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Biomedical subjects

K F Rabe

Publications and source records attributed to K F Rabe.

At least 55 records · Page 3Linked to original sources
PubMed2001

Sputum induction in severe asthma by a standardized protocol: predictors of excessive bronchoconstriction.

Sputum induction is a noninvasive method to evaluate airway inflammation. We investigated whether it can be safely and successfully performed in patients with severe, difficult-to-control asthma, and whether the patients at risk can be identified. Ninety-three severe asthmatics were included, all symptomatic despite inhaled corticosteroids (> or = 1,600 microg/d) and long-acting beta(2)-agonists > 1 yr. Patients with a postbronchodilator FEV(1) < 1 L and < 50% predicted were excluded from participation. Sputum induction was performed according to a strict protocol, using 0.9%, 3.0%, and 4.5% NaCl inhalation. In 74% (CI: 64 to 83%) of patients an adequate sputum sample could be obtained. Twenty-two percent (CI: 14 to 33%) developed excessive bronchoconstriction (decrease in FEV(1) > 15% from baseline) despite the continuing use of long-acting bronchodilators and pretreatment with 400 microg salbutamol. The decrease in FEV(1) was associated with increased use of rescue short-acting beta(2)-agonists in the previous 2 d (r(s) = 0.51, p = 0.002), lower postbronchodilator FEV(1) (r(s) = -0.31, p = 0.004), and lower provocative concentration of histamine causing a 20% reduction in FEV(1) (PC(20)) (r(s) = -0.52, p < 0.001). Recent use of short-acting beta(2)-agonist increased the risk for excessive bronchoconstriction 10.2-fold (CI: 1.2 to 109.8). In conclusion, sputum induction can be safely and successfully performed in patients with severe, difficult-to-control asthma if a standardized protocol is used. However, severe bronchoconstriction may occur despite regular use of long-acting beta(2)-agonist and pretreatment with salbutamol 400 microg. In particular, patients who have used additional short-acting beta(2)-agonists as rescue medication during the days preceding the induction, are at high risk.

Asthma↗
PubMed2001

Factors associated with persistent airflow limitation in severe asthma.

Persistent airflow limitation can develop in nonsmoking patients with asthma. However, the prevalence and risk factors for airways obstruction with incomplete reversibility in asthma are unknown. We assessed the prevalence of persistent airflow limitation (defined as postbronchodilator FEV(1) or FEV(1)/VC < 75% predicted) in 132 nonsmoking outpatients with severe asthma visiting chest physicians in general hospitals in The Netherlands. They had used inhaled corticosteroids (> or = 1,600 microg/d) and/or daily oral prednisone and long-acting bronchodilators for > 1 yr. In addition, we examined whether persistent airways obstruction in these patients was associated with specific clinical characteristics (age at onset, smoking history, atopic status, bronchodilator reversibility, provocative concentration of histamine causing a 20% decrease in FEV(1) [PC(20)histamine]) or markers of inflammation (exhaled nitric oxide [NO], blood eosinophils, total IgE; and eosinophilia or neutrophilia in induced sputum). Multiple logistic regression analyses were used to calculate adjusted odds ratios (OR). Persistent airflow limitation was observed in 49% of the patients in the study, and apart from older age and longer asthma duration, was strongly associated with a sputum eosinophils percent > or = 2% (OR = 7.7; confidence interval [CI]: 2.4 to 25), PC(20)histamine < or = 1.0 mg/ml (OR = 3.9; CI: 1.2 to 13), and adult onset (> or = 18 yr) of asthma (OR = 3.3; CI: 1.2 to 9). Only sputum eosinophilia appeared to be independently associated with persistent airflow limitation (OR = 8.9; CI: 1.3 to 59). In conclusion, persistent airflow limitation is common in adult patients with severe asthma, and is associated with adult onset of the disease, airway hyperresponsiveness, and most importantly, sputum eosinophilia. These findings suggest that eosinophilic airway inflammation contributes to persistent airflow limitation in severe asthma. Whether reduction of sputum eosinophils with more vigorous treatment leads to a better prognosis in severe asthma is still an open question.

Adolescent↗
PubMed2001

The effect of the vasoactive intestinal polypeptide agonist Ro 25-1553 on induced tone in isolated human airways and pulmonary artery.

