Identification of host essential factors for recombinant AAV transduction of the polarized human airway epithelium

IMPORTANCE

The essential steps of successful gene delivery by recombinant adeno-associated viruses (rAAVs) include vector internalization, intracellular trafficking, nuclear import, uncoating, double-stranded (ds)DNA conversion, and transgene expression. rAAV2.5T has a chimeric capsid of AAV2 VP1u and AAV5 VP2 and VP3 with the mutation A581T. Our investigation revealed that KIAA0319L, the multiple AAV serotype receptor, is not essential for vector internalization but remains critical for efficient vector transduction to human airway epithelia. Additionally, we identified that a novel gene WDR63, whose cellular function is not well understood, plays an important role in vector transduction of human airway epithelia but not vector internalization and nuclear entry. Our study also discovered the substantial transduction potential of rAAV2.5T in basal stem cells of human airway epithelia, underscoring its utility in gene editing of human airways. Thus, the knowledge derived from this study holds promise for the advancement of gene therapy in the treatment of pulmonary genetic diseases.

Inhibition of DNA-dependent protein kinase catalytic subunit boosts rAAV transduction of polarized human airway epithelium

Adeno-associated virus 2.5T (AAV2.5T) was selected from the directed evolution of AAV capsid library in human airway epithelia. This study found that recombinant AAV2.5T (rAAV2.5T) transduction of well-differentiated primary human airway epithelia induced a DNA damage response (DDR) characterized by the phosphorylation of replication protein A32 (RPA32), histone variant H2AX (H2A histone family member X), and all three phosphatidylinositol 3-kinase-related kinases: ataxia telangiectasia mutated kinase, ataxia telangiectasia and Rad3-related kinase (ATR), and DNA-dependent protein kinase catalytic subunit (DNA-PKcs). While suppressing the expression of ATR by a specific pharmacological inhibitor or targeted gene silencing inhibited rAAV2.5T transduction, DNA-PKcs inhibition or targeted gene silencing significantly increased rAAV2.5T transgene expression. Notably, DNA-PKcs inhibitors worked as a "booster" to further increase rAAV2.5T transgene expression after treatment with doxorubicin and did not compromise epithelial integrity. Thus, our study provides evidence that DDR is associated with rAAV transduction in well-differentiated human airway epithelia, and DNA-PKcs inhibition has the potential to boost rAAV transduction. These findings highlight that the application of DDR inhibition-associated pharmacological interventions has the potential to increase rAAV transduction and thus to reduce the required vector dose.

Severe pneumonia and pathogenic damage in human airway epithelium caused by Coxsackievirus B4

Coxsackievirus B4 (CVB4) has one of the highest proportions of fatal outcomes of other enterovirus serotypes. However, the pathogenesis of severe respiratory disease caused by CVB4 infection remains unclear. In this study, 3 of 42 (7.2%, GZ-R6, GZ-R7 and GZ-R8) patients with severe pneumonia tested positive for CVB4 infection in southern China. Three full-length genomes of pneumonia-derived CVB4 were sequenced and annotated for the first time, showing their high nucleotide similarity and clustering within genotype V. To analyze the pathogenic damage caused by CVB4 in the lungs, a well-differentiated human airway epithelium (HAE) was established and infected with the pneumonia-derived CVB4 isolate GZ-R6. The outcome was compared with that of a severe hand-foot-mouth disease (HFMD)-derived CVB4 strain GZ-HFM01. Compared with HFMD-derived CVB4, pneumonia-derived CVB4 caused more intense and rapid disruption of HAE polarity, leading to tight-junction barrier disruption, loss of cilia, and airway epithelial cell hypertrophy. More pneumonia-derived CVB4 were released from the basolateral side of the HAE than HFMD-derived CVB4. Of the 18 cytokines tested, only IL-6 and IL-1b secretion significantly increased on bilateral sides of HAE during the early stage of pneumonia-derived CVB4 infection, while multiple cytokine secretions significantly increased in HFMD-derived CVB4-infected HAE. HFMD-derived CVB4 exhibited stronger neurovirulence in the human neuroblastoma cells SH-SY5Y than pneumonia-derived CVB4, which is consistent with the clinical manifestations of patients infected with these two viruses. This study has increased the depth of our knowledge of severe pneumonia infection caused by CVB4 and will benefit its prevention and treatment.

