scholarly journals Potential Virulence Role of the Legionella pneumophila ptsP Ortholog

2001 ◽  
Vol 69 (8) ◽  
pp. 4782-4789 ◽  
Author(s):  
Futoshi Higa ◽  
Paul H. Edelstein
Keyword(s):  
Guinea Pig ◽  
Alveolar Macrophages ◽  
Legionella Pneumophila ◽  
Alveolar Epithelial Cell ◽  
A549 Cells ◽  
Epithelial Cell Line ◽  
Putative Virulence Factor ◽  
Phenotypic Properties ◽  
Minimal Growth

ABSTRACT We previously identified the Legionella pneumophila ptsP (phosphoenolpyruvate phosphotransferase) ortholog gene as a putative virulence factor in a study of signature-tagged mutagenesis using a guinea pig pneumonia model. In this study, we further defined the phenotypic properties of L. pneumophila ptsP and its complete sequence. The L. pneumophila ptsP was 2,295 bases in length. Its deduced amino acid sequence had high similarity withptsP orthologs of Pseudomonas aeruginosa, Azotobacter vinelandii, and Escherichia coli, with nearly identical lengths. Here we show that while the mutant grew well in laboratory media, it was defective in both lung and spleen multiplication in guinea pigs. It grew slowly in guinea pig alveolar macrophages despite good uptake into the cells. Furthermore, there was minimal growth in a human alveolar epithelial cell line (A549). Transcomplementation of the L. pneumophila ptsP mutant almost completely rescued its growth in alveolar macrophages, in A549 cells, and in guinea pig lung and spleen. The L. pneumophila ptsP mutant was capable of evasion of phagosome-lysosome fusion and resided in ribosome-studded phagosomes. Pore formation activity of the mutant was normal. The L. pneumophila ptsP mutant expressed DotA and IcmX in apparently normal amounts, suggesting that the ptsP mutation did not affect dotA andicmX regulation. In addition, the mutant was resistant to serum and neutrophil killing. Taken together, these findings show thatL. pneumophila ptsP is required for full in vivo virulence of L. pneumophila, most probably by affecting intracellular growth.

scholarly journals lvgA, a Novel Legionella pneumophila Virulence Factor

2003 ◽  
Vol 71 (5) ◽  
pp. 2394-2403 ◽  
Author(s):  
Paul H. Edelstein ◽  
Baofeng Hu ◽  
Futoshi Higa ◽  
Martha A. C. Edelstein
Keyword(s):  
Guinea Pig ◽  
Alveolar Macrophages ◽  
Legionella Pneumophila ◽  
Bacterial Resistance ◽  
Late Onset ◽  
Alveolar Epithelial Cell ◽  
Virulence Gene ◽  
Polymorphonuclear Neutrophils ◽  
Epithelial Cell Line ◽  
Mutant Bacterium

ABSTRACT Several novel Legionella pneumophila virulence genes were previously discovered by use of signature-tagged mutagenesis (P. H. Edelstein, M. A. Edelstein, F. Higa, and S. Falkow, Proc. Natl. Acad. Sci. 96:8190-8195, 1999). One of these mutants appeared to be defective in multiplication in guinea pig lungs and spleens, yet it multiplies normally in guinea pig alveolar macrophages. Here we report further characterization of the mutated gene and its protein and the virulence role of the gene. The complete sequence of the gene, now called lvgA, is 627 bp long, and its protein product is approximately 27 kDa in size. lvgA was present in all 50 strains of L. pneumophila tested. No significant nucleic acid or protein homology was found in the GenBank database for the gene, nor were any distinctive motifs discovered in a search of other databases. The expression of both DotA and IcmX in the lvgA mutant was normal. Subcellular fractionation studies localized LvgA to the outer membrane fraction, and protease digestion studies suggested that at least some of the protein is surface expressed. No change in bacterial lipopolysaccharide composition or reactivity to serogroup-specific antisera was detected in the mutant. Growth competition studies with alveolar macrophages showed that the mutant was outcompeted by its parent 3-fold in 24 h and 24-fold in 48 h, in contrast to what was observed with the null phenotype in parallel testing with alveolar macrophages or with the A549 alveolar epithelial cell line. This macrophage defect of the mutant bacterium was due to slower growth, as the mutant invaded alveolar macrophages normally. Electron microscopy showed that the mutant bacterium resided in a ribosome-studded phagosome in alveolar macrophages, with no distinction from its parent. The lvgA mutant was outcompeted by its parent about sixfold in guinea pig lungs and spleens; prolonged observation of infected animals showed no late-onset virulence of the mutant. Transcomplementation of the mutant restored the parental phenotype in guinea pigs. The lvgA mutant was twofold more susceptible to killing by human β-defensin 2 but not to killing by other cationic peptides, serum complement, or polymorphonuclear neutrophils. lvgA is a novel virulence gene that is responsible for pleiotropic functions involving both extracellular and intracellular bacterial resistance mechanisms.

