T cell chemotaxis and chemokine release after Staphylococcus aureus interaction with polarized airway epithelium

The Role of Staphylococcus aureus and Its Toxins in the Pathogenesis of Allergic Asthma

Bronchial asthma is one of the most common chronic diseases worldwide and affects more than 300 million patients. Allergic asthma affects the majority of asthmatic children as well as approximately 50% of adult asthmatics. It is characterized by a Th2-mediated immune response against aeroallergens. Many aspects of the overall pathophysiology are known, while the underlying mechanisms and predisposing factors remain largely elusive today. Over the last decade, respiratory colonization with Staphylococcus aureus (S. aureus), a Gram-positive facultative bacterial pathogen, came into focus as a risk factor for the development of atopic respiratory diseases. More than 30% of the world’s population is constantly colonized with S. aureus in their nasopharynx. This colonization is mostly asymptomatic, but in immunocompromised patients, it can lead to serious complications including pneumonia, sepsis, or even death. S. aureus is known for its ability to produce a wide range of proteins including toxins, serine-protease-like proteins, and protein A. In this review, we provide an overview of the current knowledge about the pathophysiology of allergic asthma and to what extent it can be affected by different toxins produced by S. aureus. Intensifying this knowledge might lead to new preventive strategies for atopic respiratory diseases.

LRP1 loss in airway epithelium exacerbates smoke-induced oxidative damage and airway remodeling

The LDL receptor-related protein 1 (LRP1) partakes in metabolic and signaling events regulated in a tissue-specific manner. The function of LRP1 in airways has not been studied. We aimed to study the function of LRP1 in smoke-induced disease. We found that bronchial epithelium of patients with chronic obstructive pulmonary disease and airway epithelium of mice exposed to smoke had increased LRP1 expression. We then knocked out LRP1 in human bronchial epithelial cells in vitro and in airway epithelial club cells in mice. In vitro, LRP1 knockdown decreased cell migration and increased transforming growth factor β activation. Tamoxifen-inducible airway-specific LRP1 knockout mice (club Lrp1-/-) induced after complete lung development had increased inflammation in the bronchoalveolar space and lung parenchyma at baseline. After 6 months of smoke exposure, club Lrp1-/- mice showed a combined restrictive and obstructive phenotype, with lower compliance, inspiratory capacity, and forced expiratory volume0.05/forced vital capacity than WT smoke-exposed mice. This was associated with increased values of Ashcroft fibrotic index. Proteomic analysis of room air exposed-club Lrp1-/- mice showed significantly decreased levels of proteins involved in cytoskeleton signaling and xenobiotic detoxification as well as decreased levels of glutathione. The proteome fingerprint created by smoke eclipsed many of the original differences, but club Lrp1-/- mice continued to have decreased lung glutathione levels and increased protein oxidative damage and airway cell proliferation. Therefore, LRP1 deficiency leads to greater lung inflammation and damage and exacerbates smoke-induced lung disease.

Role of Interleukin-10 on Nasal Polypogenesis in Patients with Chronic Rhinosinusitis with Nasal Polyps

Background and Objectives

Interleukin 10 (IL-10) is a potent anti-inflammatory cytokine. The dysregulation of IL-10 is associated with an enhanced immunopathologic response to infection, as well as with an increased risk for developing numerous autoimmune diseases. In this study, we investigated IL-10 expression in chronic rhinosinusitis with nasal polyps (CRSwNP) and assessed the possible role of IL-10 in the pathogenesis of CRSwNP.

Materials and Methods

Thirty-five patients with CRSwNP, 12 patients with chronic rhinosinusitis without NP (CRSsNP) and 10 control subjects were enrolled in this study. NP tissues and uncinated tissues (UT) were collected for analysis. Dispersed NP cells (DNPCs) were cultured in the presence or absence of IL-25 and IL-10, and a flow cytometric assay was performed to identify the constitutive cell populations of the DNPCs. Murine NP (n = 18) models were used for the in vivo experiments. Real-time PCR, immunohistochemistry, western blotting analysis and ELISA were performed to measure the expression levels of the selected inflammatory cytokines and inflammation-associated molecules.

Results

The mRNA expression levels of IL-10, IL-5, IL-17A, IL-25 and interferon gamma (IFN-γ) were significantly higher in the NP tissues than in the UT tissues. Strong positive correlations were observed between IL-10 and a variety of inflammatory cytokines (IL-5, IL-17A, IL-25, IFN-γ) and inflammation-associated molecules (B-cell activating factor; BAFF, CD19). Other than the IL-25 to IL-10 ratio, the expression ratios of the other measured inflammatory cytokines to IL-10 were significantly lower in the CRSwNP group than in the CRSsNP or control groups. Administrating IL-25 into the cultured DNPCs significantly increased the production of IL-10, but administrating IL-10 had no effect on the production of IL-25.

