Higher Oxidative Burst Research Articles

Butyrate induces oxidative burst mediated apoptosis via Glucose-6-Phosphate Dehydrogenase (G6PDH) in macrophages during mycobacterial infection

Microorganisms present in the gut modulate host defence responses against infections in order to maintain immune homeostasis. This host-microbe crosstalk is regulated by gut metabolites. Butyrate is one such small chain fatty acid produced by gut microbes upon fermentation that has the potential to influence immune responses. Here we investigated the role of butyrate in macrophages during mycobacterial infection. Results demonstrate that butyrate significantly suppresses the growth kinetics of mycobacteria in culture medium as well as inhibits mycobacterial survival inside macrophages. Interestingly, butyrate alters the pentose phosphate pathway by inducing higher expression of Glucose-6-Phosphate Dehydrogenase (G6PDH) resulting in a higher oxidative burst via decreased Sod-2 and increased Nox-2 (NADPH oxidase-2) expression. Butyrate-induced G6PDH also mediated a decrease in mitochondrial membrane potential. This in turn lead to an induction of apoptosis as measured by lower expression of the anti-apoptotic protein Bcl-2 and a higher release of Cytochrome C as a result of induction of apoptosis. These results indicate that butyrate alters the metabolic status of macrophages and induces protective immune responses against mycobacterial infection.

A culture model to analyze the acute biomaterial-dependent reaction of human primary neutrophils in vitro.

Neutrophils play a pivotal role in orchestrating the immune system response to biomaterials, the onset and resolution of chronic inflammation, and macrophage polarization. However, the neutrophil response to biomaterials and the consequent impact on tissue engineering approaches is still scarcely understood. Here, we report an in vitro culture model that comprehensively describes the most important neutrophil functions in the light of tissue repair. We isolated human primary neutrophils from peripheral blood and exposed them to a panel of hard, soft, naturally- and synthetically-derived materials. The overall trend showed increased neutrophil survival on naturally derived constructs, together with higher oxidative burst, decreased myeloperoxidase and neutrophil elastase and decreased cytokine secretion compared to neutrophils on synthetic materials. The culture model is a step to better understand the immune modulation elicited by biomaterials. Further studies are needed to correlate the neutrophil response to tissue healing and to elucidate the mechanism triggering the cell response and their consequences in determining inflammation onset and resolution.

Effects of aluminium and bacterial lipopolysaccharide on oxidative stress and immune parameters in roach, Rutilus rutilus L.

Aluminium is used in diverse anthropogenic processes at the origin of pollution events in aquatic ecosystems. In the Champagne region (France), high concentrations of aluminium (Al) are detected due to vine-growing practices. In fish, little is known about the possible immune-related effects at relevant environmental concentrations. The present study analyzes the simultaneous effects of aluminium and bacterial lipopolysaccharide (LPS), alone and in combination, on toxicological biomarkers in the freshwater fish species Rutilus rutilus. For this purpose, roach treated or not with LPS were exposed to environmental concentrations of aluminium (100 μg/L) under laboratory-controlled conditions for 2, 7, 14 and 21 days. After each exposure time, we assessed hepatic lipoperoxidation, catalase activity, glutathione reductase activity and total glutathione content. We also analyzed cellular components related to the LPS-induced inflammatory response in possible target tissues, i.e. head kidney and spleen. Our results revealed a significant prooxidant effect in the liver cells and head kidney leukocytes of roach exposed to 100 μg of Al/L for 2 days. In liver, we observed more lipoperoxidation products and lower endogenous antioxidant activity levels such as glutathione reductase activity and total glutathione content. These prooxidant effects were associated with a higher oxidative burst in head kidney leukocytes, and they were all the more important in fish stimulated by LPS injection. These findings demonstrate that environmental concentrations of Al induce oxidative and immunotoxic effects in fish and are associated to an immunomodulatory process related to the inflammatory response.