Inhibition of SARS-CoV-2 Infection in Human Airway Epithelium with a Xeno-Nucleic Acid Aptamer

Background

SARS-CoV-2, the agent responsible for the COVID-19 pandemic, enters cells through viral spike glycoprotein binding to the cellular receptor, angiotensin-converting enzyme 2 (ACE2). Given the lack of effective antivirals targeting SARS-CoV-2, we previously utilized systematic evolution of ligands by exponential enrichment (SELEX) and selected fluoro-arabino nucleic acid (FANA) aptamer R8-9 that was able to block the interaction between the viral receptor-binding domain and ACE2.

Methods

Here, we further assessed FANA-R8-9 as an entry inhibitor in contexts that recapitulate infection in vivo.

Results

We demonstrate that FANA-R8-9 inhibits spike-bearing pseudovirus particle uptake in cell lines. Then, using an in-vitro model of human airway epithelium (HAE) and SARS-CoV-2 virus, we show that FANA-R8-9 significantly reduces viral infection when added either at the time of inoculation, or several hours later. These results were specific to the R8-9 sequence, not the xeno-nucleic acid utilized to make the aptamer. Importantly, we also show that FANA-R8-9 is stable in HAE culture secretions and has no overt cytotoxic effects.

Conclusions

Together, these results suggest that FANA-R8-9 effectively prevents infection by specific SARS-CoV-2 variants and indicate that aptamer technology could be utilized to target other clinically-relevant viruses in the respiratory mucosa.

SARS-CoV-2 infection of polarized human airway epithelium induces necroptosis that causes airway epithelial barrier dysfunction

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause the ongoing pandemic of coronavirus disease 2019 (COVID19). One key feature associated with COVID-19 is excessive pro-inflammatory cytokine production that leads to severe acute respiratory distress syndrome. Although the cytokine storm induces inflammatory cell death in the host, which type of programmed cell death mechanism that occurs in various organs and cells remains elusive. Using an in vitro culture model of polarized human airway epithelium (HAE), we observed that necroptosis, but not apoptosis or pyroptosis, plays an essential role in the damage of the epithelial barrier of polarized HAE infected with SARS-CoV-2. Pharmacological inhibitors of necroptosis, necrostatin-2 and necrosulfonamide, efficiently prevented cell death and epithelial barrier dysfunction caused by SARS-CoV-2 infection. Moreover, the silencing of genes that are involved in necroptosis, RIPK1, RIPK3, and MLKL, ameliorated airway epithelial damage of the polarized HAE infected with SARS-CoV-2. This study, for the first time, confirms that SARS-CoV-2 infection triggers necroptosis that disrupts the barrier function of human airway epithelia in vitro.

Non-Polio Enterovirus C Replicate in Both Airway and Intestine Organotypic Cultures

Non-polio enteroviruses (EV) belonging to species C, which are highly prevalent in Africa, mainly among children, are poorly characterized, and their pathogenesis is mostly unknown as they are difficult to culture. In this study, human airway and intestinal organotypic models were used to investigate tissue and cellular tropism of three EV-C genotypes, EV-C99, CVA-13, and CVA-20. Clinical isolates were obtained within the two passages of culture on Caco2 cells, and all three viruses were replicated in both the human airway and intestinal organotypic cultures. We did not observe differences in viral replication between fetal and adult tissue that could potentially explain the preferential infection of infants by EV-C genotypes. Infection of the airway and the intestinal cultures indicates that they both can serve as entry sites for non-polio EV-C. Ciliated airway cells and enterocytes are the target of infection for all three viruses, as well as enteroendocrine cells for EV-C99.

