Poor antioxidant status exacerbates oxidative stress and inflammatory response to Pseudomonas aeruginosa lung infection in guinea pigs

Ascorbate deficiency increases progression of shigellosis in guinea pigs and mice infection models

Shigella spp. are the causative agents of bacterial dysentery and shigellosis, mainly in children living in developing countries. The study of Shigella entire life cycle in vivo and the evaluation of vaccine candidates' protective efficacy have been hampered by the lack of a suitable animal model of infection. None of the studies evaluated so far (rabbit, guinea pig, mouse) allowed the recapitulation of full shigellosis symptoms upon Shigella oral challenge. Historical reports have suggested that dysentery and scurvy are both metabolic diseases associated with ascorbate deficiency. Mammals, which are susceptible to Shigella infection (humans, non-human primates and guinea pigs) are among the few species unable to synthesize ascorbate. We optimized a low-ascorbate diet to induce moderate ascorbate deficiency, but not scurvy, in guinea pigs to investigate whether poor vitamin C status increases the progression of shigellosis. Moderate ascorbate deficiency increased shigellosis symptom severity during an extended period of time (up to 48 h) in all strains tested (Shigella sonnei, Shigella flexneri 5a, and 2a). At late time points, an important influx of neutrophils was observed both within the disrupted colonic mucosa and in the luminal compartment, although Shigella was able to disseminate deep into the organ to reach the sub-mucosal layer and the bloodstream. Moreover, we found that ascorbate deficiency also increased Shigella penetration into the colon epithelium layer in a Gulo-/- mouse infection model. The use of these new rodent models of shigellosis opens new doors for the study of both Shigella infection strategies and immune responses to Shigella infection.

The effects of vitamin C on respiratory, allergic and immunological diseases: an experimental and clinical-based review

Vitamin C is used in modern medicine supplements for treatment of various disorders associated with oxidative stress, inflammation and immune dysregulation. In this review article, experimental and clinical results regarding the effects of vitamin C on respiratory immunologic, and allergic diseases are reviewed. Various databases and appropriate keywords are used to search the effect of vitamin C on respiratory diseases until the end of May 2022. Books, theses and articles were included. These studies assessed the effects of vitamin C on respiratory disorders including asthma, chronic obstructive pulmonary disease (COPD), lung infection and lung cancer. Vitamin C showed relaxant effect on tracheal smooth muscle via various mechanisms. The preventive effects of vitamin C were mediated by antioxidant, immunomodulatory and anti-inflammatory mechanisms in the experimental animal models of different respiratory diseases. Some clinical studies also indicated the effect of vitamin C on lung cancer and lung infections. Therefore, vitamin C could be used a preventive and/or relieving therapy in respiratory diseases.

Human immune cell mobilization during exercise: effect of IL-6 receptor blockade

NEW FINDINGS

What is the central question of this study? Does blockade of the IL-6 receptor by tocilizumab inhibit immune cell mobilization to the blood stream in humans during an acute bout of exercise? What is the main finding and its importance? Blockade of IL-6 receptor signalling by tocilizumab attenuates mobilization of NK cells and dendritic cells to the blood stream during exercise. This implies an inhibitory effect of tocilizumab on the innate immune response to physical stress, which could be considered in clinical settings.

ABSTRACT

Immune cells are recruited from their storage organs and the endothelial walls to the blood stream in response to physiological stress. This is essential for the recognition and clearing of infected, transformed or damaged cells. One of the most potent stimuli to recruit immune cells to the circulation is exercise. Accordingly, exercise has proven beneficial in disease settings, such as cancer and diabetes. Interleukin-6 (IL-6) is released from contracting skeletal muscle in response to exercise, and rodent studies have established a link between exercise-induced IL-6 and recruitment of natural killer (NK) cells. Whether exercise-induced IL-6 is involved in regulating NK cell mobilization in humans is unclear. This study explored the effect of IL-6 receptor blockade on immune cell mobilization during an acute bout of exercise in humans. In a randomized, placebo-controlled clinical study, abdominally obese humans receiving placebo infusions or tocilizumab infusions performed an acute bout of exercise before and after the intervention. Immune cell recruitment was measured by flow cytometry. IL-6 receptor blockade attenuated the increase of NK cells by 53% (mean difference -0.49 (95% CI: -0.89 to -0.08) × 10⁹ cells L^-1 , P < 0.001) and dendritic cells by 66% (mean difference -0.14 (95% CI: -0.28 to 0.010) × 10⁹ cells L^-1 , P < 0.001) induced by an acute bout of exercises. No changes were observed for T cells, monocytes and neutrophils. Treatments which interact with the exercise-mediated immune surveillance provide relevant clinical information in pursuing the 'exercise as medicine' concept.

