Neutrophils are predominant leukocytes in the circulation, which are essential for killing invading pathogens via the activation of effector responses and the production of reactive oxygen species (ROS), also named as "oxidative burst." When infected, activated neutrophils fight bacteria, fungi, and viruses through oxidative burst, phagocytosis, degranulation, and the production of neutrophil extracellular traps (NETs) in a neutrophil death process named as "NETosis" (Mutua and Gershwin, 2021). NETs, consisting of DNA fibers decorated with modified histones and numerous antimicrobial proteins from cytoplasmic granules and the nucleus, can either be beneficial or detrimental (Mutua and Gershwin, 2021). Several pathways can lead to this death process. In response to various stimuli, NETosis traps and clears pathogens, facilitating phagocytosis by other neutrophils and phagocytes. However, excessive NETosis often results in disease due to increasing the pro-inflammatory response and perpetuating the inflammatory condition (Hellebrekers et al., 2018; Hidalgo et al., 2019; Klopf et al., 2021). Accordingly, inhibiting aberrant NETosis may alleviate the severity of various autoimmune and inflammatory diseases.
DNA ; Extracellular Traps/metabolism* ; Neutrophils/metabolism* ; Reactive Oxygen Species/metabolism* ; Respiratory Burst

The intra-articular use of hyaluronic acid (HA) for the treatment of synovitis and osteoarthritis is still controversial. As a consequence, corticosteroids remain the most frequently employed therapeutic agents, despite their potential systemic and local deleterious effects. This study examined the anti-inflammatory, antioxidant, and chondroprotective activities of low and high molecular weight hyaluronic acid (LMW-HA and HMW-HA) on lipopolysaccharide (LPS)-induced synovitis in horses compared to triamcinolone acetonide (TA). LPS was injected in the metacarpophalangeal joints, which were treated intra-articularly with either TA (as control) or LMW-HA or HMW-HA. Joint clinical evaluation and synovial fluid (SF) analysis were performed at 0, 8, 24, and 48 h. The white blood cell counts (WBC), prostaglandin E2 (PGE2), interleukin (IL)-1, IL-6, IL-10, tumor necrosis factor-α, chondroitin sulfate (CS) and HA concentrations, oxidative burst, and HA molecular weights were measured. TA reduced the lameness, swelling, and PGE2 release but increased the SF CS concentrations enormously at 24h and 48h, and decreased the SF HA modal molecular weight. These results indicate the breakdown of articular cartilage aggrecan and SF HA. In contrast, LMW-HA and HMW-HA were less effective in reducing the inflammation symptoms, but preserved the joints because only a modest increase in CS occurred at 24 h, decreasing at 48 h, and the SF HA was maintained. The HA-treatment also had anti-inflammatory actions, and LMW-HA was the most effective in reducing the release of cytokine. In summary, the HA treatment inhibited efficiently the digestion of cartilage proteoglycans and SF HA breakdown.
Adrenal Cortex Hormones ; Aggrecans ; Cartilage ; Cartilage, Articular ; Chondroitin Sulfates ; Digestion ; Dinoprostone ; Horses ; Hyaluronic Acid ; Inflammation ; Interleukin-10 ; Interleukin-6 ; Interleukins ; Joints ; Leukocyte Count ; Metacarpophalangeal Joint ; Molecular Weight ; Necrosis ; Osteoarthritis ; Proteoglycans ; Respiratory Burst ; Synovial Fluid ; Synovitis ; Triamcinolone ; Triamcinolone Acetonide

BACKGROUND: IgG-mediated anaphylaxis occurs after infusion of certain monoclonal antibody-based therapeutics. New in vitro tests are urgently needed to diagnose such reactions. We investigated whether allergens trigger neutrophil oxidative burst (OB) and if neutrophil OB occurs due to allergen-specific IgG (sIgG). METHODS: Neutrophil OB was measured by dihydrorhodamine 123 flow cytometry using a leukocyte suspension spiked with a very small patch of the allergen crude extract, Dermatophagoides farinae (Der f). The mean fluorescence intensity ratio of stimulated to unstimulated samples was calculated as the neutrophil oxidative index (NOI). RESULTS: The Der f-specific NOI (Der f-sNOI) showed a time-dependent increase after Der f extract addition. At 15 min activation, higher Der f-sIgG levels were associated with lower Der f-sNOI values in 31 subjects (P < 0.05). This inverse relationship occurs due to the initial blocking effect of free Der f-sIgG. Additionally, neutrophil OB was nearly absent (Der f-sNOI of −1) in two cases: a subject with undetectable Der f-sIgG levels and washed leukocyte suspensions deprived of Der f-sIgG. CONCLUSION: Allergens can trigger neutrophil OB via preexisting allergen-sIgG. Neutrophil OB can be easily measured in a leukocyte suspension spiked with the allergen. This assay can be used to diagnose IgG-mediated anaphylaxis.
Allergens ; Anaphylaxis* ; Dermatophagoides farinae ; Flow Cytometry ; Fluorescence ; Immunoglobulin G ; In Vitro Techniques ; Leukocytes ; Neutrophils* ; Respiratory Burst* ; Suspensions

