Chloride transport and the action of sodium cromoglycate and nedocromil sodium in asthma

Design, synthesis, and biological evaluation of 2-substituted-2,3,4,9-tetrahydrospiro-β-carboline-3-carboxylic acid derivatives as first-in-class mast cell stabilizers

Mast cell degranulation plays a momentous role in myriad diseases like asthma, eczema, allergic rhinitis, and conjunctivitis as well as anaphylactic shock; hence, there is an unmet need for developing new mast cells stabilizers. The reported mast cell stabilizers have a heterocyclic moiety and an acidic group. Furthermore, the role of tryptophan in suppression of mast cell activation is established. Hence, we prepared constrained analogs of tryptophan, which are derivatives of 2,3,4,9-tetrahydrospiro-β-carboline-3-carboxylic acid, and evaluated them for ex vivo inhibition of compound 48/80-induced mast degranulation activity. By comparing IC₅₀ (μM) values with that of the standard drug sodium cromoglycate (IC₅₀  = 0.489 ± 0.003 μM), compounds with bulky groups like heptyl (compound 9; IC₅₀  = 0.389 ± 0.015 μM) and octyl (compound 10; IC₅₀  = 0.354 ± 0.023 μM) were found to be of similar potency as sodium cromoglycate. Furthermore, the polar group-containing compounds like the chloropropyl (compound 16; IC₅₀  = 0.382 ± 0.083 μM) and benzoyl derivative (compound 14; IC₅₀  = 00.469 ± 0.032 μM) were also found to be of similar potency as sodium cromoglycate. This is a seminal study of spiro-β-carboline mast cell stabilization having a wider scope in mast cell research; yet, the mechanism of action remains elusive.

The Anti-allergic Cromones: Past, Present, and Future

The anti-allergic cromones were originally synthesized in the 1960s by Fisons Plc, and the first drug to emerge from this program, disodium cromoglycate was subsequently marketed for the treatment of asthma and other allergic conditions. Whilst early studies demonstrated that the ability of the cromones to prevent allergic reactions was due to their 'mast cell stabilizing' properties, the exact pharmacological mechanism by which this occurred, remained a mystery. Here, we briefly review the history of these drugs, recount some aspects of their pharmacology, and discuss two new explanations for their unique actions. We further suggest how these findings could be used to predict further uses for the cromones.

The novel H2 S donor 4-carboxy-phenyl isothiocyanate inhibits mast cell degranulation and renin release by decreasing intracellular calcium

BACKGROUND AND PURPOSE

Hydrogen sulfide (H₂ S) modulates many pathophysiological processes, including inflammation and allergic reactions, in which mast cells act as major effector cells. IgE receptor (FcεRI) cross linking leads to an increase in intracellular calcium ([Ca⁺² ]_i ), a critical step in mast cell degranulation. The aim of this study was to investigate the role of H₂ S in [Ca⁺² ]_i -dependent mast cell activation.

EXPERIMENTAL APPROACH

We investigated the effects of H₂ S, either endogenously produced or released by the slow H₂ S donor 4-carboxy-phenyl isothiocyanate (PhNCS-COOH), on antigenic- and non-antigenic degranulation of native murine mast cells, and human and rat (RBL-2H3) mast cell lines. We measured the release of specific mast cell degranulation markers (β-hexosaminidase and renin), as well as changes in [Ca⁺² ]_i and phosphorylation of proteins downstream of FcεRI activation.

KEY RESULTS

Endogenously produced H₂ S inhibited antigen-induced degranulation in RBL-2H3. Similarly, H₂ S released by PhNCS-COOH (10-300 μM) reduced, in a concentration-dependent manner, antigenic and non-antigenic degranulation and renin release in all mast cell types. Notably, PhNCS-COOH also prevented in a concentration-dependent mode the increase in [Ca⁺² ]_i elicited by Ca⁺² ionophore, thapsigargin and FcεRI activation. Moreover, PhNCS-COOH attenuated the phosphorylation of Syk, cPLA-2 and PLCγ1 in antigen-stimulated RBL-2H3 cells.

