Cultured human airway epithelial cells (calu-3): a model of human respiratory function, structure, and inflammatory responses

Statine-based peptidomimetic compounds as inhibitors for SARS-CoV-2 main protease (SARS-CoV‑2 Mpro)

COVID-19 is a multisystemic disease caused by the SARS-CoV-2 airborne virus, a member of the Coronaviridae family. It has a positive sense single-stranded RNA genome and encodes two non-structural proteins through viral cysteine-proteases processing. Blocking this step is crucial to control virus replication. In this work, we reported the synthesis of 23 statine-based peptidomimetics to determine their ability to inhibit the main protease (Mpro) activity of SARS-CoV-2. Among the 23 peptidomimetics, 15 compounds effectively inhibited Mpro activity by 50% or more, while three compounds (7d, 8e, and 9g) exhibited maximum inhibition above 70% and IC50 < 1 µM. Compounds 7d, 8e, and 9g inhibited roughly 80% of SARS-CoV-2 replication and proved no cytotoxicity. Molecular docking simulations show putative hydrogen bond and hydrophobic interactions between specific amino acids and these inhibitors. Molecular dynamics simulations further confirmed the stability and persisting interactions in Mpro's subsites, exhibiting favorable free energy binding (ΔGbind) values. These findings suggest the statine-based peptidomimetics as potential therapeutic agents against SARS-CoV-2 by targeting Mpro.

Highly Sensitive Real-Time Monitoring of Adenosine Receptor Activities in Nonsmall Cell Lung Cancer Cells Using Carbon Nanotube Field-Effect Transistors

Adenosine metabolism through adenosine receptors plays a critical role in lung cancer biology. Although recent studies showed the potential of targeting adenosine receptors as drug targets for lung cancer treatment, conventional methods for investigating receptor activities often suffer from various drawbacks, including low sensitivity and slow analysis speed. In this study, adenosine receptor activities in nonsmall cell lung cancer (NSCLC) cells were monitored in real time with high sensitivity through a carbon nanotube field-effect transistor (CNT-FET). In this method, we hybridized a CNT-FET with NSCLC cells expressing A2A and A2B adenosine receptors to construct a hybrid platform. This platform could detect adenosine, an endogenous ligand of adenosine receptors, down to 1 fM in real time and sensitively discriminate adenosine among other nucleosides. Furthermore, we could also utilize the platform to detect adenosine in complicated environments, such as human serum. Notably, our hybrid platform allowed us to monitor pharmacological effects between adenosine and other drugs, including dipyridamole and theophylline, even in human serum samples. These results indicate that the NSCLC cell-hybridized CNT-FET can be a practical tool for biomedical applications, such as the evaluation and screening of drug-candidate substances.

IFN-γ-mediated control of SARS-CoV-2 infection through nitric oxide

Introduction

The COVID-19 pandemic has highlighted the need to identify mechanisms of antiviral host defense against SARS-CoV-2. One such mediator is interferon-g (IFN-γ), which, when administered to infected patients, is reported to result in viral clearance and resolution of pulmonary symptoms. IFN-γ treatment of a human lung epithelial cell line triggered an antiviral activity against SARS-CoV-2, yet the mechanism for this antiviral response was not identified.

Methods

Given that IFN-γ has been shown to trigger antiviral activity via the generation of nitric oxide (NO), we investigated whether IFN-γ induction of antiviral activity against SARS-CoV-2 infection is dependent upon the generation of NO in human pulmonary epithelial cells. We treated the simian epithelial cell line Vero E6 and human pulmonary epithelial cell lines, including A549-ACE2, and Calu-3, with IFN-γ and observed the resulting induction of NO and its effects on SARS-CoV-2 replication. Pharmacological inhibition of inducible nitric oxide synthase (iNOS) was employed to assess the dependency on NO production. Additionally, the study examined the effect of interleukin-1b (IL-1β) on the IFN-g-induced NO production and its antiviral efficacy.

Results

Treatment of Vero E6 cells with IFN-γ resulted in a dose-responsive induction of NO and an inhibitory effect on SARS-CoV-2 replication. This antiviral activity was blocked by pharmacologic inhibition of iNOS. IFN-γ also triggered a NO-mediated antiviral activity in SARS-CoV-2 infected human lung epithelial cell lines A549-ACE2 and Calu-3. IL-1β enhanced IFN-γ induction of NO, but it had little effect on antiviral activity.

Discussion

Given that IFN-g has been shown to be produced by CD8+ T cells in the early response to SARS-CoV-2, our findings in human lung epithelial cell lines, of an IFN-γ-triggered, NO-dependent, links the adaptive immune response to an innate antiviral pathway in host defense against SARS-CoV-2. These results underscore the importance of IFN-γ and NO in the antiviral response and provide insights into potential therapeutic strategies for COVID-19.

Glycolytic stress deteriorates 229E virulence to improve host defense response

Viral infection treatment is a difficult task due to its complex structure and metabolism. Additionally, viruses can alter the metabolism of host cells, mutate, and readily adjust to harsh environments. Coronavirus stimulates glycolysis, weakens mitochondrial activity, and impairs infected cells. In this study, we investigated the efficacy of 2-DG in inhibiting coronavirus-induced metabolic processes and antiviral host defense systems, which have not been explored so far. 2-Deoxy-d-glucose (2-DG), a molecule restricting substrate availability, has recently gained attention as a potential antiviral drug. The results revealed that 229E human coronavirus promoted glycolysis, producing a significant increase in the concentration of fluorescent 2-NBDG, a glucose analog, particularly in the infected host cells. The addition of 2-DG decreased its viral replication and suppressed infection-induced cell death and cytopathic effects, thereby improving the antiviral host defense response. It was also observed that administration of low doses of 2-DG inhibited glucose uptake, indicating that 2-DG consumption in virus-infected host cells was mediated by high-affinity glucose transporters, whose levels were amplified upon coronavirus infection. Our findings indicated that 2-DG could be a potential drug to improve the host defense system in coronavirus-infected cells.

