Involvement of epidermal growth factor receptor-linked signaling responses in Pseudomonas fluorescens-infected alveolar epithelial cells

Lactoferrin, Quercetin, and Hydroxyapatite Act Synergistically against Pseudomonas fluorescens

Pseudomonas fluorescens is an opportunistic, psychotropic pathogen that can live in different environments, such as plant, soil, or water surfaces, and it is associated with food spoilage. Bioactive compounds can be used as antimicrobials and can be added into packaging systems. Quercetin and lactoferrin are the best candidates for the development of a complex of the two molecules absorbed on bio combability structure as hydroxyapatite. The minimum inhibiting concentration (MIC) of single components and of the complex dropped down the single MIC value against Pseudomonas fluorescens. Characterization analysis of the complex was performed by means SEM and zeta-potential analysis. Then, the synergistic activity (C_syn) of single components and the complex was calculated. Finally, the synergistic activity was confirmed, testing in vitro its anti-inflammatory activity on U937 macrophage-like human cell line. In conclusion, the peculiarity of our study consists of optimizing the specific propriety of each component: the affinity of lactoferrin for LPS; that of quercetin for the bacterial membrane. These proprieties make the complex a good candidate in food industry as antimicrobial compounds, and as functional food.

Candidalysin activates innate epithelial immune responses via epidermal growth factor receptor

Candida albicans is a fungal pathobiont, able to cause epithelial cell damage and immune activation. These functions have been attributed to its secreted toxin, candidalysin, though the molecular mechanisms are poorly understood. Here, we identify epidermal growth factor receptor (EGFR) as a critical component of candidalysin-triggered immune responses. We find that both C. albicans and candidalysin activate human epithelial EGFR receptors and candidalysin-deficient fungal mutants poorly induce EGFR phosphorylation during murine oropharyngeal candidiasis. Furthermore, inhibition of EGFR impairs candidalysin-triggered MAPK signalling and release of neutrophil activating chemokines in vitro, and diminishes neutrophil recruitment, causing significant mortality in an EGFR-inhibited zebrafish swimbladder model of infection. Investigation into the mechanism of EGFR activation revealed the requirement of matrix metalloproteinases (MMPs), EGFR ligands and calcium. We thus identify a PAMP-independent mechanism of immune stimulation and highlight candidalysin and EGFR signalling components as potential targets for prophylactic and therapeutic intervention of mucosal candidiasis.

Candida albicans is an opportunistic fungus primarily affecting immunocompromised patients. Here, the authors identify a novel mechanism of host immune stimulation and highlight candidalysin and EGFR signalling components as potential targets for prophylactic and therapeutic intervention of mucosal candidiasis.

Klebsiella pneumoniae infection biology: living to counteract host defences

Klebsiella species cause a wide range of diseases including pneumonia, urinary tract infections (UTIs), bloodstream infections and sepsis. These infections are particularly a problem among neonates, elderly and immunocompromised individuals. Klebsiella is also responsible for a significant number of community-acquired infections. A defining feature of these infections is their morbidity and mortality, and the Klebsiella strains associated with them are considered hypervirulent. The increasing isolation of multidrug-resistant strains has significantly narrowed, or in some settings completely removed, the therapeutic options for the treatment of Klebsiella infections. Not surprisingly, this pathogen has then been singled out as an 'urgent threat to human health' by several organisations. This review summarises the tremendous progress that has been made to uncover the sophisticated immune evasion strategies of K. pneumoniae. The co-evolution of Klebsiella in response to the challenge of an activated immune has made Klebsiella a formidable pathogen exploiting stealth strategies and actively suppressing innate immune defences to overcome host responses to survive in the tissues. A better understanding of Klebsiella immune evasion strategies in the context of the host-pathogen interactions is pivotal to develop new therapeutics, which can be based on antagonising the anti-immune strategies of this pathogen.