Human Airway Basal Cells Undergo Reversible Squamous Differentiation and Reshape Innate Immunity

Histological and lineage immunofluorescence examination revealed that healthy conducting airways of humans and animals harbor sporadic poorly differentiated epithelial patches mostly in the dorsal noncartilage regions that remarkably manifest squamous differentiation. In vitro analysis demonstrated that this squamous phenotype is not due to intrinsic functional change in underlying airway basal cells. Rather, it is a reversible physiological response to persistent Wnt signaling stimulation during de novo differentiation. Squamous epithelial cells have elevated gene signatures of glucose uptake and cellular glycolysis. Inhibition of glycolysis or a decrease in glucose availability suppresses Wnt-induced squamous epithelial differentiation. Compared with pseudostratified airway epithelial cells, a cascade of mucosal protective functions is impaired in squamous epithelial cells, featuring increased epithelial permeability, spontaneous epithelial unjamming, and enhanced inflammatory responses. Our study raises the possibility that the squamous differentiation naturally occurring in healthy airways identified herein may represent "vulnerable spots" within the airway mucosa that are sensitive to damage and inflammation when confronted by infection or injury. Squamous metaplasia and hyperplasia are hallmarks of many airway diseases, thereby expanding these areas of vulnerability with potential pathological consequences. Thus, investigation of physiological and reversible squamous differentiation from healthy airway basal cells may provide critical knowledge to understand pathogenic squamous remodeling, which is often nonreversible, progressive, and hyperinflammatory.

Human Airway Epithelium Responses to Invasive Fungal Infections: A Critical Partner in Innate Immunity

The lung epithelial lining serves as the primary barrier to inhaled environmental toxins, allergens, and invading pathogens. Pulmonary fungal infections are devastating and carry high mortality rates, particularly in those with compromised immune systems. While opportunistic fungi infect primarily immunocompromised individuals, endemic fungi cause disease in immune competent and compromised individuals. Unfortunately, in the case of inhaled fungal pathogens, the airway epithelial host response is vastly understudied. Furthering our lack of understanding, very few studies utilize primary human models displaying pseudostratified layers of various epithelial cell types at air-liquid interface. In this review, we focus on the diversity of the human airway epithelium and discuss the advantages and disadvantages of oncological cell lines, immortalized epithelial cells, and primary epithelial cell models. Additionally, the responses by human respiratory epithelial cells to invading fungal pathogens will be explored. Future investigations leveraging current human in vitro model systems will enable identification of the critical pathways that will inform the development of novel vaccines and therapeutics for pulmonary fungal infections.

Influenza A and respiratory syncytial virus trigger a cellular response that blocks severe acute respiratory syndrome virus 2 infection in the respiratory tract

BACKGROUND

Multiple viruses cocirculate and contribute to the burden of respiratory disease. Virus-virus interactions can decrease susceptibility to infection and this interference can have an epidemiological impact. As humans are normally exposed to a community of cocirculating respiratory viruses, experimental coinfection studies are necessary to understand the disease mechanisms of multi-pathogen systems. We aimed to characterize interactions within the respiratory tract between severe acute respiratory syndrome virus 2 (SARS-CoV-2) and two major respiratory viruses: influenza A virus (IAV), and respiratory syncytial virus (RSV).

METHODS

We performed single infections and coinfections with SARS-CoV-2 combined with IAV or RSV in cultures of human bronchial epithelial cells. We combined microscopy with quantification of viral replication in the presence or absence of an innate immune inhibitor to determine changes in virus-induced pathology, virus spread, and virus replication.

RESULTS

SARS-CoV-2 replication is inhibited by both IAV and RSV. This inhibition is dependent on a functional antiviral response and the level of inhibition is proportional to the timing of secondary viral infection.

CONCLUSIONS

Infections by other respiratory viruses might provide transient resistance to SARS-CoV-2. It would therefore be expected that the incidence of COVID-19 may decrease during periods of high circulation of IAV and RSV.Virus-virus interactions impact the infection dynamics of respiratory viruses at multiple levels, from cells to populations. Using three-dimensional cultures of airway epithelium, we showed that SARS-CoV-2 replication is impaired in coinfections with either influenza A or respiratory syncytial virus.

