Cystic fibrosis (CF) is caused by a misfunctional CFTR protein, which is believed to contributes to the regulation of the airway surface liquid (ASL) pH. This study investigated acid and base secretion in freshly excised human nasal tissues from CF patients homozygous for the ΔF508 mutation. Human nasal mucosa was collected during sinus surgery and investigated in Ussing chambers. Mucosal equilibrium pH values and rate of acid and base secretion were determined using the pH-stat technique. The equilibrium pH of nasal epithelia from ΔF508 CF patients with chronic rhinosinusitis (CRS) was pH = 7.08 ± 0.09 and significantly lower compared to nasal epithelia from CRS without CF (pH = 7.33 ± 0.06) and normal subjects (pH = 7.34 ± 0.08, n = 6). The rate of base secretion in CF nasal tissues was 11.8 ± 2.4 nmol·min−1·cm−2, which was significantly lower than normal (57.2 ± 9.2 nmol·min−1·cm−2). HCO3−secretory rate was further increased by forskolin by 16.1% in normal, but not in CF tissues. Our data suggests that CF patients exhibited significantly lower base secretion by the nasal airway epithelium. It is possible that improper regulation of ASL pH in CF may negatively impact the innate host defense system.

Background

Chronic rhinosinusitis (CRS) occurs at high frequency in patients with cystic fibrosis, suggesting that the cystic fibrosis transmembrane conductance regulator (CFTR) chloride (Cl) ion channel might be involved in the development of chronic sinusitis in the general population. CFTR Cl ion transport controls the hydration of mucosal surfaces and promotes effective mucociliary clearance. Altered ion transport, and hence disrupted mucociliary function, could play a role in the pathogenesis of sinus disease. L-ascorbate is a metabolically active component of the nasal and tracheobronchial airway lining fluids and appears to serve as an important biological effector of CFTR-mediated chloride secretion. The purpose of this study was to determine the effects of L-ascorbate on Cl ion transport in freshly excised sinonasal epithelia from normal controls and patients with CRS.

Methods

Four different types of sinonasal tissue (normal sinus mucosa, sinus mucosa from CRS, normal nasal mucosa, nasal mucosa from CRS) were obtained during endoscopic sinus surgery and mounted on sliders with open areas of 0.03 to 0.71cm2 between Ussing hemichambers. Short-circuit current (Isc) was continuously recorded, and a serosa-to-mucosa-directed Cl gradient was applied to increase the electrochemical driving force.

Results

L-ascorbate (500µM) stimulated Cl currents (ΔICl, µA/cm2) across sinonasal epithelia from normal and CRS patients. The Cl secretory response to L-ascorbate was effectively blocked by the Cl ion transport inhibitors glibenclamide and bumetanide. A maximal dose of L-ascorbate (at 1 mM) stimulated 53–70% of Cl currents elicited by the cAMP agonist forskolin. CRS sinonasal tissue was characterized by impaired Cl secretory responses to L-ascorbate that were reduced by 33% in sinus epithelial tissue and by 70% in nasal epithelial tissue when compared to normal subjects. In nasal epithelial tissue from normal subjects, Cl secretion was approximately 2-fold increased when compared to sinus epithelial tissue. In contrast, nasal versus sinus epithelial tissue from CRS patients showed no differences.

Conclusion

Topical administration of L-ascorbate to freshly excised sinus and nasal mucosa enhances chloride secretion. Given that decreased CFTR-mediated Cl secretion may contribute to the development of CRS, L-ascorbate may offer potential as a therapeutic agent for the improvement of mucociliary clearance.

Objectives

Primary ciliary dyskinesia (PCD) is an inherited disorder that produces lifelong difficulties with chronic airway inflammation. Little is known about the role of chronic airway inflammation on chloride ion transport properties in PCD. This study is to assess the cAMP-regulated chloride (Cl) ion transport properties of freshly excised nasal mucosa from PCD compared with normal and chronic rhinosinusitis (CRS).

Study Design

Electrophysiology study utilizing Ussing type hemi-chamber technique with three different types of nasal tissue (normal, CRS, PCD) obtained from patients during endoscopic surgery at tertiary referral center.