Conclusion

Increased expression of IL-10, IL-10 related inflammatory cytokine, and IL-10 related B cell activation indicated that IL-10, a potent anti-inflammatory cytokine, has a pivotal role in the pathogenesis of CRSwNPs.

Staphylococcus aureus α-toxin-mediated cation entry depolarizes membrane potential and activates p38 MAP kinase in airway epithelial cells

Membrane potential (Vm)-, Na(+)-, or Ca(2+)-sensitive fluorescent dyes were used to analyze changes in Vm or intracellular ion concentrations in airway epithelial cells treated with Staphylococcus aureus α-toxin (Hla), a major virulence factor of pathogenic strains of these bacteria. Gramicidin, a channel-forming peptide causing membrane permeability to monovalent cations, a mutated form of Hla, rHla-H35L, which forms oligomers in the plasma membranes of eukaryotic cells but fails to form functional transmembrane pores, or the cyclodextrin-derivative IB201, a blocker of the Hla pore, were used to investigate the permeability of the pore. Na(+) as well as Ca(2+) ions were able to pass the Hla pore and accumulated in the cytosol. The pore-mediated influx of calcium ions was blocked by IB201. Treatment of cells with recombinant Hla resulted in plasma membrane depolarization as well as in increases in the phosphorylation levels of paxillin (signaling pathway mediating disruption of the actin cytoskeleton) and p38 MAP kinase (signaling pathway resulting in defensive actions). p38 MAP kinase phosphorylation, but not paxillin phosphorylation, was elicited by treatment of cells with gramicidin. Although treatment of cells with rHla-H35L resulted in the formation of membrane-associated heptamers, none of these cellular effects were observed in our experiments. This indicates that formation of functional Hla-transmembrane pores is required to induce the cell physiological changes mediated by α-toxin. Specifically, the changes in ion equilibria and plasma membrane potential are important activators of p38 MAP kinase, a signal transduction module involved in host cell defense.

Impact of the Maturation of Human Primary Bone-Forming Cells on Their Behavior in Acute or Persistent Staphylococcus aureus Infection Models

Staphylococcus aureus is one of the most frequently involved pathogens in bacterial infections such as skin abscess, pneumonia, endocarditis, osteomyelitis, and implant-associated infection. As for bone homeostasis, it is partly altered during infections by S. aureus by the induction of various responses from osteoblasts, which are the bone-forming cells responsible for extracellular matrix synthesis and its mineralization. Nevertheless, bone-forming cells are a heterogeneous population with different stages of maturation and the impact of the latter on their responses toward bacteria remains unclear. We describe the impact of S. aureus on two populations of human primary bone-forming cells (HPBCs) which have distinct maturation characteristics in both acute and persistent models of interaction. Cell maturation did not influence the internalization and survival of S. aureus inside bone-forming cells or the cell death related to the infection. By studying the expression of chemokines, cytokines, and osteoclastogenic regulators by HPBCs, we observed different profiles of chemokine expression according to the degree of cell maturation. However, there was no statistical difference in the amounts of proteins released by both populations in the presence of S. aureus compared to the non-infected counterparts. Our findings show that cell maturation does not impact the behavior of HPBCs infected with S. aureus and suggest that the role of bone-forming cells may not be pivotal for the inflammatory response in osteomyelitis.

Development of an in vitro colonization model to investigate Staphylococcus aureus interactions with airway epithelia

Staphylococcus aureus is a bacterial pathogen responsible for a wide range of diseases and is also a human commensal colonizing the upper respiratory tract. Strains belonging to the clonal complex group CC30 are associated with colonization, although the colonization state itself is not clearly defined. In this work, we developed a co-culture model with S. aureus colonizing the apical surface of polarized human airway epithelial cells. The S. aureus are grown at the air-liquid interface to allow an in-depth evaluation of a simulated colonization state. Exposure to wild-type, S. aureus bacteria or conditioned media killed airway epithelial cells within 1 day, while mutant S. aureus strains lacking alpha-toxin (hla) persisted on viable cells for at least 2 days. Recent S. aureus CC30 isolates are natural hla mutants, and we observed that these strains displayed reduced toxicity toward airway epithelial cells. Quantitative real-time polymerase chain reaction of known virulence factors showed the expression profile of S. aureus grown in co-culture correlates with results from previous human colonization studies. Microarray analysis indicated significant shifts in S. aureus physiology in the co-culture model toward lipid and amino acid metabolism. The development of the in vitro colonization model will enable further study of specific S. aureus interactions with the host epithelia.

