Biomedical subjects
R Polosa
Publications and source records attributed to R Polosa.
Bronchial hyperresponsiveness and airway inflammation markers in nonasthmatics with allergic rhinitis.
Bronchial hyperresponsiveness (BHR) is a characteristic feature of asthma which is often associated with airways inflammation. However, some patients with allergic rhinitis and no clinical evidence of asthma also exhibit BHR. This study therefore investigated whether inflammatory cell infiltrate is present in the induced sputum of nonasthmatic subjects with allergic rhinitis during the pollen season and examined its relationship with airway hyperresponsiveness to inhaled methacholine and adenosine 5'-monophosphate (AMP). Twenty subjects (12 allergic rhinitis, eight nonallergic controls) underwent methacholine and AMP challenge and sputum induction with hypertonic saline on separate days. Cell differentials were calculated from whole sputum samples. A significantly greater number of eosinophils was found in the sputum of nonasthmatic subjects with allergic rhinitis compared to that of nonallergic controls, their median (range) percentages being 17.5 (4-47) and 1.5 (0-5) (p<0.001) respectively. Although sputum eosinophilia failed to be significantly associated with methacholine responsiveness (r(s)=-0.50; p=0.095), the provocative concentration of AMP causing a 20% fall in forced expiratory volume in one second correlated strongly and significantly with the absolute number of eosinophils (r(s)= -0.73; p=0.007). Eosinophil cationic protein levels in the sputum of rhinitic subjects were significantly elevated compared to controls and correlated with eosinophil number (r(s)=0.67; p=0.017). These findings support the view that bronchial eosinophilia alone is insufficient to cause asthmatic symptoms. Diverse agonists for assessing bronchial hyperresponsiveness are selectively associated with airway inflammation in allergic rhinitis.
Bronchial hyperresponsiveness and airway inflammatory markers in nonasthmatics with allergic rhinitis.
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Prevalence of atopy and urban air pollution: dirty business.
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Histamine release upon adenosine 5'-monophosphate (AMP) nasal provocation in allergic subjects.
BACKGROUND: Nasal provocation with adenosine 5'-monophosphate (AMP) elicits nasal symptoms in subjects with rhinitis. Histamine released from mast cells may play a part in AMP induced nasal responses. METHODS: Symptoms of rhinitis were recorded and histamine release in the fluid obtained by nasal lavage after AMP, guanosine 5'-monophosphate (GMP), and placebo instillations was measured in nine subjects with allergic rhinitis and nine non-allergic controls in a double blind, randomised, placebo controlled study. RESULTS: No symptoms or significant increases in histamine were observed after GMP and placebo challenge. Significantly higher levels of histamine were seen in the nasal lavage fluids of allergic subjects following AMP challenge than in nonallergic controls, the median (range) histamine concentration increasing from the baseline value of 1.62 (0.44-6.99) ng/ml to 6.45 (0.81-16.17) ng/ml at three minutes. No increase in histamine levels was seen in the non-allergic subjects in whom the median histamine concentration was 1.13 (0.29-4.25) ng/ml at baseline and 0.97 (0.31-5.89) ng/ml three minutes after AMP challenge. CONCLUSIONS: AMP elicits an immediate rise in histamine levels in the nasal lavage fluid of allergic subjects compared with non-allergic individuals. These findings indicate that the exaggerated nasal response to adenosine may reflect mast cell priming in vivo, thus supporting its application as a potential new marker of allergic inflammation.
Expression of c-erbB receptors and ligands in human bronchial mucosa.
The epidermal growth factor receptor (EGFR, c-erbB1) plays a pivotal role in maintenance and repair of epithelial tissues; however, little is known about coexpression of c-erbB receptors and their ligands in human bronchial epithelium. We therefore analyzed the expression of these molecules in cultured bronchial epithelial cells and normal bronchial mucosa, using reverse transcription-polymerase chain reaction (RT- PCR), flow cytometry, and immunohistochemistry. Messenger RNA (mRNA) encoding EGFR, c-erbB2, and c-erbB3, but not c-erbB4, was detected in primary cultures of human bronchial epithelial cells, as well as in the human bronchial epithelial-derived cell lines H292 and 16HBE 14o-. Transcripts encoding epidermal growth factor (EGF), heparin binding epidermal growth factor (HB-EGF), transforming growth factor-alpha (TGF-alpha), and amphiregulin (AR) were also detected, and expression of the three receptors and four ligands was confirmed by immunocytochemical staining of the cultured cells. Immunohistochemical analysis of resin- or paraffin-embedded sections from surgical specimens of bronchial mucosa revealed strong membrane staining for EGFR within the bronchial epithelium; this was particularly evident between basal cells and the basal aspect of columnar cells. The patterns of staining for c-erbB2 and c-erbB3 in the bronchial epithelium were similar to those for EGFR. Immunostaining for EGF, TGF-alpha, AR, HB- EGF, and betacellulin (BTC) was intense in the submucosal glands; with the exception of BTC, EGFR ligand immunoreactivity was also observed in the bronchial epithelium, where it paralleled EGFR staining. Colocalization of c-erbB receptors and ligands demonstrates the potential for productive c-erbB receptor interactions in bronchial epithelium. Further study of these interactions may help to define their role in maintenance and repair of the bronchial epithelium.
