Localization of cystic fibrosis transmembrane conductance regulator in epithelial cells of nasal polyps and postoperative polypoid mucosae

Differences and similarities between the upper and lower airway: focusing on innate immunity

The nose is the first respiratory barrier to external pathogens, allergens, pollutants, or cigarette smoke, and vigorous immune responses are triggered when external pathogens come in contact with the nasal epithelium. The mucosal epithelial cells of the nose are essential to the innate immune response against external pathogens and transmit signals that modulate the adaptive immune response. The upper and lower airways share many physiological and immunological features, but there are also numerous differences. It is crucial to understand these differences and their contribution to pathophysiology in order to optimize treatments for inflammatory diseases of the respiratory tract. This review summarizes important differences in the embryological development, histological features, microbiota, immune responses, and cellular subtypes of mucosal epithelial cells of the nose and lungs.

Expression of Cl- channels/transporters in nasal polyps

PURPOSE

Nasal polyp formation is a common sequela of prolonged chronic rhinosinusitis, but the mechanism underlying this disease state is still controversial. We compared the expressions of Cl^- channels/transporters in nasal polyps with those in inferior turbinates to explore whether a deficiency in Cl^- transport may participate in the pathophysiology of nasal polyp formation as in patients with cystic fibrosis.

METHODS

Nasal polyps and inferior turbinates were collected from 12 chronic rhinosinusitis patients with hypertrophic rhinitis and/or nasal polyps. Expressions of cystic fibrosis transmembrane conductance regulator (CFTR), pendrin, Na⁺-K⁺-2Cl^- cotransporter 1 (NKCC1), SLC26A3, TMEM16A and anion exchanger 2 (AE2) were examined by fluorescence immunohistochemistry using Alexa Fluor 488.

RESULTS

CFTR was weakly expressed on the epithelial surface of the turbinate mucosa whereas the nasal polyps showed almost no fluorescence. Pendrin was mainly expressed on the epithelial surface in both tissues. The fluorescence was moderate in the nasal polyps and strong in the turbinate mucosa. For NKCC1, moderate fluorescence was observed throughout the entire epithelial layer of the nasal polyps, but the turbinate mucosa exhibited almost no fluorescence. On the other hand, no fluorescence for SLC26A3, TMEM16A or AE2 was seen in either tissue.

CONCLUSION

These results suggest that CFTR, pendrin and NKCC1 may participate in the pathogenesis of nasal mucosal edema and play roles in the mechanism of nasal polyp formation.

Effects of rhinovirus infection on the expression and function of cystic fibrosis transmembrane conductance regulator and epithelial sodium channel in human nasal mucosa

BACKGROUND

Changes in expression and function of the cystic fibrosis transmembrane conductance regulator (CFTR) and epithelial sodium channel (ENaC) have been found to cause airway surface liquid (ASL) derangement and to impair mucociliary clearance, both of which have been linked to the pathogenesis of rhinovirus (RV) infection.

OBJECTIVES

The effects of RV infection on the expression and function of CFTR and ENaC in nasal epithelial cells were investigated.

METHODS

Nasal epithelial cells obtained from 14 turbinoplasty patients were infected with RV serotype 16 (RV-16) for 4 hours. Expression of CFTR, α-ENaC, β-ENaC, and γ-ENaC was determined by real-time polymerase chain reaction, Western blot analysis, and confocal immunofluorescence microscopy. Functional changes in the CFTR and ENaC proteins were assessed by measuring transepithelial resistance (TER) using a voltmeter combined with ion channel modulators.

RESULTS

Rhinovirus infection increased expression of CFTR, α-ENaC, β-ENaC, and γ-ENaC messenger RNA (mRNA) and protein compared with controls (P < .05 each) and increased the expression of all 4 proteins on confocal immunofluorescence microscopy. Treatment of cells with the ENaC blocker amiloride and the CFTR activator forskolin increased TER in RV-infected cells, whereas forskolin decreased TER in uninfected cells. The CFTR inhibitor NPPB, however, blocked CFTR more in RV-infected than in noninfected cells.

CONCLUSIONS

Rhinovirus increased the expression of CFTR and appeared to alter its function. In contrast, ENaC expression and function were increased by RV infection. Therefore, RV infection may impair mucociliary transport of nasal epithelium by these alterations.

Modulators of ion transport in nasal polyps: an in situ measurement of short-circuit current

Objectives

To examine possible modulators of the ion transport through the apical membrane of the nasal polyps.