BPIFA1 is a secreted biomarker of differentiating human airway epithelium

In vitro culture and differentiation of human-derived airway basal cells under air-liquid interface (ALI) into a pseudostratified mucociliated mucosal barrier has proven to be a powerful preclinical tool to study pathophysiology of respiratory epithelium. As such, identifying differentiation stage-specific biomarkers can help investigators better characterize, standardize, and validate populations of regenerating epithelial cells prior to experimentation. Here, we applied longitudinal transcriptomic analysis and observed that the pattern and the magnitude of OMG, KRT14, STC1, BPIFA1, PLA2G7, TXNIP, S100A7 expression create a unique biosignature that robustly indicates the stage of epithelial cell differentiation. We then validated our findings by quantitative hemi-nested real-time PCR from in vitro cultures sourced from multiple donors. In addition, we demonstrated that at protein-level secretion of BPIFA1 accurately reflects the gene expression profile, with very low quantities present at the time of ALI induction but escalating levels were detectable as the epithelial cells terminally differentiated. Moreover, we observed that increase in BPIFA1 secretion closely correlates with emergence of secretory cells and an anti-inflammatory phenotype as airway epithelial cells undergo mucociliary differentiation under air-liquid interface in vitro.

Krüppel-Like Factor 5 Regulates CFTR Expression Through Repression by Maintaining Chromatin Architecture Coupled with Direct Enhancer Activation

Single cell RNA-sequencing has accurately identified cell types within the human airway that express the Cystic Fibrosis Transmembrane Conductance regulator (CFTR) gene. Low abundance CFTR transcripts are seen in many secretory cells, while high levels are restricted to rare pulmonary ionocytes. Here we focus on the mechanisms coordinating basal CFTR expression in the secretory compartment. Cell-selective regulation of CFTR is achieved within its invariant topologically associating domain by the recruitment of cis-regulatory elements (CREs). CRE activity is coordinated by cell-type-selective transcription factors. One such factor, Krüppel-Like Factor 5 (KLF5), profoundly represses CFTR transcript and protein in primary human airway epithelial cells and airway cell lines. Here we reveal the mechanism of action of KLF5 upon the CFTR gene. We find that depletion or ablation of KLF5 from airway epithelial cells changes higher order chromatin structure at the CFTR locus. Critical looping interactions that are required for normal gene expression are altered, the H3K27ac active chromatin mark is redistributed, and CTCF occupancy is modified. However, mutation of a single KLF5 binding site within a pivotal airway cell CRE abolishes CFTR expression. Hence, KLF5 has both direct activating and indirect repressive effects, which together coordinate CFTR expression in the airway.

Human Bocavirus 1 Infection of Well-Differentiated Human Airway Epithelium

Human bocavirus 1 (HBoV1) is a small DNA virus that belongs to the Bocaparvovirus genus of the Parvoviridae family. HBoV1 is a common respiratory pathogen that causes mild to life-threatening acute respiratory tract infections in children and immunocompromised individuals, infecting both the upper and lower respiratory tracts. HBoV1 infection causes death of airway epithelial cells, resulting in airway injury and inflammation. In vitro, HBoV1 only infects well-differentiated (polarized) human airway epithelium cultured at an air-liquid interface (HAE-ALI), but not any dividing human cells. A full-length HBoV1 genome of 5543 nucleotides has been cloned from DNA extracted from a human nasopharyngeal swab into a plasmid called HBoV1 infectious clone pIHBoV1. Transfection of pIHBoV1 replicates efficiently in human embryonic kidney 293 (HEK293) cells and produces virions that are highly infectious. This article describes protocols for production of HBoV1 in HEK293 cells, generation of HAE-ALI cultures, and infection with HBoV1 in HAE-ALI. © 2020 Wiley Periodicals LLC. Basic Protocol 1: Human bocavirus 1 production in HEK293 cells Support Protocol 1: HEK293 cell culture and transfection Support Protocol 2: Quantification of human bocavirus 1 using real-time quantitative PCR Basic Protocol 2: Differentiation of human airway cells at an air-liquid interface Support Protocol 3: Expansion of human airway epithelial cell line CuFi-8 Support Protocol 4: Expansion of human airway basal cells Support Protocol 5: Coating of plastic dishes and permeable membranes of inserts Support Protocol 6: Transepithelial electrical resistance measurement Basic Protocol 3: Human bocavirus 1 infection in human airway epithelium cultured at an air-liquid interface Support Protocol 7: Isolation of infected human airway epithelium cells from inserts Basic Protocol 4: Transduction of airway basal cells with lentiviral vector.