Ro 25-1553 is a metabolically stable analogue of endogenous vasoactive intestinal polypeptide (VIP). This compound is a potent bronchodilator in vitro as well as in vivo. Moreover, Ro 25-1553 has been shown to be highly selective of the VPAC2 receptor. We assessed the effect of Ro 25-1553 on isolated human bronchi and pulmonary arteries in vitro. Macroscopically normal human airways and pulmonary arteries were obtained from patients undergoing surgery for lung cancer. The relaxing capability of Ro 25-1553 on bronchial and pulmonary artery tone was measured using standard techniques. Bronchial rings were pre-contracted with 0.1 mM histamine, and tone in pulmonary artery rings was induced with 10 microM PGF2alpha. Increasing concentrations of Ro 25-1553 within a range of 1 pM to 10 microM were added and isometric tension changes were recorded. Ro 25-1553 caused a concentration-dependent relaxation of airway and pulmonary artery preparations, with an EC50 of approximately 10 nM and a maximal relaxation of 70%-75% of the induced tone. The presence of VPAC2 receptors in the two tissues, though low in density, was confirmed by in situ hybridization, immunocytochemistry and ligand binding. These findings indicate that the VIP analogue Ro 25-1553 may be useful in the treatment of asthma and/or chronic obstructive pulmonary diseases.

Bronchi↗
PubMed2001

Image analysis and quantification in lung tissue.

On 9-10 September 1999, an international workshop on image analysis and quantification in lung tissue was held at the Leiden University Medical Center, Leiden, The Netherlands. Participants with expertise in pulmonary and/or pathology research discussed the validity and applicability of techniques used for quantitative examination of inflammatory cell patterns and gene expression in bronchial or parenchymal tissue in studies focusing on asthma and chronic obstructive pulmonary disease (COPD). Differences in techniques for tissue sampling and processing, immunohistochemistry, cell counting and densitometry are hampering the comparison of data between various laboratories. The main goals of the workshop were to make an inventory of the techniques that are currently available for each of these aspects, and in particular to address the validity and unresolved problems of using digital image analysis (DIA) as opposed to manual scoring methods for cell counting and assessment of gene and protein expression. Obviously, tissue sampling and handling, fixation and (immunohistochemical) staining, and microscope settings, are having a large impact on any quantitative analysis. In addition, careful choices will have to be made of the commercially available optical and recording systems as well as the application software in order to optimize quantitative DIA. Finally, it appears to be of equal importance to reach consensus on which histological areas are to be analysed. The current proceedings highlight recent advances and state of the art knowledge on digital image analysis for lung tissue, and summarize the established issues and remaining questions raised during the course of the workshop.

Animals↗
PubMed2001

Isolated airways from current smokers are hyper-responsive to histamine.

Epidemiological studies suggest that bronchial hyper-responsiveness (BHR) and elevated levels of serum IgE are more frequently found in current smokers than in ex-smokers. Since elevated serum IgE is associated with BHR under both in vivo and in vitro conditions, we aimed to assess whether smoking affects BHR independently from IgE. Lung resection material was obtained from 27 current smokers and 11 non-smokers with low serum IgE (< 100 U/mL). Peripheral airways were cut into rings and incubated overnight in the presence (passively sensitized) or absence (non-sensitized) of serum containing IgE levels above 250 U/mL. Isometric contractile responses to histamine were assessed in the organ bath. Compared with non-smokers, isolated airways from smokers showed significantly increased responses to histamine (P < 0.05, ANOVA). Passive sensitization enhanced responses in both groups by about the same amount (P < 0.05, both). In patients with low serum IgE current smoking is associated with increased bronchial responsiveness to histamine in vitro, which can be further enhanced by passive sensitization. These findings suggest that both smoking and serum IgE contribute to non-specific airway hyper-responsiveness.

Aged↗
PubMed2001

Formoterol in clinical practice--safety issues.

