both enzymatically active HNE and isolated HNE N-glycans demonstrated low micromolar concentration-dependent growth inhibition of clinically-relevant Pseudomonas aeruginosa, suggesting some bacteriostatic activity is conferred by the HNE N-glycans. Taken together, these observations support that the unusual HNE N-glycosylation, here reported for the first time, is involved in modulating multiple immune functions central to inflammation and infection.

Use of a Granulocyte Immunofluorescence Assay Designed for Humans for Detection of Antineutrophil Cytoplasmic Antibodies in Dogs with Chronic Enteropathies

BACKGROUND

Perinuclear antineutrophil cytoplasmic antibodies (pANCA) previously have been shown to be serum markers in dogs with chronic enteropathies, with dogs that have food-responsive disease (FRD) having higher frequencies of seropositivity than dogs with steroid-responsive disease (SRD). The indirect immunofluorescence (IIF) assay used in previous publications is time-consuming to perform, with low interobserver agreement.

HYPOTHESIS/OBJECTIVES

We hypothesized that a commercially available granulocyte IIF assay designed for humans could be used to detect perinuclear antineutrophil cytoplasmic antibodies in dogs.

ANIMALS

Forty-four dogs with FRD, 20 dogs with SRD, 20 control dogs, and 38 soft-coated wheaten terrier (SCWT) or SCWT-cross dogs.

METHODS

A granulocyte assay designed for humans was used to detect pANCA, cANCA, and antinuclear antibodies (ANA), as well as antibodies against proteinase-3 protein (PR-3) and myeloperoxidase protein (MPO) in archived serum samples.

RESULTS

Sensitivity of the granulocyte assay to predict FRD in dogs was 0.61 (95% confidence interval (CI), 0.45, 0.75), and specificity was 1.00 (95% CI, 0.91, 1.00). A significant association was identified between positive pANCA or cANCA result and diagnosis of FRD (P < 0.0001). Agreement between the two assays to detect ANCA in the same serum samples from SCWT with protein-losing enteropathy/protein-losing nephropathy (PLE/PLN) was substantial (kappa, 0.77; 95% CI, 0.53, 1.00). Eight ANCA-positive cases were positive for MPO or PR-3 antibodies.

CONCLUSIONS AND CLINICAL IMPORTANCE

The granulocyte immunofluorescence assay used in our pilot study was easy and quick to perform. Agreement with the previously published method was good.