Formation of endothelin by cultured airway epithelial cells

113

1 P2-Adrenoceptor agonists may exacerbate asthma by reducing the release of the anti-proliferative and anti-inflammatory molecule, heparin from mast cells in the airway. In this study, the direct effects of the clinically used bronchodilator, salbutamol, on the proliferation of airway smooth muscle cells grown in culture and stimulated with a range of mitogens have been examined.2 In mitogen-stimulated cells, salbutamol (0.1-I00 nM) inhibited [3H]-thymidine incorporation in a concentration-dependent manner. Salbutamol (100 nM) pretreatment reduced the mitogenic responses to thrombin (0.3 u ml-1), epidermal growth factor (EGF) (300 pM) and U46619 (100 nM) by 61.7 ± 6.1%, 46.9 ± 13.9% and 57.6 ± 12.7%, respectively. However, salbutamol pretreatment did not appear to reduce the small mitogenic response to endothelin-1. 3 Increases in [3H]-leucine incorporation in thrombin (0.3 u ml-')-stimulated cells were reduced by salbutamol (100 nM) by 27.7 ± 2.8%. Similarly, thrombin (0.3 u ml`)-stimulated increases in cell number were also inhibited by salbutamol (100 nM) pretreatment. Thus, the effect of salbutamol in decreasing thrombin-induced [3H]-leucine incorporation may, at least in part, be explained by inhibition of cell proliferation. 4 The inhibition of cell proliferation by salbutamol was prevented by pretreatment with either the non-selective P-adrenoceptor antagonist, propranolol (0.3 JAM) or the selective P2-adrenoceptor antagonist, ICI 118551 (50 nM).5 These results indicate that salbutamol, through activation of a P2-adrenoceptor, has a direct inhibitory effect on proliferation elicited by the mitogens thrombin, EGF, and U46619. Thus, it seems likely that this direct inhibitory action of P2-adrenoceptor agonists would override any indirect action to accelerate airway smooth muscle proliferation. These observations lead us to suggest that R2-adrenoceptor agonists exacerbate asthma by mechanisms unrelated to airway smooth muscle proliferation.

Section: Discussionmentioning

confidence: 99%

Inhibition by salbutamol of the proliferation of human airway smooth muscle cells grown in culture

Tomlinson

Wilson

Stewart

1994

113

“…More importantly > 85% of the contractions induced by ET-1 in guinea-pig airways are mediated via ETB receptors most probably present on the airway smooth muscle. As ET-1 may be an endogenous regulator of airway tone and is secreted from tracheal and bronchial epithelial cells (Black et al, 1989;Mattoli et al, 1990), endothelins may play an active role in diseases such as asthma, bronchitis and adult respiratory distress syndrome. These airway diseases are associated with vascular remodelling, reduction of airway calibre, increased microvascular permeability, ciliary function, ion transport and mucin release which are all affected by the endothelins (Wu et al, 1990;Tamaoki et al, 1991;Plews et al, 1991;Peacock et al, 1992;Helset et al, 1993).…”

Section: Discussionmentioning

confidence: 99%

Characterization of ET_B receptors mediating contractions induced by endothelin‐1 or IRL 1620 in guinea‐pig isolated airways: effects of BQ‐123, FR139317 or PD 145065

