duramycin and Cystic-Fibrosis

Our current understanding of the pathogenesis of cystic fibrosis (CF) lung disease stresses the importance of the physical and chemical properties of the airway surface liquid (ASL). In particular, the loss of cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel function in CF reduces the volume and fluidity of the ASL, thus impairing mucociliary clearance and innate antimicrobial mechanisms. Besides direct approaches to restoring mutant CFTR function, alternative therapeutic strategies may also be considered to correct the basic defect of impaired salt and water transport. Such alternative strategies are focused on the restoration of mucociliary transport by (1) reducing sodium and fluid absorption by inhibiting the ENaC channel; (2) activating alternative chloride channels; and (3) increasing airway surface hydration with osmotic agents. Therapeutic approaches directed at targets other than CFTR are attractive because they are potentially useful to all patients irrespective of their genotype. Clinical trials are underway to test the efficacy of these approaches.

Topics: Anoctamin-1; Bacteriocins; Chloride Channels; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Deoxycytosine Nucleotides; Diuretics, Osmotic; Epithelial Cells; Epithelial Sodium Channel Blockers; Epithelial Sodium Channels; Humans; Mannitol; Mucociliary Clearance; Neoplasm Proteins; Peptides; Sodium; Uridine

The lantibiotic duramycin (Moli1901, Lancovutide) has been suggested as a drug of choice in the treatment for cystic fibrosis (CF). It has been proposed that duramycin may stimulate chloride secretion through Ca²(+) -activated Cl⁻ channels (CaCC). We investigated whether duramycin exhibited any effect on Cl⁻ efflux and intracellular Ca²(+) concentration ([Ca²(+)](i)) in CF and non-CF epithelial cells. Duramycin did stimulate Cl⁻ efflux from CF bronchial epithelial cells (CFBE) in a narrow concentration range (around 1 μM). However, 100 and 250 μM of duramycin inhibited Cl⁻ efflux from CFBE cells. An inhibitor of the CF transmembrane conductance regulator (CFTR(inh)₋₁₇₂) and a blocker of the capacitative Ca²(+) entry, gadolinium chloride, inhibited the duramycin-induced Cl⁻ efflux. No effect on Cl⁻ efflux was observed in non-CF human bronchial epithelial cells (16HBE), human airway submucosal gland cell line, human pancreatic epithelial cells, CF airway submucosal gland epithelial cells, and CF pancreatic cells. The [Ca²(+)](i) was increased by 3 μM duramycin in 16HBE cells, but decreased after 1, and 3 μM of duramycin in CFBE cells. The results suggest that the mechanism responsible for the stimulation of Cl⁻ efflux by duramycin is mainly related to unspecific changes of the cell membrane or its components rather than to effects on CaCC.

Topics: Bacteriocins; Calcium; Cell Line; Chlorides; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Epithelial Cells; Humans; Ion Transport; Microscopy, Confocal; Microscopy, Fluorescence; Peptides

The amphipathic peptide duramycin is in clinical development for the treatment of cystic fibrosis. It is deposited in cellular membranes where it binds to phosphatidylethanolamine. Duramycin may thereby change the biophysical membrane properties and perturb the function of ion channels. If so, in heart tissue, its application carries the risk to elicit cardiac arrhythmias. In fact, premature ventricular complexes were observed in the electrocardiogram during toxicological testing in dogs. To study the arrhythmogenic potential of duramycin, we investigated its effects on currents through voltage-gated hERG potassium, sodium, and calcium channels in native cells, and using a heterologous expression system, by means of the whole-cell patch clamp technique; duramycin bath concentrations between 1 nM and 0.1 microM did not generate any effects on these currents. Concentrations >or=0.3 microM, however, reduced the amplitudes of all investigated currents. Moreover, sodium current fast inactivation kinetics was slowed in the presence of duramycin. A further rise in duramycin bath concentration (>or=3.3 microM) induced a leak current consistent with pore formation. The reported effects of duramycin on ion channel function are likely to arise from a change in the biophysical properties of the membrane rather than from a specific interaction of the peptide with ion channel proteins. Under therapeutic conditions (i.e., administration via inhalation), duramycin plasma concentrations are below 0.5 nM. Thus, upon inhalation, duramycin has a large safety margin and is highly unlikely to elicit arrhythmias.

Topics: Animals; Animals, Newborn; Anti-Bacterial Agents; Bacteriocins; Calcium Channels; Cell Line, Tumor; Cystic Fibrosis; Electrophysiology; Ether-A-Go-Go Potassium Channels; Humans; Mice; Myocytes, Cardiac; Patch-Clamp Techniques; Peptides; Sodium Channels; Transfection