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The volume and composition of a thin layer of liquid covering the airway surface defend the lung from inhaled pathogens and debris. Airway epithelia secrete [Cl.sup.-] into the airway surface liquid through cystic fibrosis transmembrane conductance regulator (CFTR) channels, thereby increasing the volume of airway surface liquid. The discovery that pulmonary ionocytes contain high levels of CFTR led us to predict that ionocytes drive secretion. However, we found the opposite. Elevating ionocyte abundance increased liquid absorption, whereas reducing ionocyte abundance increased secretion. In contrast to other airway epithelial cells, ionocytes contained barttin/[Cl.sup.-] channels in their basolateral membrane. Disrupting barttin/[Cl.sup.-] channel function impaired liquid absorption, and overexpressing barttin/[Cl.sup.-] channels increased absorption. Together, apical CFTR and basolateral barttin/[Cl.sup.-] channels provide an electrically conductive pathway for [Cl.sup.-] flow through ionocytes, and the transepithelial voltage generated by apical [Na.sup.+] channels drives absorption. These findings indicate that ionocytes mediate liquid absorption, and secretory cells mediate liquid secretion. Segregating these counteracting activities to distinct cell types enables epithelia to precisely control the airway surface. Moreover, the divergent role of CFTR in ionocytes and secretory cells suggests that cystic fibrosis disrupts both liquid secretion and absorption., Introduction Pulmonary ionocytes are a rare cell type accounting for approximately 1% of airway epithelial cells. Ionocytes have attracted attention because, although rare, in airway epithelia they contain about half [...]

Goblet cell metaplasia, a disabling hallmark of chronic lung disease, lacks curative treatments at present. To identify novel therapeutic targets for goblet cell metaplasia, we studied the transcriptional response profile of IL-13-exposed primary human airway epithelia in vitro and asthmatic airway epithelia in vivo. A perturbation-response profile connectivity approach identified geldanamycin, an inhibitor of heat shock protein 90 (HSP90) as a candidate therapeutic target. Our experiments confirmed that geldanamycin and other HSP90 inhibitors prevented IL-13-induced goblet cell metaplasia in vitro and in vivo. Geldanamycin also reverted established goblet cell metaplasia. Geldanamycin did not induce goblet cell death, nor did it solely block mucin synthesis or IL-13 receptor-proximal signaling. Geldanamycin affected the transcriptome of airway cells when exposed to IL-13, but not when exposed to vehicle. We hypothesized that the mechanism of action probably involves TGF-[beta], ERBB, or EHF, which would predict that geldanamycin would also revert IL-17-induced goblet cell metaplasia, a prediction confirmed by our experiments. Our findings suggest that persistent airway goblet cell metaplasia requires HSP90 activity and that HSP90 inhibitors will revert goblet cell metaplasia, despite active upstream inflammatory signaling. Moreover, HSP90 inhibitors may be a therapeutic option for airway diseases with goblet cell metaplasia of unknown mechanism., Introduction Human lungs constantly interact with the environment. In some individuals, various environmental exposures cause chronic mucus hypersecretion, leading to disability and reduced quality of life (1-3). Goblet cell metaplasia [...]

Na/K ATPase activity is essential for ion transport across epithelia. FXYD3, a γ subunit of the Na/K ATPase, is expressed in the airway, but its function remains undetermined. Single-cell RNA sequencing and immunohistochemistry revealed that FXYD3 localizes within the basolateral membrane of all airway epithelial cells. To study FXYD3 function, we reduced FXYD3 expression using siRNA. After permeabilizing the apical membrane with nystatin, epithelia pretreated with FXYD3-targeting siRNA had lower ouabain-sensitive short-circuit currents than control epithelia. FXYD3-targeting siRNA also reduced amiloride-sensitive short-circuit currents and liquid absorption across intact epithelia. These data are consistent with FXYD3 facilitating Na+ and liquid absorption. FXYD3 may be needed to maintain the high rates of Na+ and fluid absorption observed for airway and other FXYD3-expressing epithelia. [ABSTRACT FROM AUTHOR]

