MARCKS Inhibition Alters Bovine Neutrophil Responses to Salmonella Typhimurium

Neutrophils are innate immune cells that respond quickly to sites of bacterial infection and play an essential role in host defense. Interestingly, some bacterial pathogens benefit from exuberant neutrophil inflammation. Salmonella is one such pathogen that can utilize the toxic mediators released by neutrophils to colonize the intestine and cause enterocolitis. Because neutrophils can aid gut colonization during Salmonella infection, neutrophils represent a potential host-directed therapeutic target. Myristoylated alanine-rich C-kinase substrate (MARCKS) is an actin-binding protein that plays an essential role in many neutrophil effector responses. We hypothesized that inhibition of MARCKS protein would alter bovine neutrophil responses to Salmonella Typhimurium (STm) ex vivo. We used a MARCKS inhibitor peptide to investigate the role of MARCKS in neutrophil responses to STm. This study demonstrates that MARCKS inhibition attenuated STm-induced neutrophil adhesion and chemotaxis. Interestingly, MARCKS inhibition also enhanced neutrophil phagocytosis and respiratory burst in response to STm. This is the first report describing the role of MARCKS protein in neutrophil antibacterial responses.

Uridine Diphosphate Glucose (UDP-G) Activates Oxidative Stress and Respiratory Burst in Isolated Neutrophils

The extracellular purinergic agonist uridine diphosphate glucose (UDP-G) activates chemotaxis of human neutrophils (PMN) and the recruitment of PMN at the lung level, via P2Y14 purinergic receptor signaling. This effect is similar to the activation of PMN with N-formyl-methionyl-leucyl-phenylalanine (fMLP), a mechanism that also triggers the production of superoxide anion and hydrogen peroxide via the NADPH oxidase system. However, the effects of UDP-G on this system have not been studied. Defects in the intracellular phagocyte respiratory burst (RB) cause recurrent infections, immunodeficiency, and chronic and severe diseases in affected patients, often with sepsis and hypoxia. The extracellular activation of PMN by UDP-G could affect the RB and oxidative stress (OS) in situations of inflammation, infection and/or sepsis. The association of PMNs activation by UDP-G with OS and RB was studied. OS was evaluated by measuring spontaneous chemiluminescence (CL) of PMNs with a scintillation photon counter, and RB by measuring oxygen consumption with an oxygen Clark electrode at 37 °C, in non-stimulated cells and after activation (15 min) with lipopolysaccharides (LPS, 2 µg/mL), phorbol myristate acetate (PMA, 20 ng/mL), or UDP-G (100 μM). The stimulation index (SI) was calculated in order to establish the activation effect of the three agonists. After stimulation with LPS or PMA, the activated PMNs (0.1 × 106 cells/mL) showed an increase in CL (35%, p < 0.05 and 56%, p < 0.01, SI of 1.56 and 2.20, respectively). Contrariwise, the stimulation with UDP-G led to a decreased CL in a dose-dependent manner (60%, 25 μM, p < 0.05; 90%, 50-150 μM, p < 0.001). Nonetheless, despite the lack of oxidative damage, UDP-G triggered RB (SI 1.8) in a dose-dependent manner (38-50%, 100-200 μM, p < 0.0001). UDP-G is able to trigger NADPH oxidase activation in PMNs. Therefore, the prevention of OS and oxidative damage observed upon PMN stimulation with UDP-G indicates an antioxidant property of this molecule which is likely due to the activation of antioxidant defenses. Altogether, LPS and UDP-G have a synergistic effect, suggesting a key role in infection and/or sepsis.

Modulatory Effect of Beneficial Enterococci and Their Enterocins on the Blood Phagocytes in Murine Experimental Trichinellosis

Bacteriocins (enterocins) represent a new therapeutic strategy in various intestinal and non-intestinal infections. In antiparasitic defence, an oxidative inflammation of phagocytes is effective in destroying new-born Trichinella spiralis larvae. The strains Enterococcus faecium CCM8558 and E. durans ED26E/7 and their enterocins, enterocin M and a durancin-like enterocin, respectively, were administered daily, and mice were then infected with T. spiralis larvae on the seventh day of treatment. Phagotest and Bursttest kits were used to detect the phagocytosis and respiratory burst in blood leukocytes. T. spiralis infection inhibited phagocytosis from day 11 post-infection (dpi) during the migration of new-born larvae into the muscles. E. faecium CCM8558, E. durans ED26E/7, and the durancin-like enterocin increased phagocytic activity from day 11 dpi. Both strains and their enterocins (enterocin M and durancin-like) stimulated the ingestion capability of phagocytes from 18 to 32 dpi. Enterococci/enterocins therapy prevented a reduction in cells with respiratory burst caused by T. spiralis infection from 11 dpi. The enzymatic activity of phagocytes was stimulated on 18 and 25 dpi, particularly by E. faecium CCM8558 and enterocin M. Enterocin M and the durancin-like enterocin were as effective in stimulating phagocytosis as the bacterial strains that produce them. The stimulation of phagocytosis could contribute to decreased larval migration and reduced parasite burden in the host.

Sputum from People with Cystic Fibrosis Reduces the Killing of Methicillin-Resistant Staphylococcus aureus by Neutrophils and Diminishes Phagosomal Production of Reactive Oxygen Species

Cystic fibrosis (CF) airway disease is characterized by chronic polymicrobial infections and an infiltration of neutrophils (PMNs). Staphylococcus aureus has been the most prevalent respiratory pathogen in CF. In particular, methicillin-resistant S. aureus (MRSA) represents a huge clinical burden in CF due to its association with lung disease and increased resistance to antibiotics. In CF, PMNs are unable to kill and clear MRSA. The reason for this remains largely unknown. Our study found that CF PMNs are as equally capable of killing MRSA as healthy PMNs. We show that the CF sputum, however, significantly impairs the ability of human PMNs to kill CF MRSA isolates. In the absence of CF sputum, PMNs kill MRSA via intracellular mechanisms mediated by phagocytosis, rather than extracellular mechanisms via NET formation. CF sputum does not affect the phagocytosis of MRSA via healthy or CF PMNs. Our results demonstrate that CF sputum exposure impairs phagosomal levels of reactive oxygen species (ROS) in MRSA-phagocytosing PMNs. While phagosomal co-localizations of MRSA with primary granule markers, myeloperoxidase and cathepsin D, were significantly reduced upon CF sputum exposure, that of a third azurophilic granule marker, neutrophil elastase, remained unaffected. This suggests that CF sputum does not compromise the fusion of primary granules with phagosomes but diminishes phagosomal ROS levels via another, likely more specific, mechanism. Overall, we identified the airway environment as an important factor that restricts neutrophils' oxidative microbicidal activities in CF against MRSA. These results deliver new details of the complex host-pathogen interactions present in the CF lung.

Short-Term Thermal Stress Affects Immune Cell Features in the Sea Urchin Paracentrotus lividus

Due to global warming, animals are experiencing heat stress (HS), affecting many organic functions and species' survival. In this line, some characteristics of immune cells in sea urchins subjected to short-term HS were evaluated. Paracentrotus lividus adult females were randomly divided into three groups and housed in tanks at 17 °C. In two of these tanks, the temperatures were gradually increased up to 23 and 28 °C. Celomatic fluid was collected after 3 and 7 days. The coelomocytes were morphologically typed and evaluated for their mitochondrial membrane potential (MMP), lipoperoxidation extent (LPO), and hydrogen peroxide content (H₂O₂). Respiratory burst was induced by treatment with phorbol 12-myristate 13-acetate (PMA). HS caused a significant change in the coelomocytes' type distribution. MMP increased in the 23 °C-group and decreased in the 28 °C-group at both 3 and 7 days. LPO only increased in the 28 °C-group at 7 days. H₂O₂ progressively decreased together with the temperature increase. Respiratory burst was detected in all groups, but it was higher in the 17 °C group. In conclusion, the increase in temperature above the comfort zone for this animal species affects their immune cells with possible impairment of their functions.

Clinical and Laboratory Parameters of Carp Edema Virus Disease: A Case Report

In the present study, we describe a natural outbreak of carp edema virus disease (CEVD) in koi carp, concentrating on clinical manifestation, gross and microscopic pathology, immunological parameters, viral diagnostics, and phylogenetic analysis. Examination of white blood cell parameters showed increased monocyte and decreased lymphocyte counts in CEV-affected fish compared to healthy control fish. Regarding immune system functioning, the present work shows, for the first time, enhanced phagocytic activity in CEV-affected fish. Respiratory burst of phagocytes was strongly increased in diseased fish, the increase being attributed to an increased phagocyte count rather than enhancement of their metabolic activity. The present work also newly shows histopathological changes in the pancreatic tissue of diseased koi.

In memoriam: Filippo Rossi (1926-2022)

Description of the scientific life of Filippo Rossi, who died in October 2022.