Multiplicity of Mathematical Modeling Strategies to Search for Molecular and Cellular Insights into Bacteria Lung Infection

Even today two bacterial lung infections, namely pneumonia and tuberculosis, are among the 10 most frequent causes of death worldwide. These infections still lack effective treatments in many developing countries and in immunocompromised populations like infants, elderly people and transplanted patients. The interaction between bacteria and the host is a complex system of interlinked intercellular and the intracellular processes, enriched in regulatory structures like positive and negative feedback loops. Severe pathological condition can emerge when the immune system of the host fails to neutralize the infection. This failure can result in systemic spreading of pathogens or overwhelming immune response followed by a systemic inflammatory response. Mathematical modeling is a promising tool to dissect the complexity underlying pathogenesis of bacterial lung infection at the molecular, cellular and tissue levels, and also at the interfaces among levels. In this article, we introduce mathematical and computational modeling frameworks that can be used for investigating molecular and cellular mechanisms underlying bacterial lung infection. Then, we compile and discuss published results on the modeling of regulatory pathways and cell populations relevant for lung infection and inflammation. Finally, we discuss how to make use of this multiplicity of modeling approaches to open new avenues in the search of the molecular and cellular mechanisms underlying bacterial infection in the lung.

Amphiregulin suppresses epithelial cell apoptosis in lipopolysaccharide-induced lung injury in mice

BACKGROUND AND OBJECTIVE

As a member of the epidermal growth factor family, amphiregulin contributes to the regulation of cell proliferation. Amphiregulin was reported to be upregulated in damaged lung tissues in patients with chronic obstructive pulmonary disease and asthma and in lung epithelial cells in a ventilator-associated lung injury model. In this study, we investigated the effect of amphiregulin on lipopolysaccharide (LPS)-induced acute lung injury in mice.

METHODS

Acute lung injury was induced by intranasal instillation of LPS in female C57BL/6 mice, and the mice were given intraperitoneal injections of recombinant amphiregulin or phosphate-buffered saline 6 and 0.5 h before and 3 h after LPS instillation. The effect of amphiregulin on apoptosis and apoptotic pathways in a murine lung alveolar type II epithelial cell line (LA-4 cells) were examined using flow cytometry and western blotting, respectively.

RESULTS

Recombinant amphiregulin suppressed epithelial cell apoptosis in LPS-induced lung injury in mice. Western blotting revealed that amphiregulin suppressed epithelial cell apoptosis by inhibiting caspase-8 activity.

CONCLUSION

Amphiregulin signaling may be a therapeutic target for LPS-induced lung injury treatment through its prevention of epithelial cell apoptosis.

Genetic and Functional Analysis of Polymorphisms in the Human Dopamine Receptor and Transporter Genes in Small Cell Lung Cancer

The regulatory role of dopamine (DA) in endocrine, cardiovascular and renal functions has been extensively studied and used for clinical purposes. More recently DA has been indicated as a regulatory molecule for immune cells and malignant cell proliferation. We assessed the expression and the functional role DA, DA receptors, and transporters in primary small cell lung cancer (SCLC). By HPLC DA plasma levels were more elevated in SCLC patients in comparison with NSCLC patients and healthy controls. SCLC cell expressed DA D1- and D2-like receptors and membrane and vesicular transporters at protein and mRNA levels. We also investigated the effects of independent D1- or D2-like receptor stimulation on SCLC cell cultures. DA D1 receptor agonist SKF38393 induced the increase of cAMP levels and DARPP-32 protein expression without affecting SCLC growth rate. Cell treatment with the DA D1 receptor antagonist SCH23390 inhibited SKF38393 effects. In contrast, the DA D2 receptor agonist quinpirole (10 μM) counteracted, in a dose and time dependent way, SCLC cell proliferation, it did not affect cAMP levels and decreased phosphorylated AKT that was induced by DA D2 receptor antagonist sulpiride. However, in only one SCLC line, stimulation of DA D2 receptor failed to inhibit cell proliferation in vitro. This effect was associated to the existence of rs6275 and rs6277 polymorphisms in the D2 gene. These results gave more insight into DA control of lung cancer cell behavior and suggested the existence of different SCLC phenotypes.

