Small airway hyperresponsiveness in COPD: relationship between structure and function in lung slices.

The direct relationship between pulmonary structural changes and airway hyperresponsiveness (AHR) in chronic obstructive pulmonary disease (COPD) is unclear. We investigated AHR in relation to airway and parenchymal structural changes in a guinea pig model of COPD and in COPD patients. Precision-cut lung slices (PCLS) were prepared from guinea pigs challenged with lipopolysaccharide or saline two times weekly for 12 wk. Peripheral PCLS were obtained from patients with mild to moderate COPD and non-COPD controls. AHR to methacholine was measured in large and small airways using video-assisted microscopy. Airway smooth muscle mass and alveolar airspace size were determined in the same slices. A mathematical model was used to identify potential changes in biomechanical properties underlying AHR. In guinea pigs, lipopolysaccharide increased the sensitivity of large (>150 µm) airways toward methacholine by 4.4-fold and the maximal constriction of small airways (<150 µm) by 1.5-fold. Similarly increased small airway responsiveness was found in COPD patients. In both lipopolysaccharide-challenged guinea pigs and patients, airway smooth muscle mass was unaltered, whereas increased alveolar airspace correlated with small airway hyperresponsiveness in guinea pigs. Fitting the parameters of the model indicated that COPD weakens matrix mechanical properties and enhances stiffness differences between the airway and the parenchyma, in both species. In conclusion, this study demonstrates small airway hyperresponsiveness in PCLS from COPD patients. These changes may be related to reduced parenchymal retraction forces and biomechanical changes in the airway wall. PCLS from lipopolysaccharide-exposed guinea pigs may be useful to study mechanisms of small airway hyperresponsiveness in COPD.

Bronchoprotection by olodaterol is synergistically enhanced by tiotropium in a guinea pig model of allergic asthma.

The novel once-daily ß2-agonist bronchodilator drug olodaterol has recently been shown to be effective in patients with allergic asthma for >24 hours. An increased cholinergic tone common to these patients may decrease the effectiveness of ß2-agonists. This could provide a rationale for combination therapy with olodaterol and the long-acting anticholinergic tiotropium to aim for a once-daily treatment regimen. In guinea pigs, we evaluated the protective effects of olodaterol, alone and in combination with tiotropium, on airway responsiveness to histamine, which is partially mediated by a cholinergic reflex mechanism. In addition, using a guinea pig model of acute allergic asthma, we examined the cooperative effects of these bronchodilators on allergen-induced early (EAR) and late (LAR) asthmatic reactions, airway hyper-responsiveness (AHR) to histamine, and airway inflammation. It was demonstrated that the protective effect of olodaterol against histamine-induced bronchoconstriction was synergistically enhanced and prolonged in the presence of tiotropium. In addition, tiotropium synergistically augmented both the reversal of and the protection against the allergen-induced AHR after the EAR by olodaterol. Olodaterol and tiotropium were highly effective in inhibiting the magnitude of the allergen-induced EAR and LAR, and both reactions were fully inhibited by the combination of these drugs. It is remarkable that these effects were not associated with an effect on inflammatory cell infiltration in the airways. In conclusion, the results indicate that combination therapy with olodaterol and tiotropium may be highly effective in the treatment of allergen-induced asthmatic reactions and AHR.

Effects of (a Combination of) the Beta2-Adrenoceptor Agonist Indacaterol and the Muscarinic Receptor Antagonist Glycopyrrolate on Intrapulmonary Airway Constriction.