Methods

The study was conducted using the freshly-excised nasal polyps from the patients with chronic sinusitis. A voltage-sensitive vibrating probe technique was introduced to monitor the short-circuit current across the apical membrane of the polyp at 37℃.

Results

In the presence of amiloride, Adenosine 5'-triphosphate induced 4,4'-Diisothiocyanatostilbene-2,2'-disulfonic acidsensitive chloride current. Uridine 5'-diphosphate was less potent than Uridine 5'-triphosphate, and adenosine increased chloride secretion, which was blocked by the antagonist, 8-(p-sulfophenyl) theophylline on adenosine receptor. Based on the pharmacologic profiles, multiple purinergic receptors, including P2Y₂, P2Y₆, and P1 receptors, were functionally expressed. However, P2X receptor agonists (α,β-methyleneadenosine 5'-triphosphate and 2'- & 3'-O-[4-benzoyl-benzoyl] adenosine 5'-triphosphate), Cystic fibrosis conductance regulator (CFTR) activator (genistein), nitric oxide substrate (L-arginine), and nitric oxide donor (sodium nitroprusside) had no significant effect on the short circuit current.

Conclusion

Among tested drugs, P2Y receptor agonists were major modulators of ion transport in nasal polyps in situ.

Down-regulation of carbonic anhydrase isoenzymes in nasal polyps

OBJECTIVES/HYPOTHESIS

Carbonic anhydrase (CA) is a zinc metalloenzyme that participate in the biological processes of various fluid transporting epithelia, including ion and water transport. CA may thus play a role in the pathophysiology of normal nasal mucosa and nasal polyp. We evaluated the expression and pattern of distribution of mRNAs and proteins for CA isoenzymes in normal nasal mucosa and polyps.

STUDY DESIGN

This was a controlled, prospective study.

METHODS

The expression levels of 11 isoenzyme genes (I, II, III, IV, VA, VB, VI, VII, IX, XII, XIV) were evaluated in normal mucosa and polyps using semiquantitative reverse-transcriptase polymerase chain reaction. The expression and pattern of distribution of CA I, II, and IX were also investigated using immunohistochemistry and Western blot.

RESULTS

mRNAs for the 11 CA isoenzymes were detected in all normal nasal mucosa and polyps tested. Their expression levels were decreased in nasal polyp in comparison with normal nasal mucosa. CA I was detected in the epithelial cells, endothelial cells, and submucosal gland of normal nasal mucosa, but only in the endothelial cells in nasal polyp. CA II in normal mucosa was intensely expressed in the submucosal gland cells and CA IX was noted in the cytoplasm and plasma membrane of epithelial cells and submucosal glands. However, these findings were not found in nasal polyp. Western blot also showed differences in their expression levels.

CONCLUSIONS

These results indicate that CA may participate in the physiology of normal nasal mucosa, but also suggest that altered their expression in nasal polyps may cause impaired electrolyte and water transport across the epithelial cells.

P38 MAP-kinase pathway is involved in the production of CLC-3 in nasal epithelial cells with allergic rhinitis induced by interleukin-4

OBJECTIVE

The objective of this study was to evaluate the role of p38 MAP-kinase (MAPK) pathway on CLC-3 expression after interleukin-4 (IL-4) induction in primary cultured human nasal epithelial cells (HNECs) from patients with allergic rhinitis (AR).

METHODS

Cultured HNECs from five patients with AR were treated with IL-4 (20 ng/mL) with or without SB203580, a selective inhibitor of p38 MAPK, at different concentrations and durations. CLC-3 was detected in HNECs by immunohistochemistry and real-time quantitative reverse transcription-polymerase chain reaction. p38 MAPK and phosphorylated p38 MAPK (pp38 MAPK) was examined by Western blotting.

RESULTS

After exposure to SB203580, CLC-3 expression induced by IL-4 was downregulated in HNECs in a concentration and time-dependent manner. This downregulation was associated with a decrease in pp38 MAPK.

CONCLUSION

These results confirmed that IL-4 can induce CLC-3 production in HNECs with AR through a p38 MAPK-dependent pathway. Inhibitors of p38 MAPK may become an important strategy for the treatment of AR.

