1. Academic Validation
  2. Phosphodiesterase 8A Regulates CFTR Activity in Airway Epithelial Cells

Phosphodiesterase 8A Regulates CFTR Activity in Airway Epithelial Cells

  • Cell Physiol Biochem. 2021 Dec 23;55(6):784-804. doi: 10.33594/000000477.
Mark J Turner 1 2 Yukiko Sato 3 2 David Y Thomas 2 4 Kathy Abbott-Banner 5 John W Hanrahan 3 2
Affiliations

Affiliations

  • 1 Department of Physiology, McGill University, Montréal, QC, Canada, mark.turner2@mcgill.ca.
  • 2 Cystic Fibrosis Translational Research Centre, McGill University, Montréal, QC, Canada.
  • 3 Department of Physiology, McGill University, Montréal, QC, Canada.
  • 4 Department of Biochemistry, McGill University, Montréal, QC, Canada.
  • 5 Glaxo-Smith-Kline, GSK House, Brentford, UK.
Abstract

Background/aims: Cystic fibrosis transmembrane conductance regulator (CFTR), the anion channel that is defective in cystic fibrosis (CF), is phosphorylated and activated by cAMP-dependent protein kinase (PKA). cAMP levels are downregulated by a large family of phosphodiesterases that have variable expression in different cell types. We have previously observed high levels of PDE8A expression in well-differentiated primary human bronchial epithelial (pHBE) cells and thus aimed to assess whether it played a role in cAMP-dependent regulation of CFTR activity.

Methods: We assessed the effect of the selective PDE8 Inhibitor PF-04957325 (PF) on intracellular cAMP levels ([cAMP]i) in well differentiated pHBE cells from non-CF or CF donors and also in CFBE41o- cells that stably express wild-type CFTR (CFBE41o- WT) using ELISA and FRET-FLIM microscopy. CFTR channel function was also measured using electrophysiological recordings from pHBE and CFBE41o- WT cells mounted in Ussing Chambers.

Results: PDE8 inhibition elevated [cAMP]i in well-differentiated pHBE cells and stimulated wild-type CFTR-dependent ion transport under basal conditions or after cells had been pre-stimulated with physiological cAMP-elevating agents. The response to PDE8 inhibition was larger than to PDE3 or PDE5 inhibition but smaller and synergistic with that elicited by PDE4 inhibition. CRISPR Cas9-mediated knockdown of PDE8A enhanced CFTR gene and protein expression yet reduced the effect of PDE8 inhibition. Acute pharmacological inhibition PDE8 increased CFTR activity in CF pHBE cells (F508del/F508del and F508del/R117H-5T) treated with clinically-approved CFTR modulators.

Conclusion: These results provide the first evidence that PDE8A regulates CFTR and identifies PDE8A as a potential target for adjunct therapies to treat CF.

Keywords

CFTR; Cyclic nucleotide phosphodiesterases; Cystic fibrosis; cAMP signalling.

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