In cystic fibrosis (CF), the loss of cystic fibrosis transmembrane conductance regulator (CFTR) mediated Cl− and HCO3− secretion across the epithelium acidifies the airway surface liquid (ASL). Acidic ASL alters two key host defense mechanisms: Rapid ASL bacterial killing and mucociliary transport (MCT). Aerosolized tromethamine (Tham) increases ASL pH and restores the ability of ASL to rapidly kill bacteria in CF pigs. In CF pigs, clearance of insufflated microdisks is interrupted due to abnormal mucus causing microdisks to abruptly recoil. Aerosolizing a reducing agent to break disulfide bonds that link mucins improves MCT. Here, we are interested in restoring MCT in CF by aerosolizing Tham, a buffer with a pH of 8.4. Because Tham is hypertonic to serum, we use an acidified formulation as a control. We measure MCT by tracking the caudal movement of individual tantalum microdisks with serial chest computed tomography scans. Alkaline Tham improves microdisk clearance to within the range of that seen in non‐CF pigs. It also partially reverses MCT defects, including reduced microdisk recoil and elapse time until they start moving after methacholine stimulation in CF pig airways. The effect is not due to hypertonicity, as it is not seen with acidified Tham or hypertonic saline. This finding indicates acidic ASL impairs CF MCT and suggests that alkalinization of ASL pH with inhaled Tham may improve CF airway disease. [ABSTRACT FROM AUTHOR]

Objectives: In cystic fibrosis (CF), loss of CFTR-mediated bicarbonate secretion reduces the airway surface liquid (ASL) pH causing airway host defense defects. Aerosolized sodium bicarbonate can reverse these defects, but its effects are short-lived. Aerosolized tromethamine (THAM) also raises the ASL pH but its effects are much longer lasting. In this pilot study, we tested the hypothesis that nasally administered THAM would alter the nasal bacterial composition in adults with and without CF. Methods: Subjects (n = 32 total) received intranasally administered normal saline or THAM followed by a wash out period prior to receiving the other treatment. Nasal bacterial cultures were obtained prior to and after each treatment period. Results: At baseline, nasal swab bacterial counts were similar between non-CF and CF subjects, but CF subjects had reduced microbial diversity. Both nasal saline and THAM were well-tolerated. In non-CF subjects, nasal airway alkalinization decreased both the total bacterial density and the gram-positive bacterial species recovered. In both non-CF and CF subjects, THAM decreased the amount of Corynebacterium accolens detected, but increased the amount of Corynebacterium pseudodiphtheriticum recovered on nasal swabs. A reduction in Staphylococcus aureus nasal colonization was also found in subjects who grew C. pseudodiphtheriticum. Conclusions: This study shows that aerosolized THAM is safe and well-tolerated and that nasal airway alkalinization alters the composition of mucosal bacterial communities. [ABSTRACT FROM AUTHOR]

Cystic fibrosis (CF) pigs develop disease with features remarkably similar to those in people with CF, including exocrine pancreatic destruction, focal biliary cirrhosis, micro-gallbladder, vas deferens loss, airway disease, and [...]

Acute respiratory infections are responsible for more than 4 million deaths each year. Neutrophils play an essential role in the innate immune response to lung infection. These cells have an [...]

Cystic fibrosis (CF) is a life-shortening disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene (1). Although bacterial lung infection and the resulting inflammation cause most [...]

The family of zinc-and calcium-dependent matrix metalloproteases (MMPs) play an important role in remodeling of the airways in disease. Transcriptional regulation by proinflammatory cytokines increases lymphocyte-derived MMP9 levels in the airway lumen of asthmatics. Moreover, the levels of the MMP9 inhibitor, tissue inhibitor of metalloprotease (TIMP1), are decreased leading to increased protease activity. The mechanism by which MMP9 activity leads to asthma pathogenesis and remodeling remains unclear. Using a model of well-differentiated human airway epithelia, we found that apical MMP9 significantly increases transepithelial conductance. Moreover, apical MMP9 treatment decreased immunostaining of tight junction proteins suggesting disruption of barrier function. Consistent with this, viruses gained access to the epithelial basolateral surface after MMP9 treatment, which increased infection efficiency. All of these effects were blocked by TIMP1. In addition, loss of epithelial integrity correlated with increased epithelial cell death. Thus we hypothesized that MMP9 exerts its effects on the epithelium by cleaving one or more components of cell-cell junctions and triggering anoikis. Taken together, these data suggest that a component of airway remodeling associated with asthma may be directly regulated by MMP9. protease; adhesion; cell death