Long-Term Modeling of SARS-CoV-2 Infection of In Vitro Cultured Polarized Human Airway Epithelium

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) replicates throughout human airways. The polarized human airway epithelium (HAE) cultured at an airway-liquid interface (HAE-ALI) is an in vitro model mimicking the in vivo human mucociliary airway epithelium and supports the replication of SARS-CoV-2. Prior studies characterized only short-period SARS-CoV-2 infection in HAE. In this study, continuously monitoring the SARS-CoV-2 infection in HAE-ALI cultures for a long period of up to 51 days revealed that SARS-CoV-2 infection was long lasting with recurrent replication peaks appearing between an interval of approximately 7 to 10 days, which was consistent in all the tested HAE-ALI cultures derived from 4 lung bronchi of independent donors. We also identified that SARS-CoV-2 does not infect HAE from the basolateral side, and the dominant SARS-CoV-2 permissive epithelial cells are ciliated cells and goblet cells, whereas virus replication in basal cells and club cells was not detected. Notably, virus infection immediately damaged the HAE, which is demonstrated by dispersed zonula occludens-1 (ZO-1) expression without clear tight junctions and partial loss of cilia. Importantly, we identified that SARS-CoV-2 productive infection of HAE requires a high viral load of >2.5 × 105 virions per cm2 of epithelium. Thus, our studies highlight the importance of a high viral load and that epithelial renewal initiates and maintains a recurrent infection of HAE with SARS-CoV-2.IMPORTANCE The pandemic of coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has led to >35 million confirmed cases and >1 million fatalities worldwide. SARS-CoV-2 mainly replicates in human airway epithelia in COVID-19 patients. In this study, we used in vitro cultures of polarized human bronchial airway epithelium to model SARS-CoV-2 replication for a period of 21 to 51 days. We discovered that in vitro airway epithelial cultures endure a long-lasting SARS-CoV-2 propagation with recurrent peaks of progeny virus release at an interval of approximately 7 to 10 days. Our study also revealed that SARS-CoV-2 infection causes airway epithelia damage with disruption of tight junction function and loss of cilia. Importantly, SARS-CoV-2 exhibits a polarity of infection in airway epithelium only from the apical membrane; it infects ciliated and goblet cells but not basal and club cells. Furthermore, the productive infection of SARS-CoV-2 requires a high viral load of over 2.5 × 105 virions per cm2 of epithelium. Our study highlights that the proliferation of airway basal cells and regeneration of airway epithelium may contribute to the recurrent infections.

In Vitro Combinations of Baloxavir Acid and Other Inhibitors against Seasonal Influenza A Viruses

Two antiviral classes, the neuraminidase inhibitors (NAIs) and polymerase inhibitors (baloxavir marboxil and favipiravir) can be used to prevent and treat influenza infections during seasonal epidemics and pandemics. However, prolonged treatment may lead to the emergence of drug resistance. Therapeutic combinations constitute an alternative to prevent resistance and reduce antiviral doses. Therefore, we evaluated in vitro combinations of baloxavir acid (BXA) and other approved drugs against influenza A(H1N1)pdm09 and A(H3N2) subtypes. The determination of an effective concentration inhibiting virus cytopathic effects by 50% (EC50) for each drug and combination indexes (CIs) were based on cell viability. CompuSyn software was used to determine synergism, additivity or antagonism between drugs. Combinations of BXA and NAIs or favipiravir had synergistic effects on cell viability against the two influenza A subtypes. Those effects were confirmed using a physiological and predictive ex vivo reconstructed human airway epithelium model. On the other hand, the combination of BXA and ribavirin showed mixed results. Overall, BXA stands as a good candidate for combination with several existing drugs, notably oseltamivir and favipiravir, to improve in vitro antiviral activity. These results should be considered for further animal and clinical evaluations.