Aurones: A Promising Scaffold to Inhibit SARS-CoV-2 Replication

Aurones are a small subgroup of flavonoids in which the basic C6-C3-C6 skeleton is arranged as (Z)-2-benzylidenebenzofuran-3(2H)-one. These compounds are structural isomers of flavones and flavonols, natural products reported as potent inhibitors of SARS-CoV-2 replication. Herein, we report the design, synthesis, and anti-SARS-CoV-2 activity of a series of 25 aurones bearing different oxygenated groups (OH, OCH3, OCH2OCH3, OCH2O, OCF2H, and OCH2C6H4R) at the A- and/or B-rings using cell-based screening assays. We observed that 12 of the 25 compounds exhibit EC50 < 3 μM (8e, 8h, 8j, 8k, 8l, 8m, 8p, 8q, 8r, 8w, 8x, and 8y), of which five presented EC50 < 1 μM (8h, 8m, 8p, 8q, and 8w) without evident cytotoxic effect in Calu-3 cells. The substitution of the A- and/or B-ring with OCH3, OCH2OCH3, and OCF2H groups seems beneficial for the antiviral activity, while the corresponding phenolic derivatives showed a significant decrease in the anti-SARS-CoV-2 activity. The most potent compound of the series, aurone 8q (EC50 = 0.4 μM, SI = 2441.3), is 2 to 3 times more effective than the polyphenolic flavonoids myricetin (2) and baicalein (1), respectively. Investigation of the five more active compounds as inhibitors of SARS-CoV-2 3CLpro based on molecular dynamic calculations suggested that these aurones should detach from the active site of 3CLpro, and, probably, they could bind to another SARS-CoV-2 protein target (either receptor or enzyme).

AI-Driven Discovery of SARS-CoV-2 Main Protease Fragment-like Inhibitors with Antiviral Activity In Vitro

SARS-CoV-2 is the causative agent of COVID-19 and is responsible for the current global pandemic. The viral genome contains 5 major open reading frames of which the largest ORF1ab codes for two polyproteins, pp1ab and pp1a, which are subsequently cleaved into 16 nonstructural proteins (nsp) by two viral cysteine proteases encoded within the polyproteins. The main protease (Mpro, nsp5) cleaves the majority of the nsp's, making it essential for viral replication and has been successfully targeted for the development of antivirals. The first oral Mpro inhibitor, nirmatrelvir, was approved for treatment of COVID-19 in late December 2021 in combination with ritonavir as Paxlovid. Increasing the arsenal of antivirals and development of protease inhibitors and other antivirals with a varied mode of action remains a priority to reduce the likelihood for resistance emerging. Here, we report results from an artificial intelligence-driven approach followed by in vitro validation, allowing the identification of five fragment-like Mpro inhibitors with IC50 values ranging from 1.5 to 241 μM. The three most potent molecules (compounds 818, 737, and 183) were tested against SARS-CoV-2 by in vitro replication in Vero E6 and Calu-3 cells. Compound 818 was active in both cell models with an EC50 value comparable to its measured IC50 value. On the other hand, compounds 737 and 183 were only active in Calu-3, a preclinical model of respiratory cells, showing selective indexes twice as high as those for compound 818. We also show that our in silico methodology was successful in identifying both reversible and covalent inhibitors. For instance, compound 818 is a reversible chloromethylamide analogue of 8-methyl-γ-carboline, while compound 737 is an N-pyridyl-isatin that covalently inhibits Mpro. Given the small molecular weights of these fragments, their high binding efficiency in vitro and efficacy in blocking viral replication, these compounds represent good starting points for the development of potent lead molecules targeting the Mpro of SARS-CoV-2.

Aspergillus fumigatus Drives Tissue Damage via Iterative Assaults upon Mucosal Integrity and Immune Homeostasis

The human lung is constantly exposed to Aspergillus fumigatus spores, the most prevalent worldwide cause of fungal respiratory disease. Pulmonary tissue damage is a unifying feature of Aspergillus-related diseases; however, the mechanistic basis of damage is not understood. In the lungs of susceptible hosts, A. fumigatus undergoes an obligatory morphological switch involving spore germination and hyphal growth. We modeled A. fumigatus infection in cultured A549 human pneumocytes, capturing the phosphoactivation status of five host signaling pathways, nuclear translocation and DNA binding of eight host transcription factors, and expression of nine host response proteins over six time points encompassing exposures to live fungus and the secretome thereof. The resulting data set, comprised of more than 1,000 data points, reveals that pneumocytes mount differential responses to A. fumigatus spores, hyphae, and soluble secreted products via the NF-κB, JNK, and JNK + p38 pathways, respectively. Importantly, via selective degradation of host proinflammatory (IL-6 and IL-8) cytokines and growth factors (FGF-2), fungal secreted products reorchestrate the host response to fungal challenge as well as driving multiparameter epithelial damage, culminating in cytolysis. Dysregulation of NF-κB signaling, involving sequential stimulation of canonical and noncanonical signaling, was identified as a significant feature of host damage both in vitro and in a mouse model of invasive aspergillosis. Our data demonstrate that composite tissue damage results from iterative (repeated) exposures to different fungal morphotypes and secreted products and suggest that modulation of host responses to fungal challenge might represent a unified strategy for therapeutic control of pathologically distinct types of Aspergillus-related disease.