Methods

Nasal tissues were examined under short-circuit conditions and gradient-driven Cl currents were continuously recorded. The cAMP elevating agonist (forskolin) was added to stimulate CFTR-mediated Cl secretion. To prevent misinterpretation of flux measurement, Cl transport inhibitors were used at the end of all experiments. Basal Cl currents (ICl) and changes in IClto forskolin (ΔICl) were compared between normal, CRS and PCD nasal tissues.

Results

Forskolin stimulated Cl currents across all different types of nasal epithelia. The Cl secretory response was effectively blocked by the Cl ion transport inhibitors. ICl were significantly higher in normals (155.0 ± 9.3μA/cm2) compared to CRS (79.1 ± 15.0μA/cm2) and PCD (70.9 ± 20.4μA/cm2) (p = 0.005). ΔICl in CRS (14.8 ± 2.3μA/cm2) and PCD (12.2 ± 2.4μA/cm2) were markedly diminished compared to normals (28.3 ± 4.7μA/cm2) (p = 0.024).

Conclusions

PCD tissues were characterized by impaired ICl and ΔICl. Both parameters were reduced by 54.3 % and 56.9 % in PCD when compared to normals.

Introduction

One major function of the airways is to inactivate and remove pathogens from inhaled air and thereby prevent infection. The secretion of protons by the airway epithelium presents an integral part of the innate host defense mechanism and involves the proton channel (hydrogen voltage-gated channel 1, HVCN1). The purpose of this study was to measure the effect of airway inflammation on acid secretion in asthmatic and non-asthmatic patients with chronic rhinosinusitis by using freshly excised human sinonasal tissue.

Methods

Nasal or sinus mucosa from subjects with three different conditions (normal, chronic rhinosinusitis (CRS), CRS with asthma) was harvested during sinus surgery. The rate of proton (H+) secretion by each tissue was measured using the pH-stat titration technique in an Ussing type chamber. The contribution of the HVCN1 proton channel to acid secretion was identified using ZnCl2 as a blocker.

Results

Nasal epithelia isolated from subjects with a diagnosis of both chronic rhinosinusitis (CRS) and asthma had a mucosal equilibrium pH = 6.95 (n = 5), which was significantly lower than the equilibrium pH found in nasal epithelia from normal (n = 5, 7.35 ± 0.21) or from subjects with CRS without asthma (n = 5, 7.33 ± 0.15). When alkalinizing the mucosal pH to 8.0, nasal epithelia from CRS with asthma (n = 5) secreted H+ at a rate of 135.1±46.2 nmol·min−1·cm−2. This rate was significantly higher compared to normal (73.3±39.3 nmol·min−1·cm−2, n = 8) or CRS without asthma (51.4±27.7 nmol·min−1·cm−2, n = 7). Mucosal addition of ZnCl2 blocked H+ secretion by 70% in normal, 52.6% in CRS without asthma, and by 50.8% in CRS with asthma.

Conclusion

Freshly excised human nasal and sinus epithelia secrete acid across the apical cell membrane. Sinonasal tissue isolated from asthmatic CRS patients showed lower mucosal pH values and higher rates of H+ secretion than CRS and normal subjects, and ~50–70% of acid secretion was mediated by the HVCN1 H+ channel in all groups. Excessive acid secretion might contribute to epithelial injury in CRS patients with asthma.

The objective of this study was to evaluate the feasibility of sentinel lymph node biopsy by using a radiotracer lymphatic mapping technique in patients with squamous cell carcinoma of the oral cavity, and the diagnostic value of this technique. We studied twenty patients with previously untreated squamous cell carcinomas of the oral cavity and N0 necks. After the peritumoral injection of 99mTc filtered tin colloid preop-eratively, lymphoscintigraphy and intraoperative mapping using a gamma detector were performed to localize sentinel nodes. An open biopsy of the sentinel node was followed by complete neck dissection. We identified the sentinel nodes in 19 of 20 patients (95.0%) by lymphoscintigraphy and in all (100%) by intraoperative gamma detector. In all cases, the status of the sentinel node accurately predicted the pathologic status of the neck with the false negative rate being 0%. The negative predictive value for the absence of cervical metastases was 100%. In conclusion, our radio-localization technique of sentinel nodes using 99mTc filtered tin colloid in N0 squamous cell carcinomas of the oral cavity is technically feasible and appears to accurately predict the presence of the occult metastatic disease.