Bronchoconstrictive responses to inhaled ultrasonically nebulized distilled water and airway inflammation in asthma

Pharmaceutical treatment of asthma symptoms in elite athletes - doping or therapy?

Asthma, exercise-induced bronchoconstriction, and airway hyper-responsiveness are often found in elite athletes, perhaps as a consequence of their sport or maybe because asthma is a common disorder in young adults. Inhaled beta2-agonists (IBA) are frequently used in elite athletes, but due to regulations introduced by the International Olympic Committee, the use of anti-asthmatic therapy might change. Drugs that make ergogenic effect persist are prohibited in all athletes, whether or not they take part in competitions and systemic steroids and beta2-agonists are among such drugs. On the other hand, opinion is more divided about the use of inhaled corticosteroids (ICS) and IBA. In humans, no effect has been found on the oxygen uptake, performance or distance run with therapeutic doses of IBA, either in asthmatics or non-asthmatics, whereas others report an ergogenic effect and better lung function of high doses of a beta2-agonist in non-asthmatics. Anti-asthmatic treatment is necessary for asthmatics, but should not be used by non-asthmatic elite athletes due to both possible systemic effects and furthermore, side effects of both ICS and IBA.

A partial involvement of histamine in ultrasonically nebulized distilled water-induced bronchoconstriction in guinea-pigs

1. Inhalation of ultrasonically nebulized distilled water (UNDW) can induce bronchoconstriction only in asthmatics, but mechanisms of the response are not well known. We recently reported a guinea-pig model of UNDW-induced bronchoconstriction (UNDW-IB) in which UNDW induces bronchoconstriction when UNDW is inhaled 20 min after a challenge with aerosolized ovalbumin (OA) in passively sensitized, anaesthetized and artificially ventilated guinea-pigs. 2. To elucidate the role of histamine in the UNDW-IB, we examined the effects of antihistamines, diphenhydramine hydrochloride (DH) and chlorpheniramine maleate (CP), and measured histamine content in bronchoalveolar lavage fluid (BALF) in the animal model. 3. DH in doses of 0.1, 1.0 and 10 mg kg(-1) and CP in doses of 0.01, 0.1 and 1.0 mg kg(-1) administered intravenously 15 min after the OA challenge partially reduced the UNDW-IB at 1 and 2 min after the UNDW inhalation in a dose-dependent manner. Histamine content in BALF recovered 10 min after the UNDW inhalation following the OA provocation was significantly increased compared with that after saline inhalation and before the UNDW inhalation following the OA challenge. 4. Intravenous atropine in a dose of 0.5 mg kg(-1) or inhaled disodium cromoglycate in concentrations of 1 and 10 mg ml(-1) did not alter the UNDW-IB. 5. These results suggest that histamine is involved in part in the UNDW-IB in our animal model.

Bronchial hyperresponsiveness in lung transplant recipients: lack of correlation with airway inflammation

BACKGROUND

Bronchial hyperresponsiveness (BHR) to methacholine has been reported to occur in most lung transplant recipients. BHR to physical stimuli such as exercise and non-isotonic aerosols has not been as extensively studied in this subject population. This report aims to assess the presence and degree of BHR to methacholine and hypertonic saline in stable lung transplant recipients and to relate it to the presence of airway inflammation.

METHODS

Ten patients undergoing bilateral sequential lung transplantation and six heart-lung transplant recipients, all with stable lung function, were recruited 66-1167 days following transplantation. Subjects underwent a methacholine challenge and bronchoscopy for sampling of bronchoalveolar lavage fluid, transbronchial and endobronchial biopsy tissues. Hypertonic saline challenge was performed six days later.

RESULTS

Nine of the 16 transplant recipients had positive methacholine challenges (geometric mean PD20 0.18 mg, interquartile range 0.058-0.509) and three of these subjects also had positive hypertonic saline challenges (PD15 = 2.3, 33.0, and 51.5 ml). No clear relationship was found between BHR to either methacholine or hypertonic saline and levels of mast cells, eosinophils or lymphocytes in samples of biopsy tissue or lavage fluid.

CONCLUSIONS

Most of the lung transplant recipients studied were responsive to methacholine and unresponsive to hypertonic saline. BHR was not clearly related to airway inflammation, suggesting an alternative mechanism for BHR following lung transplantation from that usually assumed in asthma.

