Effect of topical nasal pharmaceuticals on sodium and chloride transport by human airway epithelia

Rhinorrhea and increased chloride secretion through the CFTR chloride channel-a systematic review

PURPOSE

Allergic and non-allergic rhinorrhea in the forms of acute or chronic rhinosinusitis can mean a watery nasal discharge that is disabling. Primary objective was to review the evidence supporting the hypothesis that rhinorrhea is due to increased chloride secretion through the CFTR chloride channel.

METHODS

The structure of the evidence review followed the EQUATOR Reporting Guidelines. Databases searched from inception to February 2022 included Pubmed, EMBASE and the Cochrane library using keywords "Rhinorrhea", "chloride", "chloride channel", "CFTR" and "randomized controlled trial". Quality assessment was according to the Oxford Centre for Evidence-based Medicine.

RESULTS

49 articles were included. They included randomized controlled trials out of which subsets of data with the outcome of rhinorrhea on 6038 participants were analysed and in vitro and animal studies. The review revealed that drugs, which activate CFTR are associated with rhinorrhea. Viruses, which cause rhinorrhea like rhinovirus were found to activate CFTR. The chloride concentration in nasal fluid showed an increase in patients with viral upper respiratory tract infection. Increased hydrostatic tissue pressure, which is an activator of CFTR was observed in allergic upper airway inflammation. In this condition exhaled breath condensate chlorine concentration was found to be significantly increased. Drugs, which can reduce CFTR function including steroids, anti-histamines, sympathomimetic and anticholinergic drugs reduced rhinorrhea in randomized controlled trials.

CONCLUSIONS

A model of CFTR activation-mediated rhinorrhea explains the effectiveness of anticholinergic, sympathomimetic, anti-histamine and steroid drugs in reducing rhinorrhea and opens up avenues for further improvement of treatment by already known specific CFTR inhibitors.

Dexamethasone reduces airway epithelial Cl- secretion by rapid non-genomic inhibition of KCNQ1, KCNN4 and KATP K+ channels

Basolateral membrane K⁺ channels play a key role in basal and agonist stimulated Cl^- transport across airway epithelial cells by generating a favourable electrical driving force for Cl^- efflux. The K⁺ channel sub-types and molecular mechanisms of regulation by hormones and secretagoues are still poorly understood. Here we have identified the type of K⁺ channels involved in cAMP and Ca²⁺ stimulated Cl^- secretion and uncovered a novel anti-secretory effect of dexamethasone mediated by inhibition of basolateral membrane K⁺ channels in a human airway cell model of 16HBE14o^- cells commonly used for ion transport studies. Dexamethasone produced a rapid inhibition of transepithelial chloride ion secretion under steady state conditions and after stimulation with cAMP agonist (forskolin) or a Ca²⁺ mobilizing agonist (ATP). Our results show three different types of K⁺ channels are targeted by dexamethasone to reduce airway secretion, namely Ca²⁺-activated secretion via KCNN4 (KCa3.1) channels and cAMP-activated secretion via KCNQ1 (Kv7.1) and KATP (Kir6.1,6.2) channels. The down-regulation of KCNN4 and KCNQ1 channel activities by dexamethasone involves rapid non-genomic activation of PKCα and PKA signalling pathways, respectively. Dexamethasone signal transduction for PKC and PKA activation was demonstrated to occur through a rapid non-genomic pathway that did not implicate the classical nuclear receptors for glucocorticoids or mineralocorticoids but occurred via a novel signalling cascade involving sequentially a G_i-protein coupled receptor, PKC, adenylyl cyclase Type IV, cAMP, PKA and ERK1/2 activation. The rapid, non-genomic, effects of dexamethasone on airway epithelial ion transport and cell signalling introduces a new paradigm for glucocorticoid actions in lung epithelia which may serve to augment the anti-inflammatory activity of the steroid and enhance its therapeutic potential in treating airway hypersecretion in asthma and COPD.

