Dose response of inhaled gallopamil (D600), a calcium channel blocker, in attenuating airway reactivity to methacholine and exercise

Pharmacological ablation of the airway smooth muscle layer-Mathematical predictions of functional improvement in asthma

Airway smooth muscle (ASM) plays a major role in acute airway narrowing and reducing ASM thickness is expected to attenuate airway hyper‐responsiveness and disease burden. There are two therapeutic approaches to reduce ASM thickness: (a) a direct approach, targeting specific airways, best exemplified by bronchial thermoplasty (BT), which delivers radiofrequency energy to the airway via bronchoscope; and (b) a pharmacological approach, targeting airways more broadly. An example of the less well‐established pharmacological approach is the calcium‐channel blocker gallopamil which in a clinical trial effectively reduced ASM thickness; other agents may act similarly. In view of established anti‐proliferative properties of the macrolide antibiotic azithromycin, we examined its effects in naive mice and report a reduction in ASM thickness of 29% (p < .01). We further considered the potential functional implications of this finding, if it were to extend to humans, by way of a mathematical model of lung function in asthmatic patients which has previously been used to understand the mechanistic action of BT. Predictions show that pharmacological reduction of ASM in all airways of this magnitude would reduce ventilation heterogeneity in asthma, and produce a therapeutic benefit similar to BT. Moreover there are differences in the expected response depending on disease severity, with the pharmacological approach exceeding the benefits provided by BT in more severe disease. Findings provide further proof of concept that pharmacological targeting of ASM thickness will be beneficial and may be facilitated by azithromycin, revealing a new mode of action of an existing agent in respiratory medicine.

Calcium channel blockers for lung function improvement in asthma: A systematic review and meta-analysis

BACKGROUND

For decades, calcium channel blockers (CCBs) have been believed to play a role in asthma treatment. However, the clinical efficacy of CCBs for lung function improvement in patients with asthma has not been qualitatively evaluated.

OBJECTIVE

To assess the effect of CCBs vs placebo on lung function test results in adults with asthma.

METHODS

Various databases were systematically searched to identify all randomized clinical trials with adults with asthma. We aimed to assess the influence of CCBs on forced expiratory volume in 1 second (FEV₁), forced vital capacity (FVC), peak expiratory flow rate (PEFR), and provocative concentration of bronchoconstrictive agents causing a 20% decrease in FEV₁ (PC₂₀) compared with a placebo. All effect estimates were pooled by the generic inverse variance method with random-effects meta-analysis. Subgroup analysis, sensitivity analysis, and heterogeneity investigation were performed.

RESULTS

Thirty eligible articles with 301 patients were included in this meta-analysis. Our results revealed that in a standard exercise test CCBs could produce a mean maximal percentage decrease in FEV₁ of 11.56% (95% confidence interval, 8.97%-14.16%; P < .001) and an increase in postdose FEV₁ by 80 mL (95% confidence interval, 0.02-0.15 mL; P = .01). However, there was no statistical significance for CCBs in postdose FVC, PEFR, or PC₂₀ of histamine and methacholine.

CONCLUSION

CCBs may be beneficial for lung function improvement in asthma, especially in exercise-induced asthma. However, there is a lack of evidence for CCBs protecting asthma patients from chemical irritation.

Airway remodeling in asthma: new mechanisms and potential for pharmacological intervention

The chronic inflammatory response within the airways of asthmatics is associated with structural changes termed airway remodeling. This remodeling process is a key feature of severe asthma. The 5-10% of patients with a severe form of the disease account for the higher morbidity and health costs related to asthma. Among the histopathological characteristics of airway remodeling, recent reports indicate that the increased mass of airway smooth muscle (ASM) plays a critical role. ASM cell proliferation in severe asthma implicates a gallopamil-sensitive calcium influx and the activation of calcium-calmodulin kinase IV leading to enhanced mitochondrial biogenesis through the activation of various transcription factors (PGC-1α, NRF-1 and mt-TFA). The altered expression and function of sarco/endoplasmic reticulum Ca(2+) pump could play a role in ASM remodeling in moderate to severe asthma. Additionally, aberrant communication between an injured airway epithelium and ASM could also contribute to disease severity. Airway remodeling is insensitive to corticosteroids and anti-leukotrienes whereas the effect of monoclonal antibodies (the anti-IgE omalizumab, the anti-interleukin-5 mepolizumab or anti-tumor necrosis factor-alpha) remains to be investigated. This review focuses on potential new therapeutic strategies targeting ASM cells, especially Ca(2+) and mitochondria-dependent pathways.

