WS1.2 Vardenafil promotes relocalization of F508del-CFTR in human and mouse airways

Abstract

Introduction Vardenafil, a clinically approved cGMP-dependent phosphodiesterase type 5 inhibitor (PDE5i), normalizes defective F508del-CFTR chloride transport across the nasal mucosa of mice carrying the F508del mutation (CF). This work aimed at evaluating the influence of vardenafil on CFTR expression and localization in mouse lungs and in human bronchial epithelial cells in culture. Methods CFTR localization was studied by immunohistostaining and evaluated by a normalized ratio of specific fluorescence (CFTR antibody clone 24-1) between the apical and the subapical compartments of cells. Incubation of slides with Pontamine Sky Blue was performed 10 minutes before immunostaining to overcome lung tissue autofluorescence. Results Immunohistostaining studies showed reduced CFTR expression in apical compartments of CF airways: in untreated conditions, the apical/subapical fluorescence ratio was lower in CF (1.48 +/- 0.09) than in WT tissues (2.24 +/- 0.12; p < 0.0001). In CF tissues, vardenafil treatment increased both the ratio of fluorescence and the peak intensity of the CFTR signal to WT values. Conclusion These data show that vardenafil acts as a CFTR corrector by promoting CFTR relocalization of the protein towards and into the apical compartment where the wild-type protein is mainly expressed. This work provides compelling support for studying cGMP pathway as therapeutic strategies in CF pharmacotherapy.