Replication of Severe Acute Respiratory Syndrome Coronavirus 2 in Human Respiratory Epithelium

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged by the end of 2019 and rapidly spread in 2020. At present, it is of utmost importance to understand the biology of the virus, rapidly assess the treatment potential of existing drugs, and develop new active compounds. While some animal models for such studies are under development, most of the research is carried out in Vero E6 cells. Here, we propose fully differentiated human airway epithelium cultures as a model for studies on SARS-CoV-2.

Currently, there are four seasonal coronaviruses associated with relatively mild respiratory tract disease in humans. However, there is also a plethora of animal coronaviruses which have the potential to cross the species border. This regularly results in the emergence of new viruses in humans. In 2002, severe acute respiratory syndrome coronavirus (SARS-CoV) emerged and rapidly disappeared in May 2003. In 2012, Middle East respiratory syndrome coronavirus (MERS-CoV) was identified as a possible threat to humans, but its pandemic potential so far is minimal, as human-to-human transmission is ineffective. The end of 2019 brought us information about severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emergence, and the virus rapidly spread in 2020, causing an unprecedented pandemic. At present, studies on the virus are carried out using a surrogate system based on the immortalized simian Vero E6 cell line. This model is convenient for diagnostics, but it has serious limitations and does not allow for understanding of the biology and evolution of the virus. Here, we show that fully differentiated human airway epithelium cultures constitute an excellent model to study infection with the novel human coronavirus SARS-CoV-2. We observed efficient replication of the virus in the tissue, with maximal replication at 2 days postinfection. The virus replicated in ciliated cells and was released apically.

IMPORTANCE Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged by the end of 2019 and rapidly spread in 2020. At present, it is of utmost importance to understand the biology of the virus, rapidly assess the treatment potential of existing drugs, and develop new active compounds. While some animal models for such studies are under development, most of the research is carried out in Vero E6 cells. Here, we propose fully differentiated human airway epithelium cultures as a model for studies on SARS-CoV-2.

SMAD Signaling Restricts Mucous Cell Differentiation in Human Airway Epithelium

Mucin-secreting goblet cell metaplasia and hyperplasia (GCMH) is a common pathological phenotype in many human respiratory diseases, including asthma, chronic obstructive pulmonary disease, cystic fibrosis, primary ciliary dyskinesia, and infections. A better understanding of how goblet cell quantities or proportions in the airway epithelium are regulated may provide novel therapeutic targets to mitigate GCMH in these devastating diseases. We identify canonical SMAD signaling as the principal pathway restricting goblet cell differentiation in human airway epithelium. Differentiated goblet cells express low levels of phosphorylated SMAD. Accordingly, inhibition of SMAD signaling markedly amplifies GCMH induced by mucous mediators. In contrast, SMAD signaling activation impedes goblet cell generation and accelerates the resolution of preexisting GCMH. SMAD signaling inhibition can override the suppressive effects imposed by a GABAergic receptor inhibitor, suggesting the GABAergic pathway likely operates through inhibition of SMAD signaling in regulating mucous differentiation. Collectively, our data demonstrate that SMAD signaling plays a determining role in mucous cell differentiation, and thus raise the possibility that dysregulation of this pathway contributes to respiratory pathophysiology during airway inflammation and pulmonary diseases. In addition, our study also highlights the potential for SMAD modulation as a therapeutic target in mitigating GCMH.

Interaction of Alt a 1 with SLC22A17 in the airway mucosa

BACKGROUND

Despite all the efforts made up to now, the reasons that facilitate a protein becoming an allergen have not been elucidated yet. Alt a 1 protein is the major fungal allergen responsible for chronic asthma, but little is known about its immunological activity. Our main purpose was to investigate the ligand-dependent interactions of Alt a 1 in the human airway epithelium.

