Effects of retinoic acid receptor-selective agonists on human nasal epithelial cell differentiation

Retinoids: Mechanisms of Action in Neuronal Cell Fate Acquisition

Neuronal differentiation has been shown to be directed by retinoid action during embryo development and has been exploited in various in vitro cell differentiation systems. In this review, we summarize the role of retinoids through the activation of their specific retinoic acid nuclear receptors during embryo development and also in a variety of in vitro strategies for neuronal differentiation, including recent efforts in driving cell specialization towards a range of neuronal subtypes and glial cells. Finally, we highlight the role of retinoic acid in recent protocols recapitulating nervous tissue complexity (cerebral organoids). Overall, we expect that this effort might pave the way for exploring the usage of specific synthetic retinoids for directing complex nervous tissue differentiation.

Compatibility of a Thermoresponsive and Controlled Release System for Promoting Sinonasal Cilia Regeneration

The current clinical goal for managing chronic rhinosinusitis (CRS), a heterogenous disease of the paranasal sinuses, is to control inflammation, yet adjunct therapies that promote mucosal regeneration can improve the long-term health of the upper airways. The small natural openings to the sinuses, however, limit the efficacy of traditional drug delivery methods (i.e., nasal sprays and irrigation). Accordingly, a conformable thermoresponsive and controlled release system ("TEMPS", Thermogel, Extended-release Microsphere-based delivery to the Paranasal Sinuses) is developed. The poly(lactic-co-glycolic acid) microsphere component enables the encapsulation of numerous therapeutics, such as retinoic acid (RA), an analog of vitamin A (VA). Studies in CRS patients and preclinical models have shown that aqueous RA or VA gels promoted the differentiation of ciliated cells and improved mucosal healing following repeat applications. In the present study, TEMPS is designed for the controlled release of RA such that a single dose of RA-TEMPS delivers bioactive drug for at least 30 days. Furthermore, as TEMPS will be in direct contact with sinonasal tissue, its compatibility with ciliated human nasal epithelium is explored. After ex vivo incubation in thermogel for 24 h, cilia motility is maintained, providing evidence that TEMPS can be compatible for application along the sinonasal epithelium.

Polarization of protease-activated receptor 2 (PAR-2) signaling is altered during airway epithelial remodeling and deciliation

Protease-activated receptor 2 (PAR-2) is activated by secreted proteases from immune cells or fungi. PAR-2 is normally expressed basolaterally in differentiated nasal ciliated cells. We hypothesized that epithelial remodeling during diseases characterized by cilial loss and squamous metaplasia may alter PAR-2 polarization. Here, using a fluorescent arrestin assay, we confirmed that the common fungal airway pathogen Aspergillus fumigatus activates heterologously-expressed PAR-2. Endogenous PAR-2 activation in submerged airway RPMI 2650 or NCI-H520 squamous cells increased intracellular calcium levels and granulocyte macrophage-colony-stimulating factor, tumor necrosis factor α, and interleukin (IL)-6 secretion. RPMI 2650 cells cultured at an air-liquid interface (ALI) responded to apically or basolaterally applied PAR-2 agonists. However, well-differentiated primary nasal epithelial ALIs responded only to basolateral PAR-2 stimulation, indicated by calcium elevation, increased cilia beat frequency, and increased fluid and cytokine secretion. We exposed primary cells to disease-related modifiers that alter epithelial morphology, including IL-13, cigarette smoke condensate, and retinoic acid deficiency, at concentrations and times that altered epithelial morphology without causing breakdown of the epithelial barrier to model early disease states. These altered primary cultures responded to both apical and basolateral PAR-2 stimulation. Imaging nasal polyps and control middle turbinate explants, we found that nasal polyps, but not turbinates, exhibit apical calcium responses to PAR-2 stimulation. However, isolated ciliated cells from both polyps and turbinates maintained basolateral PAR-2 polarization, suggesting that the calcium responses originated from nonciliated cells. Altered PAR-2 polarization in disease-remodeled epithelia may enhance apical responses and increase sensitivity to inhaled proteases.

A Three-Dimensional Human Tissue-Engineered Lung Model to Study Influenza A Infection

Influenza A virus (IAV) claims ∼250,000-500,000 lives annually worldwide. Currently, there are a few in vitro models available to study IAV immunopathology. Monolayer cultures of cell lines and primary lung cells (two-dimensional [2D] cell culture) is the most commonly used tool, however, this system does not have the in vivo-like structure of the lung and immune responses to IAV as it lacks the three-dimensional (3D) tissue structure. To recapitulate the lung physiology in vitro, a system that contains multiple cell types within a 3D environment that allows cell movement and interaction would provide a critical tool. In this study, as a first step in designing a 3D-Human Tissue-Engineered Lung Model (3D-HTLM), we describe the 3D culture of primary human small airway epithelial cells (HSAEpCs) and determined the immunophenotype of this system in response to IAV infections. We constructed a 3D chitosan-collagen scaffold and cultured HSAEpCs on these scaffolds at air-liquid interface (ALI). These 3D cultures were compared with 2D-cultured HSAEpCs for viability, morphology, marker protein expression, and cell differentiation. Results showed that the 3D-cultured HSAEpCs at ALI yielded maximum viable cells and morphologically resembled the in vivo lower airway epithelium. There were also significant increases in aquaporin-5 and cytokeratin-14 expression for HSAEpCs cultured in 3D compared to 2D. The 3D culture system was used to study the infection of HSAEpCs with two major IAV strains, H1N1 and H3N2. The HSAEpCs showed distinct changes in marker protein expression, both at mRNA and protein levels, and the release of proinflammatory cytokines. This study is the first step in the development of the 3D-HTLM, which will have wide applicability in studying pulmonary pathophysiology and therapeutics development.

