bq-123 and Asthma

In this study, we investigated the effects of the selective ET(A) (BQ-123) and ET(B) (BQ-788) receptor antagonists for endothelin-1 (ET-1) against several flogistic agent-induced paw edema formation and ovalbumin-induced allergic lung inflammation in mice. The intraplantar injection of BQ-123, but not BQ-788, significantly inhibited carrageenan-, PAF-, ET-1- and bradykinin-induced paw edema formation. The obtained inhibitions (1h after the inflammatory stimulus) were 79+/-5%, 55+/-4%, 55+/-6% and 74+/-4%, respectively. In carrageenan-induced paw edema, the mean ID(50) value for BQ-123 was 0.77 (0.27-2.23)nmol/paw. The neutrophil influx induced by carrageenan or PAF was reduced by BQ-123, with inhibitions of 55+/-2% and 72+/-4%, respectively. BQ-123 also inhibited the indirect macrophage influx induced by carrageenan (55+/-6%). However, BQ-788 failed to block the cell influx caused by either of these flogistic agents. When assessed in the bronchoalveolar lavage fluid in a murine model of asthma, both BQ-123 and BQ-788 significantly inhibited ovalbumin-induced eosinophil recruitment (78+/-6% and 71+/-8%), respectively. Neither neutrophil nor mononuclear cell counts were significantly affected by these drugs. Our findings indicate that ET(A), but not ET(B), selective ET-1 antagonists are capable of preventing the acute inflammatory responses induced by carrageenan, PAF, BK and ET-1. However, both ET(A) and ET(B) receptor antagonists were found to be effective in inhibiting the allergic response in a murine model of asthma.

Topics: Animals; Anti-Allergic Agents; Antihypertensive Agents; Asthma; Disease Models, Animal; Endothelin A Receptor Antagonists; Endothelin B Receptor Antagonists; Female; Inflammation; Male; Mice; Mice, Inbred BALB C; Oligopeptides; Peptides, Cyclic; Piperidines

Levels of endothelins are particularly high in the lung, and there is evidence that these peptides are involved in asthma. Asthma is a chronic inflammatory disease associated with lymphocyte infiltration. In the present study, we used a murine model of asthma to investigate the role of endothelins in lymphocyte and eosinophil infiltration into the airway hyperreactivity and mucus secretion. Sensitized C57Bl/6 mice were treated with endothelin ETA receptor antagonist (BQ123) or endothelin ETB receptor antagonist (BQ788) 30 min before an antigen aerosol challenge. After 24 h, dose response curves to methacholine were performed in isolated lungs, FACS analysis of lymphocytes and eosinophil counts were performed in bronchoalveolar lavage fluid and mucus index was determined by histopathology. In sensitized and antigen-challenged mice there is a marked increase in the T CD4+, T CD8+, B220+, Tgammadelta+ and NK1.1+ lymphocyte subsets. Treatment with BQ123 further increased these cell populations. The number of eosinophils, airway hyperreactivity and mucus were all reduced by BQ123 treatment. The BQ 788 had no significant effect on the parameters analyzed. Treatment with BQ123 reduced the endothelin concentration in lung homogenates, suggesting that endothelins exert a positive feedback on their synthesis. We show here that in murine asthma the ETA receptor antagonist up-regulates lymphocyte infiltration and reduces eosinophils, hyperreactivity and mucus.

Topics: Animals; Asthma; Bronchial Hyperreactivity; Bronchoalveolar Lavage Fluid; Disease Models, Animal; Endothelin A Receptor Antagonists; Eosinophils; Lung; Lymphocyte Subsets; Male; Methacholine Chloride; Mice; Mice, Inbred C57BL; Mucus; Ovalbumin; Peptides, Cyclic

To address the possible role of injured airway epithelium in initiating transdifferentiation of sub-epithelial fibroblasts into myofibroblasts and accelerating cell proliferation in sub-epithelial fibroblasts, which may be involved in airway hyperresponsiveness in asthma.. Human primary cultured sub-epithelial fibroblasts were co-cultured with human bronchial epithelial cells (16HBE) which were treated with lipopolysaccharide (LPS) plus mechanical scratch prior to co-culture. The procedure was also performed in the presence or absence of endothelin (ET) receptor A inhibitor (BQ123), transforming growth factor-beta(1) (TGF-beta(1)) neutralized antibody, respectively or simultaneously, followed by immunostaining, Western blotting and bromodeoxyuridine (BrdU) incorporation respectively to detect alpha-SMA expression and cell proliferation in the co-cultured sub-epithelial fibroblasts. Using the inhibitors specific for mitogen-activated protein kinases (MAPKs) pathways, the role of MAPKs pathways in activating the expression of alpha-SMA was evaluated. In addition, the interaction between matrix metalloproteinases (MMPs) and ET-1 was investigated by cell transfection with anti-ET-1 converting enzyme (anti-ECE) mRNA expression plasmid followed by gelatin zymography analysis.. 16HBE treated with LPS plus mechanical injury induced alpha-SMA expression in sub-epithelial fibroblasts and accelerated BrdU incorporation in the cells. BQ123, TGF-beta(1) neutralized antibody, specific inhibitors for p38 MAPK and extracellular signal-regulated kinase 1/2 (ERK1/2) were able to block the induction respectively to a certain extent. Phosphorylated p38 MAPK and ERK1/2 were detected in the sub-epithelial fibroblasts 10 min after being co-cultured with injured 16HBE. Compared to normal control (16HBE transfected with pEGFPN(2)) or those cells transfected with anti-ECE mRNA expression plasmids, ET-1 released from the 16HBE cells transfected with pEGFPN(2) into supernatants were increased significantly after the treatment described as above: 16HBE pre-transfected with pEGFP-N(2) expression plasmid before being treated with mechanical scrape plus LPS stimulation: (15.00 +/- 0.86) pg/ml; 16HBE pre-transfected with anti-ECE expression plasmid before being treated with mechanical scrape plus LPS stimulation: (7.57 +/- 0.94) pg/ml (all P < 0.01). At the same time, the activities of MMP-2 and MMP-9 were enhanced.. Injured airway epithelial cells induced the transdifferentiation of sub-epithelial fibroblasts into myofibroblasts, which may be mediated by ET-1 and TGF-beta(1) through MARKs pathways such as p38 MAPK and ERK 1/2.