Interleukin-5 production by human airway epithelial cells.
Interleukin (IL)-5 is a pleiotropic cytokine that exhibits biologic activity on cells of diverse hemopoieitic lineages. IL-5 enhances mediator release from human basophils and plays a pivotal role in the chemoattraction, proliferation, differentiation, survival, and activation of eosinophils. Th2- and Tc2-like T cells, mast cells, basophils, and eosinophils are the known cellular sources of this cytokine. Using a sensitive and novel reverse transcription-polymerase chain reaction enzyme-linked immunosorbent assay system, we found that IL-5 messenger RNA (mRNA) was constitutively expressed in bronchial biopsies obtained from healthy individuals, and that the levels of IL-5 mRNA expression decreased 1. 5 h after exposure to 0.12 ppm ozone for 2 h. Because the oxidative effects of ozone are confined to the epithelial cell surface and it is known that ozone induces epithelial damage and shedding, we hypothesized that epithelial cells might be a source of IL-5 mRNA. We demonstrate here that both transformed human bronchial epithelial cell lines (A549 and 16HBE14o-) and primary human bronchial and nasal epithelial cells grown in culture constitutively express IL-5 mRNA, which is upregulated on stimulation with tumor necrosis factor (TNF)-alpha. Culture supernatants derived from A549 cells exposed to TNF-alpha and interferon-gamma demonstrated detectable levels of IL-5 protein, and immunostaining of bronchial biopsies obtained from healthy human airways revealed the presence of IL-5 protein localized to the bronchial epithelium. To our knowledge, this is the first report demonstrating IL-5 production by human airway epithelial cells. This observation provides further evidence for the role of airway epithelium in regulating airway immune responses, in particular enhancing chemotaxis, activation, and survival of eosinophils, which could play an important role in the pathogenesis of bronchial asthma.
The epidermal growth factor receptor and its ligand family: their potential role in repair and remodelling in asthma.
The bronchial epithelium acts as a physical barrier to the ingress of airborne irritants and plays an active role in the airways immune response, reacting to a range of environmental stimuli to enable interaction with immune and inflammatory cells. It is well established that mucosal damage and epithelial cell shedding are important features of inflammatory airways diseases such as asthma. Evidence now suggests that the repairing epithelium has the potential to contribute to disease chronicity through production of an array of soluble mediators and adhesion molecules. However, the biochemical mechanisms that control epithelial maintenance and repair are poorly understood, even though avoiding or reversing the changes in the airways which are likely to result from chronic inflammation and epithelial restitution remains a significant challenge in asthma therapy. The purpose of this review is to highlight the potential of the epidermal growth factor receptor (EGFR/c-erbB) and its ligands in restitution of the bronchial epithelium. This receptor tyrosine kinase plays a pivotal role in regulation of epithelial cell behaviour, having the capacity to elicit a broad spectrum of cellular responses ranging from migration or proliferation to differentiation and enhanced survival; it also has the ability to regulate expression of various inflammatory mediators, mucins, adhesion molecules, matrix proteins, and metalloproteinases which are relevant to the chronic disease phenotype.
Spontaneous pneumomediastinum with subcutaneous emphysema: unusual presenting feature of a common condition.
Pneumomediastinum refers to the presence of free air in the mediastinum and is frequently associated with subcutaneous emphysema. It is known that a number of medical and surgical conditions may be complicated by pneumomediastinum. However, here we report the case of a young female in whom pneumomediastinum was the presenting feature of a widespread medical condition rather than its complication.
Adenosine A2B receptors: a novel therapeutic target in asthma?
Adenosine is an endogenous nucleoside that modulates many physiological processes. Its actions are mediated by interaction with specific cell membrane receptors. Four subtypes of adenosine receptor have been cloned: A1, A2A, A2B and A3. Significant advancement has been made in our understanding of the molecular pharmacology and physiological relevance of adenosine receptors but our knowledge of A2B receptors lags behind that of other receptor types. Only recently have potentially important functions been discovered for the A2B receptors, prompting a renewed interest in this receptor type. A2B receptors have been implicated in the regulation of vascular smooth muscle tone, cell growth, intestinal function and neurosecretion. In this review, Igor Feoktistov, Riccardo Polosa, Stephen Holgate and Italo Biaggioni focus on the role of A2B receptors in mast cell activation and the potential relevance of this action on asthma.
