adenosine-3--5--cyclic-phosphorothioate and Cystic-Fibrosis

Cystic fibrosis (CF) is characterized by inflammatory lung disease that significantly contributes to morbidity and mortality. Airway epithelial cells play a role in the inflammatory signaling in CF and have been reported to exhibit a number of dysfunctions in signaling cascades that modulate inflammation. Previously, we reported that the activity of nuclear factor erythroid-derived-like 2 (Nrf2), a transcription factor that regulates antioxidant and cytoprotective protein expression, is diminished in CF epithelia (7). In this report, we examined the mechanism of Nrf2 dysregulation in vitro in human airway epithelial cell lines and primary cells and in vivo in nasal epithelia excised from ΔF508 CF mutant mice. We found that cAMP-mediated signaling markedly reduces Nrf2 activity in CF vs. non-CF cells. Rp-cAMPS, a cAMP competitor, significantly corrected Nrf2 activity in CF cells, predominantly by increasing the nuclear accumulation of the transcription factor. Furthermore, we found that Rp-cAMPS significantly decreased NF-κB activation following inflammatory stimulation of CF cells. Further investigation revealed that Nrf2 and NF-κB compete for the transcriptional coactivator cAMP responsive element-binding protein (CREB) binding protein (CBP) and that Rp-cAMPS shifts CBP association in favor of Nrf2. Thus our findings provide a link between feedback to CF transmembrane regulator dysfunction and dysregulation of an inflammatory signaling pathway that modulates the coordinated activities of Nrf2 and NF-κB. Furthermore, our studies suggest that strategies that shift CBP association away from NF-κB and toward Nrf2 could have potential therapeutic efficacy for reducing inflammation in patients with CF.

Topics: Animals; Cell Line; CREB-Binding Protein; Cyclic AMP; Cyclic AMP Response Element-Binding Protein; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Epithelial Cells; Humans; Hydrogen Peroxide; Inflammation; Lung; Mice; Mice, Inbred C57BL; Mice, Transgenic; NF-E2-Related Factor 2; Respiratory Mucosa; Signal Transduction; Thionucleotides; Transcription Factor RelA

The goal of this study was to identify a mechanism regulating cholesterol accumulation in cystic fibrosis (CF) cells. Both CFTR activation and expression are regulated by the cAMP pathway, and it is hypothesized that a feedback response involving this pathway may be involved in the phenotype of cholesterol accumulation. To examine the role of the cAMP pathway in cholesterol accumulation, we treated two CF model cell lines with the Rp diastereomer of adenosine 3',5'-cyclic monophosphorothioate (Rp-cAMPS) and visualized by filipin staining. Rp-cAMPS treatment eliminated cholesterol accumulation in CF cells, whereas 8-bromo-cAMP treatment led to cholesterol accumulation in wild-type cells. To confirm these findings in an independent model system, we also examined the role of cAMP in modulating cholesterol accumulation in Niemann-Pick type C (NPC) fibroblasts. Expression of the protein related to NPC, NPC1, is also directly regulated by cAMP; therefore, it is postulated that NPC cells exhibit the same cAMP-mediated control of cholesterol accumulation. Cholesterol accumulation in NPC cells also was reduced by the presence of Rp-cAMPS. Expression of beta-arrestin-2 (betaarr2), a marker of cellular response to cAMP signaling, was significantly elevated in CF model cells, Cftr(-/-) MNE, primary tissue obtained by nasal scrapes from CF subjects, and in NPC fibroblasts compared with respective controls.