Oxidant stress stimulates Ca2+-activated chloride channels in the apical activated membrane of cultured nonciliated human nasal epithelial cells

Respiratory tissues can be damaged by the exposure of airway epithelial cells to reactive oxygen species that generate oxidative stress. We studied the effects of the hydroxyl radical *OH, for which there is no natural intra- or extracellular scavenger, on a Ca(2+)-activated chloride channel (CACC) that participates in Cl(-) secretion in the apical membrane of airway epithelial cells. We identified and characterized CACC in cell-attached and in inside-out excised membrane patches from the apical membrane of cultured nonciliated human nasal epithelial cells. In these cells, the CACC was outwardly rectified, Ca(2+)/calmodulin-kinase II, and voltage dependent. The channel was activated in cell-attached and inside-out patches in a bath solution containing millimolar [Ca(2+)] and ran down quickly. The channel was reversibly or irreversibly activated by exposure of the internal surface of the membrane to *OH, which depended on the concentration and the duration of exposure to H(2)O(2). CACC activity evoked by oxidative stress was inhibited by 1,3-dimethyl-2-thiurea, an antioxidant that scavenges hydroxyl radicals, and by the reduced form of glutathione. The oxidized SH residues could be close to the Ca(2+)/calmodulin kinase site. The reversible or irreversible activation of CACC after a period of oxidative stress without change in [Ca(2+)] is a new observation. CACC play a direct role in mucus production by goblet cells and may thus contribute to the pathogenesis of asthma.

Expression and distribution of ion transport mRNAs in human nasal mucosa and nasal polyps

CONCLUSIONS

Our results indicate that the electrogenic kidney Na(+)/HCO(3)(-) cotransporter (kNBC), KCl cotransporter (KCC1 and -4) and Ca(2+)-activated Cl(-) channel (CaCC1, -2, -3) mRNAs are expressed in normal nasal mucosa and nasal polyp, suggesting that altered expression of all CaCC mRNAs in nasal polyp may cause impaired electrolyte and water transport across the epithelial cells.

OBJECTIVE

Electrolyte transport by nasal epithelia has been suggested to be important for controlling the quantity and composition of the nasal fluid and may play an important role in the development of nasal polyps. Transepithelial transport of ions and water in various fluid-transporting epithelia is strictly dependent on the localization of specific membrane proteins in the polarized epithelial cells. In this study we investigated the expression and distribution of mRNA transcripts for kNBC, pancreatic NBC, KCC1, -2, -3, -4 and CaCC1, -2, -3 gene families in human nasal mucosa and nasal polyp.

MATERIAL AND METHODS

The expression and localization of these gene families were investigated in inferior turbinate tissues and nasal polyp using reverse transcriptase polymerase chain reaction (RT-PCR), semiquantitative RT-PCR and in situ hybridization.

RESULTS

mRNAs for kNBC, KCC1 and -4 and all the CaCC families (CaCC1, -2 and -3) are expressed in human turbinate mucosa and nasal polyp. The expression levels of kNBC and KCC1 and -4 mRNAs did not differ between nasal mucosa and nasal polyp. However, the expression levels of all the CaCC genes were significantly decreased in nasal polyp. In situ hybridization revealed that the expression of these genes was mainly localized in the epithelial layer and submucosal glands of inferior turbinate mucosa and in the epithelial layer of nasal polyp.

Expression of guanylin and uroguanylin mRNA in human nasal mucosa and nasal polyps

OBJECTIVES

Guanylin and uroguanylin are small, heat-stable peptides that were originally isolated from the small intestine and from urine, respectively. Functionally, it has been proposed that these peptides can regulate ion and water transport in various fluid-transporting epithelia. In the present study we evaluated the presence of mRNAs for human guanylin and uroguanylin in human inferior turbinate mucosa and nasal polyps.

MATERIAL AND METHODS

The expression and localization of mRNAs for both peptides were investigated in inferior turbinate tissues and nasal polyps using reverse transcriptase polymerase chain reaction and in situ hybridization.

RESULTS

mRNAs for both peptides were detected in human turbinate mucosa and nasal polyps. In situ hybridization revealed that they were localized in the epithelial layer and submucosal glands of inferior turbinate mucosa and in the epithelial layer of nasal polyps. However, their expression was noted at low levels in the superficial epithelium of nasal polyps, compared with that of inferior turbinate mucosa.

CONCLUSIONS

These results indicate that guanylin and uroguanylin in the nasal mucosa may participate in normal physiological processes, but also suggest that altered expression of these genes in nasal polyps may cause impaired electrolyte and water transport across the epithelial cells.