Modelling staphylococcal pneumonia in a human 3D lung tissue model system delineates toxin-mediated pathology

Staphylococcus aureus necrotizing pneumonia is recognized as a toxin-mediated disease, yet the tissue-destructive events remain elusive, partly as a result of lack of mechanistic studies in human lung tissue. In this study, a three-dimensional (3D) tissue model composed of human lung epithelial cells and fibroblasts was used to delineate the role of specific staphylococcal exotoxins in tissue pathology associated with severe pneumonia. To this end, the models were exposed to the mixture of exotoxins produced by S. aureus strains isolated from patients with varying severity of lung infection, namely necrotizing pneumonia or lung empyema, or to purified toxins. The necrotizing pneumonia strains secreted high levels of α-toxin and Panton-Valentine leukocidin (PVL), and triggered high cytotoxicity, inflammation, necrosis and loss of E-cadherin from the lung epithelium. In contrast, the lung empyema strain produced moderate levels of PVL, but negligible amounts of α-toxin, and triggered limited tissue damage. α-toxin had a direct damaging effect on the epithelium, as verified using toxin-deficient mutants and pure α-toxin. Moreover, PVL contributed to pathology through the lysis of neutrophils. A combination of α-toxin and PVL resulted in the most severe epithelial injury. In addition, toxin-induced release of pro-inflammatory mediators from lung tissue models resulted in enhanced neutrophil migration. Using a collection of 31 strains from patients with staphylococcal pneumonia revealed that strains producing high levels of α-toxin and PVL were cytotoxic and associated with fatal outcome. Also, the strains that produced the highest toxin levels induced significantly greater epithelial disruption. Of importance, toxin-mediated lung epithelium destruction could be inhibited by polyspecific intravenous immunoglobulin containing antibodies against α-toxin and PVL. This study introduces a novel model system for study of staphylococcal pneumonia in a human setting. The results reveal that the combination and levels of α-toxin and PVL correlate with tissue pathology and clinical outcome associated with pneumonia.

Staphylococcal protein A-formulated immune complexes suppress enterotoxin-induced cellular responses in nasal polyps

BACKGROUND

Recent studies have revealed that Staphylococcus aureus and its components participate in the pathogenesis of eosinophilic airway diseases, such as chronic rhinosinusitis with nasal polyps.

OBJECTIVE

We sought to determine whether staphylococcal protein A (SpA) from S aureus regulated cellular responses in nasal polyps, especially when coupled to immunoglobulins in immune complexes (ICs).

METHODS

Dispersed nasal polyp cells (DNPCs) or peripheral blood monocytes were cultured in vitro with SpA in the presence or absence of IgG, and IL-5, IL-13, IFN-γ, IL-17A, and IL-10 levels were measured in the supernatants. The effect of SpA exposure on staphylococcal enterotoxin B-induced cytokine production by DNPCs in the presence and absence of IgG, IgA, and autologous serum was also examined.

RESULTS

Exposure to SpA induced DNPCs to produce significantly higher IL-10, IL-13, and IL-17A levels than DNPCs without SpA, although the magnitude of the IL-17A increase was less than that of IL-10 and IL-13. SpA induced IL-10 production mainly from adherent DNPCs, and this was significantly enhanced in the presence of IgG; similar results were observed in peripheral blood monocytes. IC formation between SpA and IgG (SpA-IgG ICs) was confirmed by using native polyacrylamide gel electrophoresis. SpA-IgG ICs, but not SpA alone, almost completely suppressed staphylococcal enterotoxin B-induced IL-5, IL-13, IFN-γ, and IL-17A production by DNPCs; similar inhibition was observed in DNPCs treated with SpA in the presence of either IgA or autologous serum.

CONCLUSIONS

Our results suggest that SpA can regulate the pathogenesis of enterotoxin-induced inflammation in patients with chronic rhinosinusitis with nasal polyps through coupling to immunoglobulins.

Cellular responses to Staphylococcus aureus alpha-toxin in chronic rhinosinusitis with nasal polyps

BACKGROUND

In contrast to Staphylococcus aureus-derived superantigenic exotoxins, the role of non-superantigenic exotoxins in the pathogenesis of eosinophilic airway diseases remains obscure. We sought to characterize S. aureus alpha-toxin-induced cellular responses in chronic rhinosinusitis with nasal polyps (CRSwNP).

