Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCA102

Poster Communications

Lubiprostone activates CFTR in human bronchial epithelial cells via an EPAC dependent process

A. Hadjipanteli1, S. Ming1, R. Muimo2, C. Taylor3, L. Robson1

1. Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom. 2. Department of Infection, Immunity & Cardiovascular Disease, University of Sheffield, Sheffield, United Kingdom. 3. Sheffield Children's Hospital, Sheffield, United Kingdom.

Cystic fibrosis transmembrane conductance regulator (CFTR) plays an important role in Cl- secretion across upper airway epithelia. When this secretion is disrupted, as seen in the inherited condition cystic fibrosis, there is defective muco-cilliary clearance and an increased risk of infection. This highlights the critical role CFTR plays in upper airway function. Previous work in human bronchial epithelial cells [1] and ovine airway [2] has indicated that lubiprostone, the metabolite analogue of prostaglandin E1, activates CFTR via a prostaglandin receptor mediated process. In the current study the role that exchange protein directly activated by cAMP (EPAC) [3] plays in this activation mechanism was investigated. (16HBE14o−) cells were grown on permeable supports until confluent and then mounted in an Ussing chamber, with standard Krebs on the basolateral side and low Cl- Krebs on the apical side (solutions bubbled with 5% CO2). The transepithelial potential (Vte) was measured and the equivalent short circuit current (ISC) calculated by injection of 10 µA of current each minute. All measurements were blank insert corrected. Measurements over a 5-minute time period were taken as control, and then 1 µM lubiprostone was added to the apical side of the insert. Once steady-state was achieved 10 µM CFTRinh172 was added to provide an indication of CFTR function. This was repeated in unpaired inserts in the presence of either DMSO vehicle or 25 µM ESI-09, an inhibitor of EPAC (both added 10 minutes before the start of the experiment). Statistical significance was tested using ANOVAs or Student's t test as appropriate and assumed at the 5% level. With the vehicle controls, addition of lubiprostone shifted the Vte from 7.00 ± 0.69 mV to 17.7 ± 1.86 mV (n=9), a mean increase of 10.7 ± 1.49 mV. CFTRinh172 reversed this increase, with the Vte falling by 10.3 ± 1.62 mV to 7.33 ± 0.84 mV. Pre-incubation with ESI-09 prior to the addition of lubiprostone prevented the shift in Vte. Vte was 5.30 ± 0.69 mV and 6.51 ± 1.40 mV (n=9), in the absence and presence of lubiprostone, respectively. There was no significant difference between these. Addition of the CFTRinh172 was also without effect, Vte was 3.09 ± 0.73 mV in the presence of CFTRinh172. These data support the idea that lubiprostone activates CFTR in human airway epithelial cells through a mechanism that requires EPAC. The specific action EPAC mediates in the activation process requires future work. However, given the previous literature one possibility is that EPAC acts to stabilise CFTR in the membrane [3].

Where applicable, experiments conform with Society ethical requirements