Decreased soluble adenylyl cyclase activity in cystic fibrosis is related to defective apical bicarbonate exchange and affects ciliary beat frequency regulation.

Human airway cilia contain soluble adenylyl cyclase (sAC) that produces cAMP upon HCO(3)(-)/CO(2) stimulation to increase ciliary beat frequency (CBF). Because apical HCO(3)(-) exchange depends on cystic fibrosis transmembrane conductance regulator (CFTR), malfunctioning CFTR might impair sAC-mediated CBF regulation in cells from patients with cystic fibrosis (CF). By Western blot, sAC isoforms are equally expressed in normal and CF airway epithelial cells, but CBF decreased more in CF than normal cells upon increased apical HCO(3)(-)/CO(2) exposure in part because of greater intracellular acidification from unbalanced CO(2) influx (estimated by 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF) fluorescence). Importantly, ciliated cell-specific cAMP production (estimated by FRET fluorescence ratio changes of tagged cAMP-dependent protein kinase (PKA) subunits expressed under a ciliated cell-specific promoter) in response to increased apical HCO(3)(-)/CO(2) perfusion was higher in normal compared with CF cells. Inhibition of bicarbonate influx via CFTR (CFTR(inh)172) and inhibition of sAC (KH7) and PKA activation (H89) led to larger CBF declines in normal cells, now comparable with changes seen in CF cells. These inhibitors also reduced FRET changes in normal cells to the level of CF cells with the expected exception of H89, which does not prevent dissociation of the fluorescently tagged PKA subunits. Basolateral permeabilization and subsequent perfusion with HCO(3)(-)/CO(2) rescued CBF and FRET changes in CF cells to the level of normal cells. These results suggest that CBF regulation by sAC-produced cAMP could be impaired in CF, thereby possibly contributing to mucociliary dysfunction in this disease, at least during disease exacerbations when airway acidification is common.

Modulation of Wnt signaling is essential for the differentiation of ciliated epithelial cells in human airways.

Wnt signaling is essential for the differentiation of airway epithelial cells during development. Here, we examined the role of Wnt signaling during redifferentiation of ciliated airway epithelial cells in vitro at the air liquid interface as a model of airway epithelial repair. Phases of proliferation and differentiation were defined. Markers of squamous metaplasia and epithelial ciliation were followed while enhancing ß-catenin signaling by blocking glycogen synthase kinase 3ß with SB216763 and shRNA as well as inhibiting canonical WNT signaling with apical application of Dickkopf 1 (Dkk1). Our findings indicate that enhanced ß-catenin signaling decreases the number of ciliated cells and causes squamous changes in the epithelium, whereas treatment with DDk1 leads to an increased number of ciliated cells.

Hemodialysis vascular access survival: upper-arm native arteriovenous fistula.

Achieving Dialysis Outcomes Quality Initiative guidelines for native arteriovenous fistulae using the radiocephalic forearm fistula (lower-arm fistula [LAF]) is difficult. This study reports results using the upper-arm native arteriovenous fistula (UAF). From a prospective access database (1992 to 1998), this study was based on 204 patients (322 accesses). Average patient age was 56 +/- 1 years, 63% were men, and 47% had diabetes. A native fistula was the first access in 73% of patients (36%, LAFs; 37%, UAFs) and accounted for 48% of subsequent accesses (13%, LAFs; 35%, UAFs). Younger men were more likely to receive an LAF, but there was no demographic difference between patients receiving a UAF or arteriovenous graft (AVG). Both primary unassisted and cumulative access patencies were significantly better for UAFs than either LAFs or AVGs. For first accesses, cumulative access patency rates at 1, 3, and 5 years were 71%, 57%, and 57% for UAFs; 54%, 46%, and 36% for LAFs; and 54%, 28%, and 0% for AVGs (P < 0.01). Despite shorter access survival, AVGs required more total access procedures than either UAFs or LAFs (procedures per access: 2.5, 1.0, and 0.6 for AVGs, UAFs, and LAFs, respectively). When used, catheters were required for dialysis for a longer time for UAFs (median catheter days, 36, 53, and 56 for AVGs, LAFs, and UAFs, respectively; P < 0.05). Access flow rates were greater in UAFs (1,247 mL/min; n = 48; P < 0.01) than AVGs (851 mL/min; n = 30) or LAFs (938 mL/min; n = 31). There was no evidence that UAFs were banded or ligated for steal syndromes or heart failure more often than AVGs or LAFs. These results show that the UAF is a good alternative to an AVG for achieving Dialysis Outcomes Quality Initiative guidelines.