Adherence of Legionella pneumophila to U-937 cells, guinea-pig alveolar macrophages, and MRC-5 cells by a novel, complement-independent binding mechanism

1994 ◽  
Vol 40 (10) ◽  
pp. 865-872 ◽  
Author(s):  
Frank C. Gibson III ◽  
Arthur O. Tzianabos ◽  
Frank G. Rodgers
Keyword(s):  
Monoclonal Antibodies ◽  
Guinea Pig ◽  
Host Cell ◽  
Alveolar Macrophages ◽  
Legionella Pneumophila ◽  
Cell Receptor ◽  
Host Cells ◽  
Order Kinetic ◽  
Complement Receptors ◽  
Host Cell Receptor

In the absence of serum, Legionella pneumophila demonstrated wash-resistant adherence to U-937 cells, primary guinea-pig alveolar macrophages, and MRC-5 cells. Neither complement nor antibody was required for binding. The dynamics of adherence following inoculation of L. pneumophila at increasing 10-fold multiplicities of infection to each of the three host cell types resulted in a first-order kinetic relationship of binding, indicative of one bacterial adhesin molecule recognized by one host cell receptor moiety. Host cell receptor saturation studies showed that depending on the cell type, 2–8% of the bacterial inoculum adhered to cells under these nonopsonic conditions. Preliminary adhesin and receptor characterization studies were preformed to define the chemical composition of the binding structures on both the organism and the three different host cell surfaces. The adherence phenomenon was investigated using competitive binding assays in the presence of putative adhesin analogs as well as following treatments modifying the microbial and host cell surface membranes. Attachment was evaluated both by viable bacterial cell colony counts and by indirect immunofluorescent assay. With the exception of aldehyde treatments, the various membrane-modifying regimes and the presence of the adhesin analogs were shown to have no effect on organism or host cell viability. Data suggested that the L. pneumophila adhesin responsible for opsonin-independent binding to these host cells was a protein structure with lectin-like properties. Furthermore, this protein would appear to be intimately associated with carbohydrate or lipid structures located on the bacterial outer membrane. The receptor moiety present on all host cells responsible for binding L. pneumophila had properties consistent with a carbohydrate or complex saccharide structure. To evaluate the role of complement receptors as the structures necessary for L. pneumophila infection of macrophages, a battery of monoclonal antibodies were used to block the complement receptor (CR) types 1 (CD35), CR3 (CD 18, CD11b), and CR4 (CD18, CD11c). Blocking studies with CR-specific monoclonal antibodies indicated that CR1 and the integrin receptors CR3 and CR4 were not involved in the opsonin-independent binding of L. pneumophila to macrophage-like cells.Key words: Legionella, opsonin-independent attachment, bacterial adherence, complement receptors, adhesion–receptor interactions.

