Soluble Adenylyl Cyclase Is Localized to Cilia and Contributes to Ciliary Beat Frequency Regulation via Production of cAMP

Ciliated airway epithelial cells are subject to sustained changes in intracellular CO2/HCO3− during exacerbations of airway diseases, but the role of CO2/HCO3−-sensitive soluble adenylyl cyclase (sAC) in ciliary beat regulation is unknown. We now show not only sAC expression in human airway epithelia (by RT-PCR, Western blotting, and immunofluorescence) but also its specific localization to the axoneme (Western blotting and immunofluorescence). Real time estimations of [cAMP] changes in ciliated cells, using FRET between fluorescently tagged PKA subunits (expressed under the foxj1 promoter solely in ciliated cells), revealed CO2/HCO3−-mediated cAMP production. This cAMP production was specifically blocked by sAC inhibitors but not by transmembrane adenylyl cyclase (tmAC) inhibitors. In addition, this cAMP production stimulated ciliary beat frequency (CBF) independently of intracellular pH because PKA and sAC inhibitors were uniquely able to block CO2/HCO3−-mediated changes in CBF (while tmAC inhibitors had no effect). Thus, sAC is localized to motile airway cilia and it contributes to the regulation of human airway CBF. In addition, CO2/HCO3− increases indeed reversibly stimulate intracellular cAMP production by sAC in intact cells

Expiratory flow rate, breath hold and anatomic dead space influence electronic nose ability to detect lung cancer

BACKGROUND: Electronic noses are composites of nanosensor arrays. Numerous studies showed their potential to detect lung cancer from breath samples by analysing exhaled volatile compound pattern ("breathprint"). Expiratory flow rate, breath hold and inclusion of anatomic dead space may influence the exhaled levels of some volatile compounds; however it has not been fully addressed how these factors affect electronic nose data. Therefore, the aim of the study was to investigate these effects. METHODS: 37 healthy subjects (44 +/- 14 years) and 27 patients with lung cancer (60 +/- 10 years) participated in the study. After deep inhalation through a volatile organic compound filter, subjects exhaled at two different flow rates (50 ml/sec and 75 ml/sec) into Teflon-coated bags. The effect of breath hold was analysed after 10 seconds of deep inhalation. We also studied the effect of anatomic dead space by excluding this fraction and comparing alveolar air to mixed (alveolar + anatomic dead space) air samples. Exhaled air samples were processed with Cyranose 320 electronic nose. RESULTS: Expiratory flow rate, breath hold and the inclusion of anatomic dead space significantly altered "breathprints" in healthy individuals (p 0.05). These factors also influenced the discrimination ability of the electronic nose to detect lung cancer significantly. CONCLUSIONS: We have shown that expiratory flow, breath hold and dead space influence exhaled volatile compound pattern assessed with electronic nose. These findings suggest critical methodological recommendations to standardise sample collections for electronic nose measurements

Norepinephrine transport by the extraneuronal monoamine transporter in human bronchial arterial smooth muscle cells

Inhaled glucocorticosteroids (GSs) cause acute, alpha1-adrenoreceptor (AR)-mediated bronchial vasoconstriction. After release from sympathetic nerves, norepinephrine (NE) must be taken up into cells for deactivation by intracellular enzymes. Because postsynaptic cellular NE uptake is steroid sensitive, GSs could increase NE concentrations at alpha1-AR, causing vasoconstriction. We therefore evaluated mRNA expression of different NE transporters in human bronchial arterial smooth muscle and pharmacologically characterized NE uptake into these cells. RT-PCR demonstrated mRNA expression of the extraneuronal monoamine transporter (EMT) and organic cation transporter 1 (OCT-1). Fluorometric uptake assay showed time (within minutes)- and concentration-dependent NE uptake by freshly isolated bronchial arterial smooth muscle cells (SMC) with an estimated Km of 240 microM. Corticosterone and O-methylisoprenaline (1 microM each), but not desipramine, inhibited NE uptake, a profile indicative of NE uptake by EMT, but not OCT-1. Budesonide and methylprednisolone inhibited uptake with IC50 values of 0.9 and 5.6 microM, respectively. Corticosterone's action was reversible and not sensitive to RU-486 (GS receptor antagonist), actinomycin D (transcription inhibitor), or cycloheximide (protein synthesis inhibitor). Corticosterone made membrane impermeant by coupling to BSA also blocked NE uptake. Immunocytochemistry indicated a specific membrane binding site for corticosterone on bronchial arterial SMC. These data demonstrate that although human bronchial arterial SMC express OCT-1 and EMT, EMT is the predominant plasma membrane transporter for NE uptake. This process can be inhibited by GSs, likely via a specific membrane binding site. This nongenomic GS action (increasing NE concentrations at alpha1-AR) could explain acute bronchial vasoconstriction caused by inhaled GSs

Calcium-mediated, purinergic stimulation and polarized localization of calcium-sensitive adenylyl cyclase isoforms in human airway epithelia

Purinergic stimulation of human airway epithelia results in a prolonged increase in ciliary beat frequency that depends on calcium-mediated cAMP production [Lieb, T., Wijkstrom Frei, C., Frohock, J.I., Bookman, R.J. and Salathe, M. (2002) Prolonged increase in ciliary beat frequency after short-term purinergic stimulation in human airway epithelial cells. J. Physiol. (Lond.) 538, 633–646]. Here, fully differentiated human airway epithelial cells in culture are shown to express calcium-stimulated transmembrane adenylyl cyclase (tmAC) isoforms (types 1, 3, and 8) by reverse transcription polymerase chain reaction. Immunohistochemistry of tracheal sections and fully differentiated airway epithelial cell cultures revealed polarized expression of these tmACs, with types 1 and 8 localized to the apical membrane and thus at the position required for ciliary regulation. Real-time, ciliated-cell specific cAMP production by tmACs upon apical, purinergic stimulation with UTP was confirmed using fluorescent energy resonance transfer between fluorescently tagged PKA subunits

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 HCO3−/CO2 stimulation to increase ciliary beat frequency (CBF). Because apical HCO3− 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 HCO3−/CO2 exposure in part because of greater intracellular acidification from unbalanced CO2 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 HCO3−/CO2 perfusion was higher in normal compared with CF cells. Inhibition of bicarbonate influx via CFTR (CFTRinh172) 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 HCO3−/CO2 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