Choosing a cellular model to study SARS-CoV-2

As new pathogens emerge, new challenges must be faced. This is no different in infectious disease research, where identifying the best tools available in laboratories to conduct an investigation can, at least initially, be particularly complicated. However, in the context of an emerging virus, such as SARS-CoV-2, which was recently detected in China and has become a global threat to healthcare systems, developing models of infection and pathogenesis is urgently required. Cell-based approaches are crucial to understanding coronavirus infection biology, growth kinetics, and tropism. Usually, laboratory cell lines are the first line in experimental models to study viral pathogenicity and perform assays aimed at screening antiviral compounds which are efficient at blocking the replication of emerging viruses, saving time and resources, reducing the use of experimental animals. However, determining the ideal cell type can be challenging, especially when several researchers have to adapt their studies to specific requirements. This review strives to guide scientists who are venturing into studying SARS-CoV-2 and help them choose the right cellular models. It revisits basic concepts of virology and presents the currently available in vitro models, their advantages and disadvantages, and the known consequences of each choice.

Assessment of Antitumor and Antiproliferative Efficacy and Detection of Protein-Protein Interactions in Cancer Cells from 3D Tumor Spheroids

When compared to two-dimensional (2D) cell cultures, 3D spheroids have been considered suitable in vitro models for drug discovery research and other studies of drug activity. Based on different 3D cell culture procedures, we describe procedures we have used to obtain 3D tumor spheroids by both the hanging-drop and ultra-low-attachment plate methods and to analyze the antiproliferative and antitumor efficacy of different chemotherapeutic agents, including a peptidomimetic. We have applied this method to breast and lung cancer cell lines such as BT-474, MCF-7, A549, and Calu-3. We also describe a proximity ligation assay of the cells from the spheroid model to detect protein-protein interactions of EGFR and HER2. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Growth of 3D spheroids using the hanging-drop method Basic Protocol 2: Growth of spheroids using ultra-low-attachment plates Support Protocol 1: Cell viability assay of tumor spheroids Support Protocol 2: Antiproliferative and antitumor study in 3D tumor spheroids Support Protocol 3: Proximity ligation assay on cells derived from 3D spheroids.

The Bioactive Phenolic Agents Diaryl Ether CVB2-61 and Diarylheptanoid CVB4-57 as Connexin Hemichannel Blockers

Inflammation mediators enhance the activity of connexin (Cx) hemichannels, especially in the epithelial and endothelial tissues. As potential release routes for injury signals, such as (oligo)nucleotides, Cx hemichannels may contribute to long-lasting inflammation. Specific inhibition of Cx hemichannels may therefore be a mode of prevention and treatment of long-lasting, chronic sterile inflammation. The activity of Cx hemichannels was analysed in N2A and HeLa cells transfected with human Cx26 and Cx46 as well as in Calu-3 cells, using dye uptake as functional assay. Moreover, the possible impacts of the bioactive phenolic agents CVB2-61 and CVB4-57 on the barrier function of epithelial cells was analysed using Calu-3 cells. Both agents inhibited the dye uptake in N2A cells expressing Cx26 (>5 µM) and Cx46 (>20 µM). In Calu-3 cells, CVB2-61 and CVB4-57 reversibly inhibited the dye uptake at concentrations as low as 5 µM, without affecting the gap junction communication and barrier function, even at concentrations of 20 µM. While CVB2-61 or CVB4-57 maintained a reduced dye uptake in Calu-3 cells, an enhancement of the dye uptake in response to the stimulation of adenosine signalling was still observed after removal of the agents. The report shows that CVB2-61 and CVB4-57 reversibly block Cx hemichannels. Deciphering the mechanisms of the interactions of these agents with Cx hemichannels could allow further development of phenolic compounds to target Cx hemichannels for better and safer treatment of pathologies that involve Cx hemichannels.

Differential haplotype expression in class I MHC genes during SARS-CoV-2 infection of human lung cell lines

Introduction

Cell entry of SARS-CoV-2 causes genome-wide disruption of the transcriptional profiles of genes and biological pathways involved in the pathogenesis of COVID-19. Expression allelic imbalance is characterized by a deviation from the Mendelian expected 1:1 expression ratio and is an important source of allele-specific heterogeneity. Expression allelic imbalance can be measured by allele-specific expression analysis (ASE) across heterozygous informative expressed single nucleotide variants (eSNVs). ASE reflects many regulatory biological phenomena that can be assessed by combining genome and transcriptome information. ASE contributes to the interindividual variability associated with the disease. We aim to estimate the transcriptome-wide impact of SARS-CoV-2 infection by analyzing eSNVs.

Methods

We compared ASE profiles in the human lung cell lines Calu-3, A459, and H522 before and after infection with SARS-CoV-2 using RNA-Seq experiments.

Results

We identified 34 differential ASE (DASE) sites in 13 genes (HLA-A, HLA-B, HLA-C, BRD2, EHD2, GFM2, GSPT1, HAVCR1, MAT2A, NQO2, SUPT6H, TNFRSF11A, UMPS), all of which are enriched in protein binding functions and play a role in COVID-19. Most DASE sites were assigned to the MHC class I locus and were predominantly upregulated upon infection. DASE sites in the MHC class I locus also occur in iPSC-derived airway epithelium basal cells infected with SARS-CoV-2. Using an RNA-Seq haplotype reconstruction approach, we found DASE sites and adjacent eSNVs in phase (i.e., predicted on the same DNA strand), demonstrating differential haplotype expression upon infection. We found a bias towards the expression of the HLA alleles with a higher binding affinity to SARS-CoV-2 epitopes.

Discussion

Independent of gene expression compensation, SARS-CoV-2 infection of human lung cell lines induces transcriptional allelic switching at the MHC loci. This suggests a response mechanism to SARS-CoV-2 infection that swaps HLA alleles with poor epitope binding affinity, an expectation supported by publicly available proteome data.