Topics: 8-Bromo Cyclic Adenosine Monophosphate; Animals; Arrestins; beta-Arrestin 2; beta-Arrestins; Cell Line; Cholesterol; Cyclic AMP; Cyclic AMP Response Element-Binding Protein; Cystic Fibrosis; Epithelium; Fibroblasts; Humans; Mice; Niemann-Pick Disease, Type C; Phosphorylation; Protein Transport; Receptors, Adrenergic, beta-2; Thionucleotides

Previously, we reported that in the isolated perfused rabbit lung, red blood cells (RBCs) obtained from either rabbits or healthy humans were a required component of the perfusate to unmask evidence of nitric oxide (NO) participation in regulation of the pulmonary circulation. In addition, we found that mechanical deformation of rabbit and healthy human RBCs released ATP, a known agonist for enhanced NO synthesis. In contrast, RBCs obtained from patients with cystic fibrosis (CF) did not release ATP in response to mechanical deformation. The coexistence of airway disease and alveolar hypoxia in patients with CF precluded the drawing of conclusions relating a defect in RBC ATP release with the pulmonary hypertension associated with CF. Airway disease and alveolar hypoxia are not, however, features of primary pulmonary hypertension (PPH), a human condition of unknown etiology. We postulated that a defect in NO generation might contribute to the increased pulmonary vascular resistance in PPH, and as a first step, we hypothesized that RBCs obtained from patients with PPH would not release ATP. In contrast to RBCs of healthy humans, when RBCs of PPH patients were passed through filters (average pore size 12, 8, or 5 microm), ATP was not released and the RBCs exhibited reduced deformability. Moreover, when incubated with the active cAMP analogue, Sp-cAMP (100 microM), an activator of the CF transmembrane conductance regulator, ATP was not released. These results demonstrate that RBCs obtained from patients with PPH fail to release ATP whether the stimulus is mechanical or pharmacological. Thus, failure of RBCs to release ATP in patients with PPH might be a major pathogenetic factor that accounts for the heretofore unknown etiology of their pulmonary hypertension.

Topics: Adenosine Triphosphate; Adult; Animals; Case-Control Studies; Cyclic AMP; Cystic Fibrosis; Erythrocyte Deformability; Erythrocytes; Female; Humans; Hypertension, Pulmonary; In Vitro Techniques; Male; Rabbits; Stress, Mechanical; Thionucleotides

Epithelia of humans and mice with cystic fibrosis are unable to secrete chloride in response to a chloride gradient or to cAMP-elevating agents. Bioelectrical properties measured using the nasal transepithelial potential difference (TEPD) assay are believed to reflect these cystic fibrosis transmembrane conductance regulator (CFTR)-dependent chloride transport defects. Although the response to forskolin is CFTR mediated, the mechanisms responsible for the response to a chloride gradient are unknown. TEPD measurements performed on inbred mice were used to compare the responses to low chloride and forskolin in vivo. Both responses show little correlation between or within inbred strains of mice, suggesting they are mediated through partially distinct mechanisms. In addition, these responses were assayed in the presence of several chloride channel inhibitors, including DIDS, diphenylamine-2-carboxylate, glibenclamide, and 5-nitro-2-(3-phenylpropylamino)-benzoic acid, and a protein kinase A inhibitor, the Rp diastereomer of adenosine 3',5'-cyclic monophosphothioate (Rp-cAMPS). The responses to low chloride and forskolin demonstrate significantly different pharmacological profiles to both DIDS and Rp-cAMPS, indicating that channels in addition to CFTR contribute to the low chloride response.

Topics: 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; Amiloride; Animals; Chloride Channels; Chlorides; Colforsin; Cyclic AMP; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Disease Models, Animal; Female; Humans; Ion Transport; Membrane Potentials; Mice; Mice, Inbred Strains; Nasal Mucosa; Thionucleotides

Specific mutations in the cystic fibrosis transmembrane conductance regulator (CFTR), the most common autosomal recessive fatal genetic disease of Caucasians, result in the loss of epithelial cell adenosine 3',5'-cyclic-monophosphate (cAMP)-stimulated Cl- conductance. We show that the influx of a fluorescent dye, dihydrorhodamine 6G (dR6G), is increased in cells expressing human CFTR after retrovirus- and adenovirus-mediated gene transfer. dR6G influx is stimulated by cAMP and is inhibited by antagonists of cAMP action. Dye uptake is ATP-dependent and inhibited by Cl- removal or the addition of 10 mM SCN-. Increased staining is associated with functional activation of CFTR Cl- permeability. dR6G staining enables both the fluorescent assessment of CFTR function and the identification of successfully corrected cells after gene therapy.

