The effect of ambroxol on chloride transport, CFTR and ENaC in cystic fibrosis airway epithelial cells

Abstract

Ambroxol, a mucokinetic anti-inflammatory drug, has been used for treatment of cystic fibrosis (CF). The respiratory epithelium is covered by the airway surface liquid (ASL), the thickness and composition of which is determined by Cl(-) efflux via the cystic fibrosis transmembrane conductance regulator (CFTR) and Na(+) influx via the epithelial Na(+) channel (ENaC). In cells expressing wt-CFTR, ambroxol increased the Cl(-) conductance, but not the bicarbonate conductance of the CFTR channels. We investigated whether treatment with ambroxol enhances chloride transport and/or CFTR and ENaC expression in CF airway epithelial cells (CFBE) cells. CFBE cells were treated with 100 µM ambroxol for 2, 4 or 8 h. mRNA expression for CFTR and ENaC subunits was analysed by real-time polymerase chain reaction (RT-PCR); protein expression was measured by Western blot. The effect of ambroxol on Cl(-) transport was measured by Cl(-) efflux measurements with a fluorescent chloride probe. Ambroxol significantly stimulated Cl(-) efflux from CFBE cells (a sixfold increase after 8 h treatment), and enhanced the expression of the mRNA of CFTR and α-ENaC, and of the CFTR protein. No significant difference was observed in β-ENaC after exposure to ambroxol, whereas mRNA expression of γ-ENaC was reduced. No significant effects of ambroxol on the ENaC subunits were observed by Western blot. Ambroxol did not significantly affect the intracellular Ca(2+) concentration. Upregulation of CFTR and enhanced Cl(-) efflux after ambroxol treatment should promote transepithelial ion and water transport, which may improve hydration of the mucus, and therefore be beneficial to CF-patients.

An animal study on the effect of topically administered ambroxol for dry eye

“…The transconjunctival fluid transport powered by the osmotic pressure gradient is carried out by aquaporins. Evidence shows that ambroxol can up-regulate the expression of CFTR protein and enhance the transmembrane secretion of chloride ions on the surface of respiratory epithelial cells [26]. In addition to promoting the function of AQP molecule, we speculate that ambroxol in the conjunctiva could also stimulate the function of CFTR, thereby increasing the secretion of tears.…”

Quantitative phase imaging to study transmembrane water fluxes regulated by CFTR and AQP3 in living human airway epithelial CFBE cells and CHO cells

“…Since the imaging technique used here is based on light deformation when passing through cells, it could be possible that when the CFBE cells are cultured as non-polarized monolayer, we can only detect limited variations of the optical signal because of a flatter shape than CHO cells. The difference in responses amplitude can also be due to the fact that CHO cells are commonly used to study transfected ion channels activities [61] whereas CFBE cells are more complex systems expressing numerous proteins such as the ENaC and TMEM16A channels [62,63] possibly activating regulatory pathways limiting large amplitude transmembrane water fluxes.…”

Disease-Modifying Agents for the Treatment of Cystic Fibrosis

“…53 Cyclic tetrapeptides provide correction by modulating the protein homeostasis environment through both epigenetic and nonepigenetic mechanisms. 55 VX-770 (12) was the first agent approved to treat the underlying cause of CF. 55 VX-770 (12) was the first agent approved to treat the underlying cause of CF.…”