Necessity of dual blockade of endothelin ETA and ETB receptor subtypes for antagonism of endothelin-1-induced contraction in human bronchi

1. Endothelin (ET)-1 has been postulated to be involved in the development of obstructive airway diseases in man. In the present study, we attempted to characterize ET receptor subtypes mediating ET-1-induced contraction in human isolated bronchi. The ET receptor antagonists used in the present study were BQ-123 (ETA receptor-selective), BQ-788 (ETB receptor-selective) and BQ-928 (ETA/ETB dual). Sarafotoxin S6c (S6c) was also used as an ETB receptor-selective agonist. 2. In human bronchi, ET-1 and S6c (10(-12)M to 10(-7) M) produced concentration-dependent contraction with almost equal potency (pD2: 8.88 +/- 0.16 for ET-1 and 9.42 +/- 0.15 for S6c). The contraction induced by S6c was competitively antagonized by BQ-788 alone (1 and 10 microM) with a pKB value of 7.49 +/- 0.21, suggesting that the stimulation of ETB receptors causes a contraction of human bronchi. However, contrary to expectation, the concentration-response curves for ET-1 were not affected by BQ-788. The ET-1- and S6c-induced contractions were not affected by BQ-123 (10 microM). Thus, ET-1-induced contraction of human bronchi is not antagonized by BQ-123 alone or by BQ-788 alone. 3. Combined treatment with 10 microM BQ-123 and 10 microM BQ-788 significantly antagonized the contraction induced by ET-1 with a dose-ratio of 11. BQ-928 also significantly antagonized ET-1-induced contraction with a pKB value of 6.32 +/- 0.24. 4. The specific binding of [125I]-ET-1 to human bronchial membrane preparations was inhibited by BQ-123 (100 pM to 1 microM) by approximately 40%. Combination treatment with BQ-788 (100 pM to 1 microM) completely inhibited the BQ-123-resistant component of [125I]-ET-1 specific binding. 5. In conclusion, the present study demonstrates that BQ-788 alone cannot inhibit ET-1-induced contractions in human bronchi, although human bronchial ETB receptors are BQ-788-sensitive. Furthermore, it was shown that blockade of both receptor subtypes antagonizes ET-1-induced contraction, and that both receptor subtypes co-exist in human bronchial smooth muscles. These findings suggest that ETA receptors as well as ETB receptors are involved in ET-1-induced contraction in human bronchi. If ET-1 is involved in human airway diseases, dual blockade of ETA and ETB receptors may be necessary to treat the diseases.

Constitutive expression of endothelin in bronchial epithelial cells of patients with symptomatic and asymptomatic asthma and modulation by histamine and interleukin-1

BACKGROUND

An upregulation of endothelin-1 expression occurs in bronchial epithelial cells of asthmatic patients. This peptide may mediate bronchoconstriction in asthma, but the mechanisms that modulate endothelin-I synthesis and release are unknown.

OBJECTIVE

This study was done to compare the pattern of endothelin-1 expression in patients with symptomatic and asymptomatic asthma and evaluate the ability of inflammatory factors to upregulate endothelin-1 synthesis and release in the epithelial cells of subjects who are free of symptoms.

METHODS

Two groups of 10 asthmatic patients were selected. One group had symptomatic asthma with airflow obstruction and moderately to severely increased airway responsiveness. The second group was free of symptoms: they did not show airflow obstruction, and airway responsiveness was borderline or slightly increased. Bronchial biopsy specimens were obtained by means of bronchoscopy and used for immunohistochemical evaluation, epithelial cell isolation, and stimulation experiments with interleukin-1 and histamine.

RESULTS

Endothelin-1 immunoreactivity was detected in vivo in the bronchial epithelial cells of all the patients with symptoms and in only two subjects without current symptoms. Incubation of bronchial epithelial cells from patients with asymptomatic asthma with interleukin-1 or histamine, for 8 to 24 hours, resulted in increased expression of endothelin-1 messenger RNA and release of appreciable amounts of the peptide to the culture medium. Those effects were dose- and time-dependent. Histamine and interleukin-1 were effective at concentrations similar to those detected in the bronchoalveolar lavage of patients with symptomatic asthma.

CONCLUSION

Endothelin-expression is upregulated in bronchial epithelial cells of asthmatic patients with symptoms and evidence of functional derangement as compared with patients without symptoms and airflow obstruction. Exposure of cells from patients with asymptomatic asthma to factors that are released during acute exacerbation of the disease induces endothelin synthesis and release.