Transcriptional mechanisms coordinating tight junction assembly during epithelial differentiation

Epithelial tissues form a selective barrier via direct cell-cell interactions to separate and establish concentration gradients between the different compartments of the body. Proper function and formation of this barrier rely on the establishment of distinct intercellular junction complexes. These complexes include tight junctions, adherens junctions, desmosomes, and gap junctions. The tight junction is by far the most diverse junctional complex in the epithelial barrier. Its composition varies greatly across different epithelial tissues to confer various barrier properties. Thus, epithelial cells rely on tightly regulated transcriptional mechanisms to ensure proper formation of the epithelial barrier and to achieve tight junction diversity. Here, we review different transcriptional mechanisms utilized during embryogenesis and disease development to promote tight junction assembly and maintenance of intercellular barrier integrity. We focus particularly on the Grainyhead-like transcription factors and ligand-activated nuclear hormone receptors, two central families of proteins in epithelialization.

Differentiation of human bronchial epithelial cells: role of hydrocortisone in development of ion transport pathways involved in mucociliary clearance

Glucocorticoids strongly influence the mucosal-defense functions performed by the bronchial epithelium, and inhaled corticosteroids are critical in the treatment of patients with inflammatory airway diseases such as asthma, chronic obstructive pulmonary disease, and cystic fibrosis. A common pathology associated with these diseases is reduced mucociliary clearance, a defense mechanism involving the coordinated transport of salt, water, and mucus by the bronchial epithelium, ultimately leading to retention of pathogens and particles in the airways and to further disease progression. In the present study we investigated the role of hydrocortisone (HC) in differentiation and development of the ion transport phenotype of normal human bronchial epithelial cells under air-liquid interface conditions. Normal human bronchial epithelial cells differentiated in the absence of HC (HC0) showed significantly less benzamil-sensitive short-circuit current than controls, as well as a reduced response after stimulation with the selective β2-adrenergic receptor agonist salbutamol. Apical membrane localization of epithelial Na(+) channel α-subunits was similarly reduced in HC0 cells compared with controls, supporting a role of HC in the trafficking and density of Na(+) channels in the plasma membrane. Additionally, glucocorticoid exposure during differentiation regulated the transcription of cystic fibrosis transmembrane conductance regulator and β2-adrenergic receptor mRNAs and appeared to be necessary for the expression of cystic fibrosis transmembrane conductance regulator-dependent anion secretion in response to β2-agonists. HC had no significant effect on surface cell differentiation but did modulate the expression of mucin mRNAs. These findings indicate that glucocorticoids support mucosal defense by regulating critical transport pathways essential for effective mucociliary clearance.

Diet Quality Scores and Risk of Nasopharyngeal Carcinoma in Chinese Adults: A Case-Control Study

Many studies show that dietary factors may affect the risk of nasopharyngeal carcinoma (NPC). We examined the association between overall diet quality and NPC risk in a Chinese population. This case-control study included 600 NPC patients and 600 matched controls between 2009 and 2011 in Guangzhou, China. Habitual dietary intake and various covariates were assessed via face-to-face interviews. Diet quality scores were calculated according to the Healthy Eating Index-2005 (HEI-2005), the alternate Healthy Eating Index (aHEI), the Diet Quality Index-International (DQI-I), and the alternate Mediterranean Diet Score (aMed). After adjustment for various lifestyle and dietary factors, greater diet quality scores on the HEI-2005, aHEI, and DQI-I—but not on the aMed—showed a significant association with a lower risk of NPC (p-trends, <0.001–0.001). The odds ratios (95% confidence interval) comparing the extreme quartiles of the three significant scores were 0.47 (0.32–0.68) (HEI-2005), 0.48 (0.33–0.70) (aHEI), and 0.43 (0.30–0.62) (DQI-I). In gender-stratified analyses, the favorable association remained significant in men but not in women. We found that adherence to the predefined dietary patterns represented by the HEI-2005, aHEI, and DQI-I scales predicted a lower risk of NPC in adults from south China, especially in men.

Retinoic acid improves morphology of cultured peritoneal mesothelial cells from patients undergoing dialysis

Patients undergoing continuous ambulatory peritoneal dialysis are classified according to their peritoneal permeability as low transporter (low solute permeability) or High transporter (high solute permeability). Factors that determine the differences in permeability between them have not been fully disclosed. We investigated morphological features of cultured human peritoneal mesothelial cells from low or high transporter patients and its response to All trans retinoic Acid (ATRA, vitamin A active metabolite), as compared to non-uremic human peritoneal mesothelial cells. Control cells were isolated from human omentum. High or low transporter cells were obtained from dialysis effluents. Cells were cultured in media containing ATRA (0, 50, 100 or 200 nM). We studied length and distribution of microvilli and cilia (scanning electron microscopy), epithelial (cytokeratin, claudin-1, ZO-1 and occludin) and mesenchymal (vimentin and α-smooth muscle actin) transition markers by immunofluorescence and Western blot, and transforming growth factor β1 expression by Western blot. Low and high transporter exhibited hypertrophic cells, reduction in claudin-1, occludin and ZO-1 expression, cytokeratin and vimentin disorganization and positive α-smooth muscle actin label. Vimentin, α-smooth muscle actin and transforming growth factor-β1 were overexpressed in low transporter. Ciliated cells were diminished in low and high transporters. Microvilli number and length were severely reduced in high transporter. ATRA reduced hypertrophic cells number in low transporter. It also improved cytokeratin and vimentin organization, decreased vimentin and α-smooth muscle actin expression, and increased claudin 1, occludin and ZO-1 expression, in low and high transporter. In low transporter, ATRA reduced transforming growth factor-β1 expression. ATRA augmented percentage of ciliated cells in low and high transporter. It also augmented cilia length in high transporter. Alterations in structure, epithelial mesenchymal markers and transforming growth factor-β1 expression were differential between low and high transporter. Beneficial effects of ATRA were improved human peritoneal mesothelial cells morphology tending to normalize structures.