Lack of the Major Multifunctional Catalase KatA in Pseudomonas aeruginosa Accelerates Evolution of Antibiotic Resistance in Ciprofloxacin-Treated Biofilms

During chronic biofilm infections, Pseudomonas aeruginosa bacteria are exposed to increased oxidative stress as a result of the inflammatory response. As reactive oxygen species (ROS) are mutagenic, the evolution of resistance to ciprofloxacin (CIP) in biofilms under oxidative stress conditions was investigated. We experimentally evolved six replicate populations of P. aeruginosa lacking the major catalase KatA in colony biofilms and stationary-phase cultures for seven passages in the presence of subinhibitory levels (0.1 mg/liter) of CIP or without CIP (eight replicate lineages for controls) under aerobic conditions. In CIP-evolved biofilms, a larger CIP-resistant subpopulation was isolated in the ΔkatA strain than in the wild-type (WT) PAO1 population, suggesting oxidative stress as a promoter of the development of antibiotic resistance. A higher number of mutations identified by population sequencing were observed in evolved ΔkatA biofilm populations (CIP and control) than in WT PAO1 populations evolved under the same conditions. Genes involved in iron assimilation were found to be exclusively mutated in CIP-evolved ΔkatA biofilm populations, probably as a defense mechanism against ROS formation resulting from Fenton reactions. Furthermore, a hypermutable lineage due to mutL inactivation developed in one CIP-evolved ΔkatA biofilm lineage. In CIP-evolved biofilms of both the ΔkatA strain and WT PAO1, mutations in nfxB, the negative regulator of the MexCD-OprJ efflux pump, were observed while in CIP-evolved planktonic cultures of both the ΔkatA strain and WT PAO1, mutations in mexR and nalD, regulators of the MexAB-OprM efflux pump, were repeatedly found. In conclusion, these results emphasize the role of oxidative stress as an environmental factor that might increase the development of antibiotic resistance in in vivo biofilms.

Vitamin C mitigates oxidative stress and tumor necrosis factor-alpha in severe community-acquired pneumonia and LPS-induced macrophages

Oxidative stress is an important part of host innate immune response to foreign pathogens. However, the impact of vitamin C on oxidative stress and inflammation remains unclear in community-acquired pneumonia (CAP). We aimed to determine the effect of vitamin C on oxidative stress and inflammation. CAP patients were enrolled. Reactive oxygen species (ROS), DNA damage, superoxide dismutases (SOD) activity, tumor necrosis factor-alpha (TNF-α), and IL-6 were analyzed in CAP patients and LPS-stimulated macrophages cells. MH-S cells were transfected with RFP-LC3 plasmids. Autophagy was measured in LPS-stimulated macrophages cells. Severe CAP patients showed significantly increased ROS, DNA damage, TNF-α, and IL-6. SOD was significantly decreased in severe CAP. Vitamin C significantly decreased ROS, DNA damage, TNF-α, and IL-6. Vitamin C inhibited LPS-induced ROS, DNA damage, TNF-α, IL-6, and p38 in macrophages cells. Vitamin C inhibited autophagy in LPS-induced macrophages cells. These findings indicated that severe CAP exhibited significantly increased oxidative stress, DNA damage, and proinflammatory mediator. Vitamin C mitigated oxidative stress and proinflammatory mediator suggesting a possible mechanism for vitamin C in severe CAP.

Oxidative modification of proteins in pediatric cystic fibrosis with bacterial infections

Pseudomonas aeruginosa and Staphylococcus aureus cause chronic lung infection in cystic fibrosis (CF) patients, inducing chronic oxidative stress. Several markers of plasma protein oxidative damage and glycoxidation and activities of erythrocyte antioxidant enzymes have been compared in stable CF patients chronically infected with Pseudomonas aeruginosa (n = 12) and Staphylococcus aureus (n = 10) in relation to healthy subjects (n = 11). Concentration of nitric oxide was also measured in the exhaled air from the lower respiratory tract of patients with CF. Elevated glycophore (4.22 ± 0.91 and 4.19 ± 1.04 versus control 3.18 ± 0.53 fluorescence units (FU)/mg protein; P < 0.05) and carbonyl group levels (1.9 ± 0.64, 1.87 ± 0.45 versus control 0.94 ± 0.19 nmol/mg protein; P < 0.05) as well as increased glutathione S-transferase activity (2.51 ± 0.88 and 2.57 ± 0.79 U/g Hb versus 0.77 ± 0.16 U/g Hb; P < 0.05) were noted in Pseudomonas aeruginosa and Staphylococcus aureus infected CF. Kynurenine level (4.91 ± 1.22 versus 3.89 ± 0.54 FU/mg protein; P < 0.05) was elevated only in Staphylococcus aureus infected CF. These results confirm oxidative stress in CF and demonstrate the usefulness of the glycophore level and protein carbonyl groups as markers of oxidative modifications of plasma proteins in this disease.

