Monocyte Oxidative Burst Activity Research Articles

Pelargonidin-3-O-glucoside and its metabolites have modest anti-inflammatory effects in human whole blood cultures

This study hypothesized that the predominant strawberry anthocyanin, pelargonidin-3-O-glucoside (Pg-3-glc), and 3 of its plasma metabolites (4-hydroxybenzoic acid, protocatechuic acid, and phloroglucinaldehyde [PGA]) would affect phagocytosis, oxidative burst, and the production of selected pro- and anti-inflammatory cytokines in a whole blood culture model. For the assessment of phagocytosis and oxidative burst activity of monocytes and neutrophils, whole blood was preincubated in the presence or absence of the test compounds at concentrations up to 5 μmol/L, followed by analysis of phagocytic and oxidative burst activity using commercially available test kits. For the cytokine analysis, diluted whole blood was stimulated with lipopolysaccharide in the presence or absence of the test compounds at concentrations up to 5 μmol/L. Concentrations of selected cytokines (tumor necrosis factor-α, interleukin [IL]-1β, IL-6, IL-8, and IL-10) were determined using a cytometric bead array kit. There were no effects of any of the test compounds on phagocytosis of opsonized or nonopsonized Escherichia coli or on oxidative burst activity. Pg-3-glc and PGA at 0.08 μmol/L increased the concentration of IL-10 (P<.01 and P<.001, respectively), but there was no effect on tumor necrosis factor-α, IL-1β, IL-6, and IL-8, and there were no effects of the other compounds. In conclusion, this study demonstrated a lack of effect of these compounds on the opsonization, engulfment, and subsequent destruction of bacteria. Pg-3-glc and PGA, at physiologically relevant concentrations, had anti-inflammatory properties; however, effects were modest, only observed at the lowest dose tested and limited to IL-10.

Consumption of Bifidobacterium lactis Bi-07 by healthy elderly adults enhances phagocytic activity of monocytes and granulocytes.

Elderly adults have alterations in their gut microbiota and immune functions that are associated with higher susceptibility to infections and metabolic disorders. Probiotics and prebiotics, and their synbiotic combinations are food supplements that have been shown to improve both gut and immune function. The objective of this randomised, double-blind, placebo-controlled, cross-over human clinical trial was to study immune function and the gut microbiota in healthy elderly adults. Volunteers (n 37) consumed prebiotic galacto-oligosaccharides (GOS; 8g/d), probiotic Bifidobacterium lactis Bi-07 (Bi-07; 10(9) colony-forming units/d), their combination (Bi-07+GOS) and maltodextrin control (8g/d) in four 3-week periods separated by 4-week wash-out periods. Immune function was analysed by determining the phagocytic and oxidative burst activity of monocytes and granulocytes, whole-blood response to lipopolysaccharide, plasma chemokine concentrations and salivary IgA levels. Gut microbiota composition and faecal SCFA content were determined using 16S ribosomal RNA fluorescence in situ hybridisation and HPLC, respectively. Primary statistical analyses indicated the presence of carry-over effects and thus measurements from only the first supplementation period were considered valid. Subsequent statistical analysis showed that consumption of Bi-07 improved the phagocytic activity of monocytes (P<0·001) and granulocytes (P=0·02). Other parameters were unchanged. We have for the first time shown that the probiotic Bi-07 may provide health benefits to elderly individuals by improving the phagocytic activity of monocytes and granulocytes. The present results also suggest that in the elderly, the effects of some probiotics and prebiotics may last longer than in adults.

Influence of Banana Versus Sports Beverage Ingestion On Phagocytic Cell Responses To 75-Km Cycling Time Trials

PURPOSE: The purpose of this project was to compare the acute effect of ingesting bananas (BAN) versus a 6% carbohydrate sports drink (CHO) on phagocytic cell responses to 75-km cycling in cyclists. DESIGN: Trained cyclists (N=14, age 37±1.9 y, Wattsmax 379±12.5) completed two 75-km cycling time trials (3 weeks apart, randomized, crossover) while ingesting BAN or CHO. Subjects ingested 0.4 gm/kg carbohydrate from BAN or CHO, and then cycled on CompuTrainers (RacerMate Inc., Seattle, WA) for 75-km at the fastest pace possible while ingesting 0.2 gm/kg carbohydrate from BAN or CHO every 15 min. Blood samples were taken pre-exercise, immediately following and 1-h post-exercise, and analyzed for granulocyte and monocyte phagocytosis (PHAG) and oxidative burst activity (OBA) using a flow cytometric procedure with FITC-labeled bacteria (Staphylococcus aureus; Molecular Probes, Eugene, OR) and hydroethidine (HE; Molecular Probes). All blood samples were prepared at the same ratio of eight bacteria per phagocytic cell. RESULTS: The time to complete the 75-km cycling trials did not differ between BAN and CHO (2.41±0.06 and 2.36±0.05 h, respectively, P=0.258). Exercise caused significant increases (P<0.001) above baseline levels in granulocyte PHAG (25% immediately- and 41% 1-h-post-exercise) and monocyte PHAG (50% and 72%, respectively), with no differences between BAN and CHO trials (interaction effects, P=0.215 and 0.191, respectively). Granulocyte and monocyte OBA did not differ between BAN and CHO trials and did not change with exercise (interaction effects, P=0.697 and 0.810, respectively). CONCLUSIONS: Bacterial phagocytosis but not OBA by blood granulocytes and monocytes was strongly increased following 75-km cycling time trials, with no differences between BAN and CHO conditions. The increase in phagocytosis with unchanged OBA reflects an inflammatory response to the physiologic stress of heavy exertion. Supported by a grant from Dole Foods, Inc.