Emerging SARS-CoV-2 Genotypes Show Different Replication Patterns in Human Pulmonary and Intestinal Epithelial Cells

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) quickly spread worldwide following its emergence in Wuhan, China, and hit pandemic levels. Its tremendous incidence favoured the emergence of viral variants. The current genome diversity of SARS-CoV-2 has a clear impact on epidemiology and clinical practice, especially regarding transmission rates and the effectiveness of vaccines. In this study, we evaluated the replication of different SARS-CoV-2 isolates representing different virus genotypes which have been isolated throughout the pandemic. We used three distinct cell lines, including Vero E6 cells originating from monkeys; Caco-2 cells, an intestinal epithelium cell line originating from humans; and Calu-3 cells, a pulmonary epithelium cell line also originating from humans. We used RT-qPCR to replicate different SARS-CoV-2 genotypes by quantifying the virus released in the culture supernatant of infected cells. We found that the different viral isolates replicate similarly in Caco-2 cells, but show very different replicative capacities in Calu-3 cells. This was especially highlighted for the lineages B.1.1.7, B.1.351 and P.1, which are considered to be variants of concern. These results underscore the importance of the evaluation and characterisation of each SARS-CoV-2 isolate in order to establish the replication patterns before performing tests, and of the consideration of the ideal SARS-CoV-2 genotype-cell type pair for each assay.

Iota-Carrageenan Prevents the Replication of SARS-CoV-2 in a Human Respiratory Epithelium Cell Line in vitro

Iota-carrageenan is a sulfated polysaccharide extracted from red seaweeds, which, formulated into a nasal spray, has already been proven safe and effective in viral upper respiratory infections. In Calu-3, a human respiratory epithelium cell line, we explored the activity of a formula of iota-carrageenan and sodium chloride against SARS-CoV-2. In this study, the assayed formula, already approved as a nasal spray for human use, effectively inhibited SARS-CoV-2 infection, providing a more substantial reference for clinical studies or developments.

Nanoparticles for local delivery of siRNA in lung therapy

An overview of the application of natural and synthetic, non-viral vectors for oligonucleotide delivery into the lung is presented in this review, with a special focus on lung cancer. Due to the specificity of the respiratory tract, its structure and natural barriers, the administration of drugs (especially those based on nucleic acids) is a particular challenge. Among widely tested non-viral drug and oligonucleotides carriers, synthetic polymers seem to be most promising. Unique properties of these nanoparticles allow for essentially unlimited possibilities regarding their design and modification. This gives hope that optimal nanoparticles with ideal nucleic acid carrier properties for lung cancer therapy will eventually emanate.

Replication and single-cycle delivery of SARS-CoV-2 replicons

Molecular virology tools are critical for basic studies of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and for developing new therapeutics. Experimental systems that do not rely on viruses capable of spread are needed for potential use in lower-containment settings. In this work, we use a yeast-based reverse genetics system to develop spike-deleted SARS-CoV-2 self-replicating RNAs. These noninfectious self-replicating RNAs, or replicons, can be trans-complemented with viral glycoproteins to generate replicon delivery particles for single-cycle delivery into a range of cell types. This SARS-CoV-2 replicon system represents a convenient and versatile platform for antiviral drug screening, neutralization assays, host factor validation, and viral variant characterization.

Challenges for Targeting SARS-CoV-2 Proteases as a Therapeutic Strategy for COVID-19

Two proteases produced by the SARS-CoV-2 virus, the main protease and papain-like protease, are essential for viral replication and have become the focus of drug development programs for treatment of COVID-19. We screened a highly focused library of compounds containing covalent warheads designed to target cysteine proteases to identify new lead scaffolds for both Mpro and PLpro proteases. These efforts identified a small number of hits for the Mpro protease and no viable hits for the PLpro protease. Of the Mpro hits identified as inhibitors of the purified recombinant protease, only two compounds inhibited viral infectivity in cellular infection assays. However, we observed a substantial drop in antiviral potency upon expression of TMPRSS2, a transmembrane serine protease that acts in an alternative viral entry pathway to the lysosomal cathepsins. This loss of potency is explained by the fact that our lead Mpro inhibitors are also potent inhibitors of host cell cysteine cathepsins. To determine if this is a general property of Mpro inhibitors, we evaluated several recently reported compounds and found that they are also effective inhibitors of purified human cathepsins L and B and showed similar loss in activity in cells expressing TMPRSS2. Our results highlight the challenges of targeting Mpro and PLpro proteases and demonstrate the need to carefully assess selectivity of SARS-CoV-2 protease inhibitors to prevent clinical advancement of compounds that function through inhibition of a redundant viral entry pathway.

A New PqsR Inverse Agonist Potentiates Tobramycin Efficacy to Eradicate Pseudomonas aeruginosa Biofilms

Pseudomonas aeruginosa (PA) infections can be notoriously difficult to treat and are often accompanied by the development of antimicrobial resistance (AMR). Quorum sensing inhibitors (QSI) acting on PqsR (MvfR) - a crucial transcriptional regulator serving major functions in PA virulence - can enhance antibiotic efficacy and eventually prevent the AMR. An integrated drug discovery campaign including design, medicinal chemistry-driven hit-to-lead optimization and in-depth biological profiling of a new QSI generation is reported. The QSI possess excellent activity in inhibiting pyocyanin production and PqsR reporter-gene with IC50 values as low as 200 and 11 × 10-9 m, respectively. Drug metabolism and pharmacokinetics (DMPK) as well as safety pharmacology studies especially highlight the promising translational properties of the lead QSI for pulmonary applications. Moreover, target engagement of the lead QSI is shown in a PA mucoid lung infection mouse model. Beyond that, a significant synergistic effect of a QSI-tobramycin (Tob) combination against PA biofilms using a tailor-made squalene-derived nanoparticle (NP) formulation, which enhance the minimum biofilm eradicating concentration (MBEC) of Tob more than 32-fold is demonstrated. The novel lead QSI and the accompanying NP formulation highlight the potential of adjunctive pathoblocker-mediated therapy against PA infections opening up avenues for preclinical development.

