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Adenosine receptors and phosphodiesterase inhibitors stimulate Cl- secretion in Calu-3 cells
Bryan R Cobb1, Lijuan Fan, Timea E Kovacs
1Department of Human Genetics, Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, 35233, USA.
Abstract:
We investigated cystic fibrosis transmembrane conductance regulator (CFTR) activation by clinically used phosphodiesterase inhibitors (PDEis) in Calu-3 cell monolayers alone and in combination with A2B adenosine receptor stimulation. This receptor pathway has previously been shown to activate wild-type and mutant CFTR molecules. Several PDEis, including milrinone, cilostazol (Pletal), papaverine, rolipram, and sildenafil (Viagra), produced a short circuit current (Isc) that was glibenclamide-sensitive, achieving 20-85% of forskolin-stimulated Isc. Papaverine, cilostazol, and rolipram also augmented both the magnitude and the duration of Isc following low dose stimulation of adenosine receptors with Ado (0.1-1.0 microM, P < 0.01). Subsequent studies demonstrated that very low concentrations of cilostazol or papaverine (approximately 1/2 peak serum concentrations) were sufficient to activate Isc, and both agents markedly augmented Ado-stimulated Isc (1 microM, P < 0.01). Our results provide evidence that select PDEis, at concentrations achieved as part of systemic therapies, can activate CFTR-dependent Isc in Calu-3 cell monolayers. These studies also indicate that PDEis have the capacity to augment an endogenous CFTR-activating pathway in an "in vivo"-like model system, and supports future investigations of these agents relevant to cystic fibrosis.
Insights
Certain phosphodiesterase inhibitors (PDEis) can activate cystic fibrosis transmembrane conductance regulator (CFTR) channels in lung cells. These PDEis also enhance CFTR activation by adenosine receptor stimulation, suggesting potential therapeutic applications for cystic fibrosis.
Area of Science:
- Cell Biology
- Pharmacology
Background:
- Cystic fibrosis transmembrane conductance regulator (CFTR) dysfunction underlies cystic fibrosis.
- Adenosine receptor stimulation activates wild-type and mutant CFTR.
- Phosphodiesterase inhibitors (PDEis) are clinically used drugs with potential effects on ion channels.
Purpose of the Study:
- To investigate the activation of CFTR by clinically used PDEis.
- To determine if PDEis can augment CFTR activation by A2B adenosine receptor stimulation.
Main Methods:
- Experiments were conducted using Calu-3 cell monolayers.
- Short-circuit current (Isc) measurements were used to assess CFTR activity.
- Cells were treated with various PDEis alone and in combination with adenosine receptor agonists.
Main Results:
- Several PDEis (milrinone, cilostazol, papaverine, rolipram, sildenafil) activated glibenclamide-sensitive Isc, reaching 20-85% of forskolin-stimulated levels.
- Papaverine, cilostazol, and rolipram enhanced the magnitude and duration of Isc upon adenosine stimulation.
- Low concentrations of cilostazol and papaverine activated Isc and augmented adenosine-stimulated Isc.
Conclusions:
- Select PDEis can activate CFTR-dependent ion transport in airway epithelial cells at therapeutically relevant concentrations.
- PDEis can potentiate an endogenous pathway for CFTR activation.
- These findings support further investigation of PDEis for cystic fibrosis treatment.
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