The phosphodiesterase-5 inhibitor sildenafil is an established and approved drug to treat symptoms of a variety of human diseases. In the context of cystic fibrosis (CF), a genetic disease caused by a defective CFTR gene (e.g. ΔF508-CFTR), it was assumed that sildenafil could be a promising substance to correct impaired protein expression. This study focuses on the molecular mechanisms of sildenafil on CFTR recovery. We used ΔF508-CFTR/wt-CFTR expressing Xenopus laevis oocytes and human bronchial epithelial cell lines (CFBE41o-/16HBE14o-) to investigate the pathways of sildenafil action. Cells were treated with sildenafil and cAMP-mediated current (Im), conductance (Gm), and capacitance (Cm) were determined. Sildenafil increased Im, Gm, and Cm of wt-CFTR and functionally restored ΔF508-CFTR in oocytes. These effects were also seen in CFBE41oand 16HBE14o-cells. Transepithelial measurements revealed that sildenafil mediated increase (wt-CFTR) and restoration (ΔF508-CFTR) of channel activity. cGMP pathway blocker inhibited the activity increase but not CFTR/ΔF508-CFTR exocytosis. From these data we conclude that sildenafil mediates potentiation of CFTR activity by a cGMP-dependent and initiates cGMP-independent functional insertion of CFTR/ ΔF508-CFTR molecules into the apical membranes. Thus, sildenafil is a corrector and potentiator of CFTR/ΔF508-CFTR. Yet, the necessary high doses of the drug for CFTR recovery demonstrate that sildenafil might not be suited as a therapeutic drug for CF lung disease.

Keywords:
CFTR, cGMP, Corrector, Cystic fibrosis, Potentiator, Xenopus laevis oocyte
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© 2012 S. Karger AG, Basel
2012
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