Lactobacilli intra-tracheal administration protects from Pseudomonas aeruginosa pulmonary infection in mice – a proof of concept

2019 ◽  
Vol 10 (8) ◽  
pp. 893-900 ◽  
Author(s):  
M.S. Fangous ◽  
Y. Alexandre ◽  
N. Hymery ◽  
S. Gouriou ◽  
D. Arzur ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Murine Model ◽  
Alveolar Epithelial Cell ◽  
A549 Cells ◽  
Respiratory Pathogen ◽  
Public Health Issue ◽  
Epithelial Cell Line ◽  
High Morbidity ◽  
Respiratory Pathogens

The spreading of antibiotic resistance is a major public health issue, which requires alternative treatments to antibiotics. Lactobacilli have shown abilities to prevent pneumonia in clinical studies when given by oral route, certainly through the gut-lung axis involvement. Rationally, respiratory administration of lactobacilli has been developed and studied in murine model, to prevent from respiratory pathogens. It allows a direct effect of probiotics into the respiratory system. To our knowledge, no study has ever focused on the effect of probiotic intra-respiratory administration to prevent from Pseudomonas aeruginosa (PA) pneumonia, a major respiratory pathogen associated with high morbidity rates. In this study, we evaluated the beneficial activity of three Lactobacillus strains (Lactobacillus fermentum K.C6.3.1E, Lactobacillus zeae Od.76, Lactobacillus paracasei ES.D.88) previously screened by ourselves and known to be particularly efficient in vitro in inhibiting PAO1 virulence factors. Cytotoxic assays in alveolar epithelial cell line A549 were performed, followed by the comparison of two lactobacilli prophylactic protocols (one or two administrations) by intra-tracheal administration in a C57BL/6 murine model of PA pneumonia. A549 cells viability was improved from 23 to 75% when lactobacilli were administered before PAO1 incubation, demonstrating a protective effect (P<0.001). A significant decrease of 2 log of PAO1 was observed 4 h after PAO1 instillation (3×106 cfu/mouse) in both groups receiving lactobacilli (9×106 cfu/mouse) compared to PAO1 group (P<0.05). One single prophylactic administration of lactobacilli significantly decreased the secretion by 50% in bronchoalveolar lavages of interleukin (IL)-6 and tumour necrosis factor-α compared to PAO1. No difference of secretion was observed for the IL-10 secretion, whatever the prophylactic study design. This is the first study highlighting that direct lung administration of Lactobacillus strains protect against PA pneumonia. Next step will be to decipher the mechanisms involved before developing this novel approach for human applications.

Modification of biophysical properties of lung epithelial Na+ channels by dexamethasone

2000 ◽  
Vol 279 (3) ◽  
pp. C762-C770 ◽  
Author(s):  
A. Lazrak ◽  
A. Samanta ◽  
K. Venetsanou ◽  
P. Barbry ◽  
S. Matalon
Keyword(s):  
Cell Line ◽  
Single Channel ◽  
Alveolar Epithelial Cell ◽  
A549 Cells ◽  
Alveolar Epithelium ◽  
Housekeeping Gene ◽  
Epithelial Cell Line ◽  
Mrna Levels ◽  
Open Probability ◽  
Protein Levels

There is considerable interest in identifying the basic mechanisms by which dexamethasone alters ion transport across the adult alveolar epithelium. Herein, we incubated synchronized A549 cells, a human alveolar epithelial cell line, with dexamethasone (1 μM) for 24–48 h. When normalized to HPRT (a housekeeping gene), A549 β- and γ-subunit mRNA levels for the human amiloride-sensitive epithelial sodium channel (hENaC), assessed by RT-PCR, increased by 1.6- and 17-fold respectively, compared with control values ( P < 0.05). These changes were abolished by actinomycin D, indicating transcriptional regulation. Western blotting studies revealed that dexamethasone also increased expression of β- and γ-hENaC protein levels. In contrast, α-hENaC mRNA increased by onefold ( P > 0.05) and α-hENaC protein level was unchanged. Incubation of A549 cells with dexamethasone increased their whole cell amiloride-sensitive sodium currents twofold and decreased the K 0.5 for amiloride from 833 ± 69 to 22 ± 5.4 nM (mean ± SE; P < 0.01). Single channel recordings in the cell-attached mode showed that dexamethasone treatment increased single channel open time and open probability threefold and decreased channel conductance from 8.63 ± 0.036 to 4.4 ± 0.027 pS (mean ± SE; P < 0.01). We concluded that dexamethasone modulates the amiloride-sensitive Na+ channels by differentially regulating the expression of β- and γ-subunits at the mRNA and protein levels in the human A549 cell line, with little effect on α-hENaC subunit.