CONCLUSION AND IMPLICATIONS

Collectively, our results demonstrate that, by attenuating the phosphorylation of proteins downstream of FcεRI cross-linking on mast cells, H₂ S diminishes [Ca⁺² ]_i availability and thus mast cell degranulation and renin release. These findings suggest that PhNCS-COOH could be a strategic therapeutic tool in mast cell-mediated allergic conditions.

Air quality and temperature effects on exercise-induced bronchoconstriction

Exercise-induced bronchoconstriction (EIB) is exaggerated constriction of the airways usually soon after cessation of exercise. This is most often a response to airway dehydration in the presence of airway inflammation in a person with a responsive bronchial smooth muscle. Severity is related to water content of inspired air and level of ventilation achieved and sustained. Repetitive hyperpnea of dry air during training is associated with airway inflammatory changes and remodeling. A response during exercise that is related to pollution or allergen is considered EIB. Ozone and particulate matter are the most widespread pollutants of concern for the exercising population; chronic exposure can lead to new-onset asthma and EIB. Freshly generated emissions particulate matter less than 100 nm is most harmful. Evidence for acute and long-term effects from exercise while inhaling high levels of ozone and/or particulate matter exists. Much evidence supports a relationship between development of airway disorders and exercise in the chlorinated pool. Swimmers typically do not respond in the pool; however, a large percentage responds to a dry air exercise challenge. Studies support oxidative stress mediated pathology for pollutants and a more severe acute response occurs in the asthmatic. Winter sport athletes and swimmers have a higher prevalence of EIB, asthma and airway remodeling than other athletes and the general population. Because of fossil fuel powered ice resurfacers in ice rinks, ice rink athletes have shown high rates of EIB and asthma. For the athlete training in the urban environment, training during low traffic hours and in low traffic areas is suggested.

Drugs for asthma

Current drug therapy for asthma is highly effective and has evolved from naturally occurring substances through logical pharmaceutical developments. Pharmacology has played a critical role in asthma drug development and several key experimental observations have been published in this journal. Understanding the pharmacology of effective drug therapies has also taught us much about the underlying mechanisms of asthma. beta(2)-Adrenoceptor agonists are the most effective bronchodilators and evolved from catecholamines from the adrenal medulla, whereas corticosteroids, from the adrenal cortex, are by far the most effective controllers of the underlying inflammatory process in the airways. The current 'gold standard' of asthma therapy is a combination inhaler containing a long-acting beta(2)-agonist with a corticosteroid - an improved form of adrenal gland extract. Cromoglycate, derived from a plant product and theophylline, a dietary methyl xanthine, have also been extensively used in the therapy of asthma, but we still do not understand their molecular mechanisms. Pharmacology has played an important role in improving natural products to make effective long lasting and safe asthma therapies, but has so far been challenged to produce new classes of antiasthma therapy. The only novel class of antiasthma therapy introduced in the last 30 years are leukotriene antagonists, which are less effective than existing treatments. New, more specific, therapies targeted at specific cytokines are less effective than corticosteroids, whereas more effective therapies carry a risk of side effects that may not be acceptable. It seems likely that pharmacology, rather than molecular genetics, will remain the main approach to the further improvement of treatment for asthma.

New drugs for asthma

Asthma is a major and increasing global health problem and, despite major advances in therapy, many patients' symptoms are not adequately controlled. Treatment with combination inhalers, which contain a corticosteroid and long-acting beta(2) adrenoceptor agonist, is the most effective current therapy. There is therefore a search for new therapies, particularly safe and effective oral treatments and those that are more efficacious in severe asthma. New therapies in development include mediator antagonists and inhibitors of cytokines, although these therapies might be too specific to be very effective. New anti-inflammatory therapies include corticosteroids and inhibitors of phosphodiesterase-4, p38 mitogen-activated protein kinase and nuclear factor-kappaB. The prospects for a curative treatment are on the horizon.