Topics: 3T3 Cells; Adenoviridae; Animals; ATP Binding Cassette Transporter, Subfamily B, Member 1; Biological Transport; Bronchi; Cell Line; Chlorides; Cyclic AMP; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Endocytosis; Epithelium; Fluorescent Dyes; Gene Expression; Genetic Vectors; Humans; Kinetics; Mice; Microscopy, Fluorescence; Recombinant Proteins; Retroviridae; Rhodamines; Staining and Labeling; Thionucleotides; Transfection

Many heterologously expressed mutants of the cystic fibrosis transmembrane conductance regulator (CFTR) exhibit residual chloride channel activity that can be stimulated by agonists of the adenylate cyclase/protein kinase A pathway. Because of clinical implications for cystic fibrosis of activating mutants in vivo, we are investigating whether deltaF508, the most common disease-associated CFTR mutation, can be activated in airway epithelial cells. We have found that, 36Cl- efflux can be stimulated 19-61% above baseline by beta-adrenoreceptor agonists and cGI-phosphodiesterase inhibitors in transformed nasal polyp (CF-T43) cells homozygous for the deltaF508 mutation. The increase in 36Cl- permeability is diminished by protein kinase A inhibitors and is not mediated by an increase in intracellular calcium concentrations. Preincubation of CF-T43 cells with CFTR anti-sense oligonucleotides prevented an increase in 36Cl- efflux in response to beta-agonist and phosphodiesterase inhibitor. Primary cells isolated from CF nasal polyps gave similar results. These data indicate that endogenous levels of deltaF508 protein can be stimulated to increase 36Cl- permeability in airway epithelial cells.

Topics: 1-Methyl-3-isobutylxanthine; Adrenergic beta-Agonists; Albuterol; Base Sequence; Calcium; Cell Line; Chlorides; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Drug Synergism; Egtazic Acid; Enzyme Inhibitors; Epithelium; Humans; Isoproterenol; Kinetics; Membrane Potentials; Milrinone; Molecular Sequence Data; Oligodeoxyribonucleotides; Oligonucleotides, Antisense; Phosphodiesterase Inhibitors; Pyridones; Thionucleotides

The role of arachidonic acid metabolites in the regulation of apical cell membrane Cl- conductance and transepithelial transport of fluid and Cl- by cultured pancreatic cells from cystic fibrosis (CFPAC-1) and corrected (PAC-1) cell lines was evaluated by the use of inhibitors. CFPAC-1 cells did not exhibit an apical membrane Cl- conductance, absorbed Cl- and fluid, and did not respond to stimulation or inhibition of cAMP action. PAC-1 cells exhibited a cAMP-responsive apical Cl- conductance, which was blocked by indomethacin, a cyclooxygenase inhibitor. Ketoconazole, an epoxygenase inhibitor, had virtually no effects on PAC-1 cell Cl- conductance but caused CFPAC-1 cells to develop a cAMP-insensitive Cl- conductance, blocked Cl- and fluid absorption, and reduced transepithelial electrical resistance. Ketoconazole treatment effectively reversed the cystic fibrosis defect in these cultured cells.

Topics: Absorption; Cell Line; Cell Membrane; Chloride Channels; Chlorides; Colforsin; Cyclic AMP; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Epithelium; Humans; Hydrogen-Ion Concentration; Indomethacin; Ion Channels; Ketoconazole; Masoprocol; Membrane Potentials; Membrane Proteins; Proadifen; Thionucleotides; Transfection