Antibiotic stress selects against cooperation in the pathogenic bacterium Pseudomonas aeruginosa

Cheats are a pervasive threat to public goods production in natural and human communities, as they benefit from the commons without contributing to it. Although ecological antagonisms such as predation, parasitism, competition, and abiotic environmental stress play key roles in shaping population biology, it is unknown how such stresses generally affect the ability of cheats to undermine cooperation. We used theory and experiments to address this question in the pathogenic bacterium, Pseudomonas aeruginosa Although public goods producers were selected against in all populations, our competition experiments showed that antibiotics significantly increased the advantage of nonproducers. Moreover, the dominance of nonproducers in mixed cultures was associated with higher resistance to antibiotics than in either monoculture. Mathematical modeling indicates that accentuated costs to producer phenotypes underlie the observed patterns. Mathematical analysis further shows how these patterns should generalize to other taxa with public goods behaviors. Our findings suggest that explaining the maintenance of cooperative public goods behaviors in certain natural systems will be more challenging than previously thought. Our results also have specific implications for the control of pathogenic bacteria using antibiotics and for understanding natural bacterial ecosystems, where subinhibitory concentrations of antimicrobials frequently occur

Kinin B1 Receptor Enhances the Oxidative Stress in a Rat Model of Insulin Resistance: Outcome in Hypertension, Allodynia and Metabolic Complications

BACKGROUND: Kinin B(1) receptor (B(1)R) is induced by the oxidative stress in models of diabetes mellitus. This study aims at determining whether B(1)R activation could perpetuate the oxidative stress which leads to diabetic complications. METHODS AND FINDINGS: Young Sprague-Dawley rats were fed with 10% D-Glucose or tap water (controls) for 8-12 weeks. A selective B(1)R antagonist (SSR240612) was administered acutely (3-30 mg/kg) or daily for a period of 7 days (10 mg/kg) and the impact was measured on systolic blood pressure, allodynia, protein and/or mRNA B(1)R expression, aortic superoxide anion (O(2)(*-)) production and expression of superoxide dismutase (MnSOD) and catalase. SSR240612 reduced dose-dependently (3-30 mg/kg) high blood pressure in 12-week glucose-fed rats, but had no effect in controls. Eight-week glucose-fed rats exhibited insulin resistance (HOMA index), hypertension, tactile and cold allodynia and significant increases of plasma levels of glucose and insulin. This was associated with higher aortic levels of O(2)(*-), NADPH oxidase activity, MnSOD and catalase expression. All these abnormalities including B(1)R overexpression (spinal cord, aorta, liver and gastrocnemius muscle) were normalized by the prolonged treatment with SSR240612. The production of O(2)(*-) in the aorta of glucose-fed rats was also measured in the presence and absence of inhibitors (10-100 microM) of NADPH oxidase (apocynin), xanthine oxidase (allopurinol) or nitric oxide synthase (L-NAME) with and without Sar[D-Phe(8)]des-Arg(9)-BK (20 microM; B(1)R agonist). Data show that the greater aortic O(2)(*-) production induced by the B(1)R agonist was blocked only by apocynin. CONCLUSIONS: Activation of kinin B(1)R increased O(2)(*-) through the activation of NADPH oxidase in the vasculature. Prolonged blockade of B(1)R restored cardiovascular, sensory and metabolic abnormalities by reducing oxidative stress and B(1)R gene expression in this model

Impact of glucocorticoid receptor density on ligand-independent dimerization, cooperative ligand-binding and basal priming of transactivation: a cell culture model

Glucocorticoid receptor (GR) levels vary between tissues and individuals and are altered by physiological and pharmacological effectors. However, the effects and implications of differences in GR concentration have not been fully elucidated. Using three statistically different GR concentrations in transiently transfected COS-1 cells, we demonstrate, using co-immunoprecipitation (CoIP) and fluorescent resonance energy transfer (FRET), that high levels of wild type GR (wtGR), but not of dimerization deficient GR (GRdim), display ligand-independent dimerization. Whole-cell saturation ligand-binding experiments furthermore establish that positive cooperative ligand-binding, with a concomitant increased ligand-binding affinity, is facilitated by ligand-independent dimerization at high concentrations of wtGR, but not GRdim. The down-stream consequences of ligand-independent dimerization at high concentrations of wtGR, but not GRdim, are shown to include basal priming of the system as witnessed by ligand-independent transactivation of both a GRE-containing promoter-reporter and the endogenous glucocorticoid (GC)-responsive gene, GILZ, as well as ligand-independent loading of GR onto the GILZ promoter. Pursuant to the basal priming of the system, addition of ligand results in a significantly greater modulation of transactivation potency than would be expected solely from the increase in ligand-binding affinity. Thus ligand-independent dimerization of the GR at high concentrations primes the system, through ligand-independent DNA loading and transactivation, which together with positive cooperative ligand-binding increases the potency of GR agonists and shifts the bio-character of partial GR agonists. Clearly GR-levels are a major factor in determining the sensitivity to GCs and a critical factor regulating transcriptional programs