METHODS

Dispersed nasal polyp cells and uncinate tissue cells were prepared from patients with CRS with and without nasal polyps, respectively. Cells were incubated with various concentrations of alpha-toxin or staphylococcal enterotoxin B and then the levels of IL-5, IL-13, IFN-γ, IL-17A, and IL-10 in the cell supernatants were determined. The pathophysiological significance of alpha-toxin-induced cytokine production was also determined including radiological severity of rhinosinusitis, tissue and blood eosinophilia, serum total IgE level, and 1-s forced expiratory volume/forced vital capacity ratio (FEV1/FVC).

RESULTS

Nasal polyp cells produced substantial amounts of IL-5, IL-13, IFN-γ, IL-17A, and IL-10 in response to alpha-toxin. Cytokine production was higher in nasal polyp cells than in uncinate tissue cells. The potency of alpha-toxin in stimulating IL-5, IL-13, and IL-10 production was comparable to that of enterotoxin. Alpha-toxin-induced IFN-γ, IL-17A, and IL-10 production significantly and negatively correlated with the degree of eosinophil infiltration into nasal polyps. Conversely, alpha-toxin-induced IFN-γ and IL-10 production significantly and positively correlated with FEV1/FVC. IL-10 production was significantly lower in asthmatic patients compared to non-asthmatics

CONCLUSIONS

S. aureus-derived alpha-toxin can provoke cellular responses in nasal polyps. These responses, especially failure to synthesize IL-10, may play a role in the pathophysiology of CRSwNP.

Ezrin and moesin are required for efficient T cell adhesion and homing to lymphoid organs

T cell trafficking between the blood and lymphoid organs is a complex, multistep process that requires several highly dynamic and coordinated changes in cyto-architecture. Members of the ezrin, radixin and moesin (ERM) family of actin-binding proteins have been implicated in several aspects of this process, but studies have yielded conflicting results. Using mice with a conditional deletion of ezrin in CD4+ cells and moesin-specific siRNA, we generated T cells lacking ERM proteins, and investigated the effect on specific events required for T cell trafficking. ERM-deficient T cells migrated normally in multiple in vitro and in vivo assays, and could undergo efficient diapedesis in vitro. However, these cells were impaired in their ability to adhere to the β1 integrin ligand fibronectin, and to polarize appropriately in response to fibronectin and VCAM-1 binding. This defect was specific for β1 integrins, as adhesion and polarization in response to ICAM-1 were normal. In vivo, ERM-deficient T cells showed defects in homing to lymphoid organs. Taken together, these results show that ERM proteins are largely dispensable for T cell chemotaxis, but are important for β1 integrin function and homing to lymphoid organs.

S. aureus haemolysin A-induced IL-8 and IL-6 release from human airway epithelial cells is mediated by activation of p38- and Erk-MAP kinases and additional, cell type-specific signalling mechanisms

Soluble virulence-associated factors of Staphylococcus aureus like haemolysin A (Hla) induce secretion of chemo/cytokines from airway epithelial cells. To elucidate the potential roles of specific signalling pathways in this response, we treated 16HBE14o-, S9 or A549 cells with recombinant Hla (rHla). In a dose-dependent manner, rHla induced secretion of IL-8 in all three cell types, but IL-6 release only in 16HBE14o- and S9 cells. rHla-mediated secretion of IL-8 and IL-6 was suppressed by pre-incubation of cells with inhibitors of Erk type or p38 MAP kinases, indicating that activation of these signalling pathways is essential for IL-8 release in all three cell types and for IL-6 release in 16HBE14o- and S9 cells. The rHla-mediated phosphorylation and activation of p38 MAP kinase seem to depend on elevations in [Ca(2+)]i, an early response in rHla-treated cells. Inhibitors of calmodulin or calcium/calmodulin-dependent kinase II attenuated rHla-mediated release of IL-8 in 16HBE14o- and A549 cells and of IL-6 in 16HBE14o- cells. This indicates that rHla may mediate simultaneous activation of calmodulin-dependent processes as additional prerequisites for chemo/cytokine secretion.However, the inhibitors of calmodulin-dependent signalling did not affect rHla-induced p38 MAP kinase phosphorylation, indicating that this pathway works in parallel with p38 MAP kinase.

