Effects of inhaled beta agonist and corticosteroid treatment on nuclear transcription factors in bronchial mucosa in asthma.
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BACKGROUND: Inhaled corticosteroids and beta agonists are the most commonly used treatments in asthma and are often used together. Recent evidence suggests that many of the anti-inflammatory actions of corticosteroids are mediated by cross-talk between the activated glucocorticoid receptor (GR) and other transcription factors such as the pro-inflammatory nuclear factor kappa B (NFkappaB). Beta agonists can activate the transcription factor cAMP response element binding protein (CREB). A mutual inhibition between GR and CREB occurs in vitro which raises the possibility of a negative interaction between corticosteroid and beta agonist drugs. A study was undertaken to determine whether these interactions occur during treatment with beta2 agonists and corticosteroids in asthma. METHODS: Seven subjects who were participating in a randomised, placebo controlled, crossover study of six weeks treatment with inhaled budesonide (400 microg twice daily), terbutaline (1 mg four times daily), and combined treatment were recruited. Biopsy samples of the bronchial mucosa were obtained after each treatment and analysed for the DNA binding activity of GR, CREB, and NFkappaB. RESULTS: Budesonide increased GR activity (p<0.05) and decreased NFkappaB activity (p<0.05). No treatment combination altered CREB activity and terbutaline had no significant effects on any transcription factor. CONCLUSIONS: Inhaled corticosteroids have significant effects on GR and NFkappaB activity in bronchial mucosa. A negative interaction between inhaled corticosteroids and beta agonists was not found. (+info)
Passive IgA monoclonal antibody is no more effective than IgG at protecting mice from mucosal challenge with respiratory syncytial virus.
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Respiratory syncytial virus (RSV) is a mucosally restricted pathogen that can cause severe respiratory disease. Although parenteral administration of sufficient RSV-specific IgG can reduce severity of lower respiratory tract infection in high-risk infants, delivery of antibody by direct airway administration is an attractive alternative. Topical and parenteral administration of an IgA monoclonal antibody (MAb) specific for the RSV F glycoprotein was compared with an IgG MAb, specific for the same antigenic site, for ability to protect mice against RSV infection. Administration of RSV-specific IgG was more effective in reducing RSV titers in lung (4.6 log10 pfu/g) than IgA MAb (3.6 log10 pfu/g) when given intranasally immediately prior to infection (P=.005). RSV titers in the nose were reduced only by prophylactic administration of IgG parenterally. Therefore, topical administration of IgA is no more effective than topically administered IgG and is less effective than systemically administered IgG for protecting against RSV infection. (+info)
Differential sensitivity of normal and cystic fibrosis airway epithelial cells to epinephrine.
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1. Exposure to epinephrine has been shown to have a range of effects on cells and tissues. A recent study suggested that the proliferative ability of CF epithelial cells, exposed to high concentrations of epinephrine (200 - 300 microM), was reduced when compared to that of normal cells. This approach could potentially provide a means to effectively separate cells with functional cyclic AMP-dependent Cl-ion transport from those defective in this pathway. 2. The sensitivity to killing by epinephrine is reported here for four different CF cell lines, three normal cell lines, and two CF epithelial cell lines complemented with wild-type (wt) CF transmembrane conductance regulator (CFTR) cDNA. 3. While each cell line exhibited varying sensitivity to 200 microM epinephrine, no predictable pattern was observed between the expression of wt-CFTR and cell survival following epinephrine exposure. Overall, normal cell lines did exhibit a greater resistance to epinephrine-induced cell death although, the most resistant cell line was derived from CF tracheal epithelium (SigmaCFTE29o-). 4. The expression of exogenous wt-CFTR increased the survival of one cell line (CFDEo-) when compared to the parent line, but in another complemented line, survival was reduced. 5. These findings suggest that while epinephrine induces cell killing, it is not consistently effective for preferential selection of normal over CF cells. Although CFTR may play a role in the mechanism(s) of epinephrine killing, other factors such as cell density, proliferative ability, cell type origin and phenotype are involved. (+info)
Crucial role of the interleukin 1 receptor family member T1/ST2 in T helper cell type 2-mediated lung mucosal immune responses.
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T1/ST2 is an orphan receptor of unknown function that is expressed on the surface of murine T helper cell type 2 (Th2), but not Th1 effector cells. In vitro blockade of T1/ST2 signaling with an immunoglobulin (Ig) fusion protein suppresses both differentiation to and activation of Th2, but not Th1 effector populations. In a nascent Th2-dominated response, anti-T1/ST2 monoclonal antibody (mAb) inhibited eosinophil infiltration, interleukin 5 secretion, and IgE production. To determine if these effects were mediated by a direct effect on Th2 cells, we next used a murine adoptive transfer model of Th1- and Th2-mediated lung mucosal immune responses. Administration of either T1/ST2 mAb or T1/ST2-Ig abrogated Th2 cytokine production in vivo and the induction of an eosinophilic inflammatory response, but failed to modify Th1-mediated inflammation. Taken together, our data demonstrate an important role of T1/ST2 in Th2-mediated inflammatory responses and suggest that T1/ST2 may prove to be a novel target for the selective suppression of Th2 immune responses. (+info)
Epithelial P2X purinergic receptor channel expression and function.