Increased mucociliary differentiation and aquaporins formation of respiratory epithelial cells on retinoic acid-loaded hyaluronan-derivative membranes

While playing a major role in maintaining the mucociliary phenotype of respiratory epithelial cells (RECs), retinoids are critical determinants of their normal function. However, despite being a powerful biological agent, retinoic acid (RA) is generally not used in regenerative medicine due to its scarce bioavailability via conventional administration. Therefore, the ability to incorporate RA into biomaterials allows for a combination of the biological effects of RA and biomaterials in influencing cellular behavior. This study attempts to develop RA-loaded hyaluronan-derivative membrane (RA-HAm) and investigates how this membrane affects the mucociliary differentiation and aquaporins (AQP) formation of RECs. In a simulated in vitro culture condition, the RA release from membranes is maintained for 7days. On the seventh day, the cumulative release rate of RA from supportive biomaterials is ~87% under detect limitation. RECs cultured on RA-HAm reveal numerous mature ciliated cells and microvilli compared to aggregated cilia-like structures on hyaluronan-derivative membrane (HAm). Moreover, the expression levels of MUC5AC and AQP on RA-HAm are higher than those on HAm. The proposed model elucidates the release of hydrophobic RA from hyaluronan-derivative biomaterials. We believe that RA-loaded hyaluronan biomaterials are highly promising biomaterials for use in sinonasal surgery and tissue engineering of the respiratory system.

Development of a repeated exposure protocol of human bronchial epithelium in vitro to study the long-term effects of atmospheric particles

Chronic exposure to atmospheric particles is suspected of exacerbating chronic inflammatory respiratory diseases but the underlying mechanisms remain poorly understood. An experimental strategy using human bronchial epithelial cells (NHBE) known to be one of the main target cells of particles in the lung was developed to investigate the long term effects of repeated exposure to particles. Primary cultures of NHBE cells were grown at an air-liquid interface and subjected to repeated treatments to particles. Fate of particles, pro inflammatory response and epithelial differentiation were studied during the 5 weeks following the final treatment. Ultrastructural observations revealed the biopersistence of particles in the bronchial epithelium. The expression of cytochrome P450 1A1, was transiently induced, suggesting that organic compounds could have been metabolized. The release of GM-CSF and IL-6 (biomarkers of pro-inflammatory response), was induced by particle treatments and was maintained up to 5weeks after treatments. The release of amphiregulin and TGFα (Growth Factor) was induced after each treatment. The number of cells expressing the mucin MUC5AC, a differentiation marker, was increased in particle-exposed epithelium. The experimental strategy we developed is suitable for investigating in greater depth the long term effects of particles on bronchial epithelial cells repeatedly exposed to atmospheric particles in vitro.

Greater intake of fruit and vegetables is associated with lower risk of nasopharyngeal carcinoma in Chinese adults: a case-control study

PURPOSE

The effect of fruit and vegetable intake on the risk of nasopharyngeal carcinoma (NPC) remains uncertain due to limited published evidence. We performed a matched case-control study to investigate the relationship between the intake of fruit and vegetables and the risk of NPC.

METHODS

Between July 2009 and March 2011, 600 (448 male, 152 female), NPC incident cases from a single hospital in Guangzhou, Guangdong Province, China, a high-incidence area, were enrolled in the study. 600 controls, matched by gender, age (± 3 years) and household type (urban/rural) were also enrolled. Face-to-face interviews were used to collect habitual dietary intakes and information on various covariates.

RESULTS

Multivariate conditional logistic regression analyses showed significant, dose-dependent inverse associations between the intake of vegetables, fruit or a combination of the two and the risk of NPC, even after adjustments for social-economic status, body mass index, dietary factors and other potential covariates. The adjusted odds ratios (95% confidence intervals) for NPC in the top quartile of vegetable intake, fruit intake or a combination of the two, as compared to the lowest quartile, were 0.33 (0.22-0.50), 0.70 (0.47-1.04) and 0.37 (0.25-0.55), respectively. Dark green leafy vegetables, carrots, peppers and tomatoes, citrus fruit and pome fruit showed much more pronounced benefits with regards to NPC than other types of fruit and vegetables. Interaction analyses demonstrated that the effects of total combined vegetable and fruit intake were much more significant in subjects with a higher education level (p interaction: 0.027), and the benefits of fruit were observed in males, but not in females (p interaction: 0.088).

CONCLUSION

Our findings suggest that a greater consumption of fruit and vegetables may lower the risk of NPC in Chinese adults.

