Long-acting beta(2)-agonists in the management of asthma exacerbations

Exchange protein directly activated by cAMP (Epac) protects against airway inflammation and airway remodeling in asthmatic mice

Background

β₂ receptor agonists induce airway smooth muscle relaxation by increasing intracellular cAMP production. PKA is the traditional downstream signaling pathway of cAMP. Exchange protein directly activated by cAMP (Epac) was identified as another important signaling molecule of cAMP recently. The role of Epac in asthmatic airway inflammation and airway remodeling is unclear.

Methods

We established OVA-sensitized and -challenged acute and chronic asthma mice models to explore the expression of Epac at first. Then, airway inflammation and airway hyperresponsiveness in acute asthma mice model and airway remodeling in chronic asthma mice model were observed respectively after treatment with Epac-selective cAMP analogue 8-pCPT-2′-O-Me-cAMP (8pCPT) and Epac inhibitor ESI-09. Next, the effects of 8pCPT and ESI-09 on the proliferation and apoptosis of in vitro cultured mouse airway smooth muscle cells (ASMCs) were detected with CCK-8 assays and Annexin-V staining. Lastly, the effects of 8pCPT and ESI-09 on store-operated Ca²⁺ entry (SOCE) of ASMCs were examined by confocal Ca²⁺ fluorescence measurement.

Results

We found that in lung tissues of acute and chronic asthma mice models, both mRNA and protein expression of Epac1 and Epac2, two isoforms of Epac, were lower than that of control mice. In acute asthma mice model, the airway inflammatory cell infiltration, Th2 cytokines secretion and airway hyperresponsiveness were significantly attenuated by 8pCPT and aggravated by ESI-09. In chronic asthma mice model, 8pCPT decreased airway inflammatory cell infiltration and airway remodeling indexes such as collagen deposition and airway smooth muscle cell proliferation, while ESI-09 increased airway inflammation and airway remodeling. In vitro cultured mice ASMCs, 8pCPT dose-dependently inhibited, whereas ESI-09 promoted ASMCs proliferation. Interestingly, 8pCPT promoted the apoptosis of ASMCs, whereas ESI-09 had no effect on ASMCs apoptosis. Lastly, confocal Ca²⁺ fluorescence examination found that 8pCPT could inhibit SOCE in ASMCs at 100 μM, and ESI-09 promoted SOCE of ASMCs at 10 μM and 100 μM. In addition, the promoting effect of ESI-09 on ASMCs proliferation was inhibited by store-operated Ca²⁺ channel blocker, SKF-96365.

Conclusions

Our results suggest that Epac has a protecting effect on asthmatic airway inflammation and airway remodeling, and Epac reduces ASMCs proliferation by inhibiting SOCE in part.

Biophysical fragment screening of the β1-adrenergic receptor: identification of high affinity arylpiperazine leads using structure-based drug design

Biophysical fragment screening of a thermostabilized β1-adrenergic receptor (β1AR) using surface plasmon resonance (SPR) enabled the identification of moderate affinity, high ligand efficiency (LE) arylpiperazine hits 7 and 8. Subsequent hit to lead follow-up confirmed the activity of the chemotype, and a structure-based design approach using protein-ligand crystal structures of the β1AR resulted in the identification of several fragments that bound with higher affinity, including indole 19 and quinoline 20. In the first example of GPCR crystallography with ligands derived from fragment screening, structures of the stabilized β1AR complexed with 19 and 20 were determined at resolutions of 2.8 and 2.7 Å, respectively.

A comparative study of efficacy and safety of arformoterol and salbutamol nebulization as rescue therapy in acute non-severe asthma

Arformoterol, a long-acting beta-2 agonist, has a rapid onset and long duration of action. Its role as rescue medication in acute asthma attack is undetermined. To compare the efficacy and tolerability of arformoterol with salbutamol nebulization, a study was conducted among 50 patients with acute non-severe asthma. Patients were randomly assigned to group 1 (n = 25) and group 2 (n = 25) who received three doses of salbutamol and arformoterol nebulization, respectively, at 20-min intervals. The peak expiratory flow rate (PEFR) was measured at the baseline and 5 min after each dose. The demographics and baseline characteristics were comparable between the two groups. The mean PEFR significantly increased in both these groups when compared with the baseline. The increases in the PEFR in two groups were similar after the third dose. The adverse effects in both these groups were minor. Arformoterol was as effective and safe as salbutamol in acute non-severe asthma.

Budesonide/formoterol: a review of its use as maintenance and reliever inhalation therapy in asthma

The use of combination budesonide/formoterol dry powder inhaler (Symbicort Turbuhaler) for both daily maintenance therapy and as-needed relief of breakthrough symptoms using a single inhaler is a new approach to asthma management that is indicated in patients with persistent asthma not adequately controlled by conventional regimens using reliever therapy with a short-acting beta(2)-adrenoceptor agonist alone. The administration of additional corticosteroid with each reliever inhalation in response to symptoms is expected to provide improved control of airway inflammation.Budesonide/formoterol maintenance and reliever therapy reduced the risk of severe asthma exacerbations compared with conventional regimens using a short-acting beta(2)-adrenoceptor agonist alone as reliever therapy in the majority of trials, while providing similar or better daily asthma control than higher fixed maintenance doses of budesonide or inhaled corticosteroid/long-acting beta(2)-adrenoceptor agonist combination therapy in patients with generally moderate to severe, uncontrolled, persistent asthma. The strategy offers the convenience of a single inhaler and simplifies treatment by providing immediate additional anti-inflammatory medication in response to asthma symptoms and immediate step-down when symptoms abate. The improved efficacy, with respect to exacerbation prevention, observed with budesonide/formoterol maintenance and reliever therapy in all double-blind comparative trials was achieved with a lower mean daily dose of inhaled corticosteroid or with fewer daily inhalations of reliever medication. Budesonide/formoterol maintenance and reliever therapy was well tolerated with an incidence of adverse events similar to that with conventional regimens. Therefore, it offers a new approach to therapy in patients with uncontrolled, persistent asthma; providing improved efficacy with a lower overall drug load.

A randomised, double-blind, placebo-controlled study to evaluate the role of formoterol in the management of acute asthma

AIM

To evaluate the efficacy and tolerability of formoterol delivered by Aerolizer in the emergency department.

METHODS

A single-centre, double-blind, randomised, placebo-controlled, parallel group study was conducted in patients seeking emergent care for an acute exacerbation of asthma. Patients were randomly assigned to one of two groups: group 1 (salbutamol), receiving a total dose of 600 microg salbutamol (200+200+200) delivered by a meter-dose inhaler into a spacer device as two puffs at 20 min intervals; and group 2 (formoterol), receiving formoterol 24 microg (12+12) as two dry powder capsules each containing 12 microg of formoterol via Aerolizer at 20 min intervals. The peak expiratory flow rate (PEFR) was measured at baseline and 5 min after the second and third doses.

RESULTS

60 subjects receiving salbutamol (n = 28) or formoterol (n = 32) completed the study. Age, gender, baseline PEFR, duration of asthma and previous medication were balanced between the two groups. Mean PEFR increased significantly over baseline values in both the salbutamol and formoterol groups (63% in the salbutamol group, p = 0.001, and 55% in the formoterol group, p = 0.001). No significant difference was observed in the increase in PEFR between the groups (p = 0.99, 95% CI -29.62 to 29.59). The proportion of patients reporting adverse events was similar in the two groups.

CONCLUSION

Formoterol was found to be well tolerated and as effective as salbutamol in the management of acute asthma. Further studies are needed to follow the patients after discharge from the emergency room to compare the long-term effect of formoterol on patients' stability.