Ivacaftor (VX-770)

Ivacaftor (VX-770) (10 μM) significantly increases the forskolin-stimulated Cl^- secretion (I_T) by ~4-fold with an EC50 of 100 nM in the recombinant Fisher rat thyroid (FRT) cells expressing G551D gating mutation of CFTR, and by ~6-fold with an EC50 of 25 nM in the recombinant cells expressing temperature-corrected F508del processing mutation of CFTR. Consistent with the increases in the forskolin-stimulated I_T, this compound increases the open probability (P_o) of G551D-, F508del-, and wild-type CFTR by ~6-fold, ~5-fold and ~2-fold, respectively, indicating that it acts directly on CFTR to increase its gating activity. In primary cultured human CF bronchial epithelia (HBE) carrying the G551D and F508del CFTR mutations, Ivacaftor potently increases the forskolin-stimulated I_T by ~10-fold from 5% to a maximum level of 48% of that measured in non-CF HBE, with an EC50 of 236 nM displaying ~70-fold more potency compared with the commonly used CFTR potentiator genistein, which has an EC50 of 16 μM. In HBE with F508del homozygous CFTR, it causes a significant increase in the forskolin-stimulated I_T with an EC50 of 22 nM, to a less extent from 4% to 16% of non-CF HBE compared with the effect in G551D/F508del HBE. Due to CFTR potentiation, this compound inhibits excessive ENaC-mediated Na⁺ and fluid absorption with an IC50 of 43 nM, and decreases the response, resulting in an increase in the surface fluid and cilia beat frequency (CBF) in G551D/F508del HBE. [1]

• Enregistrements en chambre d'Ussing

  L'effet d'Ivacaftor (VX-770) sur la sécrétion de Cl^- médiatisée par CFTR est caractérisé en mesurant l'I_T médiatisée par CFTR dans des chambres utilisant des cellules thyroïdiennes de rat Fisher (FRT) recombinantes exprimant G551D, ou F508del CFTR. Les cellules sont cultivées sur des inserts de culture cellulaire Costar Snapwell maintenus à 37 °C avant l'enregistrement. Les inserts de culture cellulaire sont montés dans une chambre d'Ussing pour enregistrer l'I_T en mode de voltage-clamp (V_hold = 0 mV). Pour les cellules FRT, la membrane basolatérale est un gradient de Cl^- basolatéral à apical est établi. La solution de bain basolatéral contient 135 mM de NaCl, 1,2 mM de CaCl₂, 1,2 mM de MgCl₂, 2,4 mM de K₂HPO₄, 0,6 mM de KHPO₄, 10 mM de N-2-hydroxyéthylpipérazine-N

• Lignées cellulaires

  FRT and NIH 3T3 cells

• Concentrations

  100/25 nM

• Temps d'incubation

  24 h

• Méthode

  Cells were treated with various concentrations of Ivacaftor (VX-770).

• Modèles animaux

  Male Sprague-Dawley rats

• Posologies

  3 mg/kg

• Administration

  i.v.