Chemotaxis of T-cells after infection of human choroid plexus papilloma cells with Echovirus 30 in an in vitro model of the blood-cerebrospinal fluid barrier

Enterovirus is the most common pathogen causing viral meningitis especially in children. Besides the blood-brain barrier (BBB) the choroid plexus, which forms the blood-cerebrospinal-fluid (CSF) barrier (BCSFB), was shown to be involved in the pathogenesis of enteroviral meningitis. In a human in vitro model of the BCSFB consisting of human choroid plexus papilloma cells (HIBCPP), the permissiveness of plexus epithelial cells for Echovirus 30 (EV30) was analyzed by immunoblotting and quantitative real-time PCR (Q-PCR). HIBCPP could be directly infected by EV30 from the apical as well as from the physiological relevant basolateral side. During an infection period of 5h no alterations of barrier function and cell viability could be observed. Analysis of the cytokine/chemokine-profile following enteroviral infection with a cytometric bead array (CBA) and Q-PCR revealed an enhanced secretion of PanGRO (CXCL1, CXCL2 and CXCL3), IL8 and CCL5. Q-PCR showed a significant upregulation of CXCL1, CXCL2 and CXCL3 in a time dependant manner. However, there was only a minor effect of HIBCPP-infection with EV30 on transepithelial T lymphocyte migration with or without the chemoattractant CXCL12. Moreover, CXCL3 did not significantly enhance T cell migrations. Therefore additional factors must be involved for the in vivo reported enhanced T cell migration into the CNS in the context of enteroviral meningitis. As HIBCPP are permissive for infection with EV30, they constitute a valuable human in vitro model to study viral infection at the BCSFB.

RahU: an inducible and functionally pleiotropic protein in Pseudomonas aeruginosa modulates innate immunity and inflammation in host cells

The aim of this study was to define the functional role of a recently identified RahU protein from Pseudomonas aeruginosa in macrophages and its role in bacterial defense. Recombinant (r)-RahU had no significant effect on cell apoptosis or cell viability in human monocytic THP-1 cells. Gene expression array of murine macrophage cells (RAW 264.7) stimulated with LPS showed modulation of common transcripts (by r-RahU and predisone) involved in inflammation. Functional cellular analysis showed RAW cells incubated with r-RahU at 1.0-10 μg/ml (0.06-0.6 μM) inhibited accumulation of nitric oxide (NO) in the presence of LPS by 10-50%. The IC(50) of r-RahU (0.6 μM) was distinct from the known inhibitors of NO production: prednisone (50 μM) and L-NMMA (100 μM). r-RahU also significantly inhibited chemotactic activity of THP-1 cells toward CCL2 or chemotactic supernatants from apoptotic T-cells. These reports show previously unknown pleiotropic properties of RahU in modulating both microbial physiology and host innate immunity.

Dapsone inhibits IL-8 secretion from human bronchial epithelial cells stimulated with lipopolysaccharide and resolves airway inflammation in the ferret

BACKGROUND

IL-8 is an important activator and chemoattractant for neutrophils that is produced by normal human bronchial epithelial (NHBE) cells through mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) p65 pathways. Dapsone, a synthetic sulfone, is widely used to treat chronic neutrophil dermatoses. We investigated the effects of dapsone on polarized IL-8 secretion from lipopolysaccharide (LPS)-stimulated NHBE cells and further evaluated its ability to decrease LPS-induced inflammation in the ferret airway.

METHODS

NHBE cells were grown at air-liquid interface (ALI) to ciliated differentiation. Baseline and endotoxin (LPS)-stimulated IL-8 secretion was measured by enzyme-linked immunosorbent assay at air and basal sides with and without dapsone. Western blotting was used to determine signaling pathways. In vivo, ferrets were exposed to intratracheal LPS over a period of 5 days. Once inflammation was established, oral or nebulized dapsone was administered for 5 days. Intraepithelial neutrophil accumulation was analyzed histologically, and mucociliary transport was measured on the excised trachea.

RESULTS

Dapsone, 1 μg/mL, did not influence unstimulated (basal) IL-8 secretion. Apical LPS stimulation induced both apical and basolateral IL-8, but basolateral LPS increased only basolateral IL-8. Dapsone inhibited polarized IL-8 secretion from ALI-conditioned cells. Dapsone also decreased LPS-induced IL-8 mRNA level. LPS led to phosphorylation of extracellular signal-regulated kinase 1/2, but not p38 MAPK or c-Jun NH(2)-terminal kinase. LPS also induced NF-κB p65 phosphorylation, an effect that was inhibited by dapsone. Both oral and aerosol dapsone decreased LPS-induced intraepithelial neutrophil accumulation, but only treatment with aerosol dapsone restored mucociliary transport to normal.

CONCLUSIONS

Dapsone, given either systemically or as an aerosol, may be useful in treating neutrophilic airway inflammation.