Cytotoxic, genotoxic and pro-inflammatory effects of zinc oxide nanoparticles in human nasal mucosa cells in vitro

Despite increasing application of zinc oxide nanoparticles (ZnO-NPs) for industrial purposes, data about potential toxic properties is contradictory. The current study focused on the cyto- and genotoxicity of ZnO-NPs in comparison to ZnO powder in primary human nasal mucosa cells cultured in the air-liquid interface. Additionally, IL-8 secretion as a marker for pro-inflammatory effects was measured. Particle morphology and intracellular distribution were evaluated by transmission electron microscopy (TEM). ZnO-NPs were transferred into the cytoplasm in 10% of the cells, whereas an intranuclear distribution could only be observed in 1.5%. While no cyto- or genotoxicity could be seen for ZnO powder in the dimethylthiazolyl-diphenyl-tetrazolium-bromide (MTT) test, the trypan blue exclusion test, and the single-cell microgel electrophoresis (comet) assay, cytotoxic effects were shown at a ZnO-NP concentration of 50 μg/ml (P<0.01). A significant enhancement in DNA damage was observed starting from ZnO-NP concentrations of 10 μg/ml (P<0.05) in comparison to the control. IL-8 secretion into the basolateral culture medium was increased at ZnO-NP concentrations of 5 μg/ml (P<0.05), as shown by ELISA. Our data indicates cyto- and genotoxic properties as well as a pro-inflammatory potential of ZnO-NPs in nasal mucosa cells. Thus, caution should be taken concerning their industrial and dermatological application. Additionally, further investigation on repetitive NP exposure is needed to estimate the impact of repair mechanisms.

Increased mucociliary differentiation of human respiratory epithelial cells on hyaluronan-derivative membranes

The selection of a scaffold to facilitate mucociliary differentiation of respiratory epithelial cells (RECs) is crucial in the development of tissue engineering of respiratory epithelium. However, how the differentiation of RECs is influenced by the biomaterials has never been thoroughly explored. Previously, hyaluronan derivatives were considered as unsuitable biomaterials for culture of respiratory epithelium. In contrast, this study demonstrates that the membranous scaffolds made from benzyl esters of hyaluronic acids are capable of providing a more preferential environment for human RECs than conventionally used collagen-based scaffolds. The proliferation and mucociliary differentiation of RECs were examined by MTT assays, scanning electron microscopy, immunofluorescence, immunoblotting and gene expression. The percentage of ciliated cells in cultured RECs increased from 12.4% on collagen to 20.4% on hyaluronan-derivative membranes with a pseudostratified polarized layer that closely resembled the composition of the native epithelium. The expression levels of MUC5AC and MUC5B mRNA were higher on hyaluronan-based scaffolds than those on collagen. The presence of a hyaluronan-binding domain, CD44 and the receptor for hyaluronan-mediated motility of RECs were also demonstrated. Accordingly, the mucociliary differentiation-promoting effect of hyaluronan-derivative membranes indicates that it may be applied to the tissue engineering of respiratory epithelium.

Regression of Polypoid Nasal Mucosa after Systemic Corticosteroid Therapy: A Proteomics Study

Background

Nasal polyposis (NP) treatment and pathophysiology have always been challenging for otolaryngologists. Among the medical treatments for NP, glucocorticoids (GCs) have been always one of the mainstays but the mechanisms of their action are not well defined. Identifying and comparing the protein profile of chronic rhinosinusitis (CRS) with NP before and after treatment with GCs can help to clarify NP pathogenesis and mechanisms of corticosteroid effects on NP.

Methods

Samples of nasal polyps were taken from selected NP patients in workup for endoscopic sinus surgery. None of the patients used local or systemic GCs within 30 days before the sampling. The patients were given prednisone, 30 mg/day, for 4 days before the surgery to shrink the NP tissue. Nasal polyp samples were collected during surgery. Proteins from samples were extracted and separated by immobilized pH gradient–based two-dimensional difference gel electrophoresis (2D DIGE). Resulting 2D-gel images were statistically analyzed using Delta2D software and differently expressed protein spots were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Results

A reference map of 1963 proteins could be established. Expression of 20 proteins changed significantly (twofold, p < 0.05) after treatment of NP with GCs. Heat shock proteins and retinoic acid were induced by GCs. Ingenuity pathway analysis of all identified proteins indicated that apoptosis pathway is triggered in NP after GC administration.

Conclusion

Identifying the changes of NP proteome due to GCs and the biological functions of proteins can lead to new ways of treatment and open new fields in NP research.

Retinoid receptor subtype-selective modulators through synthetic modifications of RARgamma agonists

A series of retinoids designed to interfere with the repositioning of H12 have been synthesized to identify novel RARgamma antagonists based on the structure of known RARgamma agonists. The transcriptional activities of the novel ligands were revealed by cell-based reporting assays, using engineered cells containg RAR subtype-selective fusions of the RAR ligand-binding domains with the yeast GAL4 activator DNA-binding domain and the cognate luciferase reporter gene. Whereas none of the ligands exhibited features of a selective RARgamma antagonist, some of them are endowed with interesting activities. In particular 24a acts as a pan-RAR agonist that induces at high concentration a higher transactivation potential on RARalpha than TTNPB and synergizes at low concentration with TTNPB-bound RARalpha but not RARbeta or RARgamma. Similarly, 24c synergizes with TTNPB-bound RARgamma and exhibits RARalpha,beta antagonist activity. Compounds 24b and 25b are strong RARalpha,beta-selective antagonists without agonist or antagonist activities for RARgamma. Compounds 24b and 24c display weak RXR antagonist activity. In addition several pan-antagonists and partial agonist/antagonists have been defined.