Anaphylaxis after prednisone.
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Bronchodilator response to salbutamol after spontaneous recovery from nonspecific bronchial provocation tests in asthma.
Assessment of airway responsiveness by bronchoprovocation and bronchodilatation tests is important in the diagnostic work-up protocol of bronchial asthma and it would be convenient to undertake both tests on the same occasion. However, it is not known whether this can be done accurately. Therefore, this study evaluated the effect of a prior bronchial provocation test on the bronchodilator response to salbutamol after spontaneous recovery of the forced expiratory volume in one second (FEV1) in a group of asthmatic subjects. On two separate occasions at the same time of day, concentration-response studies with inhaled histamine or methacholine, or a sham challenge with normal saline were carried out in a blinded, randomized manner. Changes in airway calibre were followed as FEV1 and agonist responsiveness expressed as the provocative concentration causing a 20% fall in FEV1 (PC20). After either spontaneous recovery or a fixed-duration wait of 45 min (when appropriate), the subjects received 2x100 microg of salbutamol from a metered dose inhaler with a spacer. The bronchodilator response to salbutamol was expressed as a percentage of initial FEV1 (deltaFEV1% init). Bronchial challenge with both agonists failed to alter significantly the airway response to salbutamol, with the deltaFEV1% init mean value (range) being 16.9% (9.0-31.9) and 17.5% (11.6-31.2) on the sham and histamine/methacholine challenge day respectively. It was shown that the degree of bronchodilatation achieved after salbutamol 200 microg is not affected by prior bronchoprovocation testing when enough time is allowed for the airways to recover spontaneously to baseline forced expiratory volume in one second. Thus evaluation of airway responsiveness by both bronchial provocation tests and bronchodilator testing can be assessed reliably within a few hours in asthmatic patients.
Sputum eosinophilia is more closely associated with airway responsiveness to bradykinin than methacholine in asthma.
Hyperresponsiveness of the airways to various spasmogenic stimuli is a characteristic feature of bronchial asthma. However, the association between the different stimuli to which asthmatic airways are hyperresponsive and airways inflammation is not completely understood. We have investigated the relationship between airway inflammation and airway hyperresponsiveness in asthma, as assessed by bronchoprovocation tests to methacholine and bradykinin, two well defined bronchoconstrictor agonists. Sputum induction by hypertonic saline and methacholine and bradykinin challenges were performed in 14 nonsmoking subjects with mild-to-moderate asthma. Airway responsiveness to either agonist did not correlate with sputum neutrophils, lymphocytes, and macrophages. Whilst the absolute number of eosinophilia failed to be significantly related to methacholine responsiveness (r=-0.47; p=0.09), it correlated markedly and significantly with provocative concentration of methacholine causing a 20% fall in forced expiratory volume in one second (r=0.72; p<0.01). When expressed as % of total cell counts, sputum eosinophils correlated with both types of responsiveness (r=-056; p=0.04 and r=-0.76, p<0.001, respectively). Although the concentration of eosinophil cationic protein (ECP) in the sputum correlated with the absolute numbers of eosinophils (r=0.62; p<0.02), no correlation was found between ECP levels and the airway responsiveness to any of the agonists tested. In subjects with mild-to-moderate asthma, airway responsiveness to bradykinin is more strongly associated with the magnitude of eosinophilic inflammation in the airways than methacholine. This finding underlines the selectivity of diverse agonists in assessing airway hyperresponsiveness and cellular inflammation in asthma.
Time course of changes in adenosine 5'-monophosphate airway responsiveness with inhaled heparin in allergic asthma.