The Effects of Fluticasone Propionate on Nasal Epithelial Potential Difference

Background

Human airway epithelium maintains homeostasis of the fluid and salt composition at the airway surface by a regulated transport of sodium and chloride ions. The volume and composition of airway surface liquid have been shown to be important in the pathogenesis of cystic fibrosis, nasal inflammatory disease, and nasal polyposis. The presence of functional epithelial sodium and chloride channels in the airway epithelium can be evaluated electrically by measuring the voltage across the nasal epithelium (Vt). Because fluticasone propionate is commonly used to treat nasal inflammatory diseases, we tested its effect on the nasal ion transport.

Methods

A single-blind prospective trial was performed on 12 healthy volunteers. Subjects were randomized to receive either fluticasone propionate or normal saline nasal spray twice daily for 2 weeks. We measured the nasal voltage at baseline, days 3 and 14, and 2 weeks after cessation of treatment. The basal voltage, the change in voltage after perfusion with amiloride (sodium channel blocker), and the change in voltage after perfusion with isoproterenol in a low-chloride buffer (chloride channel activator) were recorded. Saccharin clearance times were measured also.

Results

Two-week treatment with fluticasone propionate resulted in a significant increase in the change in Vt after perfusion with amiloride. There was no significant change in the group treated with normal saline. These findings also were observed on day 3 and were reversed completely after the 2-week washout period. The increase in amiloride-sensitive Vt did not result in a decrease in mucociliary clearance.

Conclusions

This study suggests that one effect of fluticasone propionate use on nasal mucosa in normal volunteers is increased epithelial sodium absorption.

Using Drugs to Probe the Variability of Trans-Epithelial Airway Resistance

Background

Precision medicine aims to combat the variability of the therapeutic response to a given medicine by delivering the right medicine to the right patient. However, the application of precision medicine is predicated on a prior quantitation of the variance of the reference range of normality. Airway pathophysiology provides a good example due to a very variable first line of defence against airborne assault. Humans differ in their susceptibility to inhaled pollutants and pathogens in part due to the magnitude of trans-epithelial resistance that determines the degree of epithelial penetration to the submucosal space. This initial ‘set-point’ may drive a sentinel event in airway disease pathogenesis. Epithelia differentiated in vitro from airway biopsies are commonly used to model trans-epithelial resistance but the ‘reference range of normality’ remains problematic. We investigated the range of electrophysiological characteristics of human airway epithelia grown at air-liquid interface in vitro from healthy volunteers focusing on the inter- and intra-subject variability both at baseline and after sequential exposure to drugs modulating ion transport.

Methodology/Principal Findings

Brushed nasal airway epithelial cells were differentiated at air-liquid interface generating 137 pseudostratified ciliated epithelia from 18 donors. A positively-skewed baseline range exists for trans-epithelial resistance (Min/Max: 309/2963 Ω·cm²), trans-epithelial voltage (-62.3/-1.8 mV) and calculated equivalent current (-125.0/-3.2 μA/cm²; all non-normal, P<0.001). A minority of healthy humans manifest a dramatic amiloride sensitivity to voltage and trans-epithelial resistance that is further discriminated by prior modulation of cAMP-stimulated chloride transport.

Conclusions/Significance

Healthy epithelia show log-order differences in their ion transport characteristics, likely reflective of their initial set-points of basal trans-epithelial resistance and sodium transport. Our data may guide the choice of the background set point in subjects with airway diseases and frame the reference range for the future delivery of precision airway medicine.

Effect of azelastine on cardiac repolarization of guinea-pig cardiomyocytes, hERG K⁺ channel, and human L-type and T-type Ca²⁺ channel