Size-partitioning of an urban aerosol to identify particle determinants involved in the proinflammatory response induced in airway epithelial cells

Background

The contribution of air particles in human cardio-respiratory diseases has been enlightened by several epidemiological studies. However the respective involvement of coarse, fine and ultrafine particles in health effects is still unclear. The aim of the present study is to determine which size fraction from a chemically characterized background aerosol has the most important short term biological effect and to decipher the determinants of such a behaviour.

Results

Ambient aerosols were collected at an urban background site in Paris using four 13-stage low pressure cascade impactors running in parallel (winter and summer 2005) in order to separate four size-classes (PM_0.03–0.17 (defined here as ultrafine particles), PM_0.17–1 (fine), PM_1–2.5(intermediate) and PM_2.5–10 (coarse)). Accordingly, their chemical composition and their pro-inflammatory potential on human airway epithelial cells were investigated. Considering isomass exposures (same particle concentrations for each size fractions) the pro-inflammatory response characterized by Granulocyte Macrophage-Colony Stimulating Factor (GM-CSF) release was found to decrease with aerosol size with no seasonal dependency. When cells were exposed to isovolume of particle suspensions in order to respect the particle proportions observed in ambient air, the GM-CSF release was maximal with the fine fraction. In presence of a recombinant endotoxin neutralizing protein, the GM-CSF release induced by particles is reduced for all size-fractions, with exception of the ultra-fine fraction which response is not modified. The different aerosol size-fractions were found to display important chemical differences related to the various contributing primary and secondary sources and aerosol age. The GM-CSF release was correlated to the organic component of the aerosols and especially its water soluble fraction. Finally, Cytochrome P450 1A1 activity that reflects PAH bioavailability varied as a function of the season: it was maximal for the fine fraction in winter and for the ultrafine fraction in summer.

Conclusion

In the frame of future regulations, a particular attention should thus be paid to the ultrafine/fine (here referred to as PM1) fraction due to their overwhelming anthropogenic origin and predominance in the urban aerosol and their pro-inflammatory potential.

Inducible expression of beta defensins by human respiratory epithelial cells exposed to Aspergillus fumigatus organisms

Background

Aspergillus fumigatus, a saprophytic mould, is responsible for life-threatening, invasive pulmonary diseases in immunocompromised hosts. The role of the airway epithelium involves a complex interaction with the inhaled pathogen. Antimicrobial peptides with direct antifungal and chemotactic activities may boost antifungal immune response.

Results

The inducible expression of defensins by human bronchial epithelial 16HBE cells and A549 pneumocyte cells exposed to A. fumigatus was investigated. Using RT-PCR and real time PCR, we showed an activation of hBD2 and hBD9 defensin genes: the expression was higher in cells exposed to swollen conidia (SC), compared to resting conidia (RC) or hyphal fragments (HF). The kinetics of defensin expression was different for each one, evoking a putative distinct function for each investigated defensin. The decrease of defensin expression in the presence of heat-inactivated serum indicated a possible link between defensins and the proteins of the host complement system. The presence of defensin peptide hBD2 was revealed using immunofluorescence that showed a punctual cytoplasmic and perinuclear staining. Quantification of the cells stained with anti hBD2 antibody demonstrated that SC induced a greater number of cells that synthesized hBD2, compared to RC or HF. Labelling of the cells with anti-hBD-2 antibody showed a positive immunofluorescence signal around RC or SC in contrast to HF. This suggests co-localisation of hBD2 and digested conidia. The HBD2 level was highest in the supernatants of cells exposed to SC, as was determined by sandwich ELISA. Experiments using neutralising anti-interleukine-1β antibody reflect the autocrine mechanism of defensin expression induced by SC. Investigation of defensin expression at transcriptional and post-transcriptional levels demonstrated the requirement of transcription as well as new protein synthesis during A. fumigatus defensin induction. Finally, induced defensin expression in primary culture of human respiratory cells exposed to A. fumigatus points to the biological significance of described phenomena.

Conclusion

Our findings provide evidence that respiratory epithelium might play an important role in the immune response during Aspergillus infection. Understanding the mechanisms of regulation of defensin expression may thus lead to new approaches that could enhance expression of antimicrobial peptides for potential therapeutic use during aspergillosis treatment.

Increased communication among nasal epithelial cells in air-liquid interface culture

OBJECTIVE/HYPOTHESIS

The retinoid acid (RA) sufficient air-liquid interface (ALI) cell culture model, but not the classical submerged single layer (SSL) cell culture model, can achieve ciliary differentiation of nasal epithelial cells. Because gap junction mediated intercellular communication (GJIC) may contribute to differentiation in numerous cell types, this study compared the extent of GJIC and the expression of Connexin 43 (Cx43) in nasal epithelial cells in both SSL and ALI cultures.

METHODS

Cell morphology was examined via optical and scanning electron microscope, and the number of cells with ciliary beating were counted. Lucifer Yellow dye transfer test using the scrape loading method was performed to assess the GJIC. Cx43 expression was measured with reverse-transcription polymerase chain reaction (RT-PCR) and quantitative (Q)-PCR.

RESULTS

Nasal epithelial cells in ALI culture exhibited increased numbers of ciliated cells compared with SSL culture during the 3-week culture period. On day 20, GJIC was increased in ALI culture (ALI % - SSL % = 9.6 +/- 1.2%, n = 5). Accordingly, Cx43 expression was increased via RT-PCR (4.22-fold) and Q-PCR (5.3 +/- 1.1-fold, n = 5) examination.