Battistini

Warner

Fournier

et al. 1994

We have characterized the receptors mediating contractions to endothelin‐1 (ET‐1) or IRL 1620, an ETB receptor selective agonist, in isolated strips of tissue prepared from different parts of the guinea‐pig airways. We used as antagonists BQ‐123 and FR139317 (ETA receptor‐selective) and PD 145065 (ETA/ETB receptor non‐selective). ET‐1 and IRL 1620 (10−10 m to 10−6 m) caused similar concentration‐dependent contractions of strips of guinea‐pig trachea and upper bronchus. In the guinea‐pig trachea without epithelium or lung parenchyma, IRL 1620 was less potent than ET‐1. In the trachea, contraction to ET‐1 (< 10−8 m) was preceded by a transient relaxation which was inhibited by BQ‐123 (10−5 m) or FR 139317 (10−5 m) or by the removal of the epithelium. The concentration‐response curve to ET‐1 in the trachea was shifted to the right by PD 145065 (10−5 m to 10−4 m). PD 145065 (10−4 m) also inhibited the response to ET‐1 (3 × 10−7 m) by 55%. Contractions induced by IRL 1620 were not affected by BQ‐123 (10−6 m) or FR139317 (10−6 m) but were significantly attenuated by 10−5 m of either antagonist. PD 145065 at 10−6 m strongly attenuated and at 10−5 m abolished contractions induced by IRL 1620. In the trachea, removal of the epithelium potentiated the effects of both agonists. BQ‐123 (10−5 m) had no effect on contractions of the trachea without epithelium induced by ET‐1, but FR139317 (10−5 m) caused a significant inhibition. PD 145065 (10−5 m to 10−4 m) caused a shift to the right of the ET‐1 concentration‐response curve without affecting the contractile effect at 3 × 10−7 m. All three antagonists inhibited contractions induced by IRL 1620. In the upper bronchus, BQ‐123 (10−5 m) did not affect contractions induced by ET‐1, while FR139317 (10−5 m) attenuated (20–26%) only contractions induced by 1–3 × 10−7 m ET‐1. PD 145065 (10−5 m to 10−4 m) caused a shift to the right of the ET‐1 concentration‐response curve. The contractions induced by IRL 1620 were inhibited by BQ‐123 or FR139317 (10−5 m to 10−4 m). PD 145065 (10−6 m) strongly inhibited contractions induced by IRL 1620 and PD 145065 (10−5 m) totally abolished them. The contractile action of ET‐1 in the lung parenchyma was significantly and similarly attenuated by BQ‐123 (10−5 m) or indomethacin (10−5 m), while FR139317 (10−5 m) was less effective. PD 145065 (10−6 to 10−5 m) inhibited contractions to ET‐1. IRL 1620, which is less potent than ET‐1 in this preparation, was antagonized by PD 145065 (10−5 to 10−6 m) but unaffected by BQ‐123 (10−6 m to 10−5 m) or FR139317 (10−6 m). Thus, ETB receptors mediate contractions to ET‐1 in all four guinea‐pig airway preparations. In addition, contractions to ET‐1 in the trachea and lung parenchyma are mediated in part by ETA receptors. In the latter tissue, these ETA receptors mediate contraction through the release of cyclo‐oxygenase metabolites. Similarly, ETA receptors located on the epithelial cells also mediate the release of prostanoids in the trachea with epithelium but they are responsible for transient relaxations. Intere...

“…Recently, the release of ET-1 by cultured tracheal epithelial cells has also been reported (Black et al, 1989). Its production in the vicinity of airway smooth muscle suggests that ET-1 could affect adjacent local airway tone.…”

Section: Introductionmentioning

confidence: 94%

Pharmacological modulation of endothelin‐induced contraction of guinea‐pig isolated airways and thromboxane release

Filep

Battistini

Sirois

1991

1The aim of the present experiments was to study the possible involvement of known bronchoconstrictor substances in mediating the myotropic action of endothelin-l (ET-1, human-porcine endothelin) in guinea-pig isolated airways. 2 ET-1 (1-100nm) caused a dose-dependent contraction of guinea-pig trachea, upper bronchus and parenchyma. The contractions developed slowly, reaching maximal values 4-6 min after addition of the peptide. 3 The contractile action of ET-1 was significantly attenuated by indomethacin (10uM), a cyclo-oxygenase blocker, BM 13505 (5,UM), a thromboxane receptor antagonist, FPL 55712 (19 pM) and YM 16638 (1pM), antagonists of the sulphidopeptide leukotrienes, BN 52021 (10pM) and WEB 2086 (1 pM), plateletactivating factor receptor antagonists in all three tissue preparations studied.4 Pretreatment of the airway tissues with compound U 75302 (3 guM), a selective leukotriene B4 receptor antagonist, or with a mixture of antagonists containing methysergide (0.75,UM), phentolamine (0.4UM), propranolol (13juM), atropine (0.4 pM) and diphenhydramine (0.45 pM) did not modify the myotropic action of ET-1. 5 ET-1, 10 and lOOnM induced three, and nine fold increases in thromboxane A2 release from lung parenchymal strips. 6 ET-1-induced thromboxane A2 release was completely abolished by indomethacin, and was significantly attenuated by BN 52021, WEB 2086 and FPL 55712. Neither BM 13505 nor YM 16638 exerted a significant effect on thromboxane release. 7 The present findings show that contraction of guinea-pig airway smooth muscle by ET-1 is mediated, in part, by the release of thromboxane A2, sulphidopeptide leukotrienes and platelet-activating factor, and suggest that the increased thromboxane A2 release following ET-1 is partly a consequence of enhanced synthesis of sulphidopeptide leukotrienes and platelet-activating factor.