Interferon Lambda Delays the Emergence of Influenza Virus Resistance to Oseltamivir

Influenza viruses are a leading cause of morbidity and mortality worldwide. These air-borne pathogens are able to cross the species barrier, leading to regular seasonal epidemics and sporadic pandemics. Influenza viruses also possess a high genetic variability, which allows for the acquisition of resistance mutations to antivirals. Combination therapies with two or more drugs targeting different mechanisms of viral replication have been considered an advantageous option to not only enhance the effectiveness of the individual treatments, but also reduce the likelihood of resistance emergence. Using an in vitro infection model, we assessed the barrier to viral resistance of a combination therapy with the neuraminidase inhibitor oseltamivir and human interferon lambda against the pandemic H1N1 A/Netherlands/602/2009 (H1N1pdm09) virus. We serially passaged the virus in a cell line derived from human bronchial epithelial cells in the presence or absence of increasing concentrations of oseltamivir alone or oseltamivir plus interferon lambda. While the treatment with oseltamivir alone quickly induced the emergence of antiviral resistance through a single mutation in the neuraminidase gene, the co-administration of interferon lambda delayed the emergence of drug-resistant influenza virus variants. Our results suggest a possible clinical application of interferon lambda in combination with oseltamivir to treat influenza.

Long-term evolution of the epithelial cell secretome in preclinical 3D models of the human bronchial epithelium

The human bronchial epithelium is the first line of defense against atmospheric particles, pollutants, and respiratory pathogens such as the novel SARS-CoV-2. The epithelial cells form a tight barrier and secrete proteins that are major components of the mucosal immune response. Functional in vitro models of the human lung are essential for screening the epithelial response and assessing the toxicity and barrier crossing of drugs, inhaled particles, and pollutants. However, there is a lack of models to investigate the effect of chronic exposure without resorting to animal testing. Here, we developed a 3D model of the human bronchial epithelium using Calu-3 cell line and demonstrated its viability and functionality for 21 days without subculturing. We investigated the effect of reduced Fetal Bovine Serum supplementation in the basal medium and defined the minimal supplementation needed to maintain a functional epithelium, so that the amount of exogenous serum proteins could be reduced during drug testing. The long-term evolution of the epithelial cell secretome was fully characterized by quantitative mass spectrometry in two preclinical models using Calu-3 or primary NHBE cells. 408 common secreted proteins were identified while significant differences in protein abundance were observed with time, suggesting that 7-10 days are necessary to establish a mature secretome in the Calu-3 model. The associated Reactome pathways highlight the role of the secreted proteins in the immune response of the bronchial epithelium. We suggest this preclinical 3D model can be used to evaluate the long-term toxicity of drugs or particles on the human bronchial epithelium, and subsequently to investigate their effect on the epithelial cell secretions.

Development of an In Vitro Airway Epithelial-Endothelial Cell Culture Model on a Flexible Porous Poly(Trimethylene Carbonate) Membrane Based on Calu-3 Airway Epithelial Cells and Lung Microvascular Endothelial Cells

Due to the continuing high impact of lung diseases on society and the emergence of new respiratory viruses, such as SARS-CoV-2, there is a great need for in vitro lung models that more accurately recapitulate the in vivo situation than current models based on lung epithelial cell cultures on stiff membranes. Therefore, we developed an in vitro airway epithelial–endothelial cell culture model based on Calu-3 human lung epithelial cells and human lung microvascular endothelial cells (LMVECs), cultured on opposite sides of flexible porous poly(trimethylene carbonate) (PTMC) membranes. Calu-3 cells, cultured for two weeks at an air–liquid interface (ALI), showed good expression of the tight junction (TJ) protein Zonula Occludens 1 (ZO-1). LMVECs cultured submerged for three weeks were CD31-positive, but the expression was diffuse and not localized at the cell membrane. Barrier functions of the Calu-3 cell cultures and the co-cultures with LMVECs were good, as determined by electrical resistance measurements and fluorescein isothiocyanate-dextran (FITC-dextran) permeability assays. Importantly, the Calu-3/LMVEC co-cultures showed better cell viability and barrier function than mono-cultures. Moreover, there was no evidence for epithelial- and endothelial-to-mesenchymal transition (EMT and EndoMT, respectively) based on staining for the mesenchymal markers vimentin and α-SMA, respectively. These results indicate the potential of this new airway epithelial–endothelial model for lung research. In addition, since the PTMC membrane is flexible, the model can be expanded by introducing cyclic stretch for enabling mechanical stimulation of the cells. Furthermore, the model can form the basis for biomimetic airway epithelial–endothelial and alveolar–endothelial models with primary lung epithelial cells.

Human ACE2 peptide-mimics block SARS-CoV-2 pulmonary cells infection

In light of the recent accumulated knowledge on SARS-CoV-2 and its mode of human cells invasion, the binding of viral spike glycoprotein to human Angiotensin Converting Enzyme 2 (hACE2) receptor plays a central role in cell entry. We designed a series of peptides mimicking the N-terminal helix of hACE2 protein which contains most of the contacting residues at the binding site, exhibiting a high helical folding propensity in aqueous solution. Our best peptide-mimics are able to block SARS-CoV-2 human pulmonary cell infection with an inhibitory concentration (IC₅₀) in the nanomolar range upon binding to the virus spike protein with high affinity. These first-in-class blocking peptide mimics represent powerful tools that might be used in prophylactic and therapeutic approaches to fight the coronavirus disease 2019 (COVID-19).

Karoyan et al. present a method to inhibit SARS-CoV-2 by means of a peptide-mimic approach. They design a series of peptides mimicking the N-terminal helix of hACE2 protein and their best peptide-mimic blocks SARS-CoV-2 human pulmonary cell infection with an IC50 in nanomolar range.