CONCLUSIONS

RA sufficient ALI culture manifested more differentiated nasal epithelial cell status with ciliogenesis. Cx43, being the responsible molecule for GJIC, increased in parallel. Consequently, as in primary cultured limbal epithelial cells, Cx43 expression and extent of GJIC may serve as markers for the differentiation status of nasal epithelial cells.

Rehabilitation of surgically traumatized paranasal sinus mucosa using retinoic acid

BACKGROUND

Paranasal sinus mucosa that regenerates after surgical stripping is characterized by sparse, dysmorphic cilia. Although such dysfunctional mucosal changes are thought to be irreversible, the potential rehabilitation of deciliated mucosa by topical therapies has not been explored. This study evaluated the effect of topical retinoic acid (RA) in rehabilitating deciliated sinus mucosa that has regenerated after surgical stripping.

METHODS

Twelve New Zealand rabbits underwent bilateral maxillary sinus mucosal stripping and were allowed to remucosalize for 10 days. In the first treatment arm (n = 6), 0.01% RA was applied to the regenerated mucosa of the left maxillary sinus and an aqueous control was placed contralaterally. In the second treatment arm, the regenerated mucosa was surgically restripped bilaterally before applying RA and control. After 14 additional days, mucosa was harvested and examined by scanning electron microscopy for ciliary density, orientation, and morphology.

RESULTS

In the first treatment arm, no significant differences in ciliary density, orientation, or morphology were noted between RA-treated sinuses and controls. In the second arm, RA-treated sinuses showed improved ciliary density, morphology, and orientation compared with controls.

CONCLUSION

RA does not appear to significantly enhance ciliogenesis when applied after mucosal regeneration has occurred. However, if deciliated mucosa is restripped and allowed to regenerate in the presence of RA, ciliary ultrastructural features may be enhanced. RA may have therapeutic value in rehabilitating deciliated sinus mucosa when applied before mucociliary differentiation of regenerating mucosa.

Expression of Toll-like receptors in cultured nasal epithelial cells

CONCLUSIONS

Nasal epithelial cells are constitutively equipped with all Toll-like receptors (TLRs) which are essential for innate immunity. Both mRNA and protein levels of TLR3 expression increased in more differentiated nasal epithelial cells. Considering that the ligand for TLR3 is viral dsRNA, this result is in good accordance with previous reports demonstrating that more differentiated airway epithelial cells have increased resistance to rhinovirus infection.

OBJECTIVE

Nasal epithelial cells use innate immune responses to combat inspired potential pathogens. TLRs are receptors that recognize pathogen-associated molecular patterns of microbes. Therefore, we investigated the expression of TLRs in cultured nasal epithelial cells obtained from nasal polyps.

MATERIALS AND METHODS

Submerged single layer (SSL) and air-liquid interface (ALI) nasal epithelial cell cultures with or without 10(-7) M retinoid acid (+/- RA) were created.

RESULTS

ALI + RA culture developed ciliary differentiation as observed by light and scanning electron microscopic examination in 3 weeks. It had higher interleukin (IL)-8 basal secretion (21.9 vs 0.82-1.45 ng/ml) and transepithelial potential (-20.4 mV). TLR1-10 mRNA expression in cultured nasal epithelial cells was determined by RT-PCR. Only TLR3 mRNA significantly increased at day 20 vs day 1 (n=5, p=0.02) in ALI + RA cell culture. Higher TLR3 protein was also expressed at day 20 in ALI + RA cell culture but not in SSL culture by western blotting.

Interleukin-13 interferes with CFTR and AQP5 expression and localization during human airway epithelial cell differentiation

Interleukin-13 (IL-13) is a central regulator of Th2-dominated respiratory disorders such as asthma. Lesions of the airway epithelial barrier frequently observed in chronic respiratory inflammatory diseases are repaired through proliferation, migration and differentiation of epithelial cells. Our work is focused on the effects of IL-13 in human cellular models of airway epithelial cell regeneration. We have previously shown that IL-13 altered epithelial cell polarity during mucociliary differentiation of human nasal epithelial cells. In particular, the cytokine inhibited ezrin expression and interfered with its apical localization during epithelial cell differentiation in vitro. Here we show that CFTR expression is enhanced in the presence of the cytokine, that two additional CFTR protein isoforms are expressed in IL-13-treated cells and that part of the protein is retained within the endoplasmic reticulum. We further show that aquaporin 5 expression, a water channel localized within the apical membrane of epithelial cells, is completely abolished in the presence of the cytokine. These results show that IL-13 interferes with ion and water channel expression and localization during epithelial regeneration and may thereby influence mucus composition and hydration.

Linkage analysis localises a Kartagener syndrome gene to a 3.5 cM region on chromosome 15q24-25

BACKGROUND

Primary ciliary dyskinesia (PCD) is a genetic disorder caused by ciliary immotility/dysmotility due to ultrastructural defects of the cilia. Kartagener syndrome (KS), a subtype of PCD, is characterised by situs inversus accompanying the typical PCD symptoms of bronchiectasis and chronic sinusitis. In most cases, PCD is transmitted as an autosomal recessive trait, but its genetic basis is unclear due to extensive genetic heterogeneity.

METHODS

In a genome-wide search for PCD loci performed in 52 KS families and in 18 PCD families with no situs inversus present (CDO, ciliary dysfunction-only), the maximal pairwise LOD score of 3.36 with D15S205 in the KS families indicated linkage of a KS locus to the long arm of chromosome 15. In the follow-up study, 65 additional microsatellite markers encompassing D15S205 were analysed.