While short-acting beta2-agonists are seen as the cornerstone of treatment as relief medication for asthma, current guidelines recommend long-acting beta2-agonists as maintenance therapy in combination with inhaled corticosteroids in patients with moderate to severe asthma, poorly controlled on present treatment. Although evidence has shown that formoterol, with its fast- and long-acting profile, is effective when used both as regular and as-needed therapy in all types of asthma, there has been some concern about the potential of beta2-agonists with long-acting profiles to produce side effects with a longer duration than seen with short-acting beta2-agonists. Also, where formoterol is used as needed, a higher total daily dose would be anticipated than when taken twice daily for regular maintenance therapy and this again has led to some concern. In a number of studies, formoterol has been shown to be well tolerated, and although systemic effects expected with this class of drugs did occur, formoterol had significantly less effect on serum potassium, pulse, blood pressure, cardiac frequency and QT interval compared with terbutaline. In addition, the duration of effects was equivalent to that observed with terbutaline and salbutamol and the relative therapeutic index of formoterol compared with salbutamol was found to be 2.5. Furthermore, studies looking at long-term use of formoterol have shown there is no reduction in bronchodilatory effect, and thus, no development of tolerance. In conclusion, formoterol is well tolerated in high doses, producing side effects typical of its class, but with a duration no longer than occurs with short-acting beta2-agonists. These observations, and the lack of tolerance development, suggest that formoterol may be appropriate treatment for patients with asthma of all types and severities on an as-needed basis or as regular treatment.

Acute Disease↗
PubMed2001

Persistent airflow limitation in adult-onset nonatopic asthma is associated with serologic evidence of Chlamydia pneumoniae infection.

BACKGROUND: Persistent airflow limitation may develop in patients with asthma, particularly in adults with nonatopic (intrinsic) disease. Although the underlying mechanisms are still unknown, respiratory infections might be involved. OBJECTIVE: We investigated the annual loss of lung function in relation to seropositivity to Chlamydia pneumoniae in different subgroups of patients with severe asthma according to age at onset of asthma and atopic status. METHODS: One hundred one nonsmoking outpatients with a pulmonologist's diagnosis of severe asthma (32 men and 69 women; mean age, 46.0 years; range, 18-75 years) were included in a cross-sectional study. C pneumoniae-specific serum IgG and IgA were measured by means of ELISA. The estimated decline in lung function was calculated from the relationship between postbronchodilator FEV(1)/vital capacity (percent predicted) and the duration of asthma and expressed as the slope of the regression line. RESULTS: Patients with adult-onset nonatopic asthma and positive IgG antibodies to C pneumoniae had a significantly steeper slope of the regression line compared with the other subgroups of asthmatic patients (P =.001), being indicative of a 4-fold greater estimated decline in postbronchodilator FEV(1)/vital capacity (2.3% vs 0.5% predicted per year of asthma duration). CONCLUSION: These results suggest that C pneumoniae infection might promote the development of persistent airflow limitation in patients with nonatopic adult-onset asthma. It remains to be established whether viable pathogens that are accessible for therapeutic intervention are still present in the lower airways.

Adolescent↗
PubMed2001

Initiation of apoptosis by actin cytoskeletal derangement in human airway epithelial cells.

Changes in epithelial cell shape can lead to cell death and detachment. Actin filaments are cleaved during apoptosis, but whether disruption in the actin cytoskeletal network, as one manifestation of cell shape change, can itself induce apoptosis is not known. We tested this hypothesis in the airway epithelial cell line 1HAEo(-) and in primary airway epithelial cells by preventing actin filament elongation with cytochalasin D or by aggregating actin filaments with jasplakinolide. Disruption of actin filament integrity promptly induced apoptosis in adherent epithelial cells within 5 h. Jasplakinolide-induced apoptosis did not disrupt focal adhesions, whereas cytochalasin D-induced apoptosis decreased focal adhesion protein expression and occurred despite ligation of the fibronectin receptor. Death induction was abrogated by the caspase inhibitors z-VAD-fmk and Ac-DEVD-cho but not by blocking the Fas (CD95) receptor. Whereas cytochalasin D--induced apoptosis was associated with cleavage of pro-caspase-8, jasplakinolide-induced apoptosis was not. Both agents induced formation of a death-inducing signaling complex. These data demonstrate that disruption of actin filament integrity with either cytochalasin D or jasplakinolide induces apoptosis in airway epithelial cells but by different mechanisms, and suggest that actin may be an early modulator of apoptotic commitment.

Actins↗
PubMed2001

Pharmacological treatment of asthma today.