CXCR2 Antagonist RIST4721 Acts as a Potent Chemotaxis Inhibitor of Mature Neutrophils Derived from Ex Vivo-Cultured Mouse Bone Marrow

Neutrophils act as critical mediators of innate immunity, which depends on their rapid responses to chemokines followed by their migration towards sites of infection during chemotaxis. Chemokine receptors expressed on the surface of neutrophils mediate chemotaxis by activating contractile machinery as the cells escape from capillary beds and then attack pathogens. Neutrophils also contribute to inflammatory responses, which support pathogen destruction but can lead to acute and chronic inflammatory disorders. CXCR2, a G-protein-coupled chemokine receptor expressed on both myeloid and epithelial cells, is well-characterized for its capacities to bind multiple chemokines, including interleukin-8 and growth-related oncogene alpha in humans or keratinocyte chemokine (KC) in mice. Here we show that a small molecule CXCR2 antagonist termed RIST4721 can effectively inhibit KC-stimulated chemotaxis by neutrophils derived from ex vivo-cultured mouse bone marrow in a potent and dose-dependent manner. Antagonistic properties of RIST4721 are thoroughly characterized, including the maximal, half-maximal and minimum concentrations required to inhibit chemotaxis. Importantly, RIST4721-treated neutrophils exhibit robust phagocytosis and reactive oxygen species production, confirming drug specificity to chemotaxis inhibition. Together our data indicate that RIST4721 acts to inhibit inflammation mediated and potentiated by neutrophils and therefore promises to facilitate treatment of a host of inflammatory conditions.

Roles of mitochondria in neutrophils

Neutrophils are the most abundant leukocyte in human blood. They are critical for fighting infections and are involved in inflammatory diseases. Mitochondria are indispensable for eukaryotic cells, as they control the biochemical processes of respiration and energy production. Mitochondria in neutrophils have been underestimated since glycolysis is a major metabolic pathway for fuel production in neutrophils. However, several studies have shown that mitochondria are greatly involved in multiple neutrophil functions as well as neutrophil-related diseases. In this review, we focus on how mitochondrial components, metabolism, and related genes regulate neutrophil functions and relevant diseases.

Method Matters: Effect of Purification Technology on Neutrophil Phenotype and Function

Neutrophils are the most abundant leukocytes in human blood and the first cells responding to infection and injury. Due to their limited ex vivo lifespan and the impossibility to cryopreserve or expand them in vitro, neutrophils need to be purified from fresh blood for immediate use in experiments. Importantly, neutrophil purification methods may artificially modify the phenotype and functional characteristics of the isolated cells. The aim of this study was to expose the effects of ‘classical’ density-gradient purification versus the more expensive but faster immunomagnetic isolation on neutrophil phenotype and functionality. We found that in the absence of inflammatory stimuli, density-gradient-derived neutrophils showed increased polarization responses as well as enhanced release of reactive oxygen species (ROS), neutrophil extracellular traps (NETs) and granular proteins compared to cells derived from immunomagnetic isolation, which yields mostly quiescent neutrophils. Upon exposure to pro-inflammatory mediators, immunomagnetic isolation-derived neutrophils were significantly more responsive in polarization, ROS production, phagocytosis, NETosis and degranulation assays, in comparison to density-gradient-derived cells. We found no difference in chemotactic response in Multiscreen and under-agarose migration assays, but Boyden assays showed reduced chemotaxis of immunomagnetic isolation-derived neutrophils. Finally, we confirmed that density-gradient purification induces artificial activation of neutrophils, evidenced by e.g. higher expression of CD66b, formyl peptide receptor 1 (FPR1) and CD35, and the appearance of a separate neutrophil population expressing surface molecules atypical for neutrophils (e.g. CXCR3, MHC-II and CD14). Based on these results, we recommend using immunomagnetic separation of neutrophils for studying neutrophil polarization, phagocytosis, ROS production, degranulation and NETosis, whereas for Boyden chemotaxis assays, the density-gradient purification is more suitable.

Improvement of the antibody-dependent respiratory burst assay for assessing protective immune responses to malaria

The antibody-dependent respiratory burst (ADRB) assay is a sensitive isoluminol-based chemiluminescence (CL) functional assay designed to assess the capacity of opsonizing antibodies against merozoites to induce neutrophil respiratory burst. ADRB was shown to measure protective immunity against malaria in endemic areas, but the assay needed further improvement to ensure better sensitivity and reproducibility. Here, we adjusted parameters such as the freezing-thawing procedure of merozoites, merozoites's concentration and the buffer solution's pH, and we used the improved assay to measure ADRB activity of 207 sera from 97 and 110 individuals living, respectively, in Dielmo and Ndiop villages with differing malaria endemicity. The improvement led to increased CL intensity and assay sensitivity, and a higher reproducibility. In both areas, ADRB activity correlated with malaria endemicity and individual's age discriminated groups with and without clinical malaria episodes, and significantly correlated with in vivo clinical protection from Plasmodium falciparum malaria. Our results demonstrate that the improved ADRB assay can be valuably used to assess acquired immunity during monitoring by control programmes and/or clinical trials.

The Antibacterial Activity of Erythrocytes From Goose (Anser domesticus) Can Be Associated With Phagocytosis and Respiratory Burst Generation

In the lumen of blood vessels, there are large numbers of erythrocytes, which are approximately 95% of the total blood cells. Although the function of erythrocytes is to transport oxygen in the organism, recent studies have shown that mammalian and teleost erythrocytes are involved in the immune response against bacterial infections. However, the immune mechanisms used by avian erythrocytes are not yet clear. Here, we demonstrated that erythrocytes from goose have the ability to phagocytose as well as conduct antimicrobial activity. Firstly, we revealed the phagocytosis or adhesion activity of goose erythrocytes for latex beads 0.1-1.0 μm in diameter by fluorescence microscopy, and scanning and transmission electron microscopy. The low cytometry results also proved that goose erythrocytes had a wide range of phagocytic or adhesion activity for different bacteria. Followed, the low cytometry analysis data further explored that the goose erythrocytes contain the ability to produce reactive oxygen species (ROS) and inducible nitric oxide synthase (iNOS) in response to bacterial stimulation, and also up-regulated the expression of NOX family includes NOX1 and NOX5. Finally, we also found that goose erythrocytes showed a powerful antibacterial activity against all the three bacteria, meanwhile the stimulation of three kinds of bacteria up-regulated the expression of inflammatory factors, and increased the production of antioxidant enzymes to protect the cells from oxidative damage. Herein, our results demonstrate that goose Erythrocytes possess a certain phagocytic capacity and antioxidant system, and that the antimicrobial activity of erythrocytes can occurred through the production of unique respiratory burst against foreign pathogenic bacteria, which provides new clues to the interaction between bacteria and avian erythrocytes.

Plasma and wound fluids from trauma patients suppress neutrophil extracellular respiratory burst

BACKGROUND

Trauma increases susceptibility to secondary bacterial infections. The events suppressing antimicrobial immunity are unclear. Polymorphonuclear neutrophils (PMNs) migrate toward bacteria using chemotaxis, trap them in extracellular neutrophil extracellular traps, and kill them using respiratory burst (RB). We hypothesized that plasma and wound fluids from trauma patients alter PMN function.

METHODS

Volunteer PMNs were incubated in plasma or wound fluids from trauma patients (days 0 and 1, days 2 and 3), and their functions were compared with PMNs incubated in volunteer plasma. Chemotaxis was assessed in transwells. Luminometry assessed total and intracellular RB responses to receptor-dependent and independent stimulants. Neutrophil extracellular trap formation was assessed using elastase assays. The role of tissue necrosis in creating functionally suppressive systemic PMN environments was assessed using a novel pig model where PMNs were incubated in uninjured pig plasma or plasma from pigs undergoing intraperitoneal instillation of liver slurry.

RESULTS

Both plasma and wound fluids from trauma patients markedly suppress total PMN RB. Intracellular RB is unchanged, implicating suppression of extracellular RB. Wound fluids are more suppressive than plasma. Biofluids suppressed RB maximally early after injury and their effects decayed with time. Chemotaxis and neutrophil extracellular trap formation were suppressed by biofluids similarly. Lastly, plasma from pigs undergoing abdominal liver slurry instillation suppressed PMN RB, paralleling suppression by human trauma biofluids.

CONCLUSION

Trauma plasma and wound fluids suppress RB and other key PMNs antimicrobial functions. Circulating suppressive signals can be derived from injured or necrotic tissue at wound sites, suggesting a key mechanism by which tissue injuries can put the host at risk for infection.

Anti-Inflammatory and Antimicrobial Volatile Oils: Fennel and Cumin Inhibit Neutrophilic Inflammation via Regulating Calcium and MAPKs

Neutrophilic inflammatory diseases, such as chronic obstructive pulmonary disease (COPD), acute respiratory distress syndrome (ARDS), or psoriasis, exert a huge burden on the global health system due to the lack of safe and effective treatments. Volatile oils from terrestrial plants showed impressive therapeutic effects against disorders of the skin, digestive system, lungs, liver, metabolism, and nervous system. However, their effect on the immune system and neutrophil function is still elusive. Fennel, cumin, marjoram, lavender, caraway, and anise are the common nutraceuticals that are widely used in the Mediterranean diet. The volatile oils of these herbs were screened for various biological activities, including anti-inflammatory, anti-allergic, antimicrobial, and antiviral effects. Several oils showed anti-inflammatory and antimicrobial potential. Fennel (Foeniculum vulgare) and cumin (Cuminum cyminum) fruits' volatile oils significantly suppressed the activation of human neutrophils, including respiratory burst and the degranulation induced by formyl peptide receptor agonists fMLF/CB and MMK1 in the human neutrophils (IC₅₀, 3.8–17.2 µg/ml). The cytotoxic effect and free-radical scavenging effects (ABTS, DPPH) of these oils did not account for the observed effects. Both fennel and cumin volatile oils significantly shortened calcium influx recovery time and inhibited phosphorylation of mitogen-activated protein kinases (p38, JNK, and ERK) expression. The gas chromatography–mass spectrometry analysis of these oils revealed the presence of estragole and cuminaldehyde as the major components of fennel and cumin volatile oils, respectively. Our findings suggested that cumin and fennel, common in the Mediterranean diet, hold the potential to be applied for the treatment of neutrophilic inflammatory diseases.