Topics: Actins; Asthma; Cell Differentiation; Cell Line, Transformed; Cell Proliferation; Cell Transdifferentiation; Coculture Techniques; Endothelin-1; Epithelial Cells; Fibroblasts; Humans; Lipopolysaccharides; Mitogen-Activated Protein Kinase 3; p38 Mitogen-Activated Protein Kinases; Peptides, Cyclic; Phosphorylation; Protein Kinase Inhibitors; Respiratory Mucosa; Transfection; Transforming Growth Factor beta1

An increasing number of studies have been performed to address a possible role for endothelin-1 (ET-1) as a significant mediator in asthma. However, the effects of subthreshold concentrations of ET-1, which cannot elicit bronchial smooth muscle contraction itself, in asthma has yet to be determined. This study determined these effects of ET-1 on capsaicin-induced bronchoconstriction in anaesthetized guinea-pigs. Aerosolized ET-1 administered at doses of 10(-9) M and higher induced a dose-dependent increase in pulmonary resistance, but ET-1 at 10(-10) M did not have any bronchoconstrictive effect. However, this subthreshold concentration of ET-1 potentiated capsaicin-induced bronchoconstriction. In addition, the potentiation of capsaicin-induced bronchoconstriction by this subthreshold concentration of ET-1 was completely abolished by BQ788 (ET(B) receptor antagonist), but not BQ123 (ET(A) receptor antagonists). Immunoreactive substance P (SP) levels in bronchoalveolar lavage fluid after capsaicin administration were significantly higher than those after solvent administration. However, ET-1 alone did not significantly stimulate immunoreactive SP release and ET-1 (10(-10) M) did not potentiate capsaicin-induced immunoreactive SP release. In contrast, ET-1 (10(-10) M) potentiated exogenous neurokinin A- and SP-induced bronchoconstriction. These findings suggest that a subthreshold concentration of endothelin-1 does not potentiate the tachykinin release induced by capsaicin but the airway smooth muscle contraction through endothelin-B receptors.

Topics: Aerosols; Airway Resistance; Anesthesia; Animals; Asthma; Bronchoalveolar Lavage Fluid; Bronchoconstriction; Capsaicin; Dose-Response Relationship, Drug; Endothelin Receptor Antagonists; Endothelin-1; Guinea Pigs; Male; Neurokinin A; Oligopeptides; Peptides, Cyclic; Piperidines; Substance P

To explore the pathophysiological roles of endothelin isopeptides and receptor subtypes in asthmatic responses, a guinea pig model for asthma was used to test the effects of antiendothelin (ET) serum and selective ET receptor antagonists for antigen-induced specific airway conductance changes as measured by whole-body plethysmography. In this model, all of the animals so far tested demonstrated both the immediate and late asthmatic responses. Although preimmune serum had no apparent effects, anti-ET antiserum suppressed the maximal reduction of specific airway conductance in both the immediate and late asthmatic responses, which suggested that ET(s) are involved in the pathophysiology of both the immediate and late asthmatic responses. The ETB selective antagonists, BQ788 and RES701-1, blocked the immediate asthmatic response but not the late asthmatic response, whereas the ETA antagonists, BQ123 and (Shionogi) 97-139, suppressed only the late asthmatic response without influencing the immediate asthmatic response. In vitro constrictive responses of isolated tracheas and bronchi to ET1 were inhibited mainly by BQ123 and BQ788, respectively, which suggested that distribution of ETA and ETB receptors for bronchoconstriction are topographically distinct along airways. Furthermore, thromboxane A2 and platelet activating factor (PAF) antagonists were effective in suppressing the late asthmatic response but not the immediate asthmatic response. Taken together, our present observations suggest that ET(s) influences pulmonary functions by constricting airway smooth muscle via ETB receptors during the immediate asthmatic response and by modulating pulmonary inflammation via ETA receptors during the late asthmatic response, respectively.

Topics: Analysis of Variance; Animals; Asthma; Dose-Response Relationship, Drug; Endothelins; Female; Guinea Pigs; Oligopeptides; Peptides, Cyclic; Piperidines; Time Factors; Trachea

[125I]-endothelin-1 ([125I]-ET-1) binding was assessed by autoradiography in peripheral airway smooth muscle and alveolar wall tissue in human non-asthmatic and asthmatic peripheral lung. Levels of specific binding to these structures were similar in both non-asthmatic and asthmatic lung. The use of the receptor subtype-selective ligands, BQ-123 (ETA) and sarafotoxin S6c (ETB), demonstrated the existence of both ETA and ETB sites in airway smooth muscle and in alveoli. In airway smooth muscle from both sources, the great majority of sites were of the ETB subtype. Quantitative analyses of asthmatic and non-asthmatic alveolar wall tissue demonstrated that 29-32% of specific [125I]-ET-1 binding was to ETA sites and 68-71% was to ETB sites. Thus, asthma was not associated with any significant alteration in the densities of ETA and ETB receptors in peripheral human lung.

Topics: Adolescent; Adult; Asthma; Autoradiography; Endothelin Receptor Antagonists; Female; Humans; Lung; Male; Peptides, Cyclic; Receptors, Endothelin