The platelet-rich plasma (PRP) and antimicrobial peptides neutrophil extract (AMP extract) were prepared from rabbit neutrophils as two autologous blood-derived preparations, which could be applied locally to enhance healing process of tissues. Both preparations were analyzed using the MALDI TOF method for accurate qualitative assay. Growth factors (PDGF and VEGF) and microbicidal protein were reported in PRP. In AMP extract a-defensins, namely; NP-1, -2, -3a, -3b, -4, and -5 and cathelicidins represented among other by 15-kDa antibacterial protein (p15s) were detected. In the second part of our study the influence of antimicrobial extract on macrophages in vitro was tested. Then, degranulation of neutrophils in vitro and generation of reactive intermediates by these cells under the influence of AMP extract were assessed. As estimated, the addition of AMP extract into cultures of macrophages decreased superoxide anion generation after 5 days of incubation. Furthermore, AMP extract inhibited degranulation and respiratory burst in neutrophils, therefore in this regard it suppress proinflammatory effect of two studied populations of leukocytes.
Cathelicidins ; In Vitro Techniques ; Intercellular Signaling Peptides and Proteins ; Leukocytes ; Macrophages ; Methods ; Neutrophils* ; Peptides ; Platelet-Rich Plasma* ; Respiratory Burst ; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization ; Superoxides

Probiotics that are able to provide beneficial effects on animal health have become important ingredients of dog foods. This study was conducted to characterize the probiotic potentials of two strains, Lactobacillus reuteri BCLR-42 and Lactobacillus plantarum BCLP-51, that were derived from feces of healthy dogs and evaluated based on tolerance to low pH and bile acid, antimicrobial activities, enzyme profiles, sensitivity to antibiotics, and innate immune enhancing potentials. Both strains showed survival of more than 90% at pH 3 and 0.2% bile acid and exhibited broad antimicrobial activities against indicator bacteria. Moreover, both strains showed high sensitivity to antibiotics, except vancomycin, metronidazole, and gentamicin. The alkaline phosphatase was negligible (score 0), whereas they showed strong beta galactosidase activity (score range 5 or 3, respectively). The phagocytosis and oxidative burst activities of canine granulocytes were significantly enhanced in response to both strains. These results show that both strains have the capability to act as probiotics and the potential for application as ingredients in dog foods.
Alkaline Phosphatase ; Animals ; Anti-Bacterial Agents ; Bacteria ; beta-Galactosidase ; Bile ; Dogs* ; Feces ; Gentamicins ; Granulocytes ; Hydrogen-Ion Concentration ; Lactobacillus plantarum* ; Lactobacillus reuteri* ; Lactobacillus* ; Metronidazole ; Phagocytosis ; Probiotics* ; Respiratory Burst ; Vancomycin

