The purpose of this study was to determine the role of NADPH oxidase in H + secretion by airway epithelia. In whole cell patch clamp recordings primary human tracheal epithelial cells (hTE) and the
...human serous gland cell line Calu-3 expressed a functionally similar zincblockable plasma membrane H + conductance. However, the rate of H + secretion of confluent epithelial monolayers measured in Ussing chambers was 9-fold larger in hTE compared with Calu-3. In
hTE H + secretion was blocked by mucosal ZnCl 2 and the NADPH oxidase blockers acetovanillone and 4-(2-aminoethyl)benzenesulfonyl fluoride (AEBSF), whereas these same blockers
had no effect in Calu-3. We determined levels of transcripts for the NADPH oxidase transmembrane isoforms (Nox1 through -5,
Duox1 and -2, and p22 phox ) and found Duox1, -2, and p22 phox to be highly expressed in hTE, as well as the intracellular subunits p40 phox , p47 phox , and p67 phox . In contrast, Calu-3 lacked transcripts for Duox1, p40 phox , and p47 phox . Anti-Duox antibody staining resulted in prominent apical staining in hTE but no significant staining in Calu-3. When treated
with amiloride to block the Na + /H + exchanger, intracellular pH in hTE acidified at significantly higher rates than in Calu-3, and treatment with AEBSF blocked
acidification. These data suggest a role for an apically located Duox-based NADPH oxidase during intracellular H + production and H + secretion, but not in H + conduction.
Confocal imaging was used to characterize interactions of Pseudomonas aeruginosa (PA, expressing GFP or labeled with Syto 11) with CF airway epithelial cells (CFBE41o-, grown as confluent monolayers ...with unknown polarity on coverglasses) in control conditions and following scratch wounding. Epithelia and PAO1-GFP or PAK-GFP (2 MOI) were incubated with Ringer containing typical extracellular salts, pH and glucose and propidium iodide (PI, to identify dead cells). PAO1 and PAK swam randomly over and did not bind to nonwounded CFBE41o- cells. PA migrated rapidly (began within 20 sec, maximum by 5 mins) and massively (10-80 fold increase, termed "swarming"), but transiently (random swimming after 15 mins), to wounds, particularly near cells that took up PI. Some PA remained immobilized on cells near the wound. PA swam randomly over intact CFBE41o- monolayers and wounded monolayers that had been incubated with medium for 1 hr. Expression of CFTR and altered pH of the media did not affect PA interactions with CFBE41o- wounds. In contrast, PAO1 swarming and immobilization along wounds was abolished in PAO1 (PAO1ΔcheYZABW, no expression of chemotaxis regulatory components cheY, cheZ, cheA, cheB and cheW) and greatly reduced in PAO1 that did not express amino acid receptors pctA, B and C (PAO1ΔpctABC) and in PAO1 incubated in Ringer containing a high concentration of mixed amino acids. Non-piliated PAKΔpilA swarmed normally towards wounded areas but bound infrequently to CFBE41o- cells. In contrast, both swarming and binding of PA to CFBE41o- cells near wounds were prevented in non-flagellated PAKΔfliC. Data are consistent with the idea that (i) PA use amino acid sensor-driven chemotaxis and flagella-driven swimming to swarm to CF airway epithelial cells near wounds and (ii) PA use pili to bind to epithelial cells near wounds.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Department of Molecular and Cell Biology, University of California, Berkeley, California
The lack of functional cystic fibrosis (CF) transmembrane conductance regulator (CFTR) in the apical membranes ...of CF airway epithelial cells abolishes cAMP-stimulated anion transport, and bacteria, eventually including Pseudomonas aeruginosa , bind to and accumulate in the mucus. Flagellin released from P. aeruginosa triggers airway epithelial Toll-like receptor 5 and subsequent NF- B signaling and production and release of proinflammatory cytokines that recruit neutrophils to the infected region. This response has been termed hyperinflammatory because so many neutrophils accumulate; a response that damages CF lung tissue. We first review the contradictory data both for and against the idea that epithelial cells exhibit larger-than-normal proinflammatory signaling in CF compared with non-CF cells and then review proposals that might explain how reduced CFTR function could activate such proinflammatory signaling. It is concluded that apparent exaggerated innate immune response of CF airway epithelial cells may have resulted not from direct effects of CFTR on cellular signaling or inflammatory mediator production but from indirect effects resulting from the absence of CFTRs apical membrane channel function. Thus, loss of Cl , HCO 3 , and glutathione secretion may lead to reduced volume and increased acidification and oxidation of the airway surface liquid. These changes concentrate proinflammatory mediators, reduce mucociliary clearance of bacteria and subsequently activate cellular signaling. Loss of apical CFTR will also hyperpolarize basolateral membrane potentials, potentially leading to increases in cytosolic Ca 2+ , intracellular Ca 2+ , and NF- B signaling. This hyperinflammatory effect of CF on intracellular Ca 2+ and NF- B signaling would be most prominently expressed during exposure to both P. aeruginosa and also endocrine, paracrine, or nervous agonists that activate Ca 2+ signaling in the airway epithelia.