Microbiology, genomics, and clinical significance of the Pseudomonas fluorescens species complex, an unappreciated colonizer of humans

Pseudomonas fluorescens is not generally considered a bacterial pathogen in humans; however, multiple culture-based and culture-independent studies have identified it at low levels in the indigenous microbiota of various body sites. With recent advances in comparative genomics, many isolates originally identified as the "species" P. fluorescens are now being reclassified as novel Pseudomonas species within the P. fluorescens "species complex." Although most widely studied for its role in the soil and the rhizosphere, P. fluorescens possesses a number of functional traits that provide it with the capability to grow and thrive in mammalian hosts. While significantly less virulent than P. aeruginosa, P. fluorescens can cause bacteremia in humans, with most reported cases being attributable either to transfusion of contaminated blood products or to use of contaminated equipment associated with intravenous infusions. Although not suspected of being an etiologic agent of pulmonary disease, there are a number of reports identifying it in respiratory samples. There is also an intriguing association between P. fluorescens and human disease, in that approximately 50% of Crohn's disease patients develop serum antibodies to P. fluorescens. Altogether, these reports are beginning to highlight a far more common, intriguing, and potentially complex association between humans and P. fluorescens during health and disease.

Preliminary phytochemical screening and antibacterial properties of crude stem bark extracts and fractions of Parkia biglobosa (Jacq.)

A methanolic crude extract of Parkia biglobosa was prepared and later partitioned in succession with different solvents of increasing polarity ranging from n-hexane, chloroform and ethyl acetate to butanol. Phytochemical screening of the extract revealed the presence of alkaloids, tannins, saponins, flavonoids, steroids, glycoside and sugars. The inhibition zones exhibited by the extract against the tested bacteria ranged between 14 ± 0.00 mm (against Escherichia coli) and 28 ± 0.71 mm (against Pseudomonas aeruginosa). The MIC of the methanolic extract of P. biglobosa against isolates ranged between 0.63 mg/mL and 5 mg/mL, while the MIC values exhibited by the n-hexane and aqueous fractions ranged between 0.63 mg/mL and 10 mg/mL. Overall the extract and fractions of P. biglobosa used in this work were found to possess antimicrobial properties which compared favourably with those of streptomycin. These observations make this plant a potential source of bioactive compounds that can be used in management of bacterial infections. The use of this plant as herbal medicaments in African countries and the reports on the toxicity of the plant further show that the plant is non-toxic to humans.

Flagellin/Toll-like receptor 5 response was specifically attenuated by keratan sulfate disaccharide via decreased EGFR phosphorylation in normal human bronchial epithelial cells

Bacterial or viral infection of the airway plays a critical role in the pathogenesis and exacerbation of chronic obstructive pulmonary disease (COPD) which is expected to be the 3rd leading cause of death by 2020. The induction of inflammatory responses in immune cells as well as airway epithelial cells is observed in the disease process. There is thus a pressing need for the development of new therapeutics. Keratan sulfate (KS) is the major glycosaminoglycans (GAGs) of airway secretions, and is synthesized by epithelial cells on the airway surface. Here we report that a KS disaccharide, [SO3(-)-6]Galβ1-4[SO3(-)-6]GlcNAc, designated as L4, suppressed the production of Interleukin-8 (IL-8) stimulated by flagellin, a Toll-like receptor (TLR) 5 agonist, in normal human bronchial epithelial (NHBE) cells. Such suppressions were not observed by other L4 analogues, N-acetyllactosamine or chondroitin-6-sulfate disaccharide. Moreover, treatment of NHBE cells with L4 inhibited the flagellin-stimulated phosphorylation of epidermal growth factor receptor (EGFR), the down stream signaling pathway of TLRs in NHBE cells. These results suggest that L4 specifically blocks the interaction of flagellin with TLR5 and subsequently suppresses IL-8 production in NHBE cells. Taken together, L4 represents a potential molecule for prevention and treatment of airway inflammatory responses to bacteria infections, which play a critical role in exacerbation of COPD.