Bronchial smooth muscle remodeling involves calcium-dependent enhanced mitochondrial biogenesis in asthma

Asthma and chronic obstructive pulmonary disease (COPD) are characterized by different patterns of airway remodeling, which all include an increased mass of bronchial smooth muscle (BSM). A remaining major question concerns the mechanisms underlying such a remodeling of BSM. Because mitochondria play a major role in both cell proliferation and apoptosis, we hypothesized that mitochondrial activation in BSM could play a role in this remodeling. We describe that both the mitochondrial mass and oxygen consumption were higher in the BSM from asthmatic subjects than in that from both COPD and controls. This feature, which is specific to asthma, was related to an enhanced mitochondrial biogenesis through up-regulation of peroxisome proliferator-activated receptor gamma coactivator (PGC)-1alpha, nuclear respiratory factor-1, and mitochondrial transcription factor A. The priming event of such activation was an alteration in BSM calcium homeostasis. BSM cell apoptosis was not different in the three groups of subjects. Asthmatic BSM was, however, characterized by increased cell growth and proliferation. Both characteristics were completely abrogated in mitochondria-deficient asthmatic BSM cells. Conversely, in both COPD and control BSM cells, induction of mitochondrial biogenesis reproduced these characteristics. Thus, BSM in asthmatic patients is characterized by an altered calcium homeostasis that increases mitochondrial biogenesis, which, in turn, enhances cell proliferation, leading to airway remodeling.

Efficacy of calcium channel blockers as maintenance therapy for asthma

AIMS

Previous bronchoprovocation studies indicate that nifedipine attenuates airway responsiveness to several stimuli whereas diltiazem has no effect. The aim of this study was to determine whether such studies predict the efficacy of calcium channel blockers as maintenance therapy for persistent asthma.

METHODS

Twenty-one otherwise healthy adults with persistent asthma, mean age 25 years, completed treatment with maximum tolerated doses of placebo (P), nifedipine (N), and diltiazem (D) in a double-blind, randomized, three-treatment, three-period, crossover manner, each for 4 weeks. Frequency and severity of asthmatic symptoms were recorded twice daily, as well as peak expiratory flow and frequency of 'prn' use of inhaled terbutaline. Blood pressure, heart rate, P-R interval of the ECG and spirometry were measured biweekly. At the end of each treatment, airway responsiveness to exercise was measured.

RESULTS

The mean (s.e. mean)% of days with wheeze was 69plus minus7% during P, 75plus minus6% during N and 72plus minus6% during D (P=0.7). FEV1 was 79plus minus2% of predicted during P, 81plus minus2% during N and 79plus minus2% during D (P=0.6). The decrease in FEV1 after exercise was 32plus minus4% during P, 32plus minus5% during N and 27plus minus4% during D (P=0.5). Heart rate was elevated during N (P=0.0002) whereas P-R interval was prolonged during D (P=0.0001).

CONCLUSIONS

Maintenance therapy with calcium channel blockers, at doses that produce cardiovascular effects, do not suppress the signs and symptoms of persistent asthma. Previous bronchoprovocation studies did not predict these results.

Relative amount of albuterol delivered to lung receptors from a metered-dose inhaler and nebulizer solution. Bioassay by histamine bronchoprovocation

