Detrimental effects of albuterol on airway responsiveness requires airway inflammation and is independent of β-receptor affinity in murine models of asthma

Background

Inhaled short acting β2-agonists (SABA), e.g. albuterol, are used for quick reversal of bronchoconstriction in asthmatics. While SABA are not recommended for maintenance therapy, it is not uncommon to find patients who frequently use SABA over a long period of time and there is a suspicion that long term exposure to SABA could be detrimental to lung function. To test this hypothesis we studied the effect of long-term inhaled albuterol stereoisomers on immediate allergic response (IAR) and airway hyperresponsiveness (AHR) in mouse models of asthma.

Methods

Balb/C mice were sensitized and challenged with ovalbumin (OVA) and then we studied the IAR to inhaled allergen and the AHR to inhaled methacholine. The mice were pretreated with nebulizations of either racemic (RS)-albuterol or the single isomers (S)- and (R)-albuterol twice daily over 7 days prior to harvest.

Results

We found that all forms of albuterol produced a significant increase of IAR measured as respiratory elastance. Similarly, we found that AHR was elevated by albuterol. At the same time a mouse strain that is intrinsically hyperresponsive (A/J mouse) was not affected by the albuterol isomers nor was AHR induced by epithelial disruption with Poly-L-lysine affected by albuterol.

Conclusions

We conclude that long term inhalation treatment with either isomer of albuterol is capable of precipitating IAR and AHR in allergically inflamed airways but not in intrinsically hyperresponsive mice or immunologically naïve mice. Because (S)-albuterol, which lacks affinity for the β2-receptor, did not differ from (R)-albuterol, we speculate that isomer-independent properties of the albuterol molecule, other than β2-agonism, are responsible for the effect on AHR.     

Cyclopentane-based human NK1 antagonists. Part 2: development of potent, orally active, water-soluble derivatives

The synthesis and optimization of a cyclopentane-based hNK1 antagonist scaffold 3, having four chiral centers, will be discussed in the context of its enhanced water solubility properties relative to the marketed anti-emetic hNK1 antagonist EMEND (Aprepitant). Sub-nanomolar hNK1 binding was achieved and oral activity comparable to Aprepitant in two in vivo models will be described.     

Association of current smoking with airway inflammation in chronic obstructive pulmonary disease and asymptomatic smokers

Background

Inflammation in the airways and lung parenchyma underlies fixed airway obstruction in chronic obstructive pulmonary disease. The exact role of smoking as promoting factor of inflammation in chronic obstructive pulmonary disease is not clear, partly because studies often do not distinguish between current and ex-smokers.

Methods

We investigated airway inflammation in sputum and bronchial biopsies of 34 smokers with chronic obstructive pulmonary disease (9 Global initiative for Chronic Obstructive Lung Disease stage 0, 9 stage I, 10 stage II and 6 stage III) and 26 asymptomatic smokers, and its relationship with past and present smoking habits and airway obstruction.

Results

Neutrophil percentage, interleukin-8 and eosinophilic-cationic-protein levels in sputum were higher in chronic obstructive pulmonary disease (stage I-III) than asymptomatic smokers. Inflammatory cell numbers in bronchial biopsies were similar in both groups. Current smoking correlated positively with macrophages: in bronchial biopsies in both groups, and in sputum in chronic obstructive pulmonary disease. Pack-years smoking correlated positively with biopsy macrophages only in chronic obstructive pulmonary disease.

Conclusion

Inflammatory effects of current smoking may mask the underlying ongoing inflammatory process pertinent to chronic obstructive pulmonary disease. This may have implications for future studies, which should avoid including mixed populations of smokers and ex-smokers.     

Fused tricyclic pyrrolizinones that exhibit pseudo-irreversible blockade of the NK1 receptor

Previously, we had disclosed a novel class of hNK₁ antagonists based on the 5,5-fused pyrrolidine core. These compounds displayed subnanomolar hNK₁ affinity along with good efficacy in a gerbil foot-tapping (GFT) model, but unfortunately they had low to moderate functional antagonist (IP-1) activity. To elaborate on the SAR of this class of hNK₁ compounds and to improve functional activity, we have designed and synthesized a new class of hNK₁ antagonist with a third fused ring. Compared to the 5,5-fused pyrrolidine class, these 5,5,5-fused tricyclic hNK₁ antagonists maintain subnanomolar hNK₁ binding affinity with highly improved functional IP-1 activity (<10% SP remaining). A fused tricyclic methyl, hydroxyl geminally substituted pyrrolizinone (compound 20) had excellent functional IP (<2% SP remaining), hNK₁ binding affinity, off-target selectivity, pharmacokinetic profile and in vivo activity. Complete inhibition of agonist activity was observed at both 0 and 24 h in the gerbil foot-tapping model with an ID₅₀ of 0.02 mpk at both 0 and 24 h, respectively.     

Inhaled salmeterol and/or fluticasone alters structure/function in a murine model of allergic airways disease

Background

The relationship between airway structural changes (remodeling) and airways hyperresponsiveness (AHR) is unclear. Asthma guidelines suggest treating persistent asthma with inhaled corticosteroids and long acting β-agonists (LABA). We examined the link between physiological function and structural changes following treatment fluticasone and salmeterol separately or in combination in a mouse model of allergic asthma.

