Sildenafil acts as potentiator and corrector of CFTR but might be not suitable for the treatment of CF lung disease

Abstract

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 (I m ), conductance (G m ), and capacitance (C m ) were determined. Sildenafil increased I m , G m , and C m 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. Copyright © 2012 S. Karger AG, Basel.