Azelastine is a second generation histamine H₁-receptor antagonist used as an anti-asthmatic and anti-allergic drug that can induce QT prolongation and torsades de pointes. We investigated the acute effects of azelastine on human ether-a-go-go-related gene (hERG) channels, action potential duration (APD), and L-type (I(Ca,L)) and T-type Ca²⁺ current (I(Ca,T)) to determine the electrophysiological basis for its proarrhythmic potential. Azelastine increased the APD at 90% of repolarization concentration dependently, with an IC₅₀ of 1.08 nM in guinea-pig ventricular myocytes. We examined the effects of azelastine on the hERG channels expressed in Xenopus oocytes and HEK293 cells using two-microelectrode voltage-clamp and patch-clamp techniques. Azelastine induced a concentration-dependent decrease of the hERG current amplitude at the end of the voltage steps and tail currents. The IC₅₀ for the azelastine-induced block of the hERG currents expressed in HEK293 cells was 11.43 nM, while the drug inhibited I(Ca,L) and I(Ca,T) with IC₅₀ values of 7.60 and 26.21 μM, respectively. The S6 domain mutations, Y652A partially attenuated and F656A abolished hERG current block. These results suggest that azelastine is a potent blocker of hERG channels rather than I(Ca,L) or I(Ca,T), providing molecular mechanisms for the arrhythmogenic side effects during the clinical administration of azelastine.

Effectiveness of PTC124 treatment of cystic fibrosis caused by nonsense mutations: a prospective phase II trial

BACKGROUND

In about 10% of patients worldwide and more than 50% of patients in Israel, cystic fibrosis results from nonsense mutations (premature stop codons) in the messenger RNA (mRNA) for the cystic fibrosis transmembrane conductance regulator (CFTR). PTC124 is an orally bioavailable small molecule that is designed to induce ribosomes to selectively read through premature stop codons during mRNA translation, to produce functional CFTR.

METHODS

This phase II prospective trial recruited adults with cystic fibrosis who had at least one nonsense mutation in the CFTR gene. Patients were assessed in two 28-day cycles. During the first cycle, patients received PTC124 at 16 mg/kg per day in three doses every day for 14 days, followed by 14 days without treatment; in the second cycle, patients received 40 mg/kg of PTC124 in three doses every day for 14 days, followed by 14 days without treatment. The primary outcome had three components: change in CFTR-mediated total chloride transport; proportion of patients who responded to treatment; and normalisation of chloride transport, as assessed by transepithelial nasal potential difference (PD) at baseline, at the end of each 14-day treatment course, and after 14 days without treatment. The trial was registered with who.int/ictrp, and with clinicaltrials.gov, number NCT00237380.

FINDINGS

Transepithelial nasal PD was evaluated in 23 patients in the first cycle and in 21 patients in the second cycle. Mean total chloride transport increased in the first treatment phase, with a change of -7.1 (SD 7.0) mV (p<0.0001), and in the second, with a change of -3.7 (SD 7.3) mV (p=0.032). We recorded a response in total chloride transport (defined as a change in nasal PD of -5 mV or more) in 16 of the 23 patients in the first cycle's treatment phase (p<0.0001) and in eight of the 21 patients in the second cycle (p<0.0001). Total chloride transport entered the normal range for 13 of 23 patients in the first cycle's treatment phase (p=0.0003) and for nine of 21 in the second cycle (p=0.02). Two patients given PTC124 had constipation without intestinal obstruction, and four had mild dysuria. No drug-related serious adverse events were recorded.

INTERPRETATION

In patients with cystic fibrosis who have a premature stop codon in the CFTR gene, oral administration of PTC124 to suppress nonsense mutations reduces the epithelial electrophysiological abnormalities caused by CFTR dysfunction.