Effects of Milking Frequency on Phagocytosis and Oxidative Burst Activity of Phagocytes from Primiparous and Multiparous Dairy Cows During Early Lactation

The objective of this study was to investigate the effect of milking frequency on the phagocytosis and respiratory burst activity of polymorphonuclear neutrophils (PMN) and monocytes of primiparous and multiparous cows under 2 nutritional management regimens during early lactation. At calving, 12 primiparous and 12 multiparous cows were randomly assigned to 1 of 4 treatments, in which animals were milked once (OAD) or twice a day at a high or low nutritional level. Blood samples were taken 1 to 7 d before calving (prepartum) and 1 to 7, 14 to 21, and 42 to 49 d postpartum. Phagocytic and oxidative burst activity of PMN and monocytes were determined in whole blood and analyzed separately by flow cytometry. Once-a-day milking reduced significantly the percentage of phagocytic PMN and tended to decrease the number of bacteria ingested by these cells. The percentage of oxidative burst positive cells and overall respiratory burst activity of monocytes also tended to be reduced by OAD milking. The reduction of oxidative burst activity of monocytes was more pronounced 1 to 7 d postpartum compared with the prepartum sample and other postpartum samples. Oxidative burst activity of PMN and monocytes of multiparous cows was impaired compared with primiparous cows. The percentage of oxidative burst positive monocytes from multiparous cows was reduced prepartum and also 1 to 7 d postpartum. Once-a-day milking reduced the mean respiratory burst activity of PMN from primiparous cows to levels similar to that of multiparous cows. Therefore, an OAD milking regimen reduces phagocytic activity of PMN and monocytes and would be detrimental for the immune system in high-yielding dairy cows during early lactation.

The Phosphatidylinositol 3-Kinase Signaling Pathway Exerts Protective Effects during Sepsis by Controlling C5a-Mediated Activation of Innate Immune Functions

The PI3K/Akt signaling pathway has been recently suggested to have controversial functions in models of acute and chronic inflammation. Our group and others have reported previously that the complement split product C5a alters neutrophil innate immunity and cell signaling during the onset of sepsis and is involved in PI3K activation. We report in this study that in vivo inhibition of the PI3K pathway resulted in increased mortality in septic mice accompanied by strongly elevated serum levels of TNF-alpha, IL-6, MCP-1, and IL-10 during sepsis as well as decreased oxidative burst activity in blood phagocytes. PI3K inhibition in vitro resulted in significant increases in TLR-4-mediated generation of various proinflammatory cytokines in neutrophils, whereas the opposite effect was observed in PBMC. Oxidative burst and phagocytosis activity was significantly attenuated in both neutrophils and monocytes when PI3K activation was blocked. In addition, PI3K inhibition resulted in strongly elevated TLR-4-mediated generation of IL-1beta and IL-8 in neutrophils when these cells were co-stimulated with C5a. C5a-induced priming effects on neutrophil and monocyte oxidative burst activity as well as C5a-induced phagocytosis in neutrophils were strongly reduced when PI3K activation was blocked. Our data suggest that the PI3K/Akt signaling pathway controls various C5a-mediated effects on neutrophil and monocyte innate immunity and exerts an overall protective effect during experimental sepsis.

Decreased oxidative burst activity of monocytes from asymptomatic HIV-infected individuals

Although changes in function of monocytes from AIDS patients have previously been reported, the functional deficits that could occur in monocytes from asymptomatic HIV-seropositive individuals has not been extensively investigated. The goal of this study was to evaluate the oxidative burst response and cell surface marker expression of monocytes from this group. Both the oxidative burst, as measured by 2′, 7′-dichlorofluorescin diacetate oxidation, and cell surface markers were evaluated on CD14 + (Leu-M3) monocytes by two-color flow cytometry. A significantly lower oxidative burst capacity was observed in asymptomatic, seropositives after phorbol myristate acetate and calcium ionophore stimulation when compared to seronegative controls. However, differences in oxidative burst between the two groups were not observed after stimulation with heat-aggregated IgG. The oxidative burst of monocytes from seropositive HIV antigen + or antigen − subjects was not significantly different. The most significant difference in monocyte surface markers between seropositive and seronegative controls was a decrease in the proportion of complement receptor 3 + (CD11b +) cells while slightly decreased numbers of CD13 + and CD33 + monocytes were observed. The decreased expression of CD11b + cells in seropositives was found entirely within the seropositive, HIV antigen + group. Similarly, when monocytes from seropositive HIV antigen + and antigen − were compared, significantly lower numbers of CD4 + and HLA-DR + cells were noted. These results indicate that significant changes in monocyte function and surface markers occure early during the course of HIV infection and are associated with the expression of serum HIV antigen.