Prostaglandin E₂regulation of cystic fibrosis transmembrane conductance regulator activity and airway surface liquid volume requires gap junctional communication

Am J Respir Cell Mol Biol. 2011 Jan;44(1):74-82. doi: 10.1165/rcmb.2009-0361OC. Epub 2010 Feb 18.

Abstract

Stimulation of the cystic fibrosis transmembrane conductance regulator (CFTR) by protease-activated receptors (PARs) at the basolateral membranes and by adenosine receptors (ADO-Rs) at the apical membrane maintain airway surface liquid (ASL) volume, which is required to ensure hydrated and clearable mucus. Both pathways involve the release of prostaglandin E₂ (PGE₂) and the stimulation of their basolateral receptors (EP-Rs). We sought to determine whether gap junctions contribute to the coordination of these pathways for modulating CFTR activity and mucus hydration. We used RT-PCR and Western blotting to determine connexin (Cx), CD73, and EP-R expression in a Calu-3 airway epithelial cell line grown on Transwell (Corning Costar, Cambridge, MA) inserts. We used dye coupling to evaluate gap junctional intercellular communication (GJIC). We used Ussing chamber studies and X-Z confocal microscopy to monitor Cl(-) secretion and ASL volume regulation. We found that connexin 43 (Cx43)-mediated GJIC was increased either by endogenous ADO after the hydrolysis of purine nucleotides by CD73 or by the direct activation of ADO-Rs. Inhibition of phospholipase A2 and cyclooxygenase prevented ADO-dependent increases in GJIC, suggesting the involvement of PGE₂. PGE₂ was found to increase GJIC markedly by stimulating EP4-Rs. The modulation of ADO signaling also affected the PAR-dependent activation of CFTR. The reduction of GJIC by CD73 or Cx43 inhibition prevented PAR-evoked CFTR currents in Ussing chambers. The inhibition of GJIC resulted in a failure of PGE₂ to increase ASL volume in Calu-3 cells and in primary cultures of well-differentiated human airway epithelial cells. Thus, gap junctions coordinate a signaling network comprising CFTR, ADO-Rs, PARs, and EP-Rs, and are required for ASL volume homeostasis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 5'-Nucleotidase / metabolism
  • Adenosine / metabolism
  • Blotting, Western
  • Cell Communication* / drug effects
  • Cell Line
  • Cell Polarity
  • Chlorides / metabolism
  • Connexins / metabolism
  • Cyclooxygenase Inhibitors / pharmacology
  • Cystic Fibrosis Transmembrane Conductance Regulator / genetics
  • Cystic Fibrosis Transmembrane Conductance Regulator / metabolism*
  • Dinoprostone / metabolism*
  • Epithelial Cells / drug effects
  • Epithelial Cells / metabolism*
  • GPI-Linked Proteins / metabolism
  • Gap Junctions / drug effects
  • Gap Junctions / metabolism*
  • Homeostasis
  • Humans
  • Membrane Potentials
  • Microscopy, Confocal
  • Mucociliary Clearance* / drug effects
  • Mucus / metabolism*
  • Phospholipase A2 Inhibitors
  • Phospholipases A2 / metabolism
  • RNA Interference
  • Receptors, Prostaglandin E / metabolism
  • Receptors, Purinergic P1 / metabolism
  • Respiratory Mucosa / drug effects
  • Respiratory Mucosa / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction* / drug effects
  • Surface Properties
  • Time Factors

Substances

  • CFTR protein, human
  • Chlorides
  • Connexins
  • Cyclooxygenase Inhibitors
  • GPI-Linked Proteins
  • Phospholipase A2 Inhibitors
  • Receptors, Prostaglandin E
  • Receptors, Purinergic P1
  • Cystic Fibrosis Transmembrane Conductance Regulator
  • Phospholipases A2
  • 5'-Nucleotidase
  • NT5E protein, human
  • Adenosine
  • Dinoprostone