RESULTS

A maximal pairwise LOD score of 4.34 was observed with D15S154, further supporting linkage of the KS, but not the CDO, families to 15q24-25. Analysis of heterogeneity and haplotypes suggested linkage to this region in 60% of KS families.

CONCLUSIONS

Reinforced by the results of multipoint linkage, our analyses indicate that a major KS locus is localised within a 3.5 cM region on 15q, between D15S973 and D15S1037.

Retinoic acid improves ciliogenesis after surgery of the maxillary sinus in rabbits

OBJECTIVES/HYPOTHESIS

Retinoids have been shown to be important cofactors in regulating the differentiation and proliferation of ciliated epithelial cells of the respiratory tract. In particular, retinoic acid has been shown to enhance the regeneration of paranasal sinus mucosa. The objective of this study is to use scanning electron microscopy techniques to evaluate the effect of topical retinoic acid on mucosal wound healing in a rabbit model of maxillary sinus surgery. It is hypothesized that the application of topical retinoic acid will enhance ciliogenesis and improve the morphology of regenerated cilia compared with controls.

STUDY DESIGN

Prospective multi-arm controlled animal trial.

METHODS

Eighteen New Zealand white rabbits underwent surgical opening of the maxillary sinuses through a midline incision. The rabbits were divided among four experimental groups: 1) mucosal stripping alone (stripped control), 2) stripping followed by topical application of an inert aqueous gel, 3) stripping followed by application of 0.01% retinoic acid in aqueous gel, and 4) no mucosal stripping and no topical treatment (nonstripped control). After 14 days, the medial wall of the maxillary sinus was harvested and examined by scanning electron microscopy at x2,000 and x5,000 magnification. The micrographs were then rated by a blinded review panel for ciliary density, orientation, and morphology.

RESULTS

Mean scores for ciliary density, orientation, and morphology were all significantly higher for the retinoic acid treatment group compared with both the inert aqueous gel treatment group and the stripped control group (P=.004-.03 for all comparisons, Student's t test). Mean scores for the retinoic acid treatment group were numerically lower than the nonstripped control group but did not approach statistical significance for any parameter (P=.23-.31).

CONCLUSIONS

In a rabbit model of maxillary sinus surgery, topically delivered retinoic acid enhances ciliogenesis. Qualitative assessment of ciliary density, orientation, and morphology shows improved healing in retinoic acid treated sinuses compared with both untreated control sinuses and aqueous gel treated sinuses.

Responses of well-differentiated nasal epithelial cells exposed to particles: role of the epithelium in airway inflammation

Numerous epidemiological studies support the contention that ambient air pollution particles can adversely affect human health. To explain the acute inflammatory process in airways exposed to particles, a number of in vitro studies have been performed on cells grown submerged on plastic and poorly differentiated, and on cell lines, the physiology of which is somewhat different from that of well-differentiated cells. In order to obtain results using a model system in which epithelial cells are similar to those of the human airway in vivo, apical membranes of well-differentiated human nasal epithelial (HNE) cells cultured in an air-liquid interface (ALI) were exposed for 24 h to diesel exhaust particles (DEP) and Paris urban air particles (PM(2.5)). DEP and PM(2.5) (10-80 microg/cm(2)) stimulated both IL-8 and amphiregulin (ligand of EGFR) secretion exclusively towards the basal compartment. In contrast, there was no IL-1beta secretion and only weak non-reproducible secretion of TNF-alpha. IL-6 and GM-CSF were consistently stimulated towards the apical compartment and only when cells were exposed to PM(2.5). ICAM-1 protein expression on cell surfaces remained low after particle exposure, although it increased after TNF-alpha treatment. Internalization of particles, which is believed to initiate oxidative stress and proinflammatory cytokine expression, was restricted to small nanoparticles (< or =40 nm). Production of reactive oxygen species (ROS) was detected, and DEP were more efficient than PM(2.5). Collectively, our results suggest that airway epithelial cells exposed to particles augment the local inflammatory response in the lung but cannot alone initiate a systemic inflammatory response.

Regulation of vimentin by SIP1 in human epithelial breast tumor cells

The expression of Smad interacting protein-1 (SIP1; ZEB2) and the de novo expression of vimentin are frequently involved in epithelial-to-mesenchymal transitions (EMTs) under both normal and pathological conditions. In the present study, we investigated the potential role of SIP1 in the regulation of vimentin during the EMT associated with breast tumor cell migration and invasion. Examining several breast tumor cell lines displaying various degrees of invasiveness, we found SIP1 and vimentin expression only in invasive cell lines. Also, using a model of cell migration with human mammary MCF10A cells, we showed that SIP1 is induced specifically in vimentin-positive migratory cells. Furthermore, transfection of SIP1 cDNA in MCF10A cells increased their vimentin expression both at the mRNA and protein levels and enhanced their migratory abilities in Boyden Chamber assays. Inversely, inhibition of SIP1 expression by RNAi strategies in BT-549 cells and MCF10A cells decreased vimentin expression. We also showed that SIP1 transfection did not activate the TOP-FLASH reporter system, suggesting that the beta-catenin/TCF pathway is not implicated in the regulation of vimentin by SIP1. Our results therefore implicate SIP1 in the regulation of vimentin observed in the EMT associated with breast tumor cell migration, a pathway that may contribute to the metastatic progression of breast cancer.