The current concept of asthma therapy is based on a stepwise approach, depending on disease severity, and the aim is to reduce the symptoms that result from airway obstruction and inflammation, to prevent exacerbations and to maintain normal lung function. Beta2-adrenoceptor agonists and glucocorticoids are at present the most effective drugs for the treatment of airway obstruction and inflammation, with theophylline, leukotriene receptor antagonists and anticholinergics as second- or third-line therapy. There are, to date, no additional or newly developed drugs available that add substantially to the current strategies or even replace beta2-adrenoceptor agonists or glucocorticoids. New approaches in asthma therapy recommend drug combinations of inhaled steroids, primarily with long-acting beta2-adrenoceptor agonists, based on their improved efficacy and the potential for a steroid-sparing effect. Although existing drug entities are able to control the vast majority of patients with mild and moderate asthma, patients' (and doctors') adherence to guidelines and treatment strategies falls well short of the desired standards. Treatment choices, however, differ between countries and should take into account convenience to the patient and the occurrence of side-effects. Additionally, the cost of therapy and reimbursement policies also influences therapeutic strategies.

Administration, Inhalation↗
PubMed2000

Up-regulation of human eosinophil leukotriene C4 generation through contact with bronchial epithelial cells.

OBJECTIVE AND DESIGN: We studied the effect of contact with bronchial epithelial cells on the functional activity of human eosinophils, measured as the production of a bronchoconstrictor lipid mediator, leukotriene C4 (LTC4) to determine the role of cell-cell interaction in activation of airway eosinophils. MATERIALS AND METHODS: Eosinophils were isolated from peripheral blood of atopic donors. Epithelial cells were obtained from the bronchi of surgically resected lung lobes and cultured to confluence on collagen-coated plates. Eosinophils were stimulated with platelet activating factor (PAF) or serum opsonized zymosan (SOZ) after incubation with or without epithelial cells. Leukotriene C4 (LTC4) was assayed in supernatants by enzyme immunoassay. RESULTS: Bronchial epithelial cells did not produce LTC4 in response to PAF or SOZ. Eosinophils pre-incubated in collagen-coated plates for 1 h produced LTC4 in response to both PAF (130 +/- 53 fmol/10(6) eosinophils at 10 micromol/l PAF, 5 min) and SOZ (1,900 +/- 550 fmol/10(6) eosinophils at 2 mg/ml SOZ, 15 min). Eosinophils co-incubated with bronchial epithelial cells for 1 h produced significantly higher quantities of LTC4 in response to both PAF (310 +/- 94 fmol/10(6) eosinophils; P<0.01) and SOZ (5,500 +/- 1,500 fmol/10(6) eosinophils; P<0.001). Ligation of the common beta2 integrin subunit (CD18) with a monoclonal antibody inhibited PAF-stimulated and augmented SOZ-stimulated LTC4 generation by eosinophils alone but had marginal effects on the epithelium-dependent up-regulation. CONCLUSIONS: Contact with bronchial epithelial cells up-regulates the responsiveness of human eosinophils, a finding that has significant implications in the pathology of asthma.

Asthma↗
PubMed2000

The effect of the enantiomers of formoterol on inherent and induced tone in guinea-pig trachea and human bronchus.

The long-acting beta2-adrenoceptor agonist formoterol is, like all other members of this class of drugs, used as a racemate in the clinic. While the effects of the individual enantiomers have been studied on airway smooth muscle from guinea pig, comparable data on human bronchial smooth muscle are scanty or absent. Therefore, we compared the effects of the enantiomers of formoterol on inherent and induced tone in isolated human bronchi with that on guinea-pig trachea in vitro. The human bronchi either were studied under resting tension conditions or were precontracted with 10 microM carbachol or 0.1 mM histamine. The guinea-pig trachea was precontracted with 0.01, 0.1 or 1 microM carbachol. The racemate and (R,R)-formoterol caused a concentration-dependent relaxation of all preparations with an EC50 of about 1 nM. In the guinea-pig trachea, the concentration-effect curve for formoterol was moved to the right in response to an increased concentration of carbachol. In both human bronchus and guinea-pig trachea, (S,S)-formoterol was more than 1,000 times less potent than (R,R)-formoterol. Thus the relaxing effect of formoterol in human airways as well as in guinea-pig trachea was shown to lie with the (R,R)-enantiomer. Notably, (S,S)-formoterol did not exert any contractile effects within the tested concentration range in either airway preparation. Therefore, we conclude that with regard to relaxant effects the pure (R,R)-enantiomer of formoterol does not offer a benefit over the racemate.