Pseudomonas aeruginosa ; Toll-like receptor; NF- B; oxidative stress; acidic airway surface liquid; calcium
Address for reprint requests and other correspondence: T. E. Machen, Dept. of Molecular and Cell Biology, 231 LSA, Univ. of California at Berkeley, Berkeley, CA 94720-3200 (e-mail: tmachen{at}berkeley.edu )
The human airway is protected by an efficient innate defense mechanism that requires healthy secretion of airway surface liquid (ASL) to clear pathogens from the lungs. Most of the ASL in the upper ...airway is secreted by submucosal glands. In cystic fibrosis (CF), the function of airway submucosal glands is abnormal, and these abnormalities are attributed to anomalies in ion transport across the epithelia lining the different sections of the glands that function coordinately to produce the ASL. However, the ion transport properties of most of the anatomical regions of the gland have never been measured, and there is controversy regarding which segments express CFTR. This makes it difficult to determine the glandular abnormalities that may contribute to CF lung disease. Using a noninvasive, extracellular self-referencing ion-selective electrode technique, we characterized ion transport properties in all four segments of submucosal glands from wild-type and CFTR
swine. In wild-type airways, the serous acini, mucus tubules, and collecting ducts secrete Cl
and Na
into the lumen in response to carbachol and forskolin stimulation. The ciliated duct also transports Cl
and Na
but in the opposite direction, i.e., reabsorption from the ASL, which may contribute to lowering Na
and Cl
activities in the secreted fluid. In CFTR
airways, the serous acini, collecting ducts, and ciliated ducts fail to transport ions after forskolin stimulation, resulting in the production of smaller volumes of ASL with normal Cl
, Na
, and K
concentration.
N‐(3‐Oxododecanoyl)‐l‐homoserine lactone (C12) is produced by Pseudomonas aeruginosa to function as a quorum‐sensing molecule for bacteria–bacteria communication. C12 is also known to influence many ...aspects of human host cell physiology, including induction of cell death. However, the signalling pathway(s) leading to C12‐triggered cell death is (are) still not completely known. To clarify cell death signalling induced by C12, we examined mouse embryonic fibroblasts deficient in “initiator” caspases or “effector” caspases. Our data indicate that C12 selectively induces the mitochondria‐dependent intrinsic apoptotic pathway by quickly triggering mitochondrial outer membrane permeabilisation. Importantly, the activities of C12 to permeabilise mitochondria are independent of activation of both “initiator” and “effector” caspases. Furthermore, C12 directly induces mitochondrial outer membrane permeabilisation in vitro. Overall, our study suggests a mitochondrial apoptotic signalling pathway triggered by C12, in which C12 or its metabolite(s) acts on mitochondria to permeabilise mitochondria, leading to activation of apoptosis.