Expression of bronchodilatory ß2-adrenoceptors and bronchoconstrictive muscarinic M3-receptors alter with airway size. In COPD, (a combination of) ß2-agonists and muscarinic M3-antagonists (anticholinergics) are used as bronchodilators. We studied whether differential receptor expression in large and small airways affects the response to ß2-agonists and anticholinergics in COPD. Bronchoprotection by indacaterol (ß2-agonist) and glycopyrrolate (anticholinergic) against methacholine- and EFS-induced constrictions of large and small airways was measured in guinea pig and human lung slices using video-assisted microscopy. In guinea pig lung slices, glycopyrrolate (1, 3 and 10 nM) concentration-dependently protected against methacholine- and EFS-induced constrictions, with no differences between large and small intrapulmonary airways. Indacaterol (0.01, 0.1, 1 and 10 µM) also provided concentration-dependent protection, which was greater in large airways against methacholine and in small airways against EFS. Indacaterol (10 µM) and glycopyrrolate (10 nM) normalized small airway hyperresponsiveness in COPD lung slices. Synergy of low indacaterol (10 nM) and glycopyrrolate (1 nM) concentrations was greater in LPS-challenged guinea pigs (COPD model) compared to saline-challenged controls. In conclusion, glycopyrrolate similarly protects large and small airways, whereas the protective effect of indacaterol in the small, but not the large, airways depends on the contractile stimulus used. Moreover, findings in a guinea pig model indicate that the synergistic bronchoprotective effect of indacaterol and glycopyrrolate is enhanced in COPD.

Arginase inhibition protects against allergen-induced airway obstruction, hyperresponsiveness, and inflammation.

RATIONALE: In a guinea pig model of allergic asthma, using perfused tracheal preparations ex vivo, we demonstrated that L-arginine limitation due to increased arginase activity underlies a deficiency of bronchodilating nitric oxide (NO) and airway hyperresponsiveness (AHR) after the allergen-induced early and late asthmatic reaction. OBJECTIVES: Using the same animal model, we investigated the acute effects of the specific arginase inhibitor 2(S)-amino-6-boronohexanoic acid (ABH) and of L-arginine on AHR after the early and late reaction in vivo. In addition, we investigated the protection of allergen-induced asthmatic reactions, AHR, and airway inflammation by pretreatment with the drug. METHODS: Airway responsiveness to inhaled histamine was measured in permanently instrumented, freely moving guinea pigs sensitized to ovalbumin at 24 hours before allergen challenge and after the allergen-induced early and late asthmatic reactions by assessing histamine PC(100) (provocative concentration causing a 100% increase of pleural pressure) values. MEASUREMENTS AND MAIN RESULTS: Inhaled ABH acutely reversed AHR to histamine after the early reaction from 4.77 +/- 0.56-fold to 2.04 +/- 0.34-fold (P < 0.001), and a tendency to inhibition was observed after the late reaction (from 1.95 +/- 0.56-fold to 1.56 +/- 0.47-fold, P < 0.10). Quantitatively similar results were obtained with inhaled l-arginine. Remarkably, after pretreatment with ABH a 33-fold higher dose of allergen was needed to induce airway obstruction (P < 0.01). Consequently, ABH inhalation 0.5 hour before and 8 hours after allergen challenge protected against the allergen-induced early and late asthmatic reactions, AHR and inflammatory cell infiltration. CONCLUSIONS: Inhalation of ABH or l-arginine acutely reverses allergen-induced AHR after the early and late asthmatic reaction, presumably by attenuating arginase-induced substrate deficiency to NO synthase in the airways. Moreover, ABH considerably reduces the airway sensitivity to inhaled allergen and protects against allergen-induced bronchial obstructive reactions, AHR, and airway inflammation. This is the first in vivo study indicating that arginase inhibitors may have therapeutic potential in allergic asthma.

Inhalation of the Rho-kinase inhibitor Y-27632 reverses allergen-induced airway hyperresponsiveness after the early and late asthmatic reaction.

