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Phosphodiesterase expression in human epithelial cells
L C Wright1, J Seybold, A Robichaud
1Department of Thoracic Medicine, Imperial College School of Medicine at the National Heart and Lung Institute, London SW3 6LY, United Kingdom.
Abstract:
Epithelial cells play a critical role in airway inflammation and have the capacity to produce many inflammatory mediators, including bioactive lipids and proinflammatory cytokines. Intracellular levels of cAMP and cGMP are important in the control of inflammatory cell function. These cyclic nucleotides are inactivated via a family of phosphodiesterase (PDE) enzymes, providing a possible site for drug intervention in chronic inflammatory conditions. We studied the expression of PDE activity in an epithelial cell line (A549) and in primary human airway epithelial cells (HAECs). We measured PDE function using specific inhibitors to identify the PDE families present and used RT-PCR to elucidate the expression of PDE isogenes. Both A549 cells and HAECs predominantly expressed PDE4 activity, with lesser PDE1, PDE3, and PDE5 activity. RT-PCR identified HSPDE4A5 and HSPDE4D3 together with HSPDE7. Inhibition of PDE4 and PDE3 reduced secretion by these cells. Epithelial PDE may be an important target for PDE4 inhibitors in the development of the control of asthmatic inflammation, particularly when delivered via the inhaled route.
Insights
Airway epithelial cells express phosphodiesterase (PDE) enzymes, particularly PDE4. Inhibiting these enzymes reduced inflammatory secretions, suggesting PDE4 inhibitors are a potential treatment for asthma.
Area of Science:
- Pulmonary Medicine
- Cell Biology
- Pharmacology
Background:
- Epithelial cells are key players in airway inflammation, producing inflammatory mediators.
- Cyclic nucleotides like cAMP and cGMP regulate inflammatory cell function.
- Phosphodiesterase (PDE) enzymes inactivate cyclic nucleotides, presenting a therapeutic target for inflammatory diseases.
Purpose of the Study:
- To investigate the expression and function of PDE enzymes in human airway epithelial cells.
- To identify specific PDE isogenes present in epithelial cells.
- To evaluate the potential of PDE inhibition as a therapeutic strategy for airway inflammation.
Main Methods:
- Studied PDE activity in A549 cells and primary human airway epithelial cells (HAECs).
- Utilized specific PDE inhibitors to characterize enzyme families.
- Employed RT-PCR to identify PDE isogene expression.
- Assessed the impact of PDE inhibition on cellular secretion.
Main Results:
- Both A549 cells and HAECs predominantly expressed PDE4 activity, with minor PDE1, PDE3, and PDE5 activity.
- RT-PCR confirmed the expression of HSPDE4A5, HSPDE4D3, and HSPDE7.
- Inhibition of PDE4 and PDE3 significantly reduced inflammatory secretions from epithelial cells.
Conclusions:
- Epithelial cells express significant PDE4 activity.
- PDE4 enzymes are a potential therapeutic target for managing asthmatic inflammation.
- Inhaled PDE4 inhibitors may offer a targeted approach for controlling airway inflammation.