BACKGROUND: Recent studies have shown that inhaled heparin exerts a protective effect against various bronchoconstrictor stimuli in asthma, possible through an inhibition of mast cell activation. OBJECTIVE: Because adenosine 5'-monophosphate (AMP) elicits bronchoconstriction by augmenting mast cell mediator release, we have investigated the effect of inhaled heparin (15,000 units USP/ml, 4 ml) on the bronchoconstrictor response to this agonist and to methacholine in a randomized, double-blind, placebo-controlled study of 10 subjects with asthma. We also carried out a separate randomized, double-blind study in seven additional volunteers with asthma to examine in more detail the time-course of change in bronchial reactivity to inhaled AMP after treatment with nebulized heparin. RESULTS: Inhaled heparin significantly increased the provocative concentration of AMP causing a 20% decrease in forced expiratory volume in 1 second (PC20 FEV1-AMP) from the postplacebo treatment value of 22.3 mg/ml (range, 5.7 to 68.9 mg/ml) to 48.1 mg/ml (range, 5.1-196.8 mg/ml) (p < 0.01). When compared with placebo, inhaled heparin failed to alter the airway responsiveness to methacholine; the mean (range) PC20 methacholine values were 1.00 mg/ml (0.44 to 4.76 mg/ml) and 1.08 mg/ml (0.46 to 5.08 mg/ml), respectively. After placebo administration, the PC20 AMP values at 15, 60, and 180 minutes did not differ significantly from each other; their geometric mean (range) values were 26.1 mg/ml (5.9 to 85.8 mg/ml), 26.6 mg/ml (6.3 to 87.8 mg/ml), and 24.9 mg/ml (5.2 to 80.2 mg/ml), respectively. When compared with placebo, the PC20 values for AMP after administration of inhaled heparin were significantly increased up to 57.3 mg/ml (14.7 to 176.0 mg/ml) and to 52.7 mg/ml (13.9 to 90.8 mg/ml) at 15 minutes and 60 minutes, respectively. At 180 minutes, inhaled heparin failed to affect AMP airway responsiveness; the PC20 AMP was not significantly different from that of placebo, with a value of 30.6 mg/ml (4.8 to 93.3 mg/ml). CONCLUSION: Heparin administered by inhalation is effective in attenuating the airway response to AMP but not to methacholine. The time course of change in bronchial reactivity to AMP has a peak effect at 15 minutes and lasts up to 60 minutes. It is possible that the mechanism(s) underlying the protective effects of inhaled heparin in asthma may be related to an inhibitory modulation of mast cell activation.
A case of acute deterioration in asthma symptoms induced by isoniazid prophylaxis.
The present case report describes a 10-year-old boy with clinical history of steroid-dependent asthma who developed severe exacerbation of his respiratory symptoms upon isoniazid administration. Subsequent control of his asthma symptoms was re-established and maintained only after isoniazid withdrawal. This case is the first to emphasize the dangers of isoniazid administration in patients who have asthma.
Purine derivatives in the study of allergic inflammation in respiratory diseases.
Adenosine, a naturally occurring purine nucleoside, elicits dose-related bronchoconstriction in asthmatic subjects when administered by inhalation and it is recovered in increased amounts from the bronchial lavage fluid of subjects with active asthma when compared to normal controls. Although the mechanism by which adenosine mediates bronchoconstriction in asthmatic subjects is not clear, recent data indicate an important role for mast cell mediator release. We have recently shown that local airway challenge with adenosine in subjects with asthma and rhinitis provokes an increase in the levels of PGD2, histamine and tryptase. However, airway responsiveness and atopic status are the most important determinants of adenosine-induced responses, regardless of any increases in mast cell mediators in airway fluids. New discoveries suggest that the airway response to adenosine may be an index of mast cell priming and therefore may provide a useful tool to further explore the inflammatory processes in allergic asthma and rhinitis. Therefore adenosine provocation may gain increasing acceptance as an additional measure of disease activity in asthma and rhinitis.
Adenosine bronchoprovocation: a promising marker of allergic inflammation in asthma?
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Changes in neurokinin A (NKA) airway responsiveness with inhaled frusemide in asthma.
BACKGROUND: Inhaled frusemide exerts a protective effect against bronchoconstriction induced by several indirect stimuli in asthma which could be due to interference of airway nerves. A randomised, double blind, placebo controlled study was performed to investigate the effect of the potent loop diuretic, frusemide, administered by inhalation on the bronchoconstrictor response to neurokinin A (NKA) and histamine in 11 asthmatic subjects. METHODS: Subjects attended the laboratory on four separate occasions to receive nebulised frusemide (40 mg) or matched placebo 10 minutes prior to bronchial challenge with NKA and histamine in a randomised, double blind order. Changes in airway calibre were followed as forced expiratory volume in one second (FEV1) and responsiveness to the agonists was expressed as the provocative concentration causing a 20% fall in FEV1 from baseline (PC20). RESULTS: Compared with placebo, inhaled frusemide reduced the airway responsiveness to NKA in all the subjects studied, the geometric mean (range) values for PC20NKA increasing significantly (p < 0.001) from 130.3 (35.8-378.8) to 419.9 (126.5-1000) micrograms/ml after placebo and frusemide, respectively. Moreover, a small but significant change in airway responsiveness to histamine was recorded after frusemide, their geometric mean (range) PC20 values being 0.58 (0.12-3.80) and 1.04 (0.28-4.33) mg/ml after placebo and frusemide, respectively. CONCLUSIONS: The decrease in airway responsiveness to NKA after administration of frusemide by inhalation suggests that this drug may interfere with the activation of neurotransmission in human asthma.