Rapid anti-secretory effects of glucocorticoids in human airway epithelium

Glucocorticoids are anti-inflammatory molecules classically described as acting through a genomic pathway. Similar to many steroid hormones, glucocorticoids also induce rapid non-genomic responses. The present paper provides a general overview of the rapid non-genomic effects of glucocorticoids in airway and will be mainly focused on a retrospective of the authors work on rapid effects of glucocorticoids in airway epithelial cell transport. Using fluorescence microscopy, short circuit current measurements in human bronchial epithelial (16HBE14o(-)) cells, we reported rapid non-genomic effects of dexamethasone on cell signalling and ion transport. Dexamethasone (1 nM) rapidly stimulated Na(+)/H(+) exchanger activity and pH(i) regulation in 16HBE14o(-) cells. Dexamethasone also produced a rapid decrease of intracellular [Ca(2+)](i) to a new steady state concentration and inhibited the large and transient [Ca(2+)](i) increase induced by apical adenosine tri-phosphate (ATP). Dexamethasone also reduced by 1/3 the Ca(2+)-dependent Cl(-) secretion induced by apical ATP. The rapid effects of dexamethasone on intracellular pH and Ca(2+) were not affected by inhibitors of transcription, cycloheximide or by the classical glucocorticoid and mineralocorticoid receptors antagonists, RU486 and spironolactone, respectively. The rapid responses to glucocorticoid were reduced by the inhibitors of adenylated cyclase, cAMP-dependent protein kinase (PKA) and mitogen-activated protein kinase (ERK1/2). Our results demonstrate, that dexamethasone at low concentrations, rapidly regulates intracellular pH, Ca(2+) and PKA activity and inhibits Cl(-) secretion in human bronchial epithelial cells via a non-genomic mechanism which neither involve the classical glucocorticoid nor mineralocorticoid receptor.

Alpha-adrenoreceptor blockade with phenoxybenzamine does not affect the ability of the nose to condition air

The primary function of the nose is to warm and humidify air. We have previously shown that raising nasal mucosal temperature by immersing feet in warm water increases the amount of water evaporated by the nose as air passes through it (nasal conditioning capacity; Abbott D, Baroody F, Naureckas E, and Naclerio R. Am J Rhinol 15: 41-45, 2001). To investigate further the effect of nasal mucosal temperature on nasal conditioning capacity, we raised the temperature through alpha-adrenoreceptor blockade by intranasally administering phenoxybenzamine. We hypothesized that blocking alpha-adrenoreceptors during inhalation of cold, dry air would lead to an increase in nasal blood flow, surface temperature, and nasal conditioning capacity, as measured by the water gradient. After appropriate pilot studies, we performed a double-blind, placebo-controlled, two-way crossover study in nine nonatopic, healthy subjects by studying the effect of treatment with intranasal phenoxybenzamine. Nasal mucosal temperature increased significantly after administration of phenoxybenzamine and was associated with a significantly smaller net decrease in nasal mucosal temperature after exposure to cold, dry air (P < 0.05). However, there were no significant differences in nasal conditioning capacity between treatments (P > 0.05). Phenoxybenzamine decreased the symptom of rhinorrhea after exposure to cold, dry air (P < 0.05), but congestion was not different between individuals given phenoxybenzamine and placebo (P > 0.05). Our data demonstrate that phenoxybenzamine, despite raising mucosal temperature and not affecting nasal volume, did not affect the ability of the nose to warm and humidify air.

Treatment of nasal inflammation decreases the ability of subjects with asthma to condition inspired air

We previously showed that individuals with seasonal allergy have a reduced ability to condition air, which was improved by nasal inflammation. We also showed that subjects with asthma have a reduced ability to condition air. Because individuals with asthma usually have inflammation in the nose, we hypothesized that treatment with an intranasal steroid would reduce nasal inflammation and further decrease nasal conditioning capacity. We performed a randomized, double blind, placebo-controlled, 2-way crossover study on 20 subjects with asthma comparing the effect of treatment with intranasal budesonide for 2 weeks on nasal conditioning. Treatment with budesonide caused no significant effect on nasal conditioning as compared with placebo. When we evaluated the subgroup of nonsmoking subjects, budesonide caused a significant reduction in nasal conditioning. We speculate that nasal inflammation in nonsmoking individuals with asthma increases the conditioning capacity and reducing it with an intranasal steroid worsens the ability of the nose to condition air. In addition, smoking causes an increase in nasal conditioning capacity by non-steroid-dependent factors. These observations help us understand the pathophysiology of nasal conditioning, but do not negate the positive clinical benefits of budesonide on treating nasal inflammation.