CD437, a synthetic retinoid, induces apoptosis in human respiratory epithelial cells via caspase-independent mitochondrial and caspase-8-dependent pathways both up-regulated by JNK signaling pathway

The synthetic retinoid-related molecule CD437-induced apoptosis in human epithelial airway respiratory cells: the 16HBE bronchial cell line and normal nasal epithelial cells. CD437 caused apoptosis in S-phase cells and cell cycle arrest in S phase. Apoptosis was abolished by caspase-8 inhibitor z-IETD-fmk which preserved S-phase cells but was weakly inhibited by others selective caspase-inhibitors, indicating that caspase-8 activation was involved. z-VAD and z-IETD prevented the nuclear envelope fragmentation but did not block the chromatin condensation. The disruption of mitochondrial transmembrane potential was also induced by CD437 treatment. The translocation of Bax to mitochondria was demonstrated, as well as the release of cytochrome c into the cytosol and of apoptosis-inducing factor (AIF) translocated into the nucleus. z-VAD and z-IETD did not inhibit mitochondrial depolarization, Bax translocation or release of cytochrome c and AIF from mitochondria. These results suggest that CD437-induced apoptosis is executed by two converging pathways. AIF release is responsible for chromatin condensation, the first stage of apoptotic cell, via a mitochondrial pathway independent of caspase. But final stage of apoptosis requires the caspase-8-dependent nuclear envelope fragmentation. In addition, using SP600125, JNK inhibitor, we demonstrated that CD437 activates the JNK-MAP kinase signaling pathway upstream to mitochondrial and caspase-8 pathways. Conversely, JNK pathway inhibition, which suppresses S-phase apoptosis, did not prevent cell cycle arrest within S phase, confirming that these processes are triggered by distinct mechanisms.

The use of human nasal in vitro cell systems during drug discovery and development

The nasal route is widely used for the administration of drugs for both topical and systemic action. At an early stage in drug discovery and during the development process, it is essential to gain a thorough insight of the nasal absorption potential, metabolism and toxicity of the active compound and the components of the drug formulation. Human nasal epithelial cell cultures may provide a reliable screening tool for pharmaco-toxicological assessment of potential nasal drug formulations. The aim of this review is to give an overview of the information relevant for the development of a human nasal epithelial cell culture model useful during drug discovery and development. A primary goal in the development of in vitro cell culture systems is to maintain differentiated morphology and biochemical features, resembling the original tissue as closely as possible. The potential and limitations of the existing in vitro human nasal models are summarized. The following topics related to cell culture methodology are discussed: (i) primary cultures versus cell lines; (ii) cell-support substrate; (iii) medium and medium supplements; and (iv) the air-liquid interface model versus liquid-liquid. Several considerations with respect to the use of in vitro systems for pharmaceutical applications (transport, metabolism, assessment of ciliary toxicity) are also discussed.

Immunolocalization of retinoic acid receptors in the mammalian olfactory system and the effects of olfactory denervation on receptor distribution

All-trans retinoic acid (ATRA), a metabolite of vitamin A, binds to retinoic acid receptors (RARs) to mediate gene transcription in target cells. We previously found that an ATRA supplement enhanced olfactory recovery rate in adult mice after olfactory bulb deafferentation. In this study, we examined the cellular localization of RARalpha, RARbeta, and RARgamma and the effects of surgery and ATRA treatment using immunocytochemistry. Mice received a left olfactory nerve transection with the right side serving as internal control. One day after surgery, the mice were given either ATRA mixed with sesame oil or just sesame oil. In the unoperated olfactory bulb, only RARalpha immunoreactivity (ir) was observed. In the unoperated right olfactory epithelium, RARalpha-ir was found in flask-shaped cells located in the supporting cell layer, in cell clusters above the basal cell layer, in cells in the lamina propria, in some respiratory cells and in the olfactory bulb. The flask-shaped cells did not immunostain for either neurons or sustentacular cells. RARbeta-ir was localized only in the respiratory cells while no RARgamma-ir was observed in the olfactory epithelium. The density of RARalpha-ir cells was higher in the operated left olfactory epithelium and highest after ATRA treatment. This study demonstrates the presence of RARs in the olfactory system, provides additional support that the ATRA-signaling pathway may be involved in the recovery of the olfactory epithelium after injury, and suggests a role for an unstudied cell type in that process.

Cell Biology of Normal and Abnormal Ciliogenesis in the Ciliated Epithelium

Ciliogenesis is divided into four stages: (1) generation of centrioles, (2) migration of duplicated centrioles, (3) formation of the basal body-associated structures, and (4) elongation of cilia. The ultrastructural profile of ciliogenesis is fundamentally the same among various kinds of animal species. In acentriolar centriologenesis, centrioles are generated around deuterosomes by the use of fibrous granules. Components of the centriolar precursor structures, and genes that regulate the differentiation of ciliated cells, have been revealed. Ciliary abnormalities are classified into two categories: specific congenital defects of ciliary structure and acquired nonspecific anomalies of the ciliary apparatus. When ciliogenesis is disturbed, various nonspecific ciliary abnormalities develop in the cell. Inhibition of centriole migration results in the development of intracytoplasmic axonemes, cilia within periciliary sheaths, and intracellular ciliated vacuoles. Swollen cilia and the bulging type of compound cilia are formed during ciliary budding and elongation. Primary cilia can also develop from one of a pair of centrioles. They lack dynein arms and are immobile, but work as a mechanosensor and play a role during morphogenesis of the kidney. Abnormal function or structure of primary cilia results in the development of polycystic kidney disease. The axonemes of primary cilia or monocilia in the embryonic node cells are associated with dynein arms and move vortically. They have a role in determining the left-right (L-R) asymmetry of the fetus. This review also discusses the ciliogenesis of a primary cilium in the cell.