Lung infection with the fungus
Aspergillus fumigatus (
Af
)
is a common complication in cystic fibrosis (CF) and is associated with loss of pulmonary function. We established a fungal epithelial ...co-culture model to examine the impact of Af infection on CF bronchial epithelial barrier function using Af strains 10AF and AF293-GFP, and the CFBE41o- cell line homozygous for the F508del mutation with (CF
+CFTR
) and without (CF) normal CFTR expression. Following exposure of the epithelial surface to Af conidia, formation of germlings (early stages of fungal growth) was detected after 9-12 hours and hyphae (mature fungal growth) after 12-24 hours. During fungal morphogenesis, bronchial epithelial cells showed signs of damage including rounding, and partial detachment after 24 hours. Fluorescently labeled conidia were internalized after 6 hours and more internalized conidia were observed in CF compared to CF
+CFTR
cells. Infection of the apical surface with 10AF conidia, germlings, or hyphae was performed to determine growth stage-specific effects on tight junction protein zona occludens protein 1 (ZO-1) expression and transepithelial electrical resistance (TER). In response to infection with conidia or germlings, epithelial barrier function degraded time-dependently (based on ZO-1 immunofluorescence and TER) with a delayed onset in CF
+CFTR
cell monolayers and required viable fungi and apical application. Infection with hyphae caused an earlier onset and faster rate of decline in TER compared to conidia and germlings. Gliotoxin, a major Af virulence factor, caused a rapid decline in TER and induced a transient chloride secretory response in CF
+CFTR
but not CF cells. Our findings suggest growth and internalization of Af result in deleterious effects on bronchial epithelial barrier function that occurred more rapidly in the absence of CFTR. Bronchial epithelial barrier breakdown was time-dependent and morphotype-specific and mimicked by acute administration of gliotoxin. Our study also suggests a protective role for CFTR by turning on CFTR-dependent chloride transport in response to gliotoxin, a mechanism that will support mucociliary clearance, and could delay the loss of epithelial integrity during fungal development
in vivo
.
Cystic fibrosis is caused by mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR) channel, which can result in chronic lung disease. The sequence of events ...leading to lung disease is not fully understood but recent data show that the critical pathogenic event is the loss of the ability to clear bacteria due to abnormal airway surface liquid secretion (ASL). However, whether the inhalation of bacteria triggers ASL secretion and whether this is abnormal in cystic fibrosis has never been tested. Here we show, using a novel synchrotron-based in vivo imaging technique, that wild-type pigs display both a basal and a Toll-like receptor-mediated ASL secretory response to the inhalation of cystic fibrosis relevant bacteria. Both mechanisms fail in CFTR
swine, suggesting that cystic fibrosis airways do not respond to inhaled pathogens, thus favoring infection and inflammation that may eventually lead to tissue remodeling and respiratory disease.Cystic fibrosis is caused by mutations in the CFTR chloride channel, leading to reduced airway surface liquid secretion. Here the authors show that exposure to bacteria triggers secretion in wild-type but not in pig models of cystic fibrosis, suggesting an impaired response to pathogens contributes to infection.
Inhaled hypertonic saline (HTS) treatment is used to improve lung health in patients with cystic fibrosis (CF). The current consensus is that the treatment generates an osmotic gradient that draws ...water into the airways and increases airway surface liquid (ASL) volume. However, there is evidence that HTS may also stimulate active secretion of ASL by airway epithelia through the activation of sensory neurons. We tested the contribution of the nervous system and airway epithelia on HTS-stimulated ASL height increase in CF and wild-type swine airway. We used synchrotron-based imaging to investigate whether airway neurons and epithelia are involved in HTS treatment-triggered ASL secretion in CFTR
and wild-type swine. We showed that blocking parasympathetic and sensory neurons in airway resulted in ~50% reduction of the effect of HTS treatment on ASL volume in vivo. Incubating tracheal preparations with inhibitors of epithelial ion transport across airway decreased secretory responses to HTS treatment. CFTR
swine ex-vivo tracheal preparations showed substantially decreased secretory response to HTS treatment after blockage of neuronal activity. Our results indicated that HTS-triggered ASL secretion is partially mediated by the stimulation of airway neurons and the subsequent activation of active epithelia secretion; osmosis accounts for only ~50% of the effect.