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P2X purinergic receptor (P2XR) channels bind ATP and mediate Ca(2+) influx--2 signals that stimulate secretory Cl(-) transport across epithelia. We tested the hypotheses that P2XR channels are expressed by epithelia and that P2XRs transduce extracellular ATP signals into stimulation of Cl(-) transport across epithelia. Electrophysiological data and mRNA analysis of human and mouse pulmonary epithelia and other epithelial cells indicate that multiple P2XRs are broadly expressed in these tissues and that they are active on both apical and basolateral surfaces. Because P2X-selective agonists bind multiple P2XR subtypes, and because P2X agonists stimulate Cl(-) transport across nasal mucosa of cystic fibrosis (CF) patients as well as across non-CF nasal mucosa, P2XRs may provide novel targets for extracellular nucleotide therapy of CF. (+info)
Effect of fluticasone propionate and salmeterol on Pseudomonas aeruginosa infection of the respiratory mucosa in vitro.
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The purpose of this study was to investigate the effect of the corticosteroid, fluticasone propionate (FP), on Pseudomonas aeruginosa infection of the respiratory mucosa of an organ culture model in vitro. Organ cultures infected with P. aeruginosa had significantly (p< or =0.05) elevated levels of mucosal damage and significantly (p< or =0.05) less ciliated cells compared to controls. Preincubation of tissue with FP (10(-6) or 10(-5) but not 10(-7) M) prior to P. aeruginosa infection significantly (p< or =0.05) reduced the bacterially induced mucosal damage in a concentration-dependent manner. FP (10(-5) M) also significantly (p< or =0.05) prevented loss of ciliated cells. FP did not alter the density of bacteria adherent to the different mucosal features of the organ cultures, but did reduce total bacterial numbers due to the reduced amount of damaged tissue, which is a preferred site of P. aeruginosa adherence. It has previously been shown that the long-acting beta2-agonist salmeterol (4 x 10(-7)M) also reduces the mucosal damage caused by P. aeruginosa infection, probably via elevation of intracellular cyclic adenosine monophosphate concentrations. Preincubation of tissue with both 10(-7)M FP and 10(-7)M salmeterol, concentrations at which they did not by themselves influence the effect of P. aeruginosa infection, significantly (p< or =0.05) reduced P. aeruginosa-induced loss of cilia. However, there was no additional benefit from adding 4 x 10(-7)M salmeterol to 10(-6)M FP. In conclusion fluticasone propionate reduced mucosal damage caused by P. aeruginosa infection in vitro and preserved ciliated cells. There was a synergistic action with salmeterol in the preservation of ciliated cells. (+info)
M1/MUC5AC mucin released by human airways in vitro.
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A series of monoclonal antibodies which bind to a mucin known as M1 (anti-M1 MAbs) have also been shown to detect the product of the human gene MUC5AC. The aim of this investigation was to determine the concentration of the M1 mucin in the surface epithelium of human bronchial preparations by means of immunohistochemistry and in the bronchial fluid derived from human airways by means of an immunoradiometric assay. Human bronchial ring preparations from the resection material of 20 patients were challenged with methacholine, leukotriene D4, or anti-immunoglobulin E. Experiments were performed in preparations with an intact epithelium as well as in tissues in which the epithelium had been mechanically removed. The anti-M1 MAbs stained the goblet cells in the epithelium intensely and there was also light and less uniform staining in the submucosa. The M1/MUC5AC mucin in the fluids secreted by the bronchial preparations was not modified during either the experimental protocol or stimulation with the different secretagogues. However, in preparations in which the epithelium had been removed, there was a significant reduction in the amount of M1/MUC5AC mucin detected. These data suggest that the M1/MUC5AC mucin detected in the biological fluids produced by human airways in vitro may be released constantly, and principally from the goblet cells in the epithelial layer. (+info)
Arsenite exposure of cultured airway epithelial cells activates kappaB-dependent interleukin-8 gene expression in the absence of nuclear factor-kappaB nuclear translocation.
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Airway epithelial cells respond to certain environmental stresses by mounting a proinflammatory response, which is characterized by enhanced synthesis and release of the neutrophil chemotactic and activating factor interleukin-8 (IL-8). IL-8 expression is regulated at the transcriptional level in part by the transcription factor nuclear factor (NF)-kappaB. We compared intracellular signaling mediating IL-8 gene expression in bronchial epithelial cells cultured in vitro and exposed to two inducers of cellular stress, sodium arsenite (As(III)), and vanadyl sulfate (V(IV)). Unstimulated bronchial epithelial cells expressed IL-8, and exposure to both metal compounds significantly enhanced IL-8 expression. Overexpression of a dominant negative inhibitor of NF-kappaB depressed both basal and metal-induced IL-8 expression. Low levels of nuclear NF-kappaB were constitutively present in unstimulated cultures. These levels were augmented by exposure to V(IV), but not As(III). Accordingly, V(IV) induced IkappaBalpha breakdown and NF-kappaB nuclear translocation, whereas As(III) did not. However, both As(III) and V(IV) enhanced kappaB-dependent transcription. In addition, As(III) activation of an IL-8 promoter-reporter construct was partially kappaB-dependent. These data suggested that As(III) enhanced IL-8 gene transcription independently of IkappaB breakdown and nuclear translocation of NF-kappaB in part by enhancing transcription mediated by low levels of constitutive nuclear NF-kappaB. (+info)