Methods

BALB/c mice were sensitized to intraperitoneal ovalbumin (OVA) followed by six daily inhalation exposures. Treatments included 9 daily nebulized administrations of fluticasone alone (6 mg/ml), salmeterol (3 mg/ml), or the combination fluticasone and salmeterol. Lung impedance was measured following methacholine inhalation challenge. Airway inflammation, epithelial injury, mucus containing cells, and collagen content were assessed 48 hours after OVA challenge. Lungs were imaged using micro-CT.

Results and Discussion

Treatment of allergic airways disease with fluticasone alone or in combination with salmeterol reduced AHR to approximately naüve levels while salmeterol alone increased elastance by 39% compared to control. Fluticasone alone and fluticasone in combination with salmeterol both reduced inflammation to near naive levels. Mucin containing cells were also reduced with fluticasone and fluticasone in combination with salmeterol.

Conclusions

Fluticasone alone and in combination with salmeterol reduces airway inflammation and remodeling, but salmeterol alone worsens AHR: and these functional changes are consistent with the concomitant changes in mucus metaplasia.     

Acute effects of cigarette smoking on inflammation in healthy intermittent smokers

Background

Chronic smoking is the main risk factor for chronic obstructive pulmonary disease. Knowledge on the response to the initial smoke exposures might enhance the understanding of changes due to chronic smoking, since repetitive acute smoke effects may cumulate and lead to irreversible lung damage.

Methods

We investigated acute effects of smoking on inflammation in 16 healthy intermittent smokers in an open randomised cross-over study. We compared effects of smoking of two cigarettes on inflammatory markers in exhaled air, induced sputum, blood and urine at 0, 1, 3, 6, 12, 24, 48, 96 and 192 hours and outcomes without smoking. All sputum and blood parameters were log transformed and analysed using a linear mixed effect model.

Results

Significant findings were: Smoking increased exhaled carbon monoxide between 0 and 1 hour, and induced a greater decrease in blood eosinophils and sputum lymphocytes between 0 and 3 hours compared to non-smoking. Compared to non-smoking, smoking induced a greater interleukin-8 release from stimulated blood cells between 0 and 3 hours, and a greater increase in sputum lymphocytes and neutrophils between 3 and 12 hours.

Conclusion

We conclude that besides an increase in inflammation, as known from chronic smoking, there is also a suppressive effect of smoking two cigarettes on particular inflammatory parameters.     

Factors regulating the induction of ornithine decarboxylase in fetal rat liver cells in culture

Various hormonal and non-hormonal agents were tested for their ability to induce ornithine decarboxylase (EC 4.1.1.17) in primary cultures of fetal rat liver cells that retain many of the differentiated functions of hepatocytes. The only agents to induce ornithine decarboxylase in this cell type were fetal calf serum, prostaglandin E₁ and cyclic AMP derivatives. Also, the amino acid arginine would induce ornithine decarboxylase in this cell type following arginine starvation for 24 h. These observations are in contrast to the wide range of hormones, e.g. insulin, hydrocotisone, glucagon and growth hormone, that can induce ornithine decarboxylase in vivo in the adult rat liver but which are all without effect on fetal rat liver cells.     

Failure of d-cycloserine to reverse cognitive disruption induced by scopolamine or phencyclidine in primates.

The partial glycine agonist d-cycloserine may be of therapeutic use as a cognitive enhancer. We examined the ability of d-cycloserine (3-14 mg/kg i.m.) to reverse cognitive impairments induced by scopolamine (0.03 mg/kg) or PCP (0.25 mg/kg). There was no evidence for a dose-related improvement in visuospatial memory using retention intervals of 2,10 or 20 sec. A possible explanation for these findings is that central glycine function cannot be adequately increased using systemic administration of d-cycloserine in this dose range.     

Novel strategies for pharmacotherapy of depression.

Modulating monoamine activity as a therapeutic strategy continues to dominate antidepressant research, with a recent emphasis on agents with multiple targets, including combined serotonin/noradrenaline re-uptake inhibitors and numerous serotonin receptor ligands. An important new development has been the emergence of potential novel mechanisms of action, notably modulation of the activity of neuropeptides substance P and corticotrophin-releasing factor, and the intracellular messenger cyclic adenosine monophosphate. Efforts in this area have recently been rewarded by the demonstration of antidepressant efficacy of the substance P receptor antagonist MK-0869.     

Measuring the lung function in the mouse: the challenge of size

Measurement of the effects of drugs, mediators and infectious agents on various models of lung disease, as well as assessment of lung function in the intact mouse has the potential for significantly advancing our knowledge of lung disease. However, the small size of the mouse presents significant challenges for the assessment of lung function. Because of compromises made between precision and noninvasiveness, data obtained may have an uncertain bearing on the mechanical response of the lung. Nevertheless, considerable recent progress has been made in developing valid and useful measures of mouse lung function. These advances, resulting in our current ability to measure sophisticated indices of lung function in laboratory animals, are likely to lead to important insights into the mechanisms of lung disease.