| 1. |
- Bhongir, Ravi K. V., et al.
(författare)
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DNA-fragmentation is a source of bactericidal activity against Pseudomonas aeruginosa
- 2017
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Ingår i: Biochemical Journal. - 0264-6021. ; 474:3, s. 411-425
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Tidskriftsartikel (refereegranskat)abstract
- Pseudomonas aeruginosa airway infection is common in cystic fibrosis (CF), a disease also characterized by abundant extracellular DNA (eDNA) in the airways. The eDNA is mainly derived from neutrophils accumulating in the airways and contributes to a high sputum viscosity. The altered environment in the lower airways also paves the way for chronic P. aeruginosa infection. Here, we show that mice with P. aeruginosa airway infection have increased survival and decreased bacterial load after topical treatment with DNase. Furthermore, DNA from the sputum of CF patients showed increased bactericidal activity after treatment with DNase ex vivo. Both degraded DNA of neutrophil extracellular traps (NETs) and genomic DNA degraded by serum, acquired bactericidal activity against P. aeruginosa. In vitro, small synthetic DNA-fragments (<100 base pairs) but not large fragments nor genomic DNA, were bactericidal against Gram-negative but not Grampositive bacteria. The addition of divalent cations reduced bacterial killing, suggesting that chelation of divalent cations by DNA results in destabilization of the lipopolysaccharide (LPS) envelope. This is a novel antibacterial strategy where fragmentation of eDNA and DNA-fragments can be used to treat P. aeruginosa airway infection.
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| 2. |
- Kasetty, Gopinath, et al.
(författare)
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Osteopontin protects against lung injury caused by extracellular histones
- 2019
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Ingår i: Mucosal Immunology. - : Elsevier BV. - 1933-0219 .- 1935-3456. ; 12:1, s. 39-50
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Tidskriftsartikel (refereegranskat)abstract
- Extracellular histones are present in the airways because of cell death occurring during inflammation. They promote inflammation and cause tissue damage due to their cationic nature. The anionic phosphoglycoprotein osteopontin (OPN) is expressed at high levels during airway inflammation and has been ascribed both pro- and anti-inflammatory roles. In this study, it was hypothesized that OPN may neutralize the harmful activities of extracellular histones at the airway mucosal surface. In a model of histone-induced acute lung injury, OPN−/− mice showed increased inflammation and tissue injury, and succumbed within 24 h, whereas wild-type mice showed lower degrees of inflammation and no mortality. In lipopolysaccharide-induced acute lung injury, wild-type mice showed less inflammation and tissue injury than OPN−/− mice. In bronchoalveolar lavage fluid from ARDS patients, high levels of OPN and also histone–OPN complexes were detected. In addition, OPN bound to histones with high affinity in vitro, resulting in less cytotoxicity and reduced formation of tissue-damaging neutrophil extracellular traps (NETs). The interaction between OPN and histones was dependent on posttranslational modification of OPN, i.e., phosphorylation. The findings demonstrate a novel role for OPN, modulating the pro-inflammatory and cytotoxic properties of free histones.
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| 3. |
- Kasetty, Gopinath, et al.
(författare)
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Osteopontin protects against pneumococcal infection in a murine model of allergic airway inflammation
- 2019
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Ingår i: Allergy: European Journal of Allergy and Clinical Immunology. - : Wiley. - 0105-4538. ; 74:4, s. 663-674
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Tidskriftsartikel (refereegranskat)abstract
- Background: In atopic asthma, chronic Th2-biased inflammation is associated with an increased risk of pneumococcal infection. The anionic phosphoglycoprotein osteopontin (OPN) is highly expressed in asthma and has been ascribed several roles during inflammation. This study aimed to investigate whether OPN affects inflammation and vulnerability to pneumococcal infection in atopic asthma. Methods: House dust mite (HDM) extract was used to induce allergic airway inflammation in both wild-type (Spp1+/+) and OPN knockout (Spp1−/−) C57BL/6J mice, and the airway was then infected with Streptococcus pneumoniae. Parameters reflecting inflammation, tissue injury, and bacterial burden were measured. In addition, samples from humans with allergic asthma were analyzed. Results: Both allergen challenge in individuals with allergic asthma and the intranasal instillation of HDM in mice resulted in increased OPN levels in bronchoalveolar lavage fluid (BALF). More immune cells (including alveolar macrophages, neutrophils, eosinophils, and lymphocytes) and higher levels of proinflammatory cytokines were found in Spp1−/− mice than in Spp1+/+ mice. Moreover, OPN-deficient mice exhibited increased levels of markers reflecting tissue injury. Upon infection with S. pneumoniae, Spp1+/+ mice with allergic airway inflammation had a significantly lower bacterial burden in both BALF and lung tissue than did Spp1−/− mice. Furthermore, Spp1−/− mice had higher levels of cytokines and immune cells in BALF than did Spp1+/+ mice. Conclusion: OPN reduces inflammation, decreases tissue injury, and reduces bacterial loads during concurrent pneumococcal infection and allergic airway inflammation in a murine model. These findings suggest that OPN significantly affects vulnerability to pneumococcal infection in atopic asthma.
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| 4. |
- Kasetty, Gopinath, et al.
(författare)
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The nonantibiotic macrolide em703 improves survival in a model of quinolone-treated pseudomonas aeruginosa airway infection
- 2017
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Ingår i: Antimicrobial Agents and Chemotherapy. - 0066-4804. ; 61:9
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Tidskriftsartikel (refereegranskat)abstract
- Macrolide antibiotics are used as anti-inflammatory agents, e.g., for prevention of exacerbations in chronic obstructive pulmonary disease and cystic fibrosis. Several studies have shown improved outcomes after the addition of macrolides to -lactam antibiotics for treatment of severe community-acquired pneumonia. However, a beneficial effect of macrolides in treating Gram-negative bacterial airway infections, e.g., those caused by Pseudomonas aeruginosa, remains to be shown. Macrolide antibiotics have significant side effects, in particular, motility-stimulating activity in the gastrointestinal tract and promotion of bacterial resistance. In this study, EM703, a modified macrolide lacking antibiotic and motility-stimulating activities but with retained anti-inflammatory properties, was used as an adjunct treatment for experimental P. aeruginosa lung infection, in combination with a conventional antibiotic. Airway infections in BALB/cJRj mice were induced by nasal instillation of P. aeruginosa; this was followed by treatment with the quinolone levofloxacin in the absence or presence of EM703. Survival, inflammatory responses, and cellular influx to the airways were monitored. Both pretreatment and simultaneous administration of EM703 dramatically improved survival in levofloxacin-treated mice with P. aeruginosa airway infections. In addition, EM703 reduced the levels of proinflammatory cytokines, increased the numbers of leukocytes in bronchoalveolar lavage fluid, and reduced the numbers of neutrophils present in lung tissue. In summary, the findings of this study show that the immunomodulatory properties of the modified macrolide EM703 can be important when treating Gram-negative pneumonia, as exemplified by P. aeruginosa infection in this study.
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