Effect of the K+(ATP) channel opener, KCO912, on baseline and allergen induced airway hyperresponsiveness in allergic rabbits

Onion Bulb Extract Downregulates EGFR/ERK1/2/AKT Signaling Pathway and Synergizes With Steroids to Inhibit Allergic Inflammation

The treatment of allergic diseases, such as asthma, with both conventional and novel therapies presents a challenge both in terms of optimal effect and cost. On the other hand, traditional therapies utilizing natural products such as onion have been in use for centuries with demonstrated efficacy and safety but without much knowledge of their mechanims of action. In this study, we investigated if the anti-inflammatory effects of onion bulb extract (OBE) are mediated via the modulation of the EGFR/ERK1/2/AKT signaling pathway, and whether OBE can synergise with steroids to produce greater anti-inflammatory actions. Treatment with OBE inhibited the house dust mite (HDM)-induced increased phosphorylation of EGFR, ERK1/2 and AKT which resulted in the inhibition of HDM-induced increase in airway cellular influx, perivascular and peribronchial inflammation, goblet cell hyper/metaplasia, and also inhibited ex vivo eosinophil chemotaxis. Moreover, treatment with a combination of a low dose OBE and low dose dexamethasone resulted in a significant inhibition of the HDM-induced cellular influx, perivascular and peribronchial inflammation, goblet cell hyper/metaplasia, and increased the pERK1/2 levels, whereas neither treatment, when given alone, had any discernible effects. This study therefore shows that inhibition of the EGFR/ERK1/2/AKT-dependent signaling pathway is one of the key mechanisms by which OBE can mediate its anti-inflammatory effects in diseases such as asthma. Importantly, this study also demonstrates that combining OBE with steroids results in significantly enhanced anti-inflammatory effects. This action may have important potential implications for future asthma therapy.

Potassium ion channels and allergic asthma

High-conductive calcium-sensitive potassium channels (BK+Ca) and ATP-sensitive potassium (K+ATP) channels play a significant role in the airway smooth muscle cell and goblet cell function, and cytokine production. The present study evaluated the therapeutic potential of BK+Ca and K+ATP openers, NS 1619 and pinacidil, respectively, in an experimental model of allergic inflammation. Airway allergic inflammation was induced with ovalbumine in guinea pigs during 21 days, which was followed by a 14-day treatment with BK+Ca and K+ATP openers. The outcome measures were airway smooth muscle cells reactivity in vivo and in vitro, cilia beating frequency and the level of exhaled NO (ENO), and the level of pro-inflammatory cytokines in the plasma and bronchoalveolar lavage fluid. The openers of both channels decreased airway smooth muscle cells reactivity, cilia beating frequency, and cytokine levels in the serum. Furthermore, NS1619 reduced ENO and inflammatory cells infiltration. The findings confirmed the presence of beneficial effects of BK+Ca and K+ATP openers on airway defence mechanisms. Although both openers dampened pro-inflammatory cytokines and mast cells infiltration, an evident anti-inflammatory effect was provided only by NS1619. Therefore, we conclude that particularly BK+Ca channels represent a promising new drug target in treatment of airway's allergic inflammation.

Anti-tussive and bronchodilator mechanisms of action for the enaminone E121

AIMS

In this study, we investigated whether the enaminone, E121, has anti-tussive effects in a guinea pig model of cough, and if so, whether this effect is mediated via a central or peripheral site of action. We also assessed whether E121 has bronchodilator effects and the molecular mechanisms underlying any anti-tussive and/or bronchodilator effects.

MAIN METHODS

Whole body plethysmography was used to assess both cough and airway obstruction. A stereotaxic apparatus was used to administer drugs intracerebroventricularly (i.c.v.). Effects of E121 were examined in vitro on contractile effects in guinea pig bronchioles.

KEY FINDINGS

Pre-treatment of animals with E121 resulted in a significant inhibition in the citric acid-induced cough and airway obstruction compared to vehicle-pretreated animals. The K(ATP) antagonist, glibenclamide, significantly inhibited the anti-tussive and bronchoprotective effects of E121. Also, intra-tracheal administration of E121 resulted in a significant inhibition of both the citric acid-induced cough response and airway obstruction compared to vehicle-pretreated animals. By contrast, i.c.v. administration had no effect. Finally, E121 significantly inhibited carbachol-induced airway smooth muscle contractions, an effect that was reduced by both glibenclamide and propranolol. Interestingly, E121 enhanced histamine-induced cAMP release in human eosinophils although it did not directly elevate cAMP levels.

SIGNIFICANCE

The enaminone, E121, has anti-tussive and bronchodilatory effects and is topically, but not centrally, active. The anti-tussive mechanism of action of E121 seems to be K(ATP) channel dependent, whereas its bronchodilatory effects appear to be mediated via activation of both K(ATP) channels and β(2) receptors. Therefore, E121 may potentially represent a novel therapy for cough, particularly cough associated with airway obstruction.

Novel adenosine 5'-triphosphate-sensitive potassium channel ligands: a patent overview (2005-2010)

INTRODUCTION

ATP-sensitive potassium channels are important metabolic regulators that link cellular metabolism to excitability. Their wide distribution in various tissues and organs makes them significant and topical targets in a large number of diseases.

AREAS COVERED

This review summarizes the current understanding of the molecular biology and pharmacology of K(ATP) channels, and the pathological states that result from aberrant expression or function of these proteins. In particular, relevant research, patents and patent applications of the past 5 years are discussed.

EXPERT OPINION

The tissue-specific K(ATP) channel modulation reflects an early discovery stage in drug design. The wide distribution of K(ATP) channels lets us consider them as valid targets for several pathologies, but on other hand the ubiquitous nature is a relevant drawback in developing an effective therapy because of the onset of side effects related to the lack of selectivity. On this basis, further investigations on both the structures and the localization of each receptor subtype should be carried out either exploring the structure-activity relationship of the already existing K(ATP) ligands or developing new selective fluorescent probes. To date, this research area still strives to design new tissue-targeted ligands that could pave the way to the development of innovative and effective drugs for clinical use.

K(ATP) channel therapeutics at the bedside

The family of potassium channel openers regroups drugs that share the property of activating adenosine triphosphate-sensitive potassium (K(ATP)) channels, metabolic sensors responsible for adjusting membrane potential-dependent functions to match cellular energetic demands. K(ATP) channels, widely represented in metabolically-active tissue, are heteromultimers composed of an inwardly rectifying potassium channel pore and a regulatory sulfonylurea receptor subunit, the site of action of potassium channel opening drugs that promote channel activity by antagonizing ATP-induced pore inhibition. The activity of K(ATP) channels is critical in the cardiovascular adaptive response to stress, maintenance of neuronal electrical stability, and hormonal homeostasis. Thereby, K(ATP) channel openers have a unique therapeutic spectrum, ranging from applications in myopreservation and vasodilatation in patients with heart or vascular disease to potential clinical use as bronchodilators, bladder relaxants, islet cell protector, antiepileptics and promoters of hair growth. While the current experience in practice with potassium channel openers remains limited, multitude of ongoing investigations aims at defining the benefit of this emerging family of therapeutics in diverse disease conditions associated with metabolic distress.