The flagellum of Pseudomonas aeruginosa has been implicated in acute pneumonia, and its flagellin is known to cause lung inflammation. However, its proinflammatory role, versus its motility function, as a cause of death by a whole bacterium has not been demonstrated. This issue was examined in a lung model of acute infection using different flagellar mutants. We found that the absence of motility does not significantly alter the LD(50), whereas the production of excess amounts of flagellin lowers it and results in early death. Next, we found that the absence of the Toll-like receptor 5 (TLR5) ligand, flagellin, results in slower clearance of this organism from the lungs and a delay in the time to death. These findings demonstrate the dual role of flagellin in host defense and in disease and suggest that the death in this model may be biphasic with flagellin playing a role early in the disease.
"Depending on the route, dose administered, and the frequency of dosing, acute lung infection with either rapid clearance of the bacteria or acute sepsis and death could take place (George et al., 1991). Using this model, it has been shown that P. aeruginosa must express several key virulence factors (Balloy et al., 2007). A literature survey about acute vs. chronic P. aeruginosa lung infections clearly shows that to induce an infection for more than 1 month, it is necessary to use an immobilizing agent such as agar, agarose, or seaweed alginate together with the bacterial suspension (Iwata and Sato, 1991; Hart et al., 1993; McMorran et al., 2001; Moser et al., 2002). "
[Show abstract][Hide abstract] ABSTRACT: Biological disease models can be difficult and costly to develop and use on a routine basis. Particularly, in vivo lung infection models performed to study lung pathologies use to be laborious, demand a great time and commonly are associated with ethical issues. When infections in experimental animals are used, they need to be refined, defined, and validated for their intended purpose. Therefore, alternative and easy to handle models of experimental infections are still needed to test the virulence of bacterial lung pathogens. Because non-mammalian models have less ethical and cost constraints as a subjects for experimentation, in some cases would be appropriated to include these models as valuable tools to explore host-pathogen interactions. Numerous scientific data have been argued to the more extensive use of several kinds of alternative models, such as, the vertebrate zebrafish (Danio rerio), and non-vertebrate insects and nematodes (e.g., Caenorhabditis elegans) in the study of diverse infectious agents that affect humans. Here, we review the use of these vertebrate and non-vertebrate models in the study of bacterial agents, which are considered the principal causes of lung injury. Curiously none of these animals have a respiratory system as in air-breathing vertebrates, where respiration takes place in lungs. Despite this fact, with the present review we sought to provide elements in favor of the use of these alternative animal models of infection to reveal the molecular signatures of host-pathogen interactions.
Frontiers in Microbiology 02/2015; 6:38. DOI:10.3389/fmicb.2015.00038 · 3.99 Impact Factor
"The well known paradox is that the TLR5-flagellin interaction is a major mediator of inflammation following exposure to Pa. Indeed, Pa mutants which overproduced flagellin, caused severe inflammation . The consequence is that some authors have proposed TLR5 as an anti-inflammatory target . "
[Show abstract][Hide abstract] ABSTRACT: Background
The aim was to measure flagellin concentrations in the expectorations of CF patients and to examine whether there are correlations with the level of respiratory insufficiency and inflammation.
Sputum samples from 31 adult patients chronically colonized with P. aeruginosa were collected and analysed for their content of flagellin and IL-8. Clinical data were extracted from patient files.
Regardless of whether patients are colonized with mucoid strains or not, they carry clones of P. aeruginosa that express flagellin. While flagellin was present in airways of all of our CF patients, it is difficult to ascertain its contribution to inflammation (IL-8) and lung function deterioration.
This is the first demonstration that flagellin is present in the sputum of patients. Thus, attempts to down regulate inflammation by the use of TLR5 (flagellin receptor) antagonists remain a possibility. However, this result needs to be extended to a larger number of patients to validate it for future research on this subject.
BMC Pulmonary Medicine 06/2014; 14(1):100. DOI:10.1186/1471-2466-14-100 · 2.40 Impact Factor
"Mice were anesthetized by i.m. with a mixture of ketamine (40 mg/Kg) and xylazine (8 mg/Kg) and infected intranasally with WT PAK strain at 107 colony-forming unit (CFU) per mouse, as described previously . Briefly, after anesthetization, mice were held by ears and 50 µl of the inoculum ((PAK 107 CFU/mouse) diluted in PBS) were gradually released into the nostrils (25 µl in each nostril) with the help of a micropipette. "
[Show abstract][Hide abstract] ABSTRACT: Pseudomonas aeruginosa is an opportunistic pathogen involved in nosocomial infections. While a number of studies have demonstrated the roles of TLR2, TLR4 and TLR5 in host defense againt P. aeruginosa infection, the implication of TLR9 in this process has been overlooked. Here, we show that P. aeruginosa DNA stimulates the inflammatory response through TLR9 pathway in both a cell line and primary alveolar macrophages (AMs). This activation requires asparagine endopeptidase- and endosomal acidification. Interestingly, TLR9-/- mice resisted to lethal lung infection by P. aeruginosa, compared to WT C57BL/6 mice. The resistance of TLR9-/- mice to P. aeruginosa infection was associated with: (i) a higher ability of TLR9-/- AMs to kill P. aeruginosa; (ii) a rapid increase in the pro-inflammatory cytokines such as TNFα, IL-1β and IL-6 production; and (iii) an increase in nitric oxide (NO) production and inductible NO synthase expression in AMs. In addition, inhibition of both IL-1β and NO production resulted in a significant decrease of P. aeruginosa clearance by AMs. Altogether these results indicate that TLR9 plays a detrimental role in pulmonary host defense toward P. aeruginosa by reducing the AMs clearance activity and production of IL-1β and NO necessary for bacteria killing.
PLoS ONE 03/2014; 9(3):e90466. DOI:10.1371/journal.pone.0090466 · 3.23 Impact Factor
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