Participation of CD11c(+) leukocytes in methicillin-resistant Staphylococcus aureus clearance from the lung

Staphylococcus aureus causes especially severe pulmonary infection, associated with high morbidity and mortality. In addition to the effects of specific virulence factors, it appears that the intensity of the host proinflammatory response, particularly in the initial stages of infection, contributes substantially to pulmonary damage. We tested the hypothesis that the CD11c(+) leukocytes are important in the host response to pulmonary infection with methicillin-resistant S. aureus (MRSA) USA300. Clodronate-induced depletion of the alveolar macrophage population resulted in increased numbers of dendritic cells (DCs) and CD4(+) cells in bronchoalveolar lavage (BAL) fluid and was associated with significantly increased mortality by 18 h following S. aureus inoculation but had no effect on bacterial load or polymorphonuclear leukocyte (PMN) numbers in the lung. These clodronate-treated mice also had increased expression of interleukin-17A/F (IL-17A/F) and CXCL10 but not of gamma interferon (IFN-γ) or tumor necrosis factor (TNF). Depletion of the dendritic cell population in mice expressing a CD11c-enhanced green fluorescent protein (EGFP)-diphtheria toxin receptor (DTR) transgene was associated with an increased bacterial load in the lung but not increased mortality. Both DCs and airway epithelial cells produced CXCL9, -10, and -11 in response to S. aureus. Pretreatment of mice with an anti-CXCR3 antibody prior to inoculation with MRSA substantially reduced CD4(+) cells and decreased pulmonary inflammation at 18 h postinfection compared to pretreatment with an IgG control. The results of these experiments suggest that CD11c(+) cells, the induction of CXCR3 ligand expression, and subsequent CD4(+) cell recruitment have an important role in the pathogenesis of severe MRSA pulmonary infection.

Innate immunity in the respiratory epithelium

The airway epithelium represents the first point of contact for inhaled foreign organisms. The protective arsenal of the airway epithelium is provided in the form of physical barriers and a vast array of receptors and antimicrobial compounds that constitute the innate immune system. Many of the known innate immune receptors, including the Toll-like receptors and nucleotide oligomerization domain-like receptors, are expressed by the airway epithelium, which leads to the production of proinflammatory cytokines and chemokines that affect microorganisms directly and recruit immune cells, such as neutrophils and T cells, to the site of infection. The airway epithelium also produces a number of resident antimicrobial proteins, such as lysozyme, lactoferrin, and mucins, as well as a swathe of cationic proteins. Dysregulation of the airway epithelial innate immune system is associated with a number of medical conditions that can result in compromised immunity and chronic inflammation of the lung. This review focuses on the innate immune capabilities of the airway epithelium and its role in protecting the lung from infection as well as the outcomes when its function is compromised.

Staphylococcus Aureus Increases Cytokine and Matrix Metalloproteinase Expression in Nasal Mucosae of Patients with Chronic Rhinosinusitis and Nasal Polyps

Background

Staphylococcus aureus is a common bacterial pathogen associated with chronic rhinosinusitis with/without nasal polyps (CRSw/sNP). We investigated the effect of S. aureus on the secretion of eotaxin, interleukin (IL)-5, IL-8, IL-13, matrix metalloproteinase (MMP) 2, MMP-9, and tissue inhibitor of MMP (TIMP) 1 in nasal mucosae from CRSwNP patients to assess the roles of these materials in NP pathogenesis.

Methods

We infected organ cultures of NP and inferior turbinate (IT) mucosae taken from patients with CRSwNP with S. aureus ATCC 25923 for 24 hours and incubated the cultures for an additional 48 hours at 37°C. S. aureus infection and staphylococcal enterotoxins were confirmed by real-time polymerase chain reaction. Eotaxin, IL-5, IL-8, IL-13, MMP-2, MMP-9, and TIMP-1 protein levels were measured by ELISA.

Results

S. aureus infection significantly increased the concentrations of eotaxin, IL-5, IL-8, and IL-13 in the IT and NP groups (p < 0.01 for all comparisons). S. aureus infection also significantly increased the concentrations of MMP-2, MMP-9, and TIMP-1 in both groups (p < 0.001 for all comparisons). After S. aureus infection, the relative increases in eotaxin (6.42 versus 3.56), IL-5 (15.29 versus 8.89), MMP-2 (1.95 versus 1.58), MMP-9 (2.34 versus 1.95), and TIMP-1 (1.45 versus 1.31) were greater in the NP group than in the IT group.

Conclusion

S. aureus infection enhances the secretion of cytokines, MMP-2, MMP-9, and TIMP-1 by both NPs and IT mucosae from patients with CRSwNP. S. aureus may play an important role in the pathogenesis of NP via tissue remodeling as well as eosinophilic inflammation.