Introduction: Vitamin D supplementation has been suggested to enhance immunity during respiratory infection season. We tested the effect of active vitamin D (calcitriol) supplementation on key airway innate immune mechanisms in vitro. Methods: Primary human airway epithelial cells (hAECs) grown at the air liquid interface were supplemented with 10−7 M calcitriol for 24 hours (or a time course) and their antimicrobial airway surface liquid (ASL) was tested for pH, viscoscity, and antibacterial and antiviral properties. We also tested hAEC ciliary beat frequency (CBF). Next, we assessed alterations to hAEC gene expression using RNA sequencing, and based on results, we measured neutrophil migration across hAECs. Results: Calcitriol supplementation enhanced ASL bacterial killing of Staphylococcus aureus (p = 0.02) but did not enhance its antiviral activity against 229E-CoV. It had no effect on ASL pH or viscosity at three timepoints. Lastly, it did not affect hAEC CBF or neutrophil migration, although there was a trend of enhanced migration in the presence of a neutrophil chemokine (p = 0.09). Supplementation significantly altered hAEC gene expression, primarily of AMP-related genes including CAMP and TREM1. Conclusion: While vitamin D supplementation did not have effects on many airway innate immune mechanisms, it may provide a useful tool to resolve respiratory bacterial infections. [ABSTRACT FROM AUTHOR]

Lack of CFTR (cystic fibrosis transmembrane conductance regulator) affects the transcriptome, composition, and function of large and small airway epithelia in people with advanced cystic fibrosis (CF); however, whether lack of CFTR causes cell-intrinsic abnormalities present at birth versus inflammation-dependent abnormalities is unclear. We performed a single-cell RNA-sequencing census of microdissected small airways from newborn CF pigs, which recapitulate CF host defense defects and pathology over time. Lack of CFTR minimally affected the transcriptome of large and small airways at birth, suggesting that infection and inflammation drive transcriptomic abnormalities in advanced CF. Importantly, common small airway epithelial cell types expressed a markedly different transcriptome than corresponding large airway cell types. Quantitative immunohistochemistry and electrophysiology of small airway epithelia demonstrated basal cells that reach the apical surface and a water and ion transport advantage. This single cell atlas highlights the archetypal nature of airway epithelial cells with location-dependent gene expression and function. [ABSTRACT FROM AUTHOR]

Pseudomonas aeruginosa uses quorum sensing, an interbacterial communication system, to regulate gene expression. The signaling molecule N-3-oxododecanoyl homoserine lactone (3OC12-HSL) is thought to play a central role in quorum sensing. Since 3OC12-HSL can be degraded by paraoxonase (PON) family members, we hypothesized that PONs regulate P. aeruginosa virulence in vivo. We chose Drosophila melanogaster as our model organism because it has been shown to be a tractable model for investigating host-pathogen interactions and lacks PONs. By using quorum-sensing--deficient P. aeruginosa, synthetic acyl-HSLs, and transgenic expression of human PON1, we investigated the role of 3OC12-HSL and PON1 on P. aeruginosa virulence. We found that P. aeruginosa virulence in flies was dependent upon 3OC12-HSL. PON1 transgenic flies expressed enzymatically active PON1 and thereby exhibited arylesterase activity and resistance to organophosphate toxicity. Moreover, PON1 flies were protected from P. aeruginosa lethality, and protection was dependent on the lactonase activity of PON1. Our findings show that PON1 can interfere with quorum sensing in vivo and provide insight into what we believe is a novel role for PON1 in the innate immune response to quorum-sensing--dependent pathogens. These results raise intriguing possibilities about human-pathogen interactions, including potential roles for PON1 as a modifier gene and for PON1 protein as a regulator of normal bacterial florae, a link between infection/inflammation and cardiovascular disease, and a potential therapeutic modality., Introduction The paraoxonase (PON) family in mammals is made up of 3 members: PON1, PON2, and PON3. PON-like proteins are evolutionarily conserved, including in Caenorhabditis elegans, but interestingly are absent [...]