Adrenergic beta-Agonists↗
PubMed2000

The effect of selective and non-selective phosphodiesterase inhibitors on allergen- and leukotriene C(4)-induced contractions in passively sensitized human airways.

Non-selective inhibitors of cyclic nucleotide phosphodiesterase (PDE) block allergen-induced contraction of passively sensitized human airways in vitro by a dual mechanism involving a direct relaxant effect on smooth muscle and inhibition of histamine and cysteinyl leukotriene (LT) release from airways. We investigated the effects of non-selective PDE inhibitors and selective inhibitors of PDE3 and PDE4 in order to determine the involvement of PDE isoenzymes in the suppression of allergic bronchoconstriction. Macroscopically normal airways from 76 patients were sensitized with IgE-rich sera (>250 u ml(-1)) containing specific antibodies against allergen (Dermatophagoides farinae). Contractile responses of bronchial rings were assessed using standard organ bath techniques. Passive sensitization caused increased contractile responses to allergen, histamine and LTC(4). Non-selective PDE inhibitors (theophylline, 3-isobutyl-1-methylxanthine [IBMX]), a PDE3-selective inhibitor (motapizone), PDE4-selective inhibitors (RP73401, rolipram, AWD 12-281) and a mixed PDE3/4 inhibitor (zardaverine) all significantly relaxed inherent bronchial tone at resting tension and to a similar degree. Theophylline, IBMX, zardaverine and the combination of motapizone and RP73401 inhibited the contractile responses to allergen and LTC(4). Pre-treatment with motapizone, RP73401, rolipram or the methylxanthine adenosine receptor antagonist, 8-phenyltheophylline, did not significantly decrease responses to either allergen or LTC(4). We conclude that combined inhibition of PDE3 and PDE4, but not selective inhibition of either isoenzyme or antagonism of adenosine receptors, is effective in suppressing allergen-induced contractions of passively sensitized human airways. The relationship between allergen- and LTC(4)-induced responses suggests that PDE inhibitors with PDE3 and PDE4 selectivity are likely to act in part through inhibition of mediator release and not simply through direct relaxant actions on airway smooth muscle.

1-Methyl-3-isobutylxanthine↗
PubMed2000

Serum immunoglobulin E levels predict human airway reactivity in vitro.

BACKGROUND: Airway hyperresponsiveness to non-specific stimuli is one characteristic feature of airway diseases such as bronchial asthma and chronic bronchitis. Until now, studies aiming to demonstrate a relationship between in vivo conditions associated with airway hyperreactivity and in vitro airway responsiveness have been inconclusive. OBJECTIVE: Since serum immunoglobulin (Ig) E is believed to be one determinant of airway reactivity in vivo, we studied whether in vitro airway reactivity in lung resection material from patients with elevated levels of serum IgE was increased as compared with patients with undetectable IgE. By this approach, we aimed to elucidate the role of circulating IgE for bronchial smooth muscle reactivity in vitro. METHODS: Bronchial rings from nine patients with total serum IgE levels above 200 U/mL and 10 patients with total serum IgE levels below 10 U/mL were passively sensitized, i.e. incubated overnight with buffer or sensitizing serum containing high levels of total IgE (> 250 U/mL). Afterwards, contractile responses to histamine were assessed in the organ bath. RESULTS: Histamine responsiveness was significantly increased in airways obtained from patients with IgE levels above 200 U/mL as compared with airways from patients with IgE levels below 10 U/mL (P < 0.05). Passive sensitization of bronchi from patients with low IgE significantly increased histamine responsiveness, as compared with non-sensitized controls from the same patients (P < 0.05). In contrast, passive sensitization of airways from patients with elevated IgE did not further increase responsiveness. There was no difference in histamine reactivity between non-passively sensitized and passively sensitized tissue preparations from patients with IgE above 200 U/mL and passively sensitized tissues from patients with IgE below 10 U/mL. CONCLUSION: Our findings reveal that elevated levels of serum IgE predict airway hyperresponsiveness to histamine in vitro. At the same time, they indicate that the in vitro model of passive sensitization, in addition to its ability to induce allergen responses, also mimics conditions of non-specific airway hyperreactivity, which are relevant under in vivo conditions.

