However, its role in CF lung disease pathogenesis remains unclear.In this study, β-epithelial Na<sup>+</sup> channel-overexpressing transgenic (βENaC-Tg) mice, a model of CF-like lung disease, were crossed with CatS null (CatS<sup>-/-</sup>) mice or treated with the CatS inhibitor VBY-999.Levels of active CatS were elevated in the lungs of βENaC-Tg mice compared with wild-type (WT) littermates.
In the present study, two mouse models of CF were examined to assess a potential protective function of Ca<sup>2+</sup>-dependent Cl<sup>-</sup> secretion, a CFTR deletion model (cftr<sup>-/-</sup>), and a CF pathology model that overexpresses the epithelial Na<sup>+</sup> channel β-subunit (βENaC), which is encoded by the Scnn1b gene, specifically in airway epithelia (Scnn1b-Tg).
SPX-101's in vivo therapeutic effect was assessed by survival of β-ENaC-transgenic mice, mucus transport in these mice, and mucus transport in a sheep model of CF.
Heterozygous variants in CFTR, SCNN1A, and SCNN1B genes associated with cystic fibrosis (CF) or CF-like disease were detected in four of our nine patients.
Whereas all have been reported in the dbSNP database, only p.Ala334Thr, p.Val573Ile, and p.Thr663Ala in SCNN1A, p.Gly442Val in SCNN1B and p.Gly183Ser in SCNN1G were previously reported in ENaC genetic studies of CF or CF-like patients.
IL-8 protein and mRNA were measured in cystic fibrosis and non-cystic fibrosis bronchoalveolar lavage fluid and bronchial brushings (n=20 per group). miRNAs decreased in the cystic fibrosis lung and predicted to target IL-8 mRNA were quantified in βENaC-transgenic, cystic fibrosis transmembrane conductance regulator (Cftr)-/- and wild-type mice, primary cystic fibrosis and non-cystic fibrosis bronchial epithelial cells and a range of cystic fibrosis versus non-cystic fibrosis airway epithelial cell lines or cells stimulated with lipopolysaccharide, Pseudomonas-conditioned medium or cystic fibrosis bronchoalveolar lavage fluid.
Our results indicate that (1) single siRNAs complementary to ENaC subunits are sufficient to reduce ENaC transcripts, Na(+) channel activity, and fluid transport, but only silencing both the α and β ENaC subunits at the same time leads to an increase of ASF (from nearly 7 µm to more than 9 µm); (2) the ASF thickness obtained in this way is about half that measured after maximal CFTR stimulation in non-CF epithelia (10-14 µm); and (3) the pharmacological rescue of mutant CFTR increases the ASF to the same extent as ENaC silencing.
Studies of the phenotype of βENaC-transgenic mice demonstrated that increased airway Na(+) absorption causes airway surface liquid (ASL) depletion, reduced mucus transport and a spontaneous CF-like lung disease with airway mucus obstruction and chronic airway inflammation.
Restoration of beclin 1 and autophagy by either beclin 1 overexpression, cystamine or antioxidants rescues the localization of the beclin 1 interactome to the endoplasmic reticulum and reverts the CF airway phenotype in vitro, in vivo in Scnn1b-transgenic and Cftr(F508del) homozygous mice, and in human CF nasal biopsies.
The CFTR gene was first analyzed in all patients by denaturing high-performance liquid chromatography followed by direct sequencing; whereas, the sodium channel non-voltage-gated 1 alpha (SCNN1A), sodium channel non-voltage-gated 1 beta (SCNN1B), and sodium channel non-voltage-gated 1 gamma (SCNN1G) subunits of the ENaC gene were analyzed by sequencing in the five patients who carried only one CF mutation.
The finding that TNFRSF1A, SCNN1B and SCNN1G are clinically relevant modulators of CF disease supports current concepts that the depletion of airway surface liquid and inadequate host inflammatory responses trigger pulmonary disease in CF.
The finding that TNFRSF1A, SCNN1B and SCNN1G are clinically relevant modulators of CF disease supports current concepts that the depletion of airway surface liquid and inadequate host inflammatory responses trigger pulmonary disease in CF.
The finding that TNFRSF1A, SCNN1B and SCNN1G are clinically relevant modulators of CF disease supports current concepts that the depletion of airway surface liquid and inadequate host inflammatory responses trigger pulmonary disease in CF.