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Cyclic AMP-dependent Cl secretion is regulated by multiple phosphodiesterase subtypes in human colonic epithelial

S M O'Grady1, X Jiang, P J Maniak

  • 1Department of Physiology, University of Minnesota, St. Paul 55108, USA. ograd001@umn.edu

The Journal of Membrane Biology
|March 14, 2002
PubMed

Insights

Inhibition of phosphodiesterase (PDE) activity in T84 cells stimulates transepithelial chloride secretion. PDE1 and PDE3 isoforms are key regulators of this secretion process, impacting cellular ion transport.

Area of Science:

  • Cellular Physiology
  • Molecular Pharmacology
  • Ion Transport Mechanisms

Background:

  • Transepithelial chloride secretion is a critical process in various physiological functions.
  • Phosphodiesterase (PDE) enzymes regulate intracellular cyclic nucleotide signaling, influencing ion transport.
  • Understanding PDE isoform roles is crucial for deciphering regulatory pathways in epithelial cells.

Purpose of the Study:

  • To investigate the role of phosphodiesterase (PDE) isoforms in regulating transepithelial chloride (Cl) secretion.
  • To identify major PDE isoforms in T84 cells and assess their contribution to cyclic nucleotide hydrolysis.
  • To determine the effect of selective PDE inhibitors on Cl secretion in cultured T84 cell monolayers.

Main Methods:

  • Cultured T84 cell monolayers grown on membrane filters were used to study transepithelial Cl secretion.
  • Ion exchange chromatography and biochemical assays identified PDE isoforms and their hydrolytic activity (cAMP, cGMP).
  • Short-circuit current (Isc) measurements assessed the impact of various PDE inhibitors on Cl secretion.

Main Results:

  • PDE4 was the most abundant isoform (70-80% of cAMP hydrolysis), followed by PDE3 (20% cytosolic, 15-30% membrane).
  • PDE5 mediated a significant portion of cGMP hydrolysis (50-75%).
  • Selective PDE3 inhibitors (terquinsin, milrinone, cilostamide) increased Isc potently; PDE1 and PDE4 inhibitors were less potent.
  • Inhibition of PDE1 and PDE3 activity enhanced Cl secretion, as evidenced by additive effects and blockage by CFTR and Na-K-2Cl cotransporter inhibitors.

Conclusions:

  • Inhibition of PDE activity in T84 cells stimulates transepithelial Cl secretion.
  • PDE1 and PDE3 isoforms play significant roles in regulating the rate of Cl secretion.
  • Targeting specific PDE isoforms may offer therapeutic strategies for conditions involving epithelial ion transport.

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