Rapid non-genomic inhibition of ATP-induced Cl- secretion by dexamethasone in human bronchial epithelium

A non-genomic antisecretory role for dexamethasone at low concentrations (0.1 nM to1 microM) is described in monolayers of human bronchial epithelial cells in primary culture and in a continuous cell line (16HBE14o- cells). Dexamethasone produced a rapid decrease of [Ca(2+)](i) (measured with fura-2 spectrofluorescence) to a new steady-state concentration. After 15 min exposure to dexamethasone (1 nM), [Ca(2+)](i) was reduced by 32 +/- 11 nM (n = 7, P < 0.0001) from a basal value of 213 +/- 36 nM (n = 7). We have shown previously that aldosterone (1 nM) also produces a rapid fall in [Ca(2+)](i); however, after the decrease in [Ca(2+)](i) induced by dexamethasone, subsequent addition of aldosterone did not produced any further lowering of [Ca(2+)](i). The rapid response to dexamethasone was insensitive to pretreatment with cycloheximide and unaffected by the glucocorticoid type II and mineralocorticoid receptor antagonists RU486 and spironolactone, respectively. The rapid [Ca(2+)](i) decrease induced by dexamethasone was inhibited by the Ca(2+)-ATPase pump inhibitor thapsigargin (1 microM), the adenylate cyclase inhibitor MDL hydrochloride (500 microM) and the protein kinase A inhibitor Rp-adenosine 3',5'-cyclic monophosphorothioate (200 microM), but was not affected by the protein kinase C inhibitor, chelerythrine chloride (0.1 microM). Treatment of 16HBE14o- cell monolayers with dexamethasone (1 nM) inhibited the large and transient [Ca(2+)](i) increase induced by apical exposure to ATP (10(-4) M). Dexamethasone (1 nM) also reduced by 30 % the Ca(2+)-dependant Cl(-) secretion induced by apical exposure to ATP (measured as the Cl(-)-sensitive short-circuit current across monolayers mounted in Ussing chambers). Our results demonstrate, for the first time, that dexamethasone at low concentrations inhibits Cl(-) secretion in human bronchial epithelial cells. The rapid inhibition of Cl(-) secretion induced by the synthetic glucocorticoid is associated with a rapid decrease in [Ca(2+)](i) via a non-genomic mechanism that does not involve the classical glucocorticoid or mineralocorticoid receptor. Rather, it is a result of rapid non-genomic stimulation of thapsigargin-sensitive Ca(2+)-ATPase, via adenylate cyclase and protein kinase A signalling.

Ocular allergy guidelines: a practical treatment algorithm

The treatment of ocular allergy requires a better understanding of the spectrum of clinical disorders involving various components of the immune system, and of interactions at the conjunctival surface. The immune response focuses primarily on the different levels of activity of Th2 lymphocytes and various other immune cells associated with allergic disorders, including mast cells, eosinophils, fibroblasts, and epithelial and endothelial cells. Ocular allergic disorders include seasonal allergic conjunctivitis (SAC), perennial allergic conjunctivitis (PAC), vernal keratoconjunctivitis (VKC), giant papillary conjunctivitis (GPC) and atopic keratoconjunctivitis (AKC), which, through immunopathological and molecular immunological techniques, can all be better appreciated as being part of a larger spectrum of an atopic disease state. In SAC, pathological changes, such as increased mast-cell activation, the presence of migratory inflammatory cells, and early signs of cellular activation at the molecular level, are minimal. In PAC, these changes are more pronounced in line with the increased duration of allergenic stimulation. In more chronic forms of allergic conjunctivitis, such as VKC in children and AKC in adults, the following changes are evident: a persistent state of mast cell, eosinophil and lymphocyte activation; noted switching from connective-tissue to mucosal-type mast cells; increased involvement of corneal pathology; and follicular development and fibrosis. The treatment of acute and more chronic forms of allergic conjunctivitis has focused in the past on symptomatic relief of symptoms, but with a better understanding of the mechanisms involved we can now provide interventional therapeutic strategies and symptomatic relief. Our advances in the basic understanding of these conditions are providing the foundation for guidelines that improve the ocular health of patients with ocular allergies.