Guinea pig ascorbate status predicts tetrahydrobiopterin plasma concentration and oxidation ratio in vivo

Tetrahydrobiopterin (BH₄) is an essential co-factor of nitric oxide synthases and is easily oxidized to dihydrobiopterin (BH₂) which promotes endothelial nitric oxide synthase uncoupling and deleterious superoxide production. Vitamin C has been shown to improve endothelial function by different mechanisms, some involving BH₄. The hypothesis of the present study was that vitamin C status, in particular low levels, influences biopterin redox status in vivo. Like humans, the guinea pig lacks the ability to synthesize vitamin C and was therefore used as model. Seven day old animals (n = 10/group) were given a diet containing 100, 250, 500, 750, 1000, or 1500 ppm vitamin C until euthanasia at age 60-64 days. Blood samples were drawn from the heart and analyzed for ascorbate, dehydroascorbic acid (DHA), BH₄ and BH₂ by high-performance liquid chromatography. Plasma BH₄ levels were found to be significantly lower in animals fed 100 ppm vitamin C compared to all other groups (P < .05 or less). BH₂ levels were not significantly different between groups but the BH₂-to-BH₄ ratio was higher in the group fed 100 ppm vitamin C (P < .001 all cases). Significant positive correlations between BH4 and ascorbate and between BH₂-to-BH₄ ratio and DHA were observed (P < .0001 both cases). Likewise, BH₂-to-BH₄ ratio was negatively correlated with ascorbate (P < .0001) as was BH₄ and DHA (P < .005). In conclusion, the redox status of plasma biopterins, essentially involved in vasodilation, depends on the vitamin C status in vivo. Thus, ingestion of insufficient quantities of vitamin C not only leads to vitamin C deficiency but also to increased BH₄ oxidation which may promote endothelial dysfunction.

Pressurized whey protein can limit bacterial burden and protein oxidation in Pseudomonas aeruginosa lung infection

BACKGROUND

Lung infection caused by Pseudomonas aeruginosa is associated with an exuberant inflammatory response, oxidative stress, and lung damage. Whey protein is a rich source of cysteine, and anti-inflammatory and immune-enhancing peptides. Anti-inflammatory and antioxidant properties of whey are augmented by hyperbaric pressure treatment. In this study, we tested whether dietary supplementation with pressurized whey protein enhances the host ability to clear P. aeruginosa infection compared with native (i.e., unpressurized) whey.

METHODS

Using a minimally invasive, non-lethal model of murine (female C57Bl/6) model of P. aeruginosa infection (mucoid strain embedded in agar beads), we studied kinetics of infection, inflammation, and oxidative stress at d 1, 3, and 7 postinfection. A parallel set of mice were fed for 4 wk a semipurified diet containing either native or pressurized whey and subsequently infected with P. aeruginosa. In these mice, the parameters mentioned previously were studied at d 1 and 3 postinfection.

RESULTS

Infection with P. aeruginosa resulted in inflammation and protein oxidation sustained beyond bacterial clearance. Animals that were fed pressurized whey had fewer bacteria at day 3 than mice on native whey. Weight loss or broncho-alveolar lavage cell content were comparable. Airway protein oxidation was attenuated, whereas airway leukocyte bacterial killing ability and oxidative burst in response to opsonized bacteria were increased in the pressurized whey-fed animals.

CONCLUSIONS

Use of nutritionally derived substances with anti-inflammatory and antioxidant properties, such as pressurized whey, aids in limiting airway bacterial infection, particularly, under conditions of ongoing oxidative stress.

Inhibitory activity of liposomal flavonoids during oxidative metabolism of human neutrophils upon stimulation with immune complexes and phorbol ester

CONTEXT AND OBJECTIVE

The massive production of reactive oxygen species by neutrophils during inflammation may cause damage to tissues. Flavonoids act as antioxidants and have anti-inflammatory effects. In this study, liposomes loaded with these compounds were evaluated as potential antioxidant carriers, in attempt to overcome their poor solubility and stability.

MATERIALS AND METHODS

Liposomes containing quercetin, myricetin, kaempferol or galangin were prepared by the ethanol injection method and analyzed as inhibitors of immune complex (IC) and phorbol ester-stimulated neutrophil oxidative metabolism by luminol (CLlum) and lucigenin-enhanced (CLluc) chemiluminescence (CL) assays. The mechanisms involved this activity of liposomal flavonoids, such as cytotoxicity and superoxide anion scavenging capacity, and their effect on phagocytosis of ICs were also investigated.

RESULTS AND DISCUSSION

The results showed that the inhibitory effect of liposomal flavonoids on CLlum and CLluc is inversely related to the number of hydroxyl groups in the flavonoid B ring. Moreover, phagocytosis of liposomes by neutrophils does not seem to necessarily promote such activity, as the liposomal flavonoids are also able to reduce CL when the cells are pretreated with cytochalasin B. Under assessed conditions, the antioxidant liposomes are not toxic to the human neutrophils and do not interfere with IC-induced phagocytosis.

CONCLUSION

The studied liposomes can be suitable carriers of flavonoids and be an alternative for the treatment of diseases in which a massive oxidative metabolism of neutrophils is involved.