Airway disease currently causes most of the morbidity and mortality in patients with cystic fibrosis (CF). However, understanding the pathogenesis of CF lung disease and developing novel therapeutic strategies have been hampered by the limitations of current models. Although the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR) has been targeted in mice, CF mice fail to develop lung or pancreatic disease like that in humans. In many respects, the anatomy, biochemistry, physiology, size, and genetics of pigs resemble those of humans. Thus pigs with a targeted CFTR gene might provide a good model for CF. Here, we review aspects of porcine airways and lung that are relevant to CF.

Background: Sustained exposure to ambient particulate matter (PM) is a global cause of mortality. Coal fly ash (CFA) is a byproduct of coal combustion and is a source of anthropogenic PM with worldwide health relevance. The airway epithelia are lined with fluid called airway surface liquid (ASL), which contains antimicrobial proteins and peptides (AMPs). Cationic AMPs bind negatively charged bacteria to exert their antimicrobial activity. PM arriving in the airways could potentially interact with AMPs in the ASL to affect their antimicrobial activity. Objectives: We hypothesized that PM can interact with ASL AMPs to impair their antimicrobial activity. Methods: We exposed pig and human airway explants, pig and human ASL, and the human cationic AMPs b-defensin-3, LL-37, and lysozyme to CFA or control. Thereafter, we assessed the antimicrobial activity of exposed airway samples using both bioluminescence and standard colonyforming unit assays. We investigated PM-AMP electrostatic interaction by attenuated total reflection Fourier-transform infrared spectroscopy and measuring the zeta potential. We also studied the adsorption of AMPs on PM. Results: We found increased bacterial survival in CFA-exposed airway explants, ASL, and AMPs. In addition, we report that PM with a negative surface charge can adsorb cationic AMPs and form negative particle-protein complexes. Conclusion: We propose that when CFA arrives at the airway, it rapidly adsorbs AMPs and creates negative complexes, thereby decreasing the functional amount of AMPs capable of killing pathogens. These results provide a novel translational insight into an early mechanism for how ambient PM increases the susceptibility of the airways to bacterial infection. https://doi.org/10.1289/EHP876, Introduction Worldwide, 3.7 million deaths were attributable to ambient air pollution in 2012 [World Health Organization (WHO) 2014]. A major constituent of ambient air pollution is particulate matter (PM), a [...]

Pseudomonas aeruginosa is an important cause of nosocomial infections and is frequently present in the airways of cystic fibrosis patients. Quorum sensing mediates P. aeruginosa's virulence and biofilm formation through density-dependent interbacterial signaling with autoinducers. N-3-oxododecanoyl homoserine lactone (3OC12-HSL) is the major autoinducer in P. aeruginosa. We have previously shown that human airway epithelia and paraoxonases (PONs) degrade 3OC 12-HSL. This study investigated the role of PON1, PON2, and PON3 in airway epithelial cell inactivation of 3OC12-HSL. All three PONs were present in murine tracheal epithelial cells, with PON2 and PON3 expressed at the highest levels. Lysates of tracheal epithelial cells from PON2, but not PON1 or PON3, knockout mice had impaired 3OC12-HSL inactivation compared with wild-type mice. In contrast, PON1-, PON2-, or PON3-targeted deletions did not affect 3OC12-HSL degradation by intact epithelia. Overexpression of PON2 enhanced 3OC 12-HSL degradation by human airway epithelial cell lysates but not by intact epithelia. Finally, using a quorum-sensing reporter strain of P. aeruginosa, we found that quorum sensing was enhanced in PON2-deficient airway epithelia. In summary, these results show that loss of PON2 impairs 3OC12-HSL degradation by airway epithelial cells and suggests that diffusion of 3OC 12-HSL into the airway cells can be the rate-limiting step for degradation of the molecule. N-3-oxododecanoyl homoserine lactone; cystic fibrosis; innate immunity; paraoxonase

