Cigarette smoke induces β2-integrin-dependent neutrophil migration across human endothelium

<p>Abstract</p> <p>Background</p> <p>Cigarette smoking induces peripheral inflammatory responses in all smokers and is the major risk factor for neutrophilic lung disease such as chronic obstructive pulmonary disease. The aim of this study was to investigate the effect of cigarette smoke on neutrophil migration and on β₂-integrin activation and function in neutrophilic transmigration through endothelium.</p> <p>Methods and results</p> <p>Utilizing freshly isolated human PMNs, the effect of cigarette smoke on migration and β₂-integrin activation and function in neutrophilic transmigration was studied. In this report, we demonstrated that cigarette smoke extract (CSE) dose dependently induced migration of neutrophils <it>in vitro</it>. Moreover, CSE promoted neutrophil adherence to fibrinogen. Using functional blocking antibodies against CD11b and CD18, it was demonstrated that Mac-1 (CD11b/CD18) is responsible for the cigarette smoke-induced firm adhesion of neutrophils to fibrinogen. Furthermore, neutrophils transmigrated through endothelium by cigarette smoke due to the activation of β₂-integrins, since pre-incubation of neutrophils with functional blocking antibodies against CD11b and CD18 attenuated this transmigration.</p> <p>Conclusion</p> <p>This is the first study to describe that cigarette smoke extract induces a direct migratory effect on neutrophils and that CSE is an activator of β₂-integrins on the cell surface. Blocking this activation of β₂-integrins might be an important target in cigarette smoke induced neutrophilic diseases.</p

The soil affects both the differential accumulation of iron between wild type and ferritin over-expressor tobacco plants and the sensitivity of their rhizosphere bacterioflora to iron stress.

Transgenic tobacco P6 over-expressing ferritin is known to activate iron transport systems and to have increased iron content. Iron phytoextraction by this transgene is then expected to be higher than that of the wild-type (WT). In the present study, the possibility to modify iron availability for bacteria via the cultivation of the transgene P6 was explored by comparing the sensitivity to iron stress of bacteria isolated from the rhizosphere of the two plant genotypes (WT and P6). This sensitivity was evaluated by measuring the bacterial density when plated on a solid media depleted (supplemented with 8-hydroxiquinoline) or not (supplemented with Fe-8-hydroxyquinoline) in iron. The experimental conditions favorable to the di.erential iron accumulation between the wild-type and transgenic tobacco were identi.ed. The two plant genotypes were grown in three soils (Hervau, Thory and Oudun) chosen for their di.erences in iron content, and the plants were yielded at three stages (vegetative, .oral bud and .owering). The highest di.erential accumulation of iron in favor of the over-expressing transgene was found in the plants at the .oral bud stage when cultivated in the Oudun and Thory soils. Since at that stage, the plant growth was signi.cantly higher in the Oudun soil, the phytoextraction of iron was the highest in this soil. At the .oral bud stage, bacteria isolated from the rhizosphere of the transgene cultivated in the Oudun and Thory soils appeared to be less susceptible to iron stress than those from the wild-type. Bacterial density recovered on agar medium depleted in iron was signi.cantly the highest in the rhizosphere of the transgene cultivated in the Oudun soil. Altogether, these data indicate that the over-expressing ferritin transgenic plants, that accumulate and extract more iron from the rhizosphere than the wild-type plants, select in their rhizosphere bacteria less susceptible to iron stress compared to those selected by the wild-type plants

Effect of Two Plant Species, Flax (Linum usitatissinum L.) and Tomato (Lycopersicon esculentum Mill.), on the Diversity of Soilborne Populations of Fluorescent Pseudomonads

Suppression of soilborne disease by fluorescent pseudomonads may be inconsistent. Inefficient root colonization by the introduced bacteria is often responsible for this inconsistency. To better understand the bacterial traits involved in root colonization, the effect of two plant species, flax (Linum usitatissinum L.) and tomato (Lycopersicon esculentum Mill.), on the diversity of soilborne populations was assessed. Fluorescent pseudomonads were isolated from an uncultivated soil and from rhizosphere, rhizoplane, and root tissue of flax and tomato cultivated in the same soil. Species and biovars were identified by classical biochemical and physiological tests. The ability of bacterial isolates to assimilate 147 different organic compounds and to show three different enzyme activities was assessed to determine their intraspecific phenotypic diversity. Numerical analysis of these characteristics allowed the clustering of isolates showing a high level (87.8%) of similarity. On the whole, the populations isolated from soil were different from those isolated from plants with respect to their phenotypic characteristics. The difference in bacteria isolated from uncultivated soil and from root tissue of flax was particularly marked. The intensity of plant selection was more strongly expressed with flax than with tomato plants. The selection was, at least partly, plant specific. The use of 10 different substrates allowed us to discriminate between flax and tomato isolates. Pseudomonas fluorescens biovars II, III, and V and Pseudomonas putida biovar A and intermediate type were well distributed among the isolates from soil, rhizosphere, and rhizoplane. Most isolates from root tissue of flax and tomato belonged to P. putida bv. A and to P. fluorescens bv. II, respectively. Phenotypic characterization of bacterial isolates was well correlated with genotypic characterization based on repetitive extragenic palindromic PCR fingerprinting

Identification of Bacterial Groups Preferentially Associated with Mycorrhizal Roots of Medicago truncatula

The genetic structures of bacterial communities associated with Medicago truncatula Gaertn. cv. Jemalong line J5 (Myc(+) Nod(+)) and its symbiosis-defective mutants TRV48 (Myc(+) Nod(−)) and TRV25 (Myc(−) Nod(−)) were compared. Plants were cultivated in a fertile soil (Châteaurenard, France) and in soil from the Mediterranean basin showing a low fertility (Mas d'Imbert, France). Plant growth, root architecture, and the efficiency of root symbiosis of the three plant genotypes were characterized in the two soils. Structures of the bacterial communities were assessed by automated-ribosomal intergenic spacer analysis (A-RISA) fingerprinting from DNA extracted from the rhizosphere soil and root tissues. As expected, the TRV25 mutant did not develop endomycorrhizal symbiosis in any of the soils, whereas mycorrhization of line J5 and the TRV48 mutant occurred in both soils but at a higher intensity in the Mas d'Imbert (low fertility) than in the Châteaurenard soil. However, modifications of plant growth and root architecture, between mycorrhizal (J5 and TRV48) and nonmycorrhizal (TRV25) plants, were recorded only when cultivated in the Mas d'Imbert soil. Similarly, the genetic structures of bacterial communities associated with mycorrhizal and nonmycorrhizal plants differed significantly in the Mas d'Imbert soil but not in the Châteaurenard soil. Multivariate analysis of the patterns allowed the identification of molecular markers, explaining these differences, and markers were further sequenced. Molecular marker analysis allowed the delineation of 211 operational taxonomic units. Some of those belonging to the Comamonadaceae and Oxalobacteraceae (β-Proteobacteria) families were found to be significantly more represented within bacterial communities associated with the J5 line and the TRV48 mutant than within those associated with the TRV25 mutant, indicating that these bacterial genera were preferentially associated with mycorrhizal roots in the Mas d'Imbert soil