METHODS

Alt a 1 with and without its ligand (holo- and apo- forms) was incubated with the pulmonary epithelial monolayer model, Calu-3 cells. Allergen transport and cytokine production were measured. Pull-down and immunofluorescence assays were employed to identify the receptor of Alt a 1 using the epithelial cell model and mouse tissues. Receptor-allergen-ligand interactions were analyzed by computational modeling.

RESULTS

The holo-form could activate human monocytes, PBMCs, and polarized airway epithelial (Calu-3) cell lines. The allergen was also transported through the monolayer, without any alteration of the epithelial integrity (TEER). Alt a 1 also induced the production of proinflammatory IL8 and specific epithelial cytokines (IL33 and IL25) by Calu-3 cells. The interaction between epithelial cells and holo-Alt a 1 was found to be mediated by the SLC22A17 receptor, and its recognition of Alt a 1 was explained in structural terms.

CONCLUSIONS

Our findings identified the Alt a 1 ligand as a central player in the interaction of the allergen with airway mucosa, shedding light into its potential role in the immunological response, while unveiling its potential as a new target for therapy intervention.

Identification of gene and microRNA changes in response to smoking in human airway epithelium by bioinformatics analyses

Smoking is a substantial risk factor for many respiratory diseases. This study aimed to identify the gene and microRNA changes related to smoking in human airway epithelium by bioinformatics analysis.From the Gene Expression Omnibus (GEO) database, the mRNA datasets GSE11906, GSE22047, GSE63127, and microRNA dataset GSE14634 were downloaded, and were analyzed using GEO2R. Functional enrichment analysis of the differentially expressed genes (DEGs) was enforced using DAVID. The protein-protein interaction (PPI) network and differentially expressed miRNAs (DEMs)- DEGs network were executed by Cytoscape.In total, 107 DEGs and 10 DEMs were determined. Gene Ontology (GO) analysis revealed that DEGs principally enriched in oxidation-reduction process, extracellular space and oxidoreductase activity. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway demonstrated that DEGs were principally enriched in metabolism of xenobiotics by cytochrome P450 and chemical carcinogenesis. The PPI network revealed 15 hub genes, including NQO1, CYP1B1, AKR1C1, CYP1A1, AKR1C3, CEACAM5, MUCL1, B3GNT6, MUC5AC, MUC12, PTGER4, CALCA, CBR1, TXNRD1, and CBR3. Cluster analysis showed that these hub genes were associated with adenocarcinoma in situ, squamous cell carcinoma, cell differentiation, inflammatory response, oxidative DNA damage, oxidative stress response and tumor necrosis factor. Hsa-miR-627-5p might have the most target genes, including ITLN1, TIMP3, PPP4R4, SLC1A2, NOVA1, RNFT2, CLDN10, TMCC3, EPHA7, SRPX2, PPP1R16B, GRM1, HS3ST3A1, SFRP2, SLC7A11, and KLHDC8A.We identified several molecular changes induced by smoking in human airway epithelium. This study may provide some candidate genes and microRNAs for assessing the risk of lung diseases caused by smoking.

Der p2 Internalization by Epithelium Synergistically Augments Toll-like Receptor-Mediated Proinflammatory Signaling

Purpose

House-dust-mite (HDM) major allergen Der p2 shares homology and function with Toll-like receptor (TLR) signaling protein myeloid differentiation-2 (MD2) and may lead to airway inflammation. Should Der p2 be internalized by human airway epithelium, it has the theoretical propensity to potentiate epithelium activation. This study aimed to demonstrate the internalization of Der p2 by airway epithelium and to investigate the effects of Der p2 on MD2 expression and epithelium activation.

Methods

Internalization of recombinant, enhanced green fluorescent protein-labelled Der p2 (rDer p2-EGFP) into human airway epithelium (BEAS-2B) was tracked by laser confocal microscopy and confirmed by immunoblotting. Reverse-transcription polymerase chain reaction (RT-PCR), immunoblotting, and immunohistochemical staining were used to determine the effect of Der p2 on MD2 expression in vitro and ex vivo. Expression of messenger RNA (mRNA) encoding receptors/cytokines was measured by RT-PCR. Secretion of interleukin-6/interleukin-8 (IL-6/IL-8) was measured by enzyme-linked immunosorbent assay (ELISA).