A clinical case documented a reversible change in airway epithelial differentiation that coincided with the initiation and discontinuation of trastuzumab, an anti-erbB2 antibody. This prompted the investigation into whether blocking the erbB2 receptor alters differentiation of the airway epithelium. To test this hypothesis, we treated an in vitro model of well-differentiated human airway epithelia with trastuzumab or heregulin-[alpha], an erbB ligand. In addition, coculturing with human lung fibroblasts tested whether in vivo subepithelial fibroblasts function as an endogenous source of ligands able to activate erbB receptors expressed by the overlying epithelial cells. Epithelia were stained with hematoxylin and eosin and used for morphometric analysis. Trastuzumab treatment decreased the ciliated cell number by 49% and increased the metaplastic, flat cell number by 640%. Heregulin-[alpha] treatment increased epithelial height and decreased the number of metaplastic and nonciliated columnar cells, whereas it increased the goblet cell number. We found that normal human lung fibroblasts express transforming growth factor-[alpha], heparin-binding epidermal-like growth factor, epiregulin, heregulin-[alpha], and amphiregulin, all of which are erbB ligands. Cocultures of airway epithelia with primary fibroblasts increased epithelial height comparable to that achieved following heregulin-[alpha] treatment. These data show that erbB2 stimulation is required for maintaining epithelial differentiation. Furthermore, the mesenchyme underlying the airway epithelium secretes a variety of erbB ligands that may direct various pathways of epithelial differentiation. trastuzumab; fibroblasts doi:10.1152/ajplung.00547.2005

Gene transfer of CFTR eDNA to airway epithelia is a promising approach to treat cystic fibrosis (CF). Most gene transfer vectors use strong viral promoters even though the endogenous CFTR promoter is very weak. To learn whether expressing CFTR at a low level in a fraction of cells would correct [Cl.sup.-] transport, we mixed freshly isolated wild-type and CF airway epithelial cells in varying proportions and generated differentiated epithelia. Epithelia with ~20% wild-type cells generated ~70% the transepithelial [Cl.sup.-] current of epithelia containing 100% wild-type cells. These data were nearly identical to those previously obtained with CFTR expressed under control of a strong promoter in a CF epithelial cell line. We also tested high level CFTR expression using the very strong cytomegalovirus (CMV) promoter as well as the cytokeratin-18 (K18) promoter. In differentiated airway epithelia, the CMV promoter generated 50-fold more transgene expression than the K18 promoter, but the K18 promoter generated more transepithelial [Cl.sup.-] current at high vector doses. Using functional studies, we found that with marked overexpression, some CFTR channels were present in the basolateral membrane where they shunted [Cl.sup.-] flow, thereby reducing net transepithelial [Cl.sup.-] transport. These results suggest that very little CFTR is required in a fraction of CF epithelial cells to complement [Cl.sup.-] transport because transepithelial [Cl.sup.-] flow is limited at the basolateral membrane. Thus they suggest a broad leeway in promoter strength for correcting the CF gene transfer, although at very high expression levels CFTR may be mislocalized to the basolateral membrane. cystic fibrosis; gene therapy; promoter; cytomegalovirus; cytokeratin-18

Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR), an epithelial chloride channel regulated by phosphorylation. Most of the disease-associated morbidity is the consequence of chronic lung infection with progressive tissue destruction. As an approach to investigate the cellular effects of CFTR mutations, we used large-scale microarray hybridization to contrast the gene expression profiles of well-differentiated primary cultures of human CF and non-CF airway epithelia grown under resting culture conditions. We surveyed the expression profiles for 10 non-CF and 10 [DELTA]F508 homozygote samples. Of the 22,283 genes represented on the Affymetrix U133A GeneChip, we found evidence of significant changes in expression in 24 genes by two-sample t-test (P < 0.00001). A second, three-filter method of comparative analysis found no significant differences between the groups. The levels of CFTR mRNA were comparable in both groups. There were no significant differences in the gene expression patterns between male and female CF specimens. There were 18 genes with significant increases and 6 genes with decreases in CF relative to non-CF samples. Although the function of many of the differentially expressed genes is unknown, one transcript that was elevated in CF, the KCl cotransporter (KCC4), is a candidate for further study. Overall, the results indicate that CFTR dysfunction has little direct impact on airway epithelial gene expression in samples grown under these conditions. cystic fibrosis transmembrane conductance regulator; airway epithelium