Differentiated HL-60 is an effector cell widely used for the opsonophagocytic-killing assay (OPKA) to measure efficacy of pneumococcal vaccines. We investigated the correlation between phenotypic expression of immunoreceptors and phagocytic ability of HL-60 cells differentiated with N,N-dimethylformamide (DMF), all-trans retinoic acid (ATRA), or 1alpha, 25-dihydroxyvitamin D3 (VitD3) for 5 days. Phenotypic change was examined by flow cytometry with specific antibodies to CD11c, CD14, CD18, CD32, and CD64. Apoptosis was determined by flow cytometry using 7-aminoactinomycin D. Function was evaluated by a standard OPKA against serotype 19F and chemiluminescence-based respiratory burst assay. The expression of CD11c and CD14 gradually increased upon exposure to all three agents, while CD14 expression increased abruptly after VitD3. The expression of CD18, CD32, and CD64 increased during differentiation with all three agents. Apoptosis remained less than 10% until day 3 but increased after differentiation by DMF or ATRA. Differentiation with ATRA or VitD3 increased the respiratory burst after day 4. DMF differentiation showed a high OPKA titer at day 1 which sustained thereafter while ATRA or VitD3-differentiated cells gradually increased. Pearson analysis between the phenotypic changes and OPKA titers suggests that CD11c might be a useful differentiation marker for HL-60 cells for use in pneumococcal OPKA.
Antibodies, Bacterial/immunology ; Antigens, CD11c/metabolism ; Antigens, CD14/metabolism ; Antigens, CD18/metabolism ; Apoptosis/*immunology ; Biological Assay ; Cell Differentiation ; Cell Line, Tumor ; Cholecalciferol/pharmacology ; Dimethylformamide/pharmacology ; Flow Cytometry ; HL-60 Cells ; Humans ; Phagocytosis/*immunology ; Pneumococcal Vaccines/*immunology ; Receptors, IgG/metabolism ; Receptors, Immunologic/*biosynthesis ; Respiratory Burst/immunology ; Streptococcus pneumoniae/*immunology ; Tretinoin/pharmacology

Differentiated HL-60 is an effector cell widely used for the opsonophagocytic-killing assay (OPKA) to measure efficacy of pneumococcal vaccines. We investigated the correlation between phenotypic expression of immunoreceptors and phagocytic ability of HL-60 cells differentiated with N,N-dimethylformamide (DMF), all-trans retinoic acid (ATRA), or 1alpha, 25-dihydroxyvitamin D3 (VitD3) for 5 days. Phenotypic change was examined by flow cytometry with specific antibodies to CD11c, CD14, CD18, CD32, and CD64. Apoptosis was determined by flow cytometry using 7-aminoactinomycin D. Function was evaluated by a standard OPKA against serotype 19F and chemiluminescence-based respiratory burst assay. The expression of CD11c and CD14 gradually increased upon exposure to all three agents, while CD14 expression increased abruptly after VitD3. The expression of CD18, CD32, and CD64 increased during differentiation with all three agents. Apoptosis remained less than 10% until day 3 but increased after differentiation by DMF or ATRA. Differentiation with ATRA or VitD3 increased the respiratory burst after day 4. DMF differentiation showed a high OPKA titer at day 1 which sustained thereafter while ATRA or VitD3-differentiated cells gradually increased. Pearson analysis between the phenotypic changes and OPKA titers suggests that CD11c might be a useful differentiation marker for HL-60 cells for use in pneumococcal OPKA.
Antibodies, Bacterial/immunology ; Antigens, CD11c/metabolism ; Antigens, CD14/metabolism ; Antigens, CD18/metabolism ; Apoptosis/*immunology ; Biological Assay ; Cell Differentiation ; Cell Line, Tumor ; Cholecalciferol/pharmacology ; Dimethylformamide/pharmacology ; Flow Cytometry ; HL-60 Cells ; Humans ; Phagocytosis/*immunology ; Pneumococcal Vaccines/*immunology ; Receptors, IgG/metabolism ; Receptors, Immunologic/*biosynthesis ; Respiratory Burst/immunology ; Streptococcus pneumoniae/*immunology ; Tretinoin/pharmacology

OBJECTIVETo investigate the effect of blood glucose instability on respiratory burst of leukocytes in patients with type 2 diabetes (T2DM).

METHODSForty-five patients with T2DM were divided into 3 groups after continuous glucose monitoring for 72 h with glucose wavy coefficient <1.5 (n=11), between 1.5 and 3.0 (n=19), and >3.0 (n=15). Peripheral blood neutrophils were isolated from the diabetic patients and normal control subjects for assay of glucose 6-phosphate dehydrogenase (G6PD) with a spectrophotometric method, detecting G6PD mRNA expression by real-time PCR, and determining reactive oxygen species level using the fluorescent probe DCFH-DA.

RESULTSCompared with the normal control group, the diabetic patients showed significantly lowered G6PD activity (F=78.739, P<0.05) and ROS level (F=384.962, P<0.05) but significantly increased G6PD mRNA expression (F=269.612, P<0.01). These changes were significantly correlated with the blood glucose wavy coefficients.