Klebsiella pneumoniae targets an EGF receptor-dependent pathway to subvert inflammation

The NF-κB transcriptional factor plays a key role governing the activation of immune responses. Klebsiella pneumoniae is an important cause of community-acquired and nosocomial pneumonia. Evidence indicates that K. pneumoniae infections are characterized by lacking an early inflammatory response. Recently, we have demonstrated that Klebsiella antagonizes the activation of NF-κB via the deubiquitinase CYLD. In this work, by applying a high-throughput siRNA gain-of-function screen interrogating the human kinome, we identified 17 kinases that when targeted by siRNA restored IL-1β-dependent NF-κB translocation in infected cells. Further characterization revealed that K. pneumoniae activates an EGF receptor (EGFR)-phosphatidylinositol 3-OH kinase (PI3K)-AKT-PAK4-ERK-GSK3β signalling pathway to attenuate the cytokine-dependent nuclear translocation of NF-κB. Our data also revealed that CYLD is a downstream effector of K. pneumoniae-induced EGFR-PI3K-AKT-PAK4-ERK-GSK3β signalling pathway. Our efforts to identify the bacterial factor(s)responsible for EGFR activation demonstrate that a capsule (CPS) mutant did not activate EGFR hence suggesting that CPS could mediate the activation of EGFR. Supporting this notion, purified CPS did activate EGFR as well as the EGFR-dependent PI3K-AKT-PAK4-ERK-GSK3β signalling pathway. CPS-mediated EGFR activation was dependent on a TLR4-MyD88-c-SRC-dependent pathway. Several promising drugs have been developed to antagonize this cascade. We propose that agents targeting this signalling pathway might provide selective alternatives for the management of K. pneumoniae pneumonias.

The role of VIP in cornea

PURPOSE

Exogenous vasoactive intestinal peptide (VIP) down-regulates pro-inflammatory but up-regulates anti-inflammatory cytokines, growth factors (GFs) and Toll-like receptors promoting healing in experimental Pseudomonas aeruginosa (P. aeruginosa) keratitis. Whether VIP is required for GF or GF receptor (R) expression in normal and infected corneas is unknown and is the purpose of this study.

METHODS

VIP knockout ((-/-)) and wild-type (WT) C57BL/6 (B6) mice were infected and tested using PCR array, real-time RT-PCR, ELISA, and immunostaining. VIP antagonist treatment studies also were done using B6 and BALB/c mice.

RESULTS

Infected corneas of VIP(-/-) versus WT B6 mice perforated earlier (2 vs. 5 days postinfection [p.i.]), and array data showed that GFs were differentially changed between groups. RT-PCR revealed that the infected cornea of VIP(-/-) versus WT mice expressed higher mRNA levels of epidermal growth factor (EGF) and hepatocyte growth factor (HGF), reduced FGF, EGFR, and HGFR, with no difference in FGFR; differences between groups were not seen in normal cornea. Immunostaining for GF and GFR in the normal cornea of VIP(-/-) versus WT mice was similar. However, at 1 day p.i., VIP(-/-) versus WT mice had more intense EGF and HGF, similar FGFR, and reduced FGF, EGFR, and HGFR staining. VIP antagonist treatment decreased protein levels for GFR at 5 days p.i. in both B6 and BALB/c mice, with no significant changes in normal cornea.

CONCLUSIONS

The data showed that endogenous VIP is not requisite for GF or GFR expression in the normal cornea but, after infection, its absence or reduction is critical for their regulation.

Pro-inflammatory NF-κB and early growth response gene 1 regulate epithelial barrier disruption by food additive carrageenan in human intestinal epithelial cells

The widely used food additive carrageenan (CGN) has been shown to induce intestinal inflammation, ulcerative colitis-like symptoms, or neoplasm in the gut epithelia in animal models, which are also clinical features of human inflammatory bowel disease. In this study, the effects of CGN on pro-inflammatory transcription factors NF-κB and early growth response gene 1 product (EGR-1) were evaluated in terms of human intestinal epithelial barrier integrity. Both pro-inflammatory transcription factors were elevated by CGN and only NF-κB activation was shown to be involved in the induction of pro-inflammatory cytokine interleukin-8. Moreover, the integrity of the in vitro epithelial monolayer under the CGN insult was maintained by both activated pro-inflammatory transcription factors NF-κB and EGR-1. Suppression of NF-κB or EGR-1 aggravated barrier disruption by CGN, which was associated with the reduced gene expression of tight junction component zonula occludens 1 and its irregular localization in the epithelial monolayer.