Exercise-induced amplification of mitogen-stimulated oxidative burst in whole blood is strongly influenced by neutrophil counts during and following exercise

This study characterized the effect of moderate- or vigorous-intensity exercise on leukocyte counts, using fingertip sampling, and mitogen-stimulated oxidative burst, measured in whole blood with a point-of-care test. In a randomized crossover design, 13 healthy adults (mean ± SD age: 22 ± 2 years; seven male, six female) cycled for 30-min, once at 52 ± 5% V ˙ O2peak and on another occasion at 74 ± 9% V ˙ O2peak . Blood was sampled at baseline, immediately post-exercise, and 15- and 60-min post-exercise. The leukocyte differential and mitogen-stimulated Reactive Oxygen Species (ROS) production were assessed. Lymphocytes increased immediately post-exercise and decreased below pre-exercise levels 15- and 60-min later. Lymphocyte mobilization immediately post-exercise was 59 ± 36% greater with vigorous- compared to moderate-intensity exercise (p < 0.01). Neutrophils increased immediately after exercise (38 ± 19%, p < 0.01) remaining elevated 60-min later (50 ± 34%, p < 0.01; averaged across intensities) and did not differ between intensities (p = 0.259). Mitogen-stimulated ROS production was amplified immediately (+32 ± 37%, p < 0.01) and 60-min post-exercise (+56 ± 57%, p < 0.01; averaged across intensities) compared to rest and did not differ with intensity (p = 0.739). Exercise-induced amplification of ROS production was abolished when correcting for neutrophil, monocyte and platelet counts and correlated most strongly with neutrophil mobilization immediately (r = 0.709, p < 0.01) and 60-min after vigorous exercise (r = 0.687, p < 0.01). Leukocyte kinetics can be assessed using fingertip blood sampling in exercise settings. Exercise-induced amplification of oxidative burst is detectable with a point-of-care test, but results are strongly influenced by neutrophil counts, which may not be routinely quantified.

Prolyl-Isomerase Pin1 Controls Key fMLP-Induced Neutrophil Functions

Neutrophils are key cells of the innate immune and inflammatory responses. They are the first blood cells to migrate to the infection site where they release high amounts of reactive oxygen species (ROS) and several peptides and enzymes required for microbial killing. However, excessive neutrophil activation can induce tissue injury participating in inflammation, thus the characterization of the enzymes involved in neutrophil activation could help to identify new pharmacological targets to treat inflammation. The prolyl-isomerase Pin1 is a ubiquitous enzyme involved in several functions, however, its role in neutrophil functions is less known. In this study, we show that the bacterial peptide N-formyl-methionyl-leucyl-phenylalanine (fMLP or fMLF), a G-protein coupled receptor (GPCR) agonist-induced Pin1 activation in human neutrophils. PiB and juglone, two Pin1 inhibitors inhibited Pin1 activity in neutrophils and consequently inhibited fMLP-induced chemotaxis and -degranulation of azurophil and specific granules as measured by myeloperoxidase and neutrophil gelatinase-associated lipocalin (NGAL) release respectively. We also showed that PiB inhibited TNFα + fMLP-induced superoxide production, confirming the effect of juglone. These data show that inhibitors of Pin1 impaired key pro-inflammatory neutrophil functions elicited by GPCR activation and suggest that Pin1 could control neutrophil inflammatory functions.

Oxidative burst and phagocytic activity of phagocytes in canine parvoviral enteritis

Canine parvoviral enteritis (CPE) is a severe disease characterized by systemic inflammation and immunosuppression. The function of circulating phagocytes (neutrophils and monocytes) in affected dogs has not been fully investigated. We characterized the functional capacity of canine phagocytes in CPE by determining their oxidative burst and phagocytic activities using flow cytometry. Blood was collected from 28 dogs with CPE and 11 healthy, age-matched, control dogs. Oxidative burst activity was assessed by stimulating phagocytes with opsonized Escherichia coli or phorbol 12-myristate 13-acetate (PMA) and measuring the percentage of phagocytes producing reactive oxygen species and the magnitude of this production. Phagocytosis was measured by incubating phagocytes with opsonized E. coli and measuring the percentage of phagocytes containing E. coli and the number of bacteria per cell. Complete blood counts and serum C-reactive protein (CRP) concentrations were also determined. Serum CRP concentration was negatively and positively correlated with segmented and band neutrophil concentrations, respectively. Overall, no differences in phagocyte function were found between dogs with CPE and healthy control dogs. However, infected dogs with neutropenia or circulating band neutrophils had decreased PMA-stimulated oxidative burst activity compared to healthy controls. Additionally, CPE dogs with neutropenia or circulating band neutrophils had decreased PMA- and E. coli-stimulated oxidative burst activity and decreased phagocytosis of E. coli compared to CPE dogs without neutropenia or band neutrophils. We conclude that phagocytes have decreased oxidative burst and phagocytic activity in neutropenic CPE dogs and in CPE dogs with circulating band neutrophils.

The role of lipid peroxidation products and antioxidant enzymes in the pathogenesis of aseptic and purulent inflammation in cats

Objective:

The work aimed to determine the state of lipid peroxidation products and the activity of the antioxidant system in cats with aseptic inflammation and purulent-inflammatory processes of varying severity.

Materials and Methods:

The intensity of the process of lipid peroxidation- antioxidant system processes in blood plasma was evaluated using commercial kits. The level of diene conjugates (DC), the content of malondialdehyde (MDA), the level of medium-weight molecules were determined from lipid peroxidation indices. The state of antioxidant protection was assessed by indicators of superoxide dismutase (SOD) activity, catalase (CT), ceruloplasmin (CP) concentration, glutathione peroxidase activity, glutathione reductase (GLR), and total antioxidant activity (AOA).

Results:

With aseptic inflammation in the blood of cats, a slow activation of peroxidation reactions occurred. The DC indicator increased by 1.4 times, the SOD level rose by 1.38 times, the amount of GLR by 1.04 times, and the activation of total AOA by 9.06. In sepsis, the values of DC, MDA, and medium-weight molecules increased by 4.4, 8.4, and 8.8 times, respectively. With abscesses in the blood of cats, an increase in CT, CP, and GLR is observed against a background of a decrease in glutathione peroxidase. With purulent wounds, the total AOA of plasma increases by 2.5 times; with abscesses, the total AOA increases by 1.9 times, and with sepsis, it decreases by 1.5 times.

Conclusion:

With surgical infections in cats, deep biochemical changes or irreversible biochemical changes (in sepsis) occur that indicate a significantly enhanced catabolic orientation of metabolic processes and the accumulation of toxic metabolites, which leads to damage and a decrease in tissue regenerative capacity.

Cystic Fibrosis Sputum Impairs the Ability of Neutrophils to Kill Staphylococcus aureus

Cystic fibrosis (CF) airway disease is characterized by chronic microbial infections and infiltration of inflammatory polymorphonuclear (PMN) granulocytes. Staphylococcus aureus (S. aureus) is a major lung pathogen in CF that persists despite the presence of PMNs and has been associated with CF lung function decline. While PMNs represent the main mechanism of the immune system to kill S. aureus, it remains largely unknown why PMNs fail to eliminate S. aureus in CF. The goal of this study was to observe how the CF airway environment affects S. aureus killing by PMNs. PMNs were isolated from the blood of healthy volunteers and CF patients. Clinical isolates of S. aureus were obtained from the airways of CF patients. The results show that PMNs from healthy volunteers were able to kill all CF isolates and laboratory strains of S. aureus tested in vitro. The extent of killing varied among strains. When PMNs were pretreated with supernatants of CF sputum, S. aureus killing was significantly inhibited suggesting that the CF airway environment compromises PMN antibacterial functions. CF blood PMNs were capable of killing S. aureus. Although bacterial killing was inhibited with CF sputum, PMN binding and phagocytosis of S. aureus was not diminished. The S. aureus-induced respiratory burst and neutrophil extracellular trap release from PMNs also remained uninhibited by CF sputum. In summary, our data demonstrate that the CF airway environment limits killing of S. aureus by PMNs and provides a new in vitro experimental model to study this phenomenon and its mechanism.