Pseudomonas aeruginosa use quorum-sensing molecules, including N-(3-oxododecanoyl)-homoserine lactone (C12), for intercellular communication. C12 activated apoptosis in mouse embryo fibroblasts (MEF) ...from both wild type (WT) and Bax/Bak double knock-out mice (WT MEF and DKO MEF that were responsive to C12, DKOR MEF): nuclei fragmented; mitochondrial membrane potential (Δψmito) depolarized; Ca2+ was released from the endoplasmic reticulum (ER), increasing cytosolic Ca2+ (Cacyto); and caspase 3/7 was activated. DKOR MEF had been isolated from a nonclonal pool of DKO MEF that were non-responsive to C12 (DKONR MEF). RNAseq analysis, quantitative PCR, and Western blots showed that WT and DKOR MEF both expressed genes associated with cancer, including paraoxonase 2 (PON2), whereas DKONR MEF expressed little PON2. Adenovirus-mediated expression of human PON2 in DKONR MEF rendered them responsive to C12: Δψmito depolarized, Cacyto increased, and caspase 3/7 activated. Human embryonic kidney 293T (HEK293T) cells expressed low levels of endogenous PON2, and these cells were also less responsive to C12. Overexpression of PON2, but not PON2-H114Q (no lactonase activity) in HEK293T cells caused them to become sensitive to C12. Because C12 may reach high levels in biofilms in lungs of cystic fibrosis (CF) patients, PON2 lactonase activity may control Δψmito, Ca2+ release from the ER, and apoptosis in CF airway epithelia. Coupled with previous data, these results also indicate that PON2 uses its lactonase activity to prevent Bax- and Bak-dependent apoptosis in response to common proapoptotic drugs like doxorubicin and staurosporine, but activates Bax- and Bak-independent apoptosis in response to C12.
Background:Pseudomonas aeruginosa use N-(3-oxododecanoyl)-homoserine lactone (C12) for intercellular communication; paraoxonase 2 (PON2) is an animal enzyme that cleaves lactones.
Results: C12 elicited apoptosis in mouse and human cells expressing PON2 with intact lactonase activity but not in cells without it.
Conclusion: PON2 mediates C12-induced apoptosis in mammalian cells.
Significance: PON2 in host cells hydrolyzes C12 and promotes C12-induced apoptosis.
A controversial hypothesis pertaining to cystic fibrosis (CF) lung disease is that the CF transmembrane conductance regulator (CFTR) channel fails to inhibit the epithelial Na+ channel (ENaC), ...yielding increased Na+ reabsorption and airway dehydration. We use a non-invasive self-referencing Na+-selective microelectrode technique to measure Na+ transport across individual folds of distal airway surface epithelium preparations from CFTR−/− (CF) and wild-type (WT) swine. We show that, under unstimulated control conditions, WT and CF epithelia exhibit similar, low rates of Na+ transport that are unaffected by the ENaC blocker amiloride. However, in the presence of the cyclic AMP (cAMP)-elevating agents forskolin+IBMX (isobutylmethylxanthine), folds of WT tissues secrete large amounts of Na+, while CFTR−/− tissues absorb small, but potentially important, amounts of Na+. In cAMP-stimulated conditions, amiloride inhibits Na+ absorption in CFTR−/− tissues but does not affect secretion in WT tissues. Our results are consistent with the hypothesis that ENaC-mediated Na+ absorption may contribute to dehydration of CF distal airways.
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•Wild-type swine distal airways respond to cAMP with large rates of Na+secretion•cAMP triggers Na+absorption across the distal airway folds in CFTR−/− swine•cAMP-triggered Na+absorption in CFTR−/− swine distal airway is mediated by ENaC•Loss of cAMP-triggered secretion and increased absorption can dehydrate CF airways
Hyperactive epithelial Na+ channel (ENaC) is believed to contribute to excessive Na+ and fluid reabsorption in cystic fibrosis airways. This hypothesis has been challenged by studies in CFTR−/− swine showing no increased Na+ reabsorption. Luan et al. report that cAMP-stimulated distal airways of CFTR−/− swine suffer from ENaC-mediated Na+ reabsorption.
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