Aged↗
PubMed2000

Involvement of protein tyrosine kinases in activation of human eosinophils by platelet-activating factor.

Activation of human eosinophils by platelet-activating factor (PAF) involves multiple signal transduction pathways. Among these, protein kinase C has been demonstrated both to mediate respiratory burst and to suppress an alternative pathway of activation of respiratory burst and arachidonic acid metabolism in eosinophils. We utilized inhibitors of protein tyrosine kinases (PTK) to elucidate the role of PTK in PAF-induced activation of eosinophils. Eosinophils were isolated from peripheral blood of atopic donors and stimulated with PAF in the absence or presence of broad-spectrum PTK inhibitors-genistein or lavendustin A; an inhibitor of mitogen-activated protein (MAP) kinase activation-tyrphostin AG126; or an inhibitor of Janus kinase 2 (Jak2)-tyrphostin B42 (AG490). PAF induced superoxide anion (O2-*) generation, leukotriene C4 (LTC4) release, intracellular calcium ion mobilization and tyrosine phosphorylation of multiple eosinophil proteins in a concentration-dependent manner. All of these responses were concentration-dependently inhibited by genistein; lavendustin A also exhibited potent inhibition of PAF-induced LTC4 release. AG126 had no effect on either O2-* generation or LTC4 release, while AG490 inhibited both responses, albeit less effectively than genistein. We conclude that PAF activates PTK in human eosinophils and that this signalling pathway is involved in eliciting respiratory burst and leukotriene production. The specific PTK(s) involved are unknown but may include Jak2.

Blotting, Western↗
PubMed2000

Immune mechanisms of smooth muscle hyperreactivity in asthma.

Asthma is characterized by bronchial hyperresponsiveness to a variety of bronchospasmogenic stimuli. To study the pathophysiologic mechanisms underlying the increased sensitivity and degree of maximal airway narrowing, various in vivo and in vitro models have been developed with methods of active and passive sensitization. These studies indicated a major role for alterations in the smooth muscle itself rather than neural dysfunction or airway inflammation as the underlying cause for the development of bronchial hyperresponsiveness. During the last years smooth muscle cells were found to exhibit not only the "classical" contractile phenotype but also a proliferative-synthetic phenotype, which is capable of producing proinflammatory cytokines, chemotaxins, and growth factors. Allergic sensitization can alter both contractile and secretory functions, thereby indicating that the smooth muscle cell could contribute directly to the persistence of airway inflammation in asthma. A better understanding of the changes within the smooth muscle cells and of the mechanisms that lead to their induction could contribute to the development of novel therapeutic approaches for the treatment of asthma.

Asthma↗
PubMed2000

Fas cross-linking induces apoptosis in human airway smooth muscle cells.

Hypertrophy and hyperplasia lead to excess accumulation of smooth muscle in the airways of human asthmatic subjects. However, little is known about mechanisms that might counterbalance these processes, thereby limiting the quantity of smooth muscle in airways. Ligation of Fas on the surface of vascular smooth muscle cells and nonmuscle airway cells can lead to apoptotic cell death. We therefore tested the hypotheses that 1) human airway smooth muscle (HASM) expresses Fas, 2) Fas cross-linking induces apoptosis in these cells, and 3) tumor necrosis factor (TNF)-alpha potentiates Fas-mediated airway myocyte killing. Immunohistochemistry using CH-11 anti-Fas monoclonal IgM antibody revealed Fas expression in normal human bronchial smooth muscle in vivo. Flow cytometry using DX2 anti-Fas monoclonal IgG antibody revealed that passage 4 cultured HASM cells express surface Fas. Surface Fas decreased partially during prolonged serum deprivation of cultured HASM cells and was upregulated by TNF-alpha stimulation. Fas cross-linking with CH-11 antibody induced apoptosis in cultured HASM cells, and this effect was reduced by long-term serum deprivation and synergistically potentiated by concomitant TNF-alpha exposure. TNF-alpha did not induce substantial apoptosis in the absence of Fas cross-linking. These data represent the first demonstration that Fas is expressed on HASM and suggest a mechanism by which Fas-mediated apoptosis could act to oppose excess smooth muscle accumulation during airway remodeling in asthma.

Antibodies, Monoclonal↗