A comparison of the pharmacological modulation of hyperalgesia and bronchial hyperresponsiveness

It has been proposed that there may be similarities in the mechanisms contributing toward hyperalgesia/allodynia observed in various clinical pain syndromes and bronchial hyperresponsiveness (BHR) in asthma. Both features are characterized by an increase in responsivity to various stimuli. In the case of pain, these include increase in responsiveness to mechanical and thermal stimuli whilst asthmatics bronchoconstrict in response to substances that are otherwise innocuous. A variety of mediators can induce hyperalgesia and pain when injected into the skin and these same mediators are also released during an inflammatory insult in the airways and in many cases can induce hyperresponsiveness experimentally. In this review, a comparison of the pharmacological modulation of afferent activity in hyperalgesia and in BHR will be made to ascertain whether any commonality exists between the treatment of these two disease states.

Activation and inhibition of mast cells degranulation affect their morphometric parameters

Activation of mast cells, the key cells of allergic inflammation, causes typical morphological changes associated with an increase in volume, that is a function of area and perimeter. The purpose of this study was to evaluate the effect of mast cell activation to degranulate, carried out by the secretagogue Compound 48/80, and of inhibition of this activation carried out by Nedocromil sodium, a mast cell stabilizing drug, on mast cell area, perimeter and shape factor by a computerized image analyzer. Mast cells were isolated and purified by peritoneal lavage of rats (purity >98%) and co-cultured with mouse 3T3 fibroblasts to which they adhere. Cultures were incubated for 10 min at 37 degrees C with culture medium alone (Enriched Medium) or Enriched Medium containing either Nedocromil (10(-4) M) or Compound 48/80 (0.3 microg/ml) or Compound 48/80 and Nedocromil (0.3 microg/ml and 10(-4) M respectively). Supernatants were then assessed for histamine release, as a marker of mast cell activation and the cell monolayers were fixed and stained with an alcoholic-acidic toluidine blue solution and examined with a computerized image analyzer connected with a light microscope. Mast cells incubated in Enriched Medium or Nedocromil possessed similar morphometric parameters. Mast cells activated with Compound 48/80 (70% histamine release) had a significant increase in area and perimeter and a decrease in shape factor in comparison to mast cells in Enriched Medium alone. Simultaneous incubation of mast cells with Compound 48/80 and Nedocromil significantly inhibited their histamine release (36% histamine release) and the increase in area and perimeter, but did not affect significantly their shape factor, in comparison with mast cells incubated with Compound 48/80 alone. These data clearly show that there is a relationship between mast cell activation, consequent histamine release and changes in cell area, perimeter and shape factor and that Nedocromil not only inhibits mast cell histamine release but also the activation induced morphometric changes in mast cells.

Insensitivity of volume-sensitive chloride currents to chromones in human airway epithelial cells

Chromones (sodium cromoglycate and sodium nedocromil) block cell swelling-activated Cl- channels in NIH-3T3 fibroblasts and endothelial cells. This has led to hypothesize that cell volume regulation might be involved in asthma pathogenesis. Using whole-cell patch-clamp experiments, we studied the effect of chromones on volume-sensitive Cl- currents in transformed human tracheal epithelial cells (9HTEo-) and in primary cultures of human bronchial epithelial cells (BE). Cl- currents activated by hypotonic shock were poorly blocked by extracellular nedocromil or cromoglycate. The block was voltage-dependent since it was observed only at positive membrane potentials. At the concentration of 5 mM, the current inhibition by both chromones at +80 mV was about 40% for 9HTEo- and only 20% for BE. Intracellular application of chromones elicited a voltage-independent inhibition in 9HTEo- cells. Under this condition, volume-sensitive Cl- currents were reduced at all membrane potentials (60 and 45% inhibition by 2 mM nedocromil and cromoglycate respectively). In contrast intracellular chromones were ineffective in BE cells. The relative refractoriness to chromones, in contrast with the high sensitivity shown by other Cl- channels, suggests that the epithelial volume-sensitive Cl- channel is not involved in asthma.