CONCLUSIONThe fluctuation of blood glucose in T2DM patients can decrease G6PD activity and lead to functional decline of the respiratory burst.

Blood Glucose ; chemistry ; Case-Control Studies ; Diabetes Mellitus, Type 2 ; metabolism ; Glucosephosphate Dehydrogenase ; metabolism ; Humans ; Neutrophils ; metabolism ; Pentose Phosphate Pathway ; Reactive Oxygen Species ; metabolism ; Respiratory Burst

OBJECTIVETo investigate the method and mechanism for exercise-related immunosuppression via the inhibitor of NADPH oxidase diphenyleneiodonium(DPI) and glutamine supplementation and on the function of neutrophils after overtraining.

METHODSFifty male Wistar rats were randomly divided into five groups: a negative control group (C), an overtraining group (E), an overtraining + DPI intervention group (D), an overtraining+ glutamine supplementation group(G) and combined glutamine + DPI intervention group(DG). After 36 - 40 h from the last training, eight rats were randomly selected from each group, and blood was sampled from the orbital vein. ELISAs were used to measure serum cytokine levels and lipid peroxidation in blood plasma. Flow cytometry was used to measure neutrophil respiratory burst and phagocytosis. The activity of NADPH oxidase was assessed by chemiluminescence and the gene expression of gp91(phox) and p47(phox) of the NADPH-oxidase subunit was checked by Western blot.

RESULTSCompared with group C, the plasma concentrations of NO increased in group G, and the NO, cytokine-induced neutrophil chemoattractant (CINC) concentrations in group DG increased significantly. The respiratory burst and phagocytosis function of neutrophils were decreased in group E, but in group DG were increased when compared with those of group E. After overtraining the expression of gp91(phox) and p47(phox) was up regulated in group E. There were no significant changes in other groups except group DG, in which the expression of gp91(phox) was down regulated. Compared with group E, the expression of gp91(phox) and p47(phox) was up regulated in group D, group G and group DG.

CONCLUSIONThe activation of NADPH oxidase is responsible for the production of superoxide anions, which may be related to the decrease in neutrophil function after over training and is the mechanism of exercise-related immunosuppression. The DPI treatment combined glutamine supplementation can reverse the decrease neutrophils function after overtraining in vitro.

Animals ; Dietary Supplements ; Glutamine ; pharmacology ; Hyperkinesis ; physiopathology ; Male ; Membrane Glycoproteins ; metabolism ; NADPH Oxidase 2 ; NADPH Oxidases ; antagonists & inhibitors ; metabolism ; Neutrophils ; metabolism ; physiology ; Onium Compounds ; pharmacology ; Oxidation-Reduction ; Rats ; Rats, Wistar ; Respiratory Burst ; physiology

The aim of this study was to examine the priming effect of sphingosine 1-phosphate (S1P) on fMLP-activated neutrophils, mainly to detect the neutrophil respiratory burst products, and to investigate the signaling pathway involved in S1P activity. Flow cytometry was used to evaluate the new isolated neutrophil; the superoxide anion output was detected indirectly by cytochrome C reduction in respiratory burst; the dihydro-rhodamine 123 was used to detect the intensity of respiratory burst; the signal transduction pathways of neutrophil respiratory burst were explored by Western blot. The results showed that after pretreated with S1P, the level of superoxide anion released by fMLP-activated neutrophils significantly increased; the Rhodamine 123 mean fluorescence intensity in S1P primed fMLP-activated neutrophils group was significantly higher than that in fMLP treatment group; PI3K and Akt proteins involved in the signal pathway of neutrophil respiratory burst. It is concluded that S1P is a new priming reagent, which primes respiratory burst of fMLP-activated neutrophils; this signal pathway may be that S1P interacts with its receptor, activates PI3K, then activates Akt-transmitting signals through NADPH oxidase, finally results in the respiratory burst.
Cells, Cultured ; Humans ; Lysophospholipids ; metabolism ; NADPH Oxidases ; metabolism ; Neutrophils ; metabolism ; physiology ; Proto-Oncogene Proteins c-akt ; metabolism ; Receptors, Lysosphingolipid ; metabolism ; Respiratory Burst ; Signal Transduction ; Sphingosine ; analogs & derivatives ; metabolism ; Superoxides ; metabolism