Alfalfa as a nutritive modulator in maintaining the innate immune response during the molting process

Forced molting of laying hens increases enteric foodborne pathogens in the reproductive tract, leading to contaminated eggs and progeny of infected hens. Currently, we lack a complete understanding of how conditions such as molting affect the immune system. Previous reports have shown that alfalfa is effective in inducing a molt as well as in producing protection against Salmonella Enteritidis organ invasion. Our laboratory has also shown that immune functions are significantly reduced during molting. The present investigation evaluates a specific parameter of immune function, heterophil function, during an induced molt in hens fed alfalfa. Three replicate experiments used hens older than 65 wk of age that were divided into 6 groups of 12 hens each and placed in individual laying cages. Two weeks before dietary changes, hens were placed on an 8L:16D photoperiod that continued for the 12-d experiment. Peripheral blood samples were taken from hens on d 0, 2, 6, and 12 of molt. Hens were randomly placed into 3 treatment groups: nonfed hens, fully fed hens, and alfalfa-fed hens. To evaluate heterophil functions, the production of an oxidative burst as well as cellular degranulation assays were performed. In addition, total and differential peripheral blood leukocyte counts were performed. When compared with the nonfed control, alfalfa-fed birds showed significantly (P < 0.05) higher oxidative burst and degranulation activities. The data confirm previous observations that heterophil functions are significantly decreased in nonfed birds and the data show that birds fed alfalfa had numerically increased heterophil functions over a 12-d molting period when compared with heterophils of nonfed controls. Commercial integrators should consider using alfalfa when developing new molting programs.

Increased CD11b neutrophil expression in Budd-Chiari syndrome or portal vein thrombosis secondary to polycythaemia vera.

Budd-Chiari syndrome and portal vein thrombosis (BCS/PVT) are frequently associated with polycythaemia vera (PV). In an attempt to elucidate the mechanisms of BCS/PVT secondary to PV (T-PV), CD11b neutrophil expression, neutrophil oxidative burst and platelet-neutrophil complexes (PNC) were assessed in 17 such patients. Three groups served as controls: BCS/PVT not secondary to PV (T-nPV; n = 20), PV without thrombosis (PV-nT; n = 16), and healthy controls (HC; n = 20). Baseline CD11b expression (in mean fluorescence intensity units) was 101 [95% confidence interval (CI): 79-128] in T-PV patients, versus 25 (95% CI: 18-35) in T-nPV, 59 (95% CI: 43-80) in PV-nT, and 34 (95% CI: 25-48) in HC (P < 0.001). After N-formyl-L-methionyl-L-leucyl-L-phenylalanine activation, T-PV patients also showed higher CD11b values: 190 (95% CI: 151-238), versus 55 (95% CI: 41-72) in T-nPV, 111 (95% CI: 81-153) in PV-nT, and 77 (95% CI: 63-95) in HC (P < 0.001). In BCS/PVT, CD11b neutrophil expression had 90% specificity and 100% sensitivity for the association with PV. Finally, PV patients had higher oxidative burst and PNC than T-nPV patients or HC (P < 0.05). These results support a role for neutrophils in BCS/PVT secondary to PV and indicate that neutrophil CD11b expression could be of use for PV screening in BCS/PVT patients.

Changes in Neutrophil Fatty Acid Composition and Its Relationship to Function Following Burn Injury in Humans

Membrane lipid composition influences a number of immune functions including those of neutrophils, an important defense against infection after burn injury that has also been implicated in causing damage to host tissues. This study investigates compositional changes in phospholipid (PL) fatty acids and functional alterations of neutrophils immediately following and during recovery from burn injury. Ten patients with>10% total body surface area burn had blood drawn at specific times (0 days to>50 days) following burn injury. Neutrophil lipids were extracted, major PL classes separated by thin layer chromatography, and fatty acid composition determined using gas liquid chromatography. Neutrophil granularity and oxidative burst were measured in whole blood before and after stimulation with phorbol myristate acetate using flow cytometry. Neutrophils were less granular and had a greater oxidative burst early ( 50 days) after burn injury. The arachidonic acid (20: 4n-6) content in all PL fractions was significantly reduced following burn injury and increased with recovery (p<0.05). The total n-6 fatty acid content of PS and PI increased with recovery (p<0.05). In conclusion, reduced 20: 4n-6 in neutrophil PL is suggestive of increased release or reduced synthesis of 20: 4n-6 early after burn. Lower granularity and higher oxidative burst immediately post-injury normalized with increases in 20: 4n-6. Compositional changes in neutrophil membranes early after burn may impact effector functions of neutrophils. Further work is needed to develop nutritional intervention strategies designed to modulate fatty acid composition of neutrophils to reduce the harmful effects of the oxidative burst while maintaining important infection defense mechanisms following burn injury.