Sulfate Import in Salmonella Typhimurium Impacts Bacterial Aggregation and the Respiratory Burst in Human Neutrophils

During enteric salmonellosis, neutrophil-generated reactive oxygen species alter the gut microenvironment, favoring survival of Salmonella Typhimurium. While type 3 secretion system 1 (T3SS-1) and flagellar motility are potent Salmonella Typhimurium agonists of the neutrophil respiratory burst in vitro, neither of these pathways alone is responsible for stimulation of a maximal respiratory burst. To identify Salmonella Typhimurium genes that impact the magnitude of the neutrophil respiratory burst, we performed a two-step screen of defined mutant libraries in coculture with human neutrophils. We first screened Salmonella Typhimurium mutants lacking defined genomic regions and then tested single-gene deletion mutants representing particular regions under selection. A subset of single-gene deletion mutants was selected for further investigation. Mutants in four genes, STM1696 (sapF), STM2201 (yeiE), STM2112 (wcaD), and STM2441 (cysA), induced an attenuated respiratory burst. We linked the altered respiratory burst to reduced T3SS-1 expression and/or altered flagellar motility for two mutants (ΔSTM1696 and ΔSTM2201). The ΔSTM2441 mutant, defective for sulfate transport, formed aggregates in minimal medium and adhered to surfaces in rich medium, suggesting a role for sulfur homeostasis in the regulation of aggregation/adherence. We linked the aggregation/adherence phenotype of the ΔSTM2441 mutant to biofilm-associated protein A and flagellins and hypothesize that aggregation caused the observed reduction in the magnitude of the neutrophil respiratory burst. Our data demonstrate that Salmonella Typhimurium has numerous mechanisms to limit the magnitude of the neutrophil respiratory burst. These data further inform our understanding of how Salmonella may alter human neutrophil antimicrobial defenses.

Effect of acute isooxic hypercapnia on oxidative activity of systemic neutrophils in endotoxemic rabbits

Introduction

Whether carbon dioxide (CO₂) affects systemic oxidative phenomena under conditions of endotoxemia is not sufficiently clarified. The study aimed to assess the impact of moderate acute hypercapnia on the respiratory burst of circulating neutrophils in mechanically ventilated endotoxemic rabbits.

Material and methods

Twenty-four endotoxemic rabbits were mechanically ventilated with standard or CO₂-enriched gas mixture in order to obtain isooxic hypercapnia. At a baseline point and following 180 min of hypercapnic ventilation, luminol-dependent chemiluminescence (CL) of circulating neutrophils and serum 2-thiobarbituric acid reactive substance (TBARS) concentrations were measured. Throughout the study, leukocyte and neutrophil counts, pH status, circulatory parameters and body temperature were also assessed.

Results

Following 180 min of hypercapnic ventilation, opsonized zymosan (OZ)-stimulated neutrophils showed lower CL vs. the control group (p = 0.004). Other parameters studied were not affected.

Conclusions

Short-term isooxic hypercapnia in endotoxemic rabbits preserves circulating neutrophil count pattern and reactive oxygen species (ROS) generation, but it may reduce phagocytosis.

Exopolysaccharide from Porphyridium cruentum (purpureum) is Not Toxic and Stimulates Immune Response against Vibriosis: The Assessment Using Zebrafish and White Shrimp Litopenaeus vannamei

Exopolysaccharides, or extracellular polysaccharides (EPS, sPS), represent a valuable metabolite compound synthesized from red microalgae. It is a non-toxic natural agent and can be applied as an immunostimulant. The toxicity test of exopolysaccharides from Porphyridium has been done in vivo using zebrafish (Danio rerio) embryonic model, or the ZET (zebrafish embryotoxicity test). The administration of extracellular polysaccharides or exopolysaccharides (EPS) from microalgae Porphyridium cruentum (synonym: P. purpureum) to shrimps Litopenaeus vannamei was investigated to determine the effect of this immunostimulant on their non-specific immune response and to test if this compound can be used as a protective agent for shrimps in relation to Vibrio infection. For immune response, exopolysaccharides were given to shrimps via the immersion method on day 1 and booster on day 8. Shrimp hemocytes were taken on day 1 (EPS administration), day 7 (no treatment), day 8 (EPS booster) and day 9 (Vibrio infection) and tested for their immune response on each treatment. The result shows that the EPS is not toxic, as represented by the normal embryonic development and the mortality data. In the Pacific white shrimps, an increase in the values of all immune parameters was shown, in line with the increasing EPS concentration, except for the differential hemocyte count (DHC). In detail, an increase was noted in total hemocytes (THC) value, phagocytotic activity (PA) and respiratory burst (RB) in line with the EPS concentration increase. These results and other previous studies indicate that EPS from Porphyridium is safe, enhances immune parameters in shrimp rapidly, and has the ability to act as an immunostimulant or an immunomodulator. It is a good modulator for the non-specific immune cells of Pacific white shrimps, and it can be used as a preventive agent against vibriosis.

Respiratory Burst and TNF-α Receptor Expression of Neutrophils after Sepsis and Severe Injury-Induced Inflammation in Children

Systemic inflammatory response syndrome (SIRS) is defined as the systemic host response to infection or a non-infectious factor. The purpose of this study was to evaluate the involvement of reactive oxygen species (ROS) in severe inflammation and to assess the discrimination strength of the neutrophil BURSTTEST assay regarding its etiology in three groups of patients (sepsis, burns, and bone fractures) who met the SIRS criteria. The neutrophil activation (respiratory burst of granulocytes as well as p55 and p75 tumor necrosis factor (TNF-α) receptor expression) was evaluated twice using flow cytometry, and the results were compared with healthy controls and among SIRS subjects. A decreased oxygen metabolism in neutrophils after E.coli stimulation and increased TNF-α receptor expression were found in septic and burned patients on admission, while ROS production augmented and TNF-α receptor expression diminished with the applied therapy. The significant differences in neutrophil respiratory burst intensity among septic and burned patients and those with sepsis and bone fractures were found (however, there were not any such differences between patients with thermal and mechanical injuries). This study indicates that the neutrophil BURSTTEST evaluation might be a clinically reliable marker for differentiating the SIRS etiology.

Staphylococcal DNA Repair Is Required for Infection

To cause infection, Staphylococcus aureus must withstand damage caused by host immune defenses. However, the mechanisms by which staphylococcal DNA is damaged and repaired during infection are poorly understood. Using a panel of transposon mutants, we identified the rexBA operon as being important for the survival of Staphylococcus aureus in whole human blood. Mutants lacking rexB were also attenuated for virulence in murine models of both systemic and skin infections. We then demonstrated that RexAB is a member of the AddAB family of helicase/nuclease complexes responsible for initiating the repair of DNA double-strand breaks. Using a fluorescent reporter system, we were able to show that neutrophils cause staphylococcal DNA double-strand breaks through reactive oxygen species (ROS) generated by the respiratory burst, which are repaired by RexAB, leading to the induction of the mutagenic SOS response. We found that RexAB homologues in Enterococcus faecalis and Streptococcus gordonii also promoted the survival of these pathogens in human blood, suggesting that DNA double-strand break repair is required for Gram-positive bacteria to survive in host tissues. Together, these data demonstrate that DNA is a target of host immune cells, leading to double-strand breaks, and that the repair of this damage by an AddAB-family enzyme enables the survival of Gram-positive pathogens during infection.IMPORTANCE To cause infection, bacteria must survive attack by the host immune system. For many bacteria, including the major human pathogen Staphylococcus aureus, the greatest threat is posed by neutrophils. These immune cells ingest the invading organisms and try to kill them with a cocktail of chemicals that includes reactive oxygen species (ROS). The ability of S. aureus to survive this attack is crucial for the progression of infection. However, it was not clear how the ROS damaged S. aureus and how the bacterium repaired this damage. In this work, we show that ROS cause breaks in the staphylococcal DNA, which must be repaired by a two-protein complex known as RexAB; otherwise, the bacterium is killed, and it cannot sustain infection. This provides information on the type of damage that neutrophils cause S. aureus and the mechanism by which this damage is repaired, enabling infection.

Stimulation and inhibition of respiratory burst in neutrophils as a result of action of weak combined magnetic fields adjusted to ICR of protonated water forms

Weak combined collinear magnetic fields (CMFs) composed of constant component, 60 μT and low-frequency alternating field, 100 nT, used in 40 min pretreatment, were shown to have diverse effects (alleviation/stimulation) depending on the frequency of the alternating component on respiratory burst intensity in neutrophil suspension after activation by N-formyl-Met-Leu-Phe recorded by luminol-dependent chemiluminescence. About 12.6 Hz frequency formally corresponding to ion cyclotron resonance (ICR) frequency of hydrated hydronium ion (Н₉О₄ ⁺) had notable stimulating effect. On the contrary, treatment with 48.5 Hz frequency corresponding to hydronium ion (Н₃О⁺) was accompanied by significant alleviation of respiratory burst intensity. CMFs-pretreated water conducted only stimulating effect of CMFs when the field was adjusted to ICR of hydrated hydronium ion form, which is direct proof of participation of water in the mechanism of this effect of CMFs.