Results

Internalization of Der p2 by BEAS-2B was confirmed by confocal microscopy and immunoblotting using rDer p2-EGFP and rDer p2, respectively. Expression of MD2 protein was increased in BEAS-2B and human nasal polyp airway epithelium cultured with rDer p2. Recombinant Der p2-cultured BEAS-2B caused little spontaneous IL-6/IL-8 secretion but significantly augmented by TLR ligand LPS. IL-6 secretion was up-regulated after MD2 transfection. Internalization of Der p2 was reduced by TLR2 RNA knockdown. Dexamethasone, calcitriol, anti-MD2/anti-TLR2 antibodies, and signalling inhibitors significantly reduced LPS+Der p2-induced IL-6/IL-8 secretion.

Conclusions

Human airway epithelium may internalize Der p2, which potentiates the response to environmental proinflammatory stimuli through MD2 and TLRs. This study highlights a novel mechanism and alleviates IL-6/IL-8 secretion in mite-induced airway inflammation.

Ambient particulate matter induces interleukin-8 expression through an alternative NF-κB (nuclear factor-kappa B) mechanism in human airway epithelial cells

BACKGROUND

Exposure to ambient air particulate matter (PM) has been shown to increase rates of cardiopulmonary morbidity and mortality, but the underlying mechanisms are still not well understood.

OBJECTIVE

We examined signaling events involved in the expression of the inflammatory gene interleukin-8 (IL-8) in human airway epithelial cells (HAECs) exposed to ambient PM collected in an urban area of Mexicali, Mexico.

METHODS

We studied IL-8 expression and regulatory signaling pathways in cultured HAECs exposed to Mexicali PM suspended in media for 0-4 hr.

RESULTS

Exposure resulted in a dose-dependent, 2- to 8-fold increase in IL-8 mRNA expression relative to controls. PM exposure induced IL-8 transcriptional activity in BEAS-2B cells that was dependent on the nuclear factor-kappa B (NF-κB) response element in the IL-8 promoter. Chromatin immunoprecipitation (ChIP) assays showed a 3-fold increase in binding of the p65 (RelA) NF-κB isoform to the IL-8 promoter sequence in HAECs exposed to PM. Western blot analyses showed elevated levels of phosphorylation of p65 but no changes in IκBα phosphorylation or degradation. IL-8 expression was blunted in a dose-dependent manner in BEAS-2B cells transduced with a lentivirus encoding a dominant negative p65 mutant in which phosphorylation sites were inactivated.

CONCLUSION

Taken together, these findings show that the increase in IL-8 mRNA expression in HAECs exposed to PM10 (PM ≤ 10 μm in aerodynamic diameter) is mediated through an NF-κB-dependent signaling mechanism that occurs through a pathway involving direct phosphorylation of the transcription factor p65 in the absence of IκBα degradation. These data show that exposure to PM10 in ambient air can induce inflammatory responses by activating specific signaling mechanisms in HAECs.

Human airway xenograft models of epithelial cell regeneration

Regeneration and restoration of the airway epithelium after mechanical, viral or bacterial injury have a determinant role in the evolution of numerous respiratory diseases such as chronic bronchitis, asthma and cystic fibrosis. The study in vivo of epithelial regeneration in animal models has shown that airway epithelial cells are able to dedifferentiate, spread, migrate over the denuded basement membrane and progressively redifferentiate to restore a functional respiratory epithelium after several weeks. Recently, human tracheal xenografts have been developed in immunodeficient severe combined immunodeficiency (SCID) and nude mice. In this review we recall that human airway cells implanted in such conditioned host grafts can regenerate a well-differentiated and functional human epithelium; we stress the interest in these humanized mice in assaying candidate progenitor and stem cells of the human airway mucosa.