BACKGROUND: In guinea pigs, we have previously demonstrated that the contribution of Rho-kinase to airway responsiveness in vivo and ex vivo is enhanced after active sensitization with ovalbumin (OA). Using conscious, unrestrained OA-sensitized guina pigs, we now investigated the role of Rho-kinase in the development of airway hyperresponsiveness (AHR) after the allergen-induced early (EAR) and late asthmatic reaction (LAR) in vivo. METHODS: Histamine and PGF2alpha PC100-values (provocation concentrations causing 100% increase in pleural pressure) were assessed before OA-challenge (basal airway responsiveness) and after the OA-induced EAR (5 h after challenge) and LAR (23 h after challenge). Thirty minutes later, saline or the specific Rho-kinase inhibitor Y-27632 (5 mM, nebulizer concentration) were nebulized, after which PC100-values were reassessed. RESULTS: In contrast to saline, Y-27632 inhalation significantly decreased the basal responsiveness toward histamine and PGF2alpha before OA-challenge, as indicated by increased PC100 -values. Both after the allergen-induced EAR and LAR, AHR to histamine and PGF2alpha was present, which was reversed by Y-27632 inhalation. Moreover, there was an increased effectiveness of Y-27632 to reduce airway responsiveness to histamine and PGF2alpha after the EAR and LAR as compared to pre-challenge conditions. Saline inhalations did not affect histamine or PGF2alpha PC100-values at all. Interestingly, under all conditions Y-27632 was significantly more effective in reducing airway responsiveness to PGF2alpha as compared to histamine. Also, there was a clear tendency (P = 0.08) to a more pronounced degree of AHR after the EAR for PGF2alpha than for histamine. CONCLUSION: The results indicate that inhalation of the Rho-kinase inhibitor Y-27632 causes a considerable bronchoprotection to both histamine and PGF2alpha. Moreover, the results are indicative of a differential involvement of Rho-kinase in the agonist-induced airway obstruction in vivo. Increased Rho-kinase activity contributes to the allergen-induced AHR to histamine and PGF2alpha after both the EAR and the LAR, which is effectively reversed by inhalation of Y-27632. Therefore, Rho-kinase can be considered as a potential pharmacotherapeutical target in allergic asthma.

Inhibition of Rho-kinase normalizes nonspecific hyperresponsiveness in passively sensitized airway smooth muscle preparations.

Currently, little is known about mechanisms underlying passive sensitization-induced nonspecific airway hyperresponsiveness. We sought to determine whether the nonspecific airway hyperresponsiveness observed after passive sensitization involves an increased role of Rho-kinase in airway smooth muscle contraction. In addition, the contribution of Rho-kinase to specific allergen-induced airway smooth muscle contraction was studied. Guinea pig tracheal smooth muscle preparations were incubated for 16 h, in the presence of serum obtained from nonsensitized guinea pigs or atopic serum obtained from actively ovalbumin-sensitized guinea pigs. After incubation, the contribution of Rho-kinase to histamine-, methacholine- or ovalbumin-induced isometric contractions was determined, using the specific Rho-kinase inhibitor Y-27632. Maximal contractions induced by histamine and methacholine were significantly increased in passively sensitized preparations, without a change in potency (-logEC50). In control preparations, Y-27632 reduced the potency of both agonists, without affecting maximal contraction. Remarkably, the increased agonist responsiveness induced by passive sensitization was fully normalized by Y-27632. Treatment with Y-27632 also reduced ovalbumin-induced contraction in these preparations. This study shows that the nonspecific airway smooth muscle hyperresponsiveness as well as the specific allergen responsiveness induced by passive sensitization are dependent on Rho-kinase. The complete inhibition by Y-27632 of the passive sensitization-induced increased responsiveness toward histamine and methacholine indicates a pivotal role of Rho-kinase in this process.

The novel compound Sul-121 inhibits airway inflammation and hyperresponsiveness in experimental models of chronic obstructive pulmonary disease.