Impaired interleukin-8 chemokine secretion by staphylococcus aureus-activated epithelium and T-cell chemotaxis in cystic fibrosis

Staphylococcus aureus is frequently isolated from lungs of patients with cystic fibrosis (CF). Upon lung infection with S. aureus, airway epithelial cells (AEC) produce high levels of chemokines that enhance T-cell chemotaxis. Although the number of lymphocytes is increased in the airways and bronchoalveolar lavage fluid of patients with CF, the mechanisms responsible for their accumulation and the role of S. aureus in this process are largely unknown. This study investigated early S. aureus impact on chemokine secretion by CF epithelial cells and chemotaxis of CF T cells. CF and non-CF AEC were grown in a cell culture model and apically stimulated with S. aureus. Supernatants were quantified for chemokine secretions and assayed for T-cell chemotaxis. CF AEC secreted constitutively larger amounts of IL-8, GROalpha, MIG, MIP-3beta, and MCP-1 than non-CF epithelial cells. S. aureus interaction with epithelial cells increased chemokine production by non-CF cells but had no effect on CF cells. Chemotaxis of T cells derived from patients with CF was greater than that of T cells from subjects without CF. Moreover, there were more CF T cells expressing CXCR1 as compared with non-CF T cells. Under our experimental conditions, inhibition of IL-8 or its receptor CXCR1 resulted in a considerable decrease in T-cell chemotaxis (up to 80%). These data suggest that IL-8 and its receptor CXCR1 are key players in the chemotaxis of CF T cells and could be used as targets to develop therapies for CF.

New microbicidal functions of tracheal glands: defective anti-infectious response to Pseudomonas aeruginosa in cystic fibrosis

Tracheal glands (TG) may play a specific role in the pathogenesis of cystic fibrosis (CF), a disease due to mutations in the cftr gene and characterized by airway inflammation and Pseudomonas aeruginosa infection. We compared the gene expression of wild-type TG cells and TG cells with the cftr DeltaF508 mutation (CF-TG cells) using microarrays covering the whole human genome. In the absence of infection, CF-TG cells constitutively exhibited an inflammatory signature, including genes that encode molecules such as IL-1alpha, IL-beta, IL-32, TNFSF14, LIF, CXCL1 and PLAU. In response to P. aeruginosa, genes associated with IFN-gamma response to infection (CXCL10, IL-24, IFNgammaR2) and other mediators of anti-infectious responses (CSF2, MMP1, MMP3, TLR2, S100 calcium-binding proteins A) were markedly up-regulated in wild-type TG cells. This microbicidal signature was silent in CF-TG cells. The deficiency of genes associated with IFN-gamma response was accompanied by the defective membrane expression of IFNgammaR2 and altered response of CF-TG cells to exogenous IFN-gamma. In addition, CF-TG cells were unable to secrete CXCL10, IL-24 and S100A8/S100A9 in response to P. aeruginosa. The differences between wild-type TG and CF-TG cells were due to the cftr mutation since gene expression was similar in wild-type TG cells and CF-TG cells transfected with a plasmid containing a functional cftr gene. Finally, we reported an altered sphingolipid metabolism in CF-TG cells, which may account for their inflammatory signature. This first comprehensive analysis of gene expression in TG cells proposes a protective role of wild-type TG against airborne pathogens and reveals an original program in which anti-infectious response was deficient in TG cells with a cftr mutation. This defective response may explain why host response does not contribute to protection against P. aeruginosa in CF.

Dynamics of neutrophil infiltration during cutaneous wound healing and infection using fluorescence imaging

Neutrophil influx is an early inflammatory response that is essential for the clearance of bacteria and cellular debris during cutaneous wounding. A non-invasive real-time fluorescence imaging technique was developed to examine the kinetics of enhanced green fluorescence protein-polymorphonuclear leukocyte (EGFP-PMN) influx within a wound. We hypothesized that infection or systemic availability would directly regulate the dynamics of EGFP-PMN recruitment and the efficiency of wound closure. Neutrophil recruitment increased dramatically over the first 24 hours from 10(6) at 4 hours up to a maximum of 5 x 10(6) EGFP-PMNs at 18 hours. A high rate of EGFP-PMN turnover was evidenced by approximately 80% decrease in EGFP signal within 6 hours. In response to wound colonization by Staphylococcus aureus or injection of GM-CSF, systemic PMNs increased twofold above saline control. This correlated with an increase in EGFP-PMN recruitment up to approximately 10(7) within the wound. Despite this effect by these distinct inflammatory drivers, wound closure occurred at a rate similar to the saline-treated control group. In summary, a non-invasive fluorescence-based imaging approach combined with genetic labeling of neutrophils provides a dynamic inner view of inflammation and the kinetics of neutrophil infiltration into the wounded skin over extended durations.