Comparison of three treatment regimens of inhaled sodium cromoglycate in the management of adult patients with severe, steroid-dependent asthma

BACKGROUND

Asthmatic patients whose asthma remains poorly controlled despite treatment with high doses of inhaled corticosteroids and co-administration of oral corticosteroids are a difficult problem in therapeutics.

OBJECTIVE

To investigate the relative efficacy of three treatment regimens of inhaled sodium cromoglycate in the treatment of adult, severe, corticosteroid-dependent patients as determined by the reduction in the dose of oral corticosteroids and change in lung function.

METHODS

Open, randomized, group comparative trial of 12 weeks duration in asthmatic patients attending a hospital outpatient department. Patients whose asthma is (1) severe according to the classification of the Japanese Society of Allergology, (2) stable, and (3) needing treatment with at least 1600 microg of inhaled beclomethasone dipropionate and 5 mg or greater of oral prednisolone per day. The three treatment regimens of inhaled sodium cromoglycate were group A received sodium cromoglycate powder at a dose of 16 mg/day administered by a metered dose inhaler. Group N received sodium cromoglycate aqueous solution at a dose of 80 mg/day administered by a nebulizer. Group C received sodium cromoglycate aqueous solution (80 mg/day) combined with salbutamol (3 mg/day) administered by a nebulizer. The main outcome measures were a change in the daily dose of oral corticosteroids and in lung function with twice daily measurements of peak expiratory flow (PEF) recorded in the morning (PEF AM) and in the evening (PEF PM).

RESULTS

Mean reduction in oral corticosteroid dose/day was group A, 3.68 mg (95% CI 1.35,5.95); group N, 3.59 mg (95% CI 0.73,6.45); and group C, 3.97 mg (95% CI 1.81,6.13). The dosage reductions are all significant but with no differences between the groups. The mean increase in PEF over the last 4 weeks of treatment compared with baseline values was significant in all groups. The increases in group C are significantly greater than those in the other groups. These changes are all significant and the increases in group C are significantly greater than those in the other groups.

CONCLUSIONS

Inhaled sodium cromoglycate may be a useful additional treatment in the management of adult patients with severe, oral steroid-dependent asthma. Of the three methods of administration compared in this trial the most useful immediate results were obtained when the drug was administered as an aqueous solution mixed with salbutamol and delivered by a powered nebulizer.

Inhibition of rat peritoneal mast cell exocytosis by frusemide: a comparison with disodium cromoglycate

Among the loop diuretics, frusemide possesses unique airway protective activities which may be due to the inhibition of airway inflammatory cells such as the mast cell. We previously reported that frusemide and disodium cromoglycate (DSCG) demonstrated a similar profile of inhibitory activities against histamine release from rat peritoneal mast cells activated by various stimuli which increased intracellular calcium via different routes. Furthermore, the inhibitory activities of both compounds demonstrated marked tachyphylaxis and we hence postulated that frusemide and DSCG might share the same mechanism of action which involves the prevention of extracellular calcium influx into the mast cell cytoplasm. The present study confirmed the postulation by (a) demonstrating that cross-tachyphylaxis exists between the two compounds and (b) extending the observations on histamine release to the influx of extracellular calcium (45Ca) into rat peritoneal mast cells.

Problems and prospects of developing effective therapy for common cold viruses

No effective treatment for common colds has yet been developed. Combination antiviral and anti-inflammatory therapies are the best hope for intervention after the onset of symptoms. Prophylaxis, especially in the form of vaccination, would have a major impact in disease prevention. These approaches offer new avenues for treating populations at risk and are of particular significance to those with asthma or chronic bronchitis.