The results of previous studies comparing bronchodilatation from beta agonists administered by metered-dose inhaler (MDI) and nebulizer solution have been conflicting. We therefore evaluated a range of albuterol doses administered by these two methods, using histamine bronchoprovocation as a bioassay for the amount of drug reaching the beta 2 receptors in the lung. Twelve stable asthmatic volunteers received, in a double-blind, randomized, crossover design on different days, placebo or one, two, four, or six puffs from an MDI attached to an InspirEase device (90 micrograms per puff) or 0.625, 1.25, 2.5, or 5.0 mg of solution delivered in 2 ml of buffered saline through a Hudson Updraft II nebulizer. The histamine concentration required to decrease FEV1 by 20 percent (PC20) was measured 1 h before and 30 min after administration of each treatment and expressed as the increase in PC20 from baseline. The dose-response curves for change in PC20 indicated that the higher doses of the nebulizer solution delivered more drug to beta 2 receptors in the lung than the lower doses from the MDI. For example, the geometric mean increase in PC20 was 1.1 +/- 1.6 (SD) after placebo, 7.5 +/- 2.7 after two puffs from the MDI, and 20.0 +/- 2.1 after 2.5 mg of nebulizer solution (p less than 0.05). Using this bioassay method and administration technique, we estimated that ten puffs from the MDI (0.9 mg) would deliver approximately the same amount of albuterol to lung receptors as 2.5 mg of the nebulizer solution. Taking into account previously published reports and the results of the present study, we conclude that differences in dose, administration technique, nebulizer system efficiency, and severity of airway obstruction can alter the amount of drug reaching the beta 2 receptors in the lungs and, thus, the clinical response.

Inhaled verapamil-induced bronchoconstriction in mild asthma

Methacholine challenges were performed in ten subjects with mild asthma at 2 h before and 20 min after placebo or 5, 10, 20, 40, 80, and 160 mg of inhaled verapamil given in a single-blind randomized crossover manner on different days. While verapamil did not have a bronchodilator effect, the 10-mg dose modestly increased the concentration of methacholine required to decrease FEV1 by 20 percent (PC20). The mean (+/- SEM) increase in PC20 from baseline was 2.1 +/- 0.2 times baseline after 10 mg of verapamil, compared to 1.1 +/- 0.1 times baseline after placebo (p less than 0.001). Unexpectedly, bronchoconstriction (greater than 10 percent decrease in FEV1) associated with cough or wheezing was observed in seven of ten subjects at doses of 20 mg or more. This adverse effect was not related to the osmolarity of the nebulized solutions. Thirty minutes before a standardized exercise challenge, 13 subjects inhaled placebo, 10 mg, or the highest dose of verapamil tolerated during the methacholine study (20 to 160 mg) in a double-blind randomized crossover manner. The exercise challenge was aborted in three subjects because of bronchospasm that occurred after administration of the higher dose. The mean (+/- SEM) maximum change in FEV1 after exercise in the ten subjects completing all three regimens of treatment was -17.1 +/- 4.0 percent after placebo, -12.7 +/- 4.3 percent after 10 mg (p less than 0.05), and -6.4 +/- 3.6 percent after the highest dose (p less than 0.05). We conclude that increasing the dose of verapamil above 10 mg did not provide greater benefit but, paradoxically, induced bronchoconstriction in most of the subjects. Because of this potential bronchoconstrictor effect, high doses of oral or intravenous verapamil should be used with caution in asthmatic subjects.

Duration of protection of calcium channel blockers against exercise-induced bronchospasm: comparison of oral diltiazem and inhaled gallopamil

The present study was conducted to determine the duration of the positive effect of oral diltiazem and inhaled gallopamil in mild asthmatic volunteers, ages 18-37 years, with a history of exercise-induced asthma and a 25-56% decrease in FEV1 after a standardized exercise challenge. Oral diltiazem 120 mg, inhaled gallopamil 10 mg, and placebo were administered in a double blind, randomized, crossover manner on different days 48 h apart. Diltiazem was administered 90 min and gallopamil 30 min before the first exercise challenge. Challenges were then repeated 3 and 6 h later. Neither diltiazem nor gallopamil significantly altered baseline FVC, FEV1, or FEF25-75. The mean maximum decrease in FEV1 after the first challenge was 16.8% after gallopamil, 25.2% after diltiazem and 30.1% after placebo. The mean post-exercise decrease in FEV1 after gallopamil was significantly smaller than after placebo. There were no significant differences in the post-exercise decreases in FEV1 between the three treatment regimens 3 and 6 h later. Thus, inhaled gallopamil provided significant protection against exercise-induced bronchospasm, but the beneficial effect was modest and short in duration.