Paracellular permeability restricts airway epithelial responses to selectively allow activation by mediators at the basolateral surface

Respiratory pathogens and toxins often assault the lung from the airway lumen. Airway epithelia may initiate and amplify inflammation in response to these attacks, but under certain conditions confinement of inflammation to the airway lumen may be beneficial to the host. Accordingly, we hypothesized that airway epithelial polarity allows different responses to basolateral vs apical stimuli that may modulate inflammation. Using primary human airway epithelial cells differentiated at an air-liquid interface in culture, we found that responses to several cytokines required basolateral mediator application. In contrast, responses to Haemophilus influenzae occurred after either basolateral or apical interaction with airway epithelia. Experiments focused on IFN-gamma receptor polarity confirmed its predominant basolateral location in cultured airway epithelia as well as in normal human airway tissue. Furthermore, physical and pharmacologic disruption of barrier function in airway epithelia allowed responses to apical application of IFN-gamma and other cytokines. These in vitro studies directly correlated with experiments in mice in which an airway epithelial response to IFN-gamma injected into the airway lumen was seen only after disruption of barrier function. The results indicate that airway epithelia with intact barrier function restrict inflammatory responses by limitation of cell activation through requiring interaction of selected mediators with the basolateral surface. However, loss of barrier integrity allows epithelial responses to these mediators if located in the airway lumen to amplify airway defenses.

Effects of murine endotoxemia on lymphocyte subsets and clearance of staphylococcal pulmonary infection

In a model of staphylococcal pneumonia initiated during systemic endotoxemia in BALB/c mice, a significant reduction of the number of circulating CD4+ and CD8+ T-lymphocytes, B-lymphocytes, and NK cells, as well as lung-resident total T- and CD4+ T-lymphocytes was demonstrated. Staphylococcus aureus exposure only induced a similar decrease of lymphocyte subsets in the blood. However, the number of lung-resident total T- and CD4+ T-lymphocytes was increased. More viable bacteria were recovered from the lungs of S. aureus-infected mice than from those animals previously treated with lipopolysaccharide (LPS) followed by a staphylococcal challenge. These results indicate that LPS-induced reduction in the number of circulating lymphocyte subsets and lung-resident total T- and CD4+ T-lymphocytes do not increase susceptibility to staphylococcal respiratory infection. Moreover, LPS challenge prior to S. aureus exposure significantly improves clearance of the bacteria in the lung.

Staphylococcus aureus enterotoxins induce IL-8 secretion by human nasal epithelial cells

Background

Staphylococcus aureus produces a set of proteins which act both as superantigens and toxins. Although their mode of action as superantigens is well understood, little is known about their effects on airway epithelial cells.

Methods

To investigate this problem, primary nasal epithelial cells derived from normal and asthmatic subjects were stimulated with staphylococcal enterotoxin A and B (SEA and SEB) and secreted (supernatants) and cell-associated (cell lysates) IL-8, TNF-α, RANTES and eotaxin were determined by specific ELISAs.

Results

Non-toxic concentrations of SEA and SEB (0.01 μg/ml and 1.0 μg/ml) induced IL-8 secretion after 24 h of culture. Pre-treatment of the cells with IFN-γ (50 IU/ml) resulted in a further increase of IL-8 secretion. In cells from healthy donors pretreated with IFN-γ, SEA at 1.0 μg/ml induced release of 1009 pg/ml IL-8 (733.0–1216 pg/ml, median (range)) while in cells from asthmatic donors the same treatment induced significantly higher IL-8 secretion – 1550 pg/ml (1168.0–2000.0 pg/ml p = 0.04). Normal cells pre-treated with IFN-γ and then cultured with SEB at 1.0 μg/ml released 904.6 pg/ml IL-8 (666.5–1169.0 pg/ml). Cells from asthmatics treated in the same way produced significantly higher amounts of IL-8 – 1665.0 pg/ml (1168.0–2000.0 pg/ml, p = 0.01). Blocking antibodies to MHC class II molecules added to cultures stimulated with SEA and SEB, reduced IL-8 secretion by about 40% in IFN-γ unstimulated cultures and 75% in IFN-γ stimulated cultures. No secretion of TNF-α, RANTES and eotaxin was noted.

Conclusion

Staphylococcal enterotoxins may have a role in the pathogenesis of asthma.