PHAIR: a biosensor for pH measurement in air-liquid interface cell culture

In many biological systems, pH can be used as a parameter to understand and study cell dynamics. However, measuring pH in live cell culture is limited by the sensor ion specificity, proximity to the cell surface, and scalability. Commercially available pH sensors are difficult to integrate into a small-scale cell culture system due to their size and are not cost-effective for disposable use. We made PHAIR-a new pH sensor that uses a micro-wire format to measure pH in vitro human airway cell culture. Tungsten micro-wires were used as the working electrodes, and silver micro-wires with a silver/silver chloride coating were used as a pseudo reference electrode. pH sensitivity, in a wide and narrow range, and stability of these sensors were tested in common standard buffer solutions as well as in culture media of human airway epithelial cells grown at the air-liquid interface in a 24 well cell culture plate. When measuring the pH of cells grown under basal and challenge conditions using PHAIR, cell viability and cytokine responses were not affected. Our results confirm that micro-wire-based sensors have the capacity for miniaturization and detection of diverse ions while maintaining sensitivity. This suggests the broad application of PHAIR in various biological experimental settings.

JUUL e-liquid exposure elicits cytoplasmic Ca2+ responses and leads to cytotoxicity in cultured airway epithelial cells

RATIONALE

The popularity of new and emerging tobacco products such as E-cigarettes (E-cigs) is rapidly expanding worldwide. However, uncertainties surrounding the potential health consequences due to the use of such products exist and warrant further study.

METHODS

Cultured A549 and Calu-3 airway epithelia were exposed to three out of the eight types of JUUL brand e-liquids ("Mint", "Virginia Tobacco" and "Menthol", all containing 3% nicotine at 1% and 3% (vol/vol) dilutions) and assessed for viability using a resazurin-based assay. Intracellular Ca2+ levels were measured using fluorescent indicators and pro-inflammatory cytokine levels were monitored by quantitative PCR (qPCR). Cultures were also analyzed by flow cytometry to evaluate apoptotic markers and cell viability.

RESULTS

Exposing the airway epithelial cells to the flavored JUUL e-liquids led to significant cytotoxicity, with the "Mint" flavor being the overall most cytotoxic. The "Mint" flavored e-liquid also led to significant elevations in intracellular Ca2+ and upregulation of the pro-inflammatory cytokine IL-6 and early apoptotic marker Annexin V.

CONCLUSIONS

JUUL e-liquid challenge resulted in a loss of airway epithelial cell viability, induced pro-inflammatory responses and eventually caused apoptosis.

ceRNA analysis of SARS-CoV-2

Viral RNAs can perturb the miRNA regulatory network, competing with host RNAs as part of their infective process. An in silico competing endogenous RNA (ceRNA) analysis has been carried on SARS-CoV-2. The results suggest that, in humans, the decrease of microRNA activity caused by viral RNAs can lead to a perturbation of vesicle trafficking and the inflammatory response, in particular by enhancing KLF10 activity. The results suggest also that, during the study of the mechanics of viral infections, it could be of general interest to investigate the competition of viral RNA with cellular transcripts for shared microRNAs.

The effect of Notch signal pathway on PM2.5-induced Muc5ac in Beas-2B cells

BACKGROUND

Atmospheric pollutants could induced over-expression of Muc5ac, which is a major pathological feature in acute exacerbation of Chronic Obstructive Pulmonary Disease (COPD) and fatal asthma. Notch signaling pathway could promote mucus cell proliferation and mucus secretion. However, the effects of Notch signaling pathway on the airway mucus secretion induced by PM_2.5 remain unknown. In this study, we investigated the role of the Notch signaling pathway on Muc5ac by atmospheric PM_2.5 in Beas-2B cell.

METHODS

The mRNA and protein levels of the Notch1-4, downstream target gene Hes1 and Muc5ac in the Notch signaling pathway were detected by qPCR and western after Beas-2B cells were exposed to PM_2.5 of different concentrations for 12h, 24h, and 48h.

RESULTS

The longer the exposure time and the higher the concentration of PM_2.5, the lower the survival rate of Beas-2B cells. The expressions of Hes1 and Muc5ac in mRNA and protein were significantly increased after PM_2.5 exposure. Correlation analysis indicated that there was a positive correlation between the expression of Muc5ac and Hes1 in mRNA and protein.

CONCLUSION

Atmospheric PM_2.5 can induce the express of Muc5ac, the Notch signaling pathway may be involved in the regulation of Muc5ac by Hes1.

Experimental Models for the Study of Central Nervous System Infection by SARS-CoV-2

INTRODUCTION

The response to the SARS-CoV-2 coronavirus epidemic requires increased research efforts to expand our knowledge of the disease. Questions related to infection rates and mechanisms, the possibility of reinfection, and potential therapeutic approaches require us not only to use the experimental models previously employed for the SARS-CoV and MERS-CoV coronaviruses but also to generate new models to respond to urgent questions.

DEVELOPMENT

We reviewed the different experimental models used in the study of central nervous system (CNS) involvement in COVID-19 both in different cell lines that have enabled identification of the virus' action mechanisms and in animal models (mice, rats, hamsters, ferrets, and primates) inoculated with the virus. Specifically, we reviewed models used to assess the presence and effects of SARS-CoV-2 on the CNS, including neural cell lines, animal models such as mouse hepatitis virus CoV (especially the 59 strain), and the use of brain organoids.

CONCLUSION

Given the clear need to increase our understanding of SARS-CoV-2, as well as its potential effects on the CNS, we must endeavor to obtain new information with cellular or animal models, with an appropriate resemblance between models and human patients.

Comparative analysis of antiviral efficacy of FDA-approved drugs against SARS-CoV-2 in human lung cells

Drug repositioning represents an effective way to control the current COVID‐19 pandemic. Previously, we identified 24 FDA‐approved drugs which exhibited substantial antiviral effect against severe acute respiratory syndrome coronavirus 2 in Vero cells. Since antiviral efficacy could be altered in different cell lines, we developed an antiviral screening assay with human lung cells, which is more appropriate than Vero cell. The comparative analysis of antiviral activities revealed that nafamostat is the most potent drug in human lung cells (IC₅₀ = 0.0022 µM).