Effect of hydrogen peroxide on the oxidative burst of neutrophils in pigs and ruminants

Background and Aim

Neutrophils represent between 20% and 75% of white blood cells in animals and play a key role in an effective immune response. The generation of reactive oxygen species (ROS) is commonly referred to as an oxidative burst and is crucial under healthy and disease conditions. Interestingly, ROS are emerging as regulators of several neutrophil functions, including their oxidative burst. The present study aimed to investigate the effect of hydrogen peroxide on the oxidative burst of neutrophils, collected from domestic animal species (namely, pig, cattle, and sheep), and exposed to different stimuli.

Materials and Methods

A total of 65 slaughtered animals were included in the present study: Twenty-two pigs, 21 cattle, and 22 sheep. Blood samples were collected at bleeding and neutrophils were then purified using ad hoc developed and species-specific protocols. Neutrophils were treated with hydrogen peroxide at micromolar-to-millimolar concentrations, alone, or combined with other stimuli (i.e., opsonized yeasts, and phorbol 12-myristate 13-acetate). The generation of ROS was evaluated using a luminol-derived chemiluminescence (CL) assay. For each animal species, data were aggregated and reported as mean area under curve±standard deviation. Finally, data were statistically analyzed by one-way ANOVA, followed by Tukey's post hoc test.

Results

Exposure of bovine and ovine neutrophils to hydrogen peroxide alone resulted in a dose-dependent enhancement of the CL response, which was significantly stronger at its highest concentration and proved particularly prominent in sheep. Opsonized yeasts and phorbol 12-myristate 13-acetate both proved capable of stimulating the generation of ROS in all animal species under study. Hydrogen peroxide negatively modulated the oxidative burst of neutrophils after exposure to those stimuli, observed response patterns varying between pigs and ruminants. Porcine neutrophils, pre-exposed to micromolar concentrations of hydrogen peroxide, showed a decreased CL response only to opsonized yeasts. Conversely, pre-exposure to hydrogen peroxide reduced the CL response of ruminant neutrophils both to yeasts and phorbol 12-myristate 13-acetate, the effect being most prominent at 1 mM concentration.

Conclusion

These results indicate that hydrogen peroxide is capable of modulating the oxidative bursts of neutrophils in a species-specific and dose-dependent manner, substantial differences existing between pigs and ruminants. Further investigation is required to fully comprehend such modulation, which is crucial for the proper management of the generation of ROS under healthy and disease conditions.

Histone H4 directly stimulates neutrophil activation through membrane permeabilization

Extracellular histones have been implicated as a cause of tissue inflammatory injury in a variety of disorders including sepsis, lung, and liver diseases. However, little is known about their interactions with neutrophils and how this might contribute to injury. Here, it is shown that histone H4 acts as neutrophil activator by inducing hydrogen peroxide production, degranulation, cell adhesion, and IL‐8 generation. Histone H4 caused permeabilization of the neutrophil membrane (a phenomenon described in other cell types) leading to accelerated cell death. H4 caused sustained rise in neutrophil intracellular calcium that is necessary for respiratory burst activation and degranulation. Convincing evidence was not found for TLRs or ATP receptors in H4 mediated activation. However, pertussis toxin and wortmannin (inhibitors of G protein and PI3K) inhibited H4‐induced hydrogen peroxide production and degranulation. These studies suggest that release of histone H4 in sites of infection or inflammation may potentiate neutrophil activation and promote additional inflammatory responses. These studies may provide a better basis for developing novel therapeutic strategies to block neutrophil extracellular trap (NET) and H4‐related pathology in sepsis and various forms of lung injury including that induced by viruses like influenza or SAR‐CoV2.

Reaction Cycles of Halogen Species in the Immune Defense: Implications for Human Health and Diseases and the Pathology and Treatment of COVID-19

There is no vaccine or specific antiviral treatment for COVID-19, which is causing a global pandemic. One current focus is drug repurposing research, but those drugs have limited therapeutic efficacies and known adverse effects. The pathology of COVID-19 is essentially unknown. Without this understanding, it is challenging to discover a successful treatment to be approved for clinical use. This paper addresses several key biological processes of reactive oxygen, halogen and nitrogen species (ROS, RHS and RNS) that play crucial physiological roles in organisms from plants to humans. These include why superoxide dismutases, the enzymes to catalyze the formation of H₂O₂, are required for protecting ROS-induced injury in cell metabolism, why the amount of ROS/RNS produced by ionizing radiation at clinically relevant doses is ~1000 fold lower than the endogenous ROS/RNS level routinely produced in the cell and why a low level of endogenous RHS plays a crucial role in phagocytosis for immune defense. Herein we propose a plausible amplification mechanism in immune defense: ozone-depleting-like halogen cyclic reactions enhancing RHS effects are responsible for all the mentioned physiological functions, which are activated by H₂O₂ and deactivated by NO signaling molecule. Our results show that the reaction cycles can be repeated thousands of times and amplify the RHS pathogen-killing (defense) effects by 100,000 fold in phagocytosis, resembling the cyclic ozone-depleting reactions in the stratosphere. It is unraveled that H₂O₂ is a required protective signaling molecule (angel) in the defense system for human health and its dysfunction can cause many diseases or conditions such as autoimmune disorders, aging and cancer. We also identify a class of potent drugs for effective treatment of invading pathogens such as HIV and SARS-CoV-2 (COVID-19), cancer and other diseases, and provide a molecular mechanism of action of the drugs or candidates.

A synthesized heterocyclic chalcone inhibits neutrophilic inflammation through K+ -dependent pH regulation

Human neutrophils have a vital role in host defense and inflammatory responses in innate immune systems. Growing evidence shows that the overproduction of reactive oxygen species and granular proteolytic enzymes from activated neutrophils is linked to the pathogenesis of acute inflammatory diseases. However, adequate therapeutic targets are still lacking to regulate neutrophil functions. Herein, we report that MVBR-28, synthesized from the Mannich bases of heterocyclic chalcone, has anti-neutrophilic inflammatory effects through regulation of intracellular pH. MVBR-28 modulates neutrophil functions by attenuating respiratory burst, degranulation, and migration. Conversely, MVBR-28 has no antioxidant effects and fails to alter elastase activity in cell-free systems. The anti-inflammatory effects of MVBR-28 are not seen through cAMP pathways. Significantly, MVBR-28 potently inhibits extracellular Ca²⁺ influx in N-formyl-methionyl-leucyl-phenylalanine (fMLF)- and thapsigargin-activated human neutrophils. Notably, MVBR-28 attenuates fMLF-induced intracellular alkalization in a K⁺ -dependent manner, which is upstream of Ca²⁺ pathways. Collectively, these findings provide new insight into Mannich bases of heterocyclic chalcone regarding the regulation of neutrophil functions and the potential for the development of MVBR-28 as a lead compound for treating neutrophilic inflammatory diseases.

Survival of Streptococcus suis in Porcine Blood Is Limited by the Antibody- and Complement-Dependent Oxidative Burst Response of Granulocytes

Bacteremia is a hallmark of invasive Streptococcus suis infections of pigs, often leading to septicemia, meningitis, or arthritis. An important defense mechanism of neutrophils is the generation of reactive oxygen species (ROS). In this study, we report high levels of ROS production by blood granulocytes after intravenous infection of a pig with high levels of S. suis-specific antibodies and comparatively low levels of bacteremia. This prompted us to investigate the working hypothesis that the immunoglobulin-mediated oxidative burst contributes to the killing of S. suis in porcine blood. Several S. suis strains representing serotypes 2, 7, and 9 proved to be highly susceptible to the oxidative burst intermediate hydrogen peroxide, already at concentrations of 0.001%. The induction of ROS in granulocytes in ex vivo-infected reconstituted blood showed an association with pathogen-specific antibody levels. Importantly, inhibition of ROS production by the NADPH oxidase inhibitor apocynin led to significantly increased bacterial survival in the presence of high specific antibody levels. The oxidative burst rate of granulocytes partially depended on complement activation, as shown by specific inhibition. Furthermore, treatment of IgG-depleted serum with a specific IgM protease or heat to inactivate complement resulted in >3-fold decreased oxidative burst activity and increased bacterial survival in reconstituted porcine blood in accordance with an IgM-complement-oxidative burst axis. In conclusion, this study highlights an important control mechanism of S. suis bacteremia in the natural host: the induction of ROS in blood granulocytes via specific immunoglobulins such as IgM.

Rituximab Treatment Modulates the Release of Hydrogen Peroxide and the Production of Proinflammatory Cytokines by Monocyte at the Onset of Type 1 Diabetes

BACKGROUND

Monocytes are the main blood innate mononuclear phagocyte and one of the most important effector cells expressing Fcγ receptor, which is critical for the interaction with Fc domain of antibodies.

OBJECTIVE

To evaluate the effect of Rituximab (RTX, a chimeric human anti-CD20 monoclonal antibody) on the functional activities of Monocytes (MOs) at the onset of human Type 1 Diabetes (T1D).

METHODS

MOs were isolated from peripheral blood mononuclear cells (PBMCs) obtained from volunteer patients with recent-onset T1D and healthy control donors.

