Activation of Delta F508 CFTR in a cystic fibrosis respiratory epithelial cell line by 4-phenylbutyrate, genistein and CPX

The cellular basis of cystic fibrosis (CF) is a defect in a cyclic adenosin e monophosphate (cAMP)-activated chloride channel (CF transmembrane conduct ance regulator) in epithelial cells that leads to decreased chloride ion tr ansport and impaired water transport across the cell membrane. This study i nvestigated whether it was possible to activate the defective chloride chan nel in cystic fibrosis respiratory epithelial cells with 4-phenylbutyrate ( 4PBA), genistein and 8-cyclopentyl-1,3-dipropylxanthine (CPX). The CF bronchial epithelial cell line CFBE41o-, which expresses the Delta F 508 mutation, was treated with these agents and loss of Cl- indicating Cl- efflux, measured by X-ray microanalysis. 8-bromo-cAMP alone did not induce Cl- efflux in CPBE41o- cells, but after i ncubation with 4PBA a significant efflux of CT occurred. Stimulation of cel ls with a combination of genistein and cAMP also induced CT efflux, whereas a combination of pretreatment with 4PBA and a combined stimulation with ge nistein and cAMP induced an even larger Cl- efflux. Cl- efflux could also b e stimulated by CPX, but this effect was not enhanced by 4PBA pretreatment. The Delta F508 mutation leads to impaired processing of the cystic fibrosis transmembrane conductance regulator. The increased efflux of chloride afte r 4-phenylbutyrate treatment can be explained by the fact that 4-phenylbuty rate allows the Delta F508 cystic fibrosis transmembrane conductance regula tor to escape degradation and to be transported to the cell surface, Genist ein and 8-cyclopentyl-1,3-dipropylxanthine act by stimulating chloride ion efflux by increasing the probability of the cystic fibrosis transmembrane c onductance regulator being open. The combination of 4-phenylbutyrate and ge nistein may be useful in a potential pharmacological therapy for cystic fib rosis patients with the Delta F508 mutation.