Diagnostics des écoulements à particule dans la création d'alliages avec apport de poudre (Actes)

International audienc

Gene transfer to human rheumatoid synovial tissue engrafted in SCID mice

Objective, To assess the feasibility of gene therapy in rheumatoid arthritis (RA) and determine the appropriate vector. Methods. Human rheumatoid synovial tissue from 6 patients with RA was transduced ex vivo with a recombinant retroviral vector (pMFG.nlsLacZ) containing the Escherichia coil beta-galactosidase (beta-gal) gene in a coculture assay in the presence of 20 ng/ml tumor necrosis factor alpha (TNF-alpha) for promoting cell division. We also conducted in vitro infection experiments using an adenoviral vector (AdCMVSp1.LacZ) containing the beta-gal gene. After gene transduction, the synovial tissue was engrafted subcutaneously in 8-week-old severe combined immunodeficiency (SCID) CB17 mice. beta-gal expression was then monitored as a function of lime (up to 21 days) and of virus dose [up to 50 colony forming units (cfu)/cell]. The efficacy of direct in vivo gene transfer was also tested by injection of 10(6) cfu of pMFG.nlsLacZ into rheumatoid synovial tissue engrafted in SCID mice. Results, When recombinant retroviral vector was used, 30 +/- 5% of ex vivo infected synovial cells were positive for staining. In synovial tissue implanted in SCID mice, beta-gal expression declined to 5% after one week, but persisted for at least 21 days. Direct injection of pMFG.nlsLacZ vector into the rheumatoid synovial tissue implanted in SCID mice allowed efficient and stable in vivo infection of the synovial tissue. Ex vivo gene transfer with adenoviral vector resulted in a 98% infection rare of the synovial lining cells. However, beta-gal activity declined 7 days after subcutaneous implantation. Conclusion. Highly efficient gene transfer in rheumatoid synovial tissue is achievable with both adenoviral and retroviral vectors, but the results were transient. Exogenous gene transfer through retroviral vectors required stimulation with TNF-alpha for synovial cell division and proviral integration. Direct in vivo gene transfer with recombinant retrovirus was shown to be efficient. Transduction of human synovial tissue engrafted in SCID mice is a potent tool for developing preclinical models of gene therapy in RA

Gene transfer to human rheumatoid synovial tissue engrafted in SCID mice

Objective, To assess the feasibility of gene therapy in rheumatoid arthritis (RA) and determine the appropriate vector. Methods. Human rheumatoid synovial tissue from 6 patients with RA was transduced ex vivo with a recombinant retroviral vector (pMFG.nlsLacZ) containing the Escherichia coil beta-galactosidase (beta-gal) gene in a coculture assay in the presence of 20 ng/ml tumor necrosis factor alpha (TNF-alpha) for promoting cell division. We also conducted in vitro infection experiments using an adenoviral vector (AdCMVSp1.LacZ) containing the beta-gal gene. After gene transduction, the synovial tissue was engrafted subcutaneously in 8-week-old severe combined immunodeficiency (SCID) CB17 mice. beta-gal expression was then monitored as a function of lime (up to 21 days) and of virus dose [up to 50 colony forming units (cfu)/cell]. The efficacy of direct in vivo gene transfer was also tested by injection of 10(6) cfu of pMFG.nlsLacZ into rheumatoid synovial tissue engrafted in SCID mice. Results, When recombinant retroviral vector was used, 30 +/- 5% of ex vivo infected synovial cells were positive for staining. In synovial tissue implanted in SCID mice, beta-gal expression declined to 5% after one week, but persisted for at least 21 days. Direct injection of pMFG.nlsLacZ vector into the rheumatoid synovial tissue implanted in SCID mice allowed efficient and stable in vivo infection of the synovial tissue. Ex vivo gene transfer with adenoviral vector resulted in a 98% infection rare of the synovial lining cells. However, beta-gal activity declined 7 days after subcutaneous implantation. Conclusion. Highly efficient gene transfer in rheumatoid synovial tissue is achievable with both adenoviral and retroviral vectors, but the results were transient. Exogenous gene transfer through retroviral vectors required stimulation with TNF-alpha for synovial cell division and proviral integration. Direct in vivo gene transfer with recombinant retrovirus was shown to be efficient. Transduction of human synovial tissue engrafted in SCID mice is a potent tool for developing preclinical models of gene therapy in RA