RESULTS

The levels of the production of Interleukin 1β (IL-1β) and IL-6 were significantly increased in MOs from patients with T1D when compared to MOs from healthy controls (respectively, p < 0.01 and p < 0.05). Similarly, Interferon γ (IFN-γ), and intracellular free Calcium Ion (ifCa2+) levels were increased in T1D MOs than in control MOs, but the difference did not reach a significant level. Conversely, the production levels of IL-4 and catalase activity, as well as of both phagocytosis and killing capacities were decreased in MOs of T1D patients compared to MOs from healthy controls, but the difference was not significant for catalase activity and killing capacity (respectively, p < 0.01, p > 0.05, p < 0.01, and p > 0.05). Additionally, treatment with RTX significantly upregulated phagocytosis (p < 0.05), markedly downregulated the release of IL-1β (p < 0.01), ifCa2+, hydrogen peroxide (H2O2), and slightly downregulated the Nitric Oxide Synthase (NOS) activity, NOS activity-to-arginase activity ratio, the levels of Lactate Dehydrogenase (LDH)-based cytotoxicity, and the production of IL-6 and IFN-γ. Moreover, RTX treatment significantly upregulated the production of IL-4 (p < 0.05), IL-10 (p < 0.01) and the catalase activity (p < 0.05).

CONCLUSION

Our study has shown for the first time that RTX can reverse the abnormal functional activities of MOs as well as their production of proinflammatory cytokines at the onset of T1D. From a therapeutic point of view, RTX may potentially be suggested at the beginning of T1D to immunomodulate innate immunity and inflammatory conditions.

Inhibitory Effects of Myrtucommuacetalone 1 (MCA-1) from Myrtus communis on Inflammatory Response in Mouse Macrophages

(1) Introduction: Reactive oxygen species (ROS) and nitric oxide (NO) are key signaling molecules that play important roles in the progression of inflammatory disorders. The objective of this study was to explore the use of myrtucommuacetalone-1 (MCA-1), as a novel compound of natural origin and a potential anti-inflammatory agent. (2) Methodology: The anti-inflammatory potential of MCA-1, which was isolated from Myrthus communis Linn, was determined by assaying superoxide, hydrogen peroxide, and nitric oxide production in macrophages. Furthermore, the effects of the compound were analyzed via phosphorylation and translocation of the transcription factor NF kappa B, which is a key regulator of iNOS activation. The effect of MCA-1 on the inducible nitric oxide synthase (iNOS) enzyme was also examined using in silico docking studies. The anticancer potential for MCA-1 was evaluated with an MTT cytotoxic assay. (3) Results: In stimulated macrophages, MCA-1 inhibited superoxide production by 48%, hydrogen peroxide by 53%, and nitric oxide (NO) with an IC₅₀ of <1 µg/mL. MCA-1 also showed a very strong binding pattern within the active site of the inducible nitric oxide synthase enzyme. Furthermore, 25 µg/mL of MCA-1 inhibited inducible nitric oxide synthase expression and abolished transcription factor (NFκB) phosphorylation and translocation to the nucleus. Cytotoxicity analyses of MCA-1 on 3T3 mouse fibroblasts, CC1 liver cell line, J774.2, macrophages and MDBK bovine kidney epithelial cell, yielded IC₅₀ values of 6.53 ± 1.2, 4.6 ± 0.7, 5 ± 0.8, and 4.6 ± 0.7, µg/mL, respectively. (4) Conclusion: Our results suggest that MCA-1, a major phloroglucinol-type compound, shows strong anti-inflammatory activity and has a potential to be a leading therapeutic agent in the future.

Neutrophils in Psoriasis

Neutrophils are the most abundant innate immune cells. The pathogenic roles of neutrophils are related to chronic inflammation and autoimmune diseases. Psoriasis is a chronic systemic inflammatory disease affecting ~2–3% of the world population. The abundant presence of neutrophils in the psoriatic skin lesions serves as a typical histopathologic hallmark of psoriasis. Recent reports indicated that oxidative stress, granular components, and neutrophil extracellular traps from psoriatic neutrophils are related to the initial and maintenance phases of psoriasis. This review provides an overview on the recent (up to 2019) advances in understanding the role of neutrophils in the pathophysiology of psoriasis, including the effects of respiratory burst, degranulation, and neutrophil extracellular trap formation on psoriatic immunity and the clinical relationships.

Prolonged exposure to hypoxia induces an autophagy-like cell survival program in human neutrophils

Neutrophils contribute to low oxygen availability at inflammatory sites through the generation of reactive oxidants. They are also functionally affected by hypoxia, which delays neutrophil apoptosis. However, the eventual fate of neutrophils in hypoxic conditions is unknown and this is important for their effective clearance and the resolution of inflammation. We have monitored the survival and function of normal human neutrophils exposed to hypoxia over a 48 h period. Apoptosis was delayed, and the cells remained intact even at 48 h. However, hypoxia promoted significant changes in neutrophil morphology with the appearance of many new cytoplasmic vesicles, often containing cell material, within 5 hours of exposure to low O₂ . This coincided with an increase in LC3B-II expression, indicative of autophagosome formation and an autophagy-like process. In hypoxic conditions, neutrophils preferentially lost myeloperoxidase, a marker of azurophil granules. Short-term (2 h) hypoxic exposure resulted in sustained potential to generate superoxide when O₂ was restored, but the capacity for oxidant production was lost with longer periods of hypoxia. Phagocytic ability was unchanged by hypoxia, and bacterial killing by neutrophils in both normoxic and hypoxic conditions was substantially diminished after 24 hours. However, pre-exposure to hypoxia resulted in an enhanced ability to kill bacteria by oxidant-independent mechanisms. Our data provide the first evidence for hypoxia as a driver of neutrophil autophagy that can influence the function and ultimate fate of these cells, including their eventual clearance and the resolution of inflammation.

Mechanisms to Evade the Phagocyte Respiratory Burst Arose by Convergent Evolution in Typhoidal Salmonella Serovars

Typhoid fever caused by Salmonella enterica serovar (S.) Typhi differs in its clinical presentation from gastroenteritis caused by S. Typhimurium and other non-typhoidal Salmonella serovars. The different clinical presentations are attributed in part to the virulence-associated capsular polysaccharide (Vi antigen) of S. Typhi, which prevents phagocytes from triggering a respiratory burst by preventing antibody-mediated complement activation. Paradoxically, the Vi antigen is absent from S. Paratyphi A, which causes a disease that is indistinguishable from typhoid fever. Here, we show that evasion of the phagocyte respiratory burst by S. Paratyphi A required very long O antigen chains containing the O2 antigen to inhibit antibody binding. We conclude that the ability to avoid the phagocyte respiratory burst is a property distinguishing typhoidal from non-typhoidal Salmonella serovars that was acquired by S. Typhi and S. Paratyphi A independently through convergent evolution.

[Neutrophil respiratory burst and the state of hemostasis in patients with ischemic and hemorrhagic stroke]

AIM

To study the relationship between the state of the respiratory burst of neutrophils and the indices of hemostasis in patients with ischemic (IS) and hemorrhagic (HS) strokes.

MATERIAL AND METHODS

Thirty-three patients with IS and 31 patients with HS were examined in the first 24 hours after an acute cerebrovascular accident (ACA). The diagnosis of ASA was confirmed by neuroimaging methods: computed tomography and magnetic resonance imaging. The determination of the respiratory burst state of blood neutrophils was carried out using chemiluminescence analysis. Indicators of vascular-platelet and coagulation hemostasis were determined in all patients.

RESULTS AND CONCLUSION

There were changes in the kinetics and activity of neutrophil respiratory burst in stroke patients. Patients with HS had higher (compared to those of patients with IS) level of spontaneous and induced synthesis of secondary ROS but with a decrease in metabolic resources for their synthesis. Activation of spontaneous and ADP-induced platelet aggregation was detected only in HS. Patients with HS had a higher level of fibrinolytic activity as compared to the patients with IS. There were positive correlations between the kinetic parameters of blood coagulation and the synthesis of primary ROS by neutrophils in patients with HS, whereas the intensity of all ROS synthesis negatively correlated with activated partial thromboplastin time. Therefore, in patients with HS the synergistic relationship between the respiratory burst of neutrophils (pro-inflammatory activity) and coagulation hemostasis was more pronounced compared to patients with IS.

Klebsiella pneumoniae ST258 Negatively Regulates the Oxidative Burst in Human Neutrophils

The epidemic clone of Klebsiella pneumoniae (Kpn), sequence type 258 (ST258), carbapenamase producer (KPC), commonly infects hospitalized patients that are left with scarce therapeutic option since carbapenems are last resort antibiotics for life-threatening bacterial infections. To improve prevention and treatment, we should better understand the biology of Kpn KPC ST258 infections. Our hypothesis was that Kpn KPC ST258 evade the first line of defense of innate immunity, the polymorphonuclear neutrophil (PMN), by decreasing its functional response. Therefore, our aim was to evaluate how the ST258 Kpn clone affects PMN responses, focusing on the respiratory burst, compared to another opportunistic pathogen, Escherichia coli (Eco). We found that Kpn KPC ST258 was unable to trigger bactericidal responses as reactive oxygen species (ROS) generation and NETosis, compared to the high induction observed with Eco, but both bacterial strains were similarly phagocytized and cause increases in cell size and CD11b expression. The absence of ROS induction was also observed with other Kpn ST258 strains negative for KPC. These results reflect certain selectivity in terms of the functions that are triggered in PMN by Kpn, which seems to evade specifically those responses critical for bacterial survival. In this sense, bactericidal mechanisms evasion was associated with a higher survival of Kpn KPC ST258 compared to Eco. To investigate the mechanisms and molecules involved in ROS inhibition, we used bacterial extracts (BE) and found that BE were able to inhibit ROS generation triggered by the well-known ROS inducer, fMLP. A sequence of experiments led us to elucidate that the polysaccharide part of LPS was responsible for this inhibition, whereas lipid A mediated the other responses that were not affected by bacteria, such as cell size increase and CD11b up-regulation. In conclusion, we unraveled a mechanism of immune evasion of Kpn KPC ST258, which may contribute to design more effective strategies for the treatment of these multi-resistant bacterial infections.

