1. An investigation of the cellular effects of novel agents and multi-drug combinations in cystic fibrosis
- Author
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Bani Melhim, Suhad, Martin, Lorraine, Downey, Damian, and Reihill, James
- Subjects
Cystic fibrosis ,CFTR modulators ,elexacafrot/tezacaftor/ivacaftor ,airway inflammation ,HEMT ,interleukin-8 ,ENaC ,cytokines ,azithromycin ,epithelial - Abstract
In cystic fibrosis (CF), airways dehydration and impaired mucociliary clearance (MCC) is due to a lack of cystic fibrosis transmembrane conductance regulator (CFTR) chloride secretion and overactive epithelial sodium channels (ENaC), which leads to hyper-absorption of Na+ and water from the airway lumen. The resulting thickened secretions and airway plugging give rise to devastating cycles of chronic infection and inflammation, leading to a progressive decline in pulmonary function strategies to improve MCC in the airways include the inhibition of overactive ENaC. As proteases released from host epithelial and inflammatory cells and bacteria in CF airways, principally trypsin-like proteases (TLPs), play a role in activating ENaC, inhibition of these channel activating proteases (CAPs) represents a novel therapeutic strategy to counteract airway surface dehydration. A library of serine trypsin-like protease (TLP) inhibitors, previously synthesized by Ferguson (2015), was initially screened in an aim to identify a potential ENaC inhibitor. Compounds which had the highest inhibitory effect against TLP activity across various models were then investigated for their ability to inhibit ENaC. Electrophysiological assessment of the four compounds however, found that none were able to effectively prevent the proteolytic activation of ENaC in differentiated primary CF HBE cells. Adenosine monophosphate-activated protein kinase (AMPK) has been implicated in the regulation ENaC. The impact of pharmacological agents stimulating the AMPK signalling pathway in modifying ENaC and inflammation was previously reported with the AMPK activator, metformin. As these experiments were carried out using an unphysiologically high concentration of metformin (5 mM), an alternative AMPK activator, salicylate at a physiological dose of 3 mM was tested which, if able to inhibit ENaC, could potentially have clinical utility in PWCF. Salicylate was shown to activate AMPK, as evident by western blotting. However, electrophysiology showed that salicylate was unable to inhibit ENaC. Inflammation in the lungs of PWCF is difficult to treat, even with established regimens that often include azithromycin (AZ). Given the emergence of elexacaftor/tezacaftor/ivacaftor (ETI), which is expected to restore CFTR activity in 90% of the CF population. The aim of this part of the study was to examine the effect of AZ and ETI, singly and in combination, to assess potential anti-inflammatory effects and investigate the effects on ion channel activity. A significant reduction in cytokines was obtained by ETI in stimulated CF HBE cells. AZ had no effect on inflammation nor on ion channel activities and it had neither synergistic or antagonistic effect when used with ETI. The incorporation of ETI to the standard of CF care provides new opportunities to reduce overall treatment burden and assess drug combination efficacy in ETI-treated patients. Potential rationalisation of regimens should be explored through clinical trials and if successful could reduce drug burden and improve medication adherence.
- Published
- 2022