The Effect of Sodium Bicarbonate, a Beneficial Adjuvant Molecule in Cystic Fibrosis, on Bronchial Epithelial Cells Expressing a Wild-Type or Mutant CFTR Channel.

Ilona Gróf,Mária A Deli,Lilla Barna,Rita Ambrus,Piroska Szabó-Révész,András Harazin,Pongsiri Jaikumpun,Ana Raquel Santa-Maria,Gabriella Fűr,Alexandra Bocsik,Fabien Gosselet,Gaszton Vizsnyiczai,Ákos Zsembery,Zoltán Rakonczay,Lóránd Kiss,Hajnalka Szabó

doi:10.3390/ijms21114024

Abstract

Clinical and experimental results with inhaled sodium bicarbonate as an adjuvant therapy in cystic fibrosis (CF) are promising due to its mucolytic and bacteriostatic properties, but its direct effect has not been studied on respiratory epithelial cells. Our aim was to establish and characterize co-culture models of human CF bronchial epithelial (CFBE) cell lines expressing a wild-type (WT) or mutant (deltaF508) CF transmembrane conductance regulator (CFTR) channel with human vascular endothelial cells and investigate the effects of bicarbonate. Vascular endothelial cells induced better barrier properties in CFBE cells as reflected by the higher resistance and lower permeability values. Activation of CFTR by cAMP decreased the electrical resistance in WT but not in mutant CFBE cell layers confirming the presence and absence of functional channels, respectively. Sodium bicarbonate (100 mM) was well-tolerated by CFBE cells: it slightly reduced the impedance of WT but not that of the mutant CFBE cells. Sodium bicarbonate significantly decreased the more-alkaline intracellular pH of the mutant CFBE cells, while the barrier properties of the models were only minimally changed. These observations indicate that sodium bicarbonate is beneficial to deltaF508-CFTR expressing CFBE cells. Thus, sodium bicarbonate may have a direct therapeutic effect on the bronchial epithelium.

Highlights

Despite recent advances, the pharmacological therapy of cystic fibrosis (CF), an autosomal recessive genetic disorder caused by the mutation of the cystic fibrosis transmembrane conductance regulator (CFTR or ABCC7) gene, is still a largely unmet medical need
Characterization of the Barrier Properties of the cystic fibrosis bronchial epithelial (CFBE) Cells in Monoculture and in Co-Culture with Endothelial Cells. Both CFBE cell lines formed good barriers by day 10 on culture inserts, the transepithelial electrical resistance (TEER) values were above 500 Ω × cm2 (Figure 1A) and the Papp for both permeability markers were low, in the range of 10−7 cm/s (Figure 1B)
The mean pixel intensity of zonula occludens protein-1 (ZO-1) staining at the cell border was higher in the case of the WT-CFTR CFBE cells (Figure 2B), while stronger β-catenin intensity was observed in the ∆F508-CFTR CFBE cells (Figure 2C)

Summary

Introduction

The pharmacological therapy of cystic fibrosis (CF), an autosomal recessive genetic disorder caused by the mutation of the cystic fibrosis transmembrane conductance regulator (CFTR or ABCC7) gene, is still a largely unmet medical need. Sodium bicarbonate restores the activity of antimicrobial peptides by regulating pH in the airway surface liquid, but has a direct bacteriostatic effects and inhibits biofilm formation of CF-related bacteria [11]. It is noteworthy, that HCO3- is necessary for chelating protons and Ca2+ for proper unfolding of secreted mucin molecules which helps to maintain the normal viscosity of the airway surface liquid [12]

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