Ca2+-Induced Mitochondrial ROS Regulate the Early Embryonic Cell Cycle

While it is appreciated that reactive oxygen species (ROS) can act as second messengers in both homeostastic and stress response signaling pathways, potential roles for ROS during early vertebrate development have remained largely unexplored. Here, we show that fertilization in Xenopus embryos triggers a rapid increase in ROS levels, which oscillate with each cell division. Furthermore, we show that the fertilization-induced Ca²⁺ wave is necessary and sufficient to induce ROS production in activated or fertilized eggs. Using chemical inhibitors, we identified mitochondria as the major source of fertilization-induced ROS production. Inhibition of mitochondrial ROS production in early embryos results in cell-cycle arrest, in part, via ROS-dependent regulation of Cdc25C activity. This study reveals a role for oscillating ROS levels in early cell cycle regulation in Xenopus embryos.

Paralogs of Common Carp Granulocyte Colony-Stimulating Factor (G-CSF) Have Different Functions Regarding Development, Trafficking and Activation of Neutrophils

Mammalian granulocyte colony-stimulating factor (G-CSF; CSF3) is a primary cytokine that promotes the development, mobilization, and activation of neutrophils and their precursors. Teleosts have been reported to possess two paralogs as a likely result of the teleost-wide whole genome duplication (WGD) event, but functional divergence of G-CSF paralogs remains poorly understood. Common carp are an allotetraploid species owing to an additional WGD event in the carp lineage and here, we report on genomic synteny, sequence similarity, and phylogeny of four common carp G-CSF paralogs (g-csfa1 and g-csfa2; g-csfb1 and g-csfb2). G-csfa1 and g-csfa2 show differential and relatively high gene expression levels, while g-csfb1 and g-csfb2 show low basal gene expression levels in most tissues. All paralogs are expressed higher in macrophages than in other leukocyte sub-types and are highly up-regulated by treatment of macrophages with mitogens. Recombinant G-CSFa1 and G-CSFb1 both promoted the proliferation of kidney hematopoietic cells, while only G-CSFb1 induced the differentiation of kidney cells along the neutrophil-lineage. Colony-forming unit assays revealed that G-CSFb1 alone stimulates the formation of CFU-G colonies from head- and trunk-kidney whereas the combination of G-CSFa1 and G-CSFb1 stimulates the formation of both CFU-G and CFU-GM colonies. Recombinant G-CSFa1 and G-CSFb1 also exhibit chemotactic activity against kidney neutrophils and up-regulation of cxcr1 mRNA expression was highest in neutrophils after G-CSFb1 stimulation. Furthermore, G-CSFb1 more than G-CSFa1 induced priming of kidney neutrophils through up-regulation of a NADPH-oxidase component p47 ^phox . In vivo administration of G-CSF paralogs increased the number of circulating blood neutrophils of carp. Our findings demonstrate that gene duplications in teleosts can lead to functional divergence between paralogs and shed light on the sub-functionalization of G-CSF paralogs in cyprinid fish.

Priming and de-priming of neutrophil responses in vitro and in vivo

The activation status of neutrophils can cycle from basal through primed to fully activated ("green-amber-red"), and at least in vitro, primed cells can spontaneously revert to a near basal phenotype. This broad range of neutrophil responsiveness confers extensive functional flexibility, allowing neutrophils to respond rapidly and appropriately to varied and evolving threats throughout the body. Primed and activated cells display dramatically enhanced bactericidal capacity (including augmented respiratory burst activity, degranulation and longevity), but this enhancement also confers the capacity for significant unintended tissue injury. Neutrophil priming and its consequences have been associated with adverse outcomes in a range of disease states, hence understanding the signalling processes that regulate the transition between basal and primed states (and back again) may offer new opportunities for therapeutic intervention in pathological settings. A wide array of host- and pathogen-derived molecules is able to modulate the functional status of these versatile cells. Reflecting this extensive repertoire of potential mediators, priming can be established by a range of signalling pathways (including mitogen-activated protein kinases, phosphoinositide 3-kinases, phospholipase D and calcium transients) and intracellular processes (including endocytosis, vesicle trafficking and the engagement of adhesion molecules). The signalling pathways engaged, and the exact cellular phenotype that results, vary according to the priming agent(s) to which the neutrophil is exposed and the precise environmental context. Herein we describe the signals that establish priming (in particular for enhanced respiratory burst, degranulation and prolonged lifespan) and describe the recently recognised process of de-priming, correlating in vitro observations with in vivo significance.

Neutrophil phagocytosis and respiratory burst activity of dairy cows during the transition period and early lactation

INTRODUCTION

Hormonal and metabolic changes, as well as energy imbalance, can affect health, production and reproductive performance of dairy cows. In the present study, we evaluated phagocytosis and respiratory burst neutrophil activity during the transition period and early lactation and compared it with biochemical and hematological parameters in dairy cows.

METHODOLOGY

Simmental cows (n = 21) were enrolled in the study. Whole blood samples were collected weekly from 3 weeks pre- calving until 6 weeks post calving. Basic metabolic and blood parameters were assessed by routine laboratory analyses, while neutrophil functions were analyzed by commercial test kits.

RESULTS

Optimal neutrophil response was observed pre and post calving. The highest value was recorded in the 6th week after calving (89.54 ± 7.61%) and being significantly higher (p < 0.01) as compared to values recorded at two and one week before and one week after calving. The percentage of activated neutrophils was high during the entire study period: from 70.80 ± 5.22% at the beginning of the study to 89.54 ± 7.61% at the end of the study. During the study period, production of Reactive Oxidative Species by neutrophils was positively correlated with β-hydroxybutyrat and non-esterified fatty acids values (0.454** and 0.423**, respectively) and calcium levels (0.164* and 0.212**, respectively).

CONCLUSIONS

The most prominent changes in all parameters had no influence on phagocytic and respiratory burst activity of neutrophils. Neutrophil function is preserved at the optimal level during the transition period and early lactation in Simmental cows.

Studies on the effects of LPS, ß-glucan and metabolic inhibitors on the respiratory burst and gene expression in Atlantic salmon macrophages

Reactive oxygen species (ROS) production in macrophage-like cells is induced as an antimicrobial defence against invading pathogens. In this study, we have explored how different stimuli and metabolic inhibitors affect the level of respiratory burst in Atlantic salmon (Salmo salar L.) head kidney macrophage-like cells. Cells stimulated in vitro by bacterial lipopolysaccharide (LPS) and ß-glucan showed increased production of ROS compared to unstimulated cells. Both stimulation and costimulation by curdlan (ß-glucan) induced a higher production of ROS compared to stimulation and costimulation by LPS. Metabolic inhibitors co-incubated with the stimulants did not, in most cases, perturb the level of ROS generation in the salmon macrophage-like cells. The NAD⁺ content as well as the NAD⁺ /NADH ratio increased in curdlan and LPS + curdlan-stimulated cells compared to control cells, which indicated increased metabolic activity in the stimulated cells. Supporting these findings, gene analysis using real-time quantitative PCR showed that arginase-1 and IL-1ß genes were highly expressed in the stimulated cells.

Mechanisms of Fish Macrophage Antimicrobial Immunity

Overcrowding conditions and temperatures shifts regularly manifest in large-scale infections of farmed fish, resulting in economic losses for the global aquaculture industries. Increased understanding of the functional mechanisms of fish antimicrobial host defenses is an important step forward in prevention of pathogen-induced morbidity and mortality in aquaculture setting. Like other vertebrates, macrophage-lineage cells are integral to fish immune responses and for this reason, much of the recent fish immunology research has focused on fish macrophage biology. These studies have revealed notable similarities as well as striking differences in the molecular strategies by which fish and higher vertebrates control their respective macrophage polarization and functionality. In this review, we address the current understanding of the biological mechanisms of teleost macrophage functional heterogeneity and immunity, focusing on the key cytokine regulators that control fish macrophage development and their antimicrobial armamentarium.