You, Yingjian, Tao Huang, Edward J. Richer, Jens-Erik Harboe Schmidt, Joseph Zabner, Zea Borok, and Steven L. Brody. Role of f-box factor foxj1 in differentiation of ciliated airway epithelial cells. Am J Physiol Lung Cell Mol Physiol 286: L650-L657, 2004. First published June 20, 2003; 10.1152/ajplung.00170.2003.--Factors required for commitment of an undifferentiated airway epithelial cell to a ciliated cell are unknown. Cell ultrastructure analysis indicates ciliated cell commitment activates a multistage program involving synthesis of cilia precursor proteins and assembly of macromolecular complexes. foxj1 is an f-box transcription factor expressed in ciliated cells and shown to be required for cilia formation by gene deletion in a mouse model. To identify a specific role for foxj1 in directing the ciliated cell phenotype, we evaluated the capacity of foxj I to induce ciliogenesis and direct cilia assembly. In a primary culture model of wild-type mouse airway epithelial cells, foxj1 expression preceded the appearance of cilia and in cultured foxj1 null cells cilia did not develop. Delivery of foxj1 to polarized epithelial cell lines and primary cultured alveolar epithelial cells failed to promote ciliogenesis. Similarly, delivery of foxj1 to wild-type airway epithelial cells did not enhance the total number of ciliated cells. In contrast, delivery of foxj1 to null cells resulted in the appearance of cilia. Analysis revealed that, in the absence of foxj1, null cells contained cilia precursor basal bodies, indicating prior commitment to ciliogenesis. However, the basal bodies were disorganized within the apical compartment and failed to dock with the apical membrane. Reconstitution of foxj1 in null cells restored normal basal body organization, resulting in axoneme growth. Thus foxj1 functions in late-stage ciliogenesis to regulate programs promoting basal body docking and axoneme formation in cells previously committed to the ciliated cell phenotype. airway; basal body; cilia; differentiation; mouse

In this study, we utilized the reverse transcriptase component of telomerase, hTERT, and human papillomavirus type 16 (HPV-16) E6 and E7 genes to transform normal and cystic fibrosis (CF) human airway epithelial (HAE) cells. One cell line, designated NuLi-1 (normal lung, University of Iowa), was derived from HAE of normal genotype; three cell lines, designated CuFi (cystic fibrosis, University of Iowa)-1, CuFi-3, and CuFi-4, were derived from HAE of various CF genotypes. When grown at the air-liquid interface, the cell lines were capable of forming polarized differentiated epithelia that exhibited transepithelial resistance and maintained the ion channel physiology expected for the genotypes. The CF transmembrane conductance regulator defect in the CuFi cell lines could be corrected by infecting from the basolateral surface using adenoviral vectors. Using nuclear factor-[kappa]B promoter reporter constructs, we also demonstrated that the NuLi and CuFi cell lines retained nuclear factor-KB responses to lipopolysaccharide. These cell lines should therefore be useful as models for studying ion physiology, therapeutic intervention for CF, and innate immunity. cystic fibrosis transmembrane conductance regulator; human papillomavirus type 16; human airway epithelial cells; telomerase

Author(s): Paola D. Vermeer [1]; Lisa A. Einwalter [1]; Thomas O. Moninger [2]; Tatiana Rokhlina [1]; Jeffrey A. Kern [3]; Joseph Zabner [1]; Michael J. Welsh (corresponding author) [1, 4] [...]

Air pollution particulate matter (PM) is associated with SARS-CoV-2 infection and severity, although mechanistic studies are lacking. We tested whether airway surface liquid (ASL) from primary human airway epithelial cells is antiviral against SARS-CoV-2 and human alphacoronavirus 229E (CoV-229E) (responsible for common colds), and whether PM (urban, indoor air pollution [IAP], volcanic ash) affected ASL antiviral activity. ASL inactivated SARS-CoV-2 and CoV-229E. Independently, urban PM also decreased SARS-CoV-2 and CoV-229E infection, and IAP PM decreased CoV-229E infection. However, in combination, urban PM impaired ASL's antiviral activity against both viruses, and the same effect occurred for IAP PM and ash against SARS-CoV-2, suggesting that PM may enhance SARS-CoV-2 infection. [ABSTRACT FROM AUTHOR]