COPD is characterized by persistent airflow limitation, neutrophilia and oxidative stress from endogenous and exogenous insults. Current COPD therapy involving anticholinergics, ß2-adrenoceptor agonists and/or corticosteroids, do not specifically target oxidative stress, nor do they reduce chronic pulmonary inflammation and disease progression in all patients. Here, we explore the effects of Sul-121, a novel compound with anti-oxidative capacity, on hyperresponsiveness (AHR) and inflammation in experimental models of COPD. Using a guinea pig model of lipopolysaccharide (LPS)-induced neutrophilia, we demonstrated that Sul-121 inhalation dose-dependently prevented LPS-induced airway neutrophilia (up to ~60%) and AHR (up to ~90%). Non-cartilaginous airways neutrophilia was inversely correlated with blood H2S, and LPS-induced attenuation of blood H2S (~60%) was prevented by Sul-121. Concomitantly, Sul-121 prevented LPS-induced production of the oxidative stress marker, malondialdehyde by ~80%. In immortalized human airway smooth muscle (ASM) cells, Sul-121 dose-dependently prevented cigarette smoke extract-induced IL-8 release parallel with inhibition of nuclear translocation of the NF-κB subunit, p65 (each ~90%). Sul-121 also diminished cellular reactive oxygen species production in ASM cells, and inhibited nuclear translocation of the anti-oxidative response regulator, Nrf2. Our data show that Sul-121 effectively inhibits airway inflammation and AHR in experimental COPD models, prospectively through inhibition of oxidative stress.

The inhaled Rho kinase inhibitor Y-27632 protects against allergen-induced acute bronchoconstriction, airway hyperresponsiveness, and inflammation.

Recently, we have shown that allergen-induced airway hyperresponsiveness (AHR) after the early (EAR) and late (LAR) asthmatic reaction in guinea pigs could be reversed acutely by inhalation of the Rho kinase inhibitor Y-27632. The present study addresses the effects of pretreatment with inhaled Y-27632 on the severity of the allergen-induced EAR and LAR, the development of AHR after these reactions, and airway inflammation. Using permanently instrumented and unrestrained ovalbumin (OA)-sensitized guinea pigs, single OA challenge-induced EAR and LAR, expressed as area under the lung function (pleural pressure, P(pl)) time-response curve, were measured, and histamine PC(100) (provocation concentration causing a 100% increase of P(pl)) values were assessed 24 h before, and at 6 and 24 h after, the OA challenge (after the EAR and LAR, respectively). Thirty minutes before and 8 h after OA challenge, saline or Y-27632 (5 mM) was nebulized. After the last PC(100) value, bronchoalveolar lavage (BAL) was performed, and the inflammatory cell profile was determined. It was demonstrated that inhalation of Y-27632 before allergen challenge markedly reduced the immediate allergen-induced peak rise in P(pl), without significantly reducing the overall EAR and LAR. Also, pretreatment with Y-27632 considerably protected against the development of AHR after the EAR and fully prevented AHR after the LAR. These effects could not be explained by a direct effect of Y-27632 on the histamine responsiveness, because of the short duration of the acute bronchoprotection of Y-27632 (<90 min). In addition, Y-27632 reduced the number of total inflammatory cells, eosinophils, macrophages, and neutrophils recovered from the BAL. Altogether, inhaled Y-27632 protects against acute allergen-induced bronchoconstriction, development of AHR after the EAR and LAR, and airway inflammation in an established guinea pig model of allergic asthma.

A guinea pig model of acute and chronic asthma using permanently instrumented and unrestrained animals.

To investigate mechanisms underlying allergen-induced asthmatic reactions, airway hyperresponsiveness and remodeling, we have developed a guinea pig model of acute and chronic asthma using unanesthetized, unrestrained animals. To measure airway function, ovalbumin (IgE)-sensitized animals are permanently instrumented with a balloon-catheter, which is implanted inside the pleural cavity and exposed at the neck of the animal. Via an external cannula, the balloon-catheter is connected to a pressure transducer, an amplifier, an A/D converter and a computer system, enabling on-line measurement of pleural pressure (P(pl))-closely correlating with airway resistance-for prolonged periods of time. Using aerosol inhalations, the method has been successfully applied to measure ovalbumin-induced early and late asthmatic reactions and airway hyperresponsiveness. Because airway function can be monitored repeatedly, intra-individual comparisons of airway responses (e.g., to study drug effects) are feasible. Moreover, this model is suitable to investigate chronic asthma and airway remodeling, which occurs after repeated allergen challenges. The protocol for establishing this model takes about 4 weeks.