Prototype of a Smart Microfluidic Platform for the Evaluation of SARS-Cov-2 Pathogenesis, Along with Estimation of the Effectiveness of Potential Drug Candidates and Antigen-Antibody Interactions in Convalescent Plasma Therapy

Originating in China during December 2019, the novel corona-virus, SARS-CoV-2, has created mayhem worldwide in a very short time. The outbreak has been so rapid and widespread that the only option to treat the patients was administering drugs already available in the market like chloroquine/hydroxychloroquine (an antimalarial drug) and remedesivir. A large number of patients have been cured but the attribution to survival by these drugs has been controversial. Till date, we do not have any specific drug or vaccine available for COVID-19 and the pandemic seems to be far from over. To handle the current challenges posed by the outbreak effectively, we need to employ innovative interdisciplinary approaches. Organ-on-chip (OOC), particularly lung-on-chip, is one such approach which combines the potential of microfluidics, cell culture and molecular biology into a single miniaturised platform. The device is realized to be capable of simulating in-vivo physiological responses of an organ. In the current study, an OOC, which is a multichannel 3D cell culture microfluidic device, is made via soft lithography technique, using polydimethylsiloxane-polymer and diverse polymeric porous/semipermeable membranes. Several polymer membranes i.e. PDMS, polyvinylidene fluoride (PVDF), nitrocellulose, polyester etc., integrated into the microdevices, were efficiently explored to realize their better cell-adhesion and viability property. We also propose for the application of a simple, smart and cost-effective lung-on-chip platform to study the SARS-CoV-2 pathogenesis in humans, drug toxicity testing and provide insights into antigen-antibody interactions. This platform will enable us to study multiple phenomena at a micro-level generating more reliable data and a better understanding of the underlying mechanisms of SARS-CoV-2 infection and pathogenesis.

Effect of continuous positive airway pressure treatment on permeability, inflammation and mucus production of human epithelial cells

Continuous positive airway pressure (CPAP) therapy is the gold standard treatment for obstructive sleep apnoea, which affects millions of people worldwide. However, this therapy normally results in symptoms such as dryness, sneezing, rhinorrhoea, post-nasal drip, nasal congestion and epistaxis in the upper airways. Using bronchial epithelial (Calu-3) and nasal epithelial (RPMI 2650) cells in an in vitro respiratory model, this study, for the first time, investigates the effect of CPAP positive pressure on the human respiratory epithelial mechanisms that regulate upper airways lubrication characteristics. To understand how the epithelium and mucus are affected by this therapy, several parameters were determined before and after positive pressure application. This work demonstrates that the positive pressure not only compresses the cells, but also reduces their permeability and mucus secretion rate, thus drying the airway surface liquid layer and altering the mucus/water ratio. It is also observed that the respiratory epithelia is equally inflamed without or with external humidification during CPAP application. These findings clearly identify the causes of the side-effects reported by patients under CPAP therapy.

Effects of xenon gas on human airway epithelial cells during hyperoxia and hypothermia

BACKGROUND

Hypothermia with xenon gas has been used to reduce brain injury and disability rate after perinatal hypoxia-ischemia. We evaluated xenon gas therapy effects in an in vitro model with or without hypothermia on cultured human airway epithelial cells (Calu-3).

METHODS

Calu-3 monolayers were grown at an air-liquid interface and exposed to one of the following conditions: 1) 21% FiO2 at 37°C (control); 2) 45% FiO2 and 50% xenon at 37°C; 3) 21% FiO2 and 50% xenon at 32°C; 4) 45% FiO2 and 50% xenon at 32°C for 24 hours. Transepithelial resistance (TER) measurements were performed and apical surface fluids were collected and assayed for total protein, IL-6, and IL-8. Three monolayers were used for immunofluorescence localization of zonula occludens-1 (ZO-1). The data were analyzed by one-way ANOVA.

RESULTS

TER decreased at 24 hours in all treatment groups. Xenon with hyperoxia and hypothermia resulted in greatest decrease in TER compared with other groups. Immunofluorescence localization of ZO-1 (XY) showed reduced density of ZO-1 rings and incomplete ring-like staining in the 45% FiO2- 50% xenon group at 32°C compared with other groups. Secretion of total protein was not different among groups. Secretion of IL-6 in 21% FiO2 with xenon group at 32°C was less than that of the control group. The secretion of IL-8 in 45% FiO2 with xenon at 32°C was greater than that of other groups.

CONCLUSION

Hyperoxia and hypothermia result in detrimental epithelial cell function and inflammation over 24-hour exposure. Xenon gas did not affect cell function or reduce inflammation.

In vitro and computational modelling of drug delivery across the outer blood-retinal barrier

The ability to produce rapid, cost-effective and human-relevant data has the potential to accelerate the development of new drug delivery systems. Intraocular drug delivery is an area undergoing rapid expansion, due to the increase in sight-threatening diseases linked to increasing age and lifestyle factors. The outer blood-retinal barrier (OBRB) is important in this area of drug delivery, as it separates the eye from the systemic blood flow. This study reports the development of complementary in vitro and in silico models to study drug transport from silicone oil across the OBRB. Monolayer cultures of a human retinal pigmented epithelium cell line, ARPE-19, were added to chambers and exposed to a controlled flow to simulate drug clearance across the OBRB. Movement of dextran molecules and release of ibuprofen from silicone oil in this model were measured. Corresponding simulations were developed using COMSOL Multiphysics computational fluid dynamics software and validated using independent in vitro datasets. Computational simulations were able to predict dextran movement and ibuprofen release, with all of the features of the experimental release profiles being observed in the simulated data. Simulated values for peak concentrations of permeated dextran and ibuprofen released from silicone oil were within 18% of the in vitro results. This model could be used as a predictive tool for drug transport across this important tissue.