Merozoite Surface Protein 1 from Plasmodium falciparum Is a Major Target of Opsonizing Antibodies in Individuals with Acquired Immunity against Malaria

Naturally acquired immunity against malaria is largely mediated by serum antibodies controlling levels of blood-stage parasites. A limited understanding of the antigenic targets and functional mechanisms of protective antibodies has hampered the development of efficient malaria vaccines. Besides directly inhibiting the growth of Plasmodium parasites, antibodies can opsonize merozoites and recruit immune effector cells such as monocytes and neutrophils. Antibodies against the vaccine candidate merozoite surface protein 1 (MSP-1) are acquired during natural infections and have been associated with protection against malaria in several epidemiological studies. Here we analyzed serum antibodies from semi-immune individuals from Burkina Faso for their potential (i) to directly inhibit the growth of P. falciparum blood stages in vitro and (ii) to opsonize merozoites and to induce the antibody-dependent respiratory burst (ADRB) activity of neutrophils. While a few sera that directly inhibited the growth of P. falciparum blood stages were identified, immunoglobulin G (IgG) from all individuals clearly mediated the activation of neutrophils. The level of neutrophil activation correlated with levels of antibodies to MSP-1, and affinity-purified MSP-1-specific antibodies elicited ADRB activity. Furthermore, immunization of nonhuman primates with recombinant full-size MSP-1 induced antibodies that efficiently opsonized P. falciparum merozoites. Reversing the function by preincubation with recombinant antigens allowed us to quantify the contribution of MSP-1 to the antiparasitic effect of serum antibodies. Our data suggest that MSP-1, especially the partially conserved subunit MSP-1₈₃, is a major target of opsonizing antibodies acquired during natural exposure to malaria. Induction of opsonizing antibodies might be a crucial effector mechanism for MSP-1-based malaria vaccines.

Decreased paraoxonase 2 enzymatic activity in monocyte/macrophages cells. A comparative in vivo and in vitro study for diabetes

AIM

To investigate peripheral blood monocytes/macrophages (Mo/Mᴓ) paraoxonase 2 (PON2) in diabetes and the factors modulating its activity.

METHODS

One hundred and eighteen patients with newly diagnosed uncomplicated type 2 diabetes mellitus were compared regarding clinical, biochemical and oxidative stress parameters with 80 healthy subjects. The capacity of the peripheral blood mononuclear cells (PBMNC) to release pro-oxidants and to neutralise them was determined by measuring the respiratory burst (RB) and the intracellular antioxidant enzyme PON2. In vitro experiments were conducted on a differentiated monocytes cell line (dU937) that was exposed to serum deprivation followed by addition of isolated lipoproteins (VLDL or LDL).

RESULTS

Paraoxonase 2 activity in Mo/Mᴓ was significantly lower in type 2 diabetes patients (0.042 ± 0.044 vs 0.165 ± 0.133U lactonase activity/mg protein in controls, p < .0005) and decreased in the obese in all groups. It was inversely correlated to parameters of adiposity (BMI and Waist Circumference), of glucose control (blood glucose, fructosamine and HbA_1c) and insulin resistance (HOMA-IR). In multivariate regression models, 15-34% of the PON2 variance was explained by diabetes. The in vitro addition of VLDL normalised the RB of serum deprived dU937 cells, S- (to 82 ± 18% of the cells incubated with serum, S+) and PON2 activity (from 0.524 ± 0.061 in S - to 0.298 ± 0.048 U/mg protein). In contrast, when LDL was added, the RB remained lower (61 ± 12% of S+, p = .03) and PON2 higher (0.580 ± 0.030 U/mg protein, p = .003).

CONCLUSIONS

The decrease in monocyte/macrophage PON2 enzymatic activity observed in type 2 diabetes cannot be totally explained by abdominal obesity and insulin resistance. The underlying molecular mechanisms need to be identified.

Multiple Phenotypic Changes Define Neutrophil Priming

Exposure to pro-inflammatory cytokines, chemokines, mitochondrial contents, and bacterial and viral products induces neutrophils to transition from a basal state into a primed one, which is currently defined as an enhanced response to activating stimuli. Although, typically associated with enhanced generation of reactive oxygen species (ROS) by the NADPH oxidase, primed neutrophils show enhanced responsiveness of exocytosis, NET formation, and chemotaxis. Phenotypic changes associated with priming also include activation of a subset of functions, including adhesion, transcription, metabolism, and rate of apoptosis. This review summarizes the breadth of phenotypic changes associated with priming and reviews current knowledge of the molecular mechanisms behind those changes. We conclude that the current definition of priming is too restrictive. Priming represents a combination of enhanced responsiveness and activated functions that regulate both adaptive and innate immune responses.

Aspergillosis in Chronic Granulomatous Disease

Patients with chronic granulomatous disease (CGD) have the highest life-time incidence of invasive aspergillosis and despite the availability of antifungal prophylaxis, infections by Aspergillus species remain the single most common infectious cause of death in CGD. Recent developments in curative treatment options, such as haematopoietic stem cell transplantation, will change the prevalence of infectious complications including invasive aspergillosis in CGD patients. However, invasive aspergillosis in a previously healthy host is often the first presenting feature of this primary immunodeficiency. Recognizing the characteristic clinical presentation and understanding how to diagnose and treat invasive aspergillosis in CGD is of utmost relevance to improve clinical outcomes. Significant differences exist in fungal epidemiology, clinical signs and symptoms, and the usefulness of non-culture based diagnostic tools between the CGD host and neutropenic patients, reflecting underlying differences in the pathogenesis of invasive aspergillosis shaped by the nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase deficiency.

Biodegradation of Single-Walled Carbon Nanotubes in Macrophages through Respiratory Burst Modulation

The biodegradation of carbon nanotubes (CNTs) may be one of major determinants of the toxic outcomes in exposed individuals. In this study, we employed a macrophage/monocyte model, Raw264.7, to investigate the feasibility of regulating the biodegradation of three types of single-walled carbon nanotubes (SWCNTs) (pristine, ox-, and OH-SWCNTs) by respiratory burst modulation. An artificial fluid mimicking the enzymatic reactions of respiratory burst was constituted to reveal the role of respiratory burst played in SWCNT biodegradation. The biodegradation of SWCNTs were characterized by Raman, ultraviolet-visible-near-infrared spectroscopy, and transmission electron microscopy. Our results showed significantly accelerated biodegradation of ox-SWCNTs and OH-SWCNTs in macrophages activated by phorbol myristate acetate (PMA), which could be prevented by N-acetyl-l-cysteine (NAC), whereas p-SWCNTs were resistant to biodegradation. Similar tendencies were observed by using the in vitro enzymatic system, and the degradation rates of these SWCNTs are in the order of OH-SWCNTs > ox-SWCNTs >> p-SWCNTs, suggesting a pivotal role of respiratory burst in accelerating the biodegradation of SWCNTs and that defect sites on SWCNTs might be a prerequisite for the biodegradation to occur. Our findings might provide invaluable clues on the development of intervention measurements for relieving the side effects of SWCNTs and would help to design safer SWCNT products with higher biodegradability and less toxicity.

Scanning Electrochemical Microscopy Imaging during Respiratory Burst in Human Cell

Phagocytic cells, such as neutrophils and monocytes, consume oxygen and generate reactive oxygen species (ROS) in response to external stimuli. Among the various ROS, the superoxide anion radical is known to be primarily produced by nicotinamide adenine dinucleotide phosphate hydrogen (NADPH) oxidase. In the current study, we attempt to evaluate the respiratory burst by monitoring the rapid consumption of oxygen by using scanning electrochemical microscopy (SECM) imaging. The respiratory burst was measured in a human monocytic cell line (THP-1 cells) derived from an acute monocytic leukemia patient under the effect of the exogenous addition of phorbol 12-myristate 13-acetate, which acts as a differentiation inducer. SECM imaging composed of a microelectrode was used to compare oxygen consumption between normal cellular respiration and during respiratory burst in THP-1 cells. Two-dimensional respiratory activity imaging was performed using XY-scan. In addition, the quantitative evaluation of oxygen consumption in THP-1 cells was performed using a Z-scan. The results obtained show higher consumption of oxygen in cells undergoing respiratory burst. SECM imaging is thus claimed to be a highly sensitive and appropriate technique compared to other existing techniques available for evaluating oxidative stress in human cells, making it potentially useful for widespread applications in biomedical research and clinical trials.

Increased metabolic activity of neutrophils in patients with chronic obstructive pulmonary disease

Aims:

To compare the metabolic activity of peripheral neutrophils in patients diagnosed with chronic obstructive pulmonary disease (COPD) with that of healthy, nonsmoking volunteers.

Materials and Methods:

Venous blood samples were taken from patients diagnosed with COPD as well as from healthy nonsmokers. Each sample was subjected to the nitro blue tetrazolium (NBT) test in which neutrophils exhibiting elevated metabolic activity were detected by light microscopy. The test was repeated after stimulation with Escherichia coli (E. coli) endotoxin with fresh samples. Neutrophils showing dye uptake were then counted in each case.

Results:

We found that the mean numbers of activated neutrophils without and with the addition of endotoxin were 19% and 23%, respectively, in the control group and 56% and 62%, respectively, in the test group. Two-sample t-test statistic revealed that there was a significant (P < 0.01) increase in neutrophilic metabolic activity in patients with COPD as compared to that in healthy volunteers. This significance remained even after stimulation using E. coli endotoxin.

Conclusion:

The results hint at a potentially relevant pathogenic mechanism in COPD related to the metabolic activity of neutrophils. By exhibiting enhanced metabolic activity, neutrophils in the COPD patients are more likely to be involved in damaging lung tissues.