scholarly journals Transport of AOPP-Albumin into Human Alveolar Epithelial A549 Cell

2018 ◽  
Vol 21 ◽  
pp. 247-255 ◽  
Author(s):  
Masashi Kawami ◽  
Tadashi Shimonakamura ◽  
Ryoko Yumoto ◽  
Mikihisa Takano
Keyword(s):  
Alveolar Epithelial Cell ◽  
A549 Cells ◽  
Alveolar Epithelial Cells ◽  
Epithelial Cell Line ◽  
Ros Generation ◽  
Alveolar Epithelial ◽  
Lung Injuries ◽  
Km Value ◽  
Human Alveolar Epithelial Cell ◽  
Fluorescence Spectrometer

Purpose. Alveolar clearance of proteins, such as albumin, plays an essential role in recovery from lung injuries. Albumin is known to be oxidized by reactive oxygen species (ROS), leading to generation of advanced oxidation protein products (AOPP)-albumin in the alveolar lining fluid. In this study, we aimed to characterize the uptake of FITC-labeled AOPP-albumin (FITC-AOPP-albumin) into human alveolar epithelial cell line, A549. Methods. FITC-AOPP-albumin uptake into A549 cells and its effect of ROS generation was evaluated using fluorescence spectrometer and flow cytometry, respectively. Results. FITC-AOPP-albumin was taken up by A549 cells in a time- and temperature-dependent fashion, and showed saturation kinetics with a Km value of 0.37 mg/mL. The uptake of FITC-AOPP-albumin was suppressed by phenylarsine oxide, a clathrin-mediated endocytosis inhibitor, but not by indomethacin and nystatin, caveolae-mediated endocytosis inhibitors, or 5-(N-ethyl-N-isopropyl) amiloride, a macropinocytosis inhibitor. AOPP-albumin induced ROS generation in A549 cells, suggesting that alveolar clearance of AOPP-albumin should be important to prevent further ROS generation. Conclusion. AOPP-albumin is transported into alveolar epithelial cells through clathrin-mediated endocytosis, which may be important to prevent further ROS generation. This article is open to POST-PUBLICATION REVIEW. Registered readers (see “For Readers”) may comment by clicking on ABSTRACT on the issue’s contents page.

Effect of matrigel on development of A549 lung epithelial cells

1993 ◽  
Vol 51 ◽  
pp. 358-359
Author(s):  
Yvonne Kress ◽  
Barry R. Bloom ◽  
Kathleen A. McDonough
Keyword(s):  
Extracellular Matrix ◽  
Cultured Cells ◽  
Alveolar Epithelial Cell ◽  
Membrane Filter ◽  
A549 Cells ◽  
Lung Epithelial Cells ◽  
Epithelial Cell Line ◽  
Polycarbonate Membrane ◽  
Extracellular Matrix Components ◽  
Matrix Components

Extracellular matrix components are known to influence the growth and differentiation of cultured cells, often causing them to behave more like their in vivo counterparts than cells grown on plastic. To develop an in vitro model in which to study the interaction of pathogenic microorganisms with the lung epithelium, we have undertaken a morphological study of the effects of extracellular matrix components on the human lung alveolar epithelial cell line A549. A549 cells were grown for varying amounts of time on plastic; Costar polycarbonate membrane filter inserts; or on Matrigel coated polycarbonate filter inserts. Cells were fixed for 1 h in 2% glutaraldehyde in 0.1 M cacodylate buffer, post-fixed in 1 % OsO4 for 45 min, dehydrated in ascending ethanol, and embedded in Spurr’s resin.A549 cells grown on a plastic slide formed an even monolayer with cells connected by wellformed junctional complexes or separated by interdigitating microvilli. The cytoplasm showed many polyribosomes, rough endoplasmic reticulum, small golgi complexes, mitochondria, occasional lysosomes and bundles of microfilaments.

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