Exposure assessment in one central hospital: A multi-approach protocol to achieve an accurate risk characterization

The bioburden in a Hospital building originates not only from patients, visitors and staff, but is also disseminated by several indoor hospital characteristics and outdoor environmental sources. This study intends to assess the exposure to bioburden in one central Hospital with a multi-approach protocol using active and passive sampling methods. The microbial contamination was also characterized through molecular tools for toxigenic species, antifungal resistance and mycotoxins and endotoxins profile. Two cytotoxicity assays (MTT and resazurin) were conducted with two cell lines (Calu-3 and THP-1), and in vitro pro-inflammatory potential was assessed in THP-1 cell line. Out of the 15 sampling locations 33.3% did not comply with Portuguese legislation regarding bacterial contamination, whereas concerning fungal contamination 60% presented I/O > 1. Toxigenic fungal species were observed in 27% of the sampled rooms (4 out of 15) and qPCR analysis successfully amplified DNA from the Aspergillus sections Flavi and Fumigati, although mycotoxins were not detected. Growth of distinct fungal species was observed on Sabouraud dextrose agar with triazole drugs, such as Aspergillus section Versicolores on 1 mg/L VORI. The highest concentrations of endotoxins were found in settled dust samples and ranged from 5.72 to 23.0 EU.mg^-1. While a considerable cytotoxic effect (cell viability < 30%) was observed in one HVAC filter sample with Calu-3 cell line, it was not observed with THP-1 cell line. In air samples a medium cytotoxic effect (61-68% cell viability) was observed in 3 out of 15 samples. The cytokine responses produced a more potent average cell response (46.8 ± 12.3 ρg/mL IL-1β; 90.8 ± 58.5 ρg/mL TNF-α) on passive samples than air samples (25.5 ± 5.2 ρg/mL IL-1β and of 19.4 ± 5.2 ρg/mL TNF-α). A multi-approach regarding parameters to assess, sampling and analysis methods should be followed to characterize the biorburden in the Hospital indoor environment. This study supports the importance of considering exposure to complex mixtures in indoor environments.

Regulation of Early Host Immune Responses Shapes the Pathogenicity of Avian Influenza A Virus

Avian influenza A viruses (IAV) can cross the species barrier and cause disease in humans. Understanding the pathogenesis of avian IAV remains a challenge. Interferon-mediated antiviral responses and multiple cytokines production are important host cellular antiviral immunity against IAV infection. To elucidate the pathogenicity of avian IAV, a system approach was adopted to investigate dysregulation of the two host cellular antiviral immune responses in contrast with human IAV. As a result, we revealed that avian IAV not only disrupted normal early host cellular interferon-mediated antiviral responses, but also caused abnormal cytokines production through different pathways. For avian IAV infection, dysregulation of STAT2 was mainly responsible for abnormal cellular interferon-mediated antiviral responses, and IRF5 and NFKB1 played crucial roles in unusual cytokines production. In contrast, for human IAV infection, IRF1, IRF7, and STAT1 contributed to cellular cytokines production. Furthermore, differential activation of pattern recognition receptors (PRRs) likely led to avian IAV-related abnormal early host cellular antiviral immunity, where TLR7 and RIG-I were activated by avian and human IAV, respectively. Finally, a pathogenesis model was proposed that combined of early host cellular interferon-mediated antiviral responses with cytokines production could partly explain the pathogenicity of avian IAV. In conclusion, our study provides a new perspective of the pathogenesis of avian IAV, which will be helpful in preventing their infections in the future.

Comparative in Vitro Cytotoxicity of Realistic Doses of Benchmark Multi-Walled Carbon Nanotubes towards Macrophages and Airway Epithelial Cells

Multi-walled carbon nanotubes (MWCNT) have many outstanding physical and chemical properties that make them useful in many applications in nanotechnology. However, these properties are reported to be potentially harmful for the human body. The effects of low and realistic doses of three well-characterized preparations of MWCNT, obtained from the Joint Research Centre (JRC) (NM-400, NM-401, and NM-402), were assessed in two murine macrophage lines, Raw264.7, of peritoneal origin, and MH-S, derived from alveolar macrophages. Macrophage viability, evaluated with two distinct methods, was significantly lowered by NM-401 (needle-like, average length 4 μm, diameter 67 nm) with IC₅₀ values of 10 μg/cm², whereas NM-400 and NM-402 (tangled, average lengths 846–1372 nm, diameter 11 nm) had much smaller effects. In contrast, at 10 μg/cm², NM-400 and NM-402 induced the M1 marker Nos2 and, consistently, a sizable accumulation of nitrites in the medium, whereas NM-401 had no significant effect. None of the MWCNT preparations induced the M2 marker Arg1. Phagocytic activity, assessed in Raw264.7 macrophages, was significantly reduced in cells exposed to NM-401, but not to NM-400 or NM-402. When tested on Calu-3 bronchial epithelial cell monolayers, the three MWCNT preparations did not affect cell viability, but decreased the trans-epithelial electrical resistance at the maximal dose tested (80 μg/cm²), with the most evident effect detected for NM-401, even at 10 μg/cm². In conclusion, among the possible structural determinants of the toxic effects exerted by MWCNT towards macrophages and airway epithelial cells, shape and length appear the most relevant at low, realistic doses.

Generation of 13C-Labeled MUC5AC Mucin Oligosaccharides for Stable Isotope Probing of Host-Associated Microbial Communities

Stable isotope probing (SIP) has emerged as a powerful tool to address key questions about microbiota structure and function. To date, diverse isotopically labeled substrates have been used to characterize in situ growth activity of specific bacterial taxa and have revealed the flux of bioavