Using CFBE41o cells, we showed that the positive SLC6A14 effect was mainly dependent on the nitric oxide (NO) synthase activity, nitrogen oxides, including NO, and phosphorylation by protein kinase G. These finding were confirmed in CF-HBE, as inducible NO synthase inhibition abrogated the functional interaction between SLC6A14 and pharmacological corrected F508del-CFTR.
An initial cohort of 808 CF patients homozygous for the common CF mutation, DeltaF508, showed significant association for polymorphisms in the endothelin receptor A gene, EDNRA (P = 0.04), but not in the related endothelin genes (EDN1, EDN2, EDN3, or EDNRB) or NOS1, NOS2A, or NOS3.
Inducible NOS mRNA expression was significantly lower in CF patients with and without bacterial infection than in healthy children (0.22 and 0.23 v 0.76; p=0.002 and p=0.01, respectively).
Based on previous work demonstrating isoprenoid-mediated regulation of CF-related alterations in signal transducer and activator of transcription-1 (Stat1) and inducible nitric oxide synthase (NOS2) expression, the hypothesis of this study is that inhibition of isoprenoid-dependent signaling will restore SMAD3 expression and signaling in a model of CF epithelium.
In contrast to a lack of NOS2 induction, the major histocompatibility complex class 2, an IFN-gamma-regulated delayed-responsive gene, is similarly induced in CF and non-CF airway epithelial (NL) cells, suggesting an NOS2-specific defect in the IFN-gamma signaling pathway.
Inhibition of the Rho GTPase pathway at the level of isoprenoid/cholesterol synthesis with mevastatin reduces PIAS1 expression, increases STAT1 activation, and restores NOS2 expression in models of CF epithelium, suggesting that pharmacological inhibition of the isoprenoid synthesis/Rho GTPase pathway may represent a potential avenue for therapeutic intervention for CF.
NO donor or NOS2 overexpression provides protection from virus infection in CF, suggesting that NO is sufficient for antiviral host defense in the human airway and is one strategy for antiviral therapy in CF children.
These complexes effect partial correction of the chloride transport defect as assessed by in vivo nasal potential difference measurements, produce immunohistochemical staining for CFTR, and restore expression of nitric oxide synthase-2 (NOS-2), which is downregulated in the epithelium of mice and humans with cystic fibrosis.
We propose that increased levels of PIAS1 diminish certain cell-signaling pathways, resulting in reduced IRF-1 and NOS2 expression in CF epithelial cells.
Human neutrophils were activated by incubation with cytokines, added to monolayers of normal (16HBE14o-) and CF (CFBE41o-) bronchial epithelial cells and co-cultured for up to 72 h. Marked up-regulation of iNOS protein expression was seen in normal bronchial epithelial cells following neutrophil co-culture but the CF cells showed a significantly smaller increase (p<0.001).
To understand better the poor resistance to infections in the CF lung, the expression of the iNOS gene was investigated in explanted lungs from patients with cystic fibrosis (n = 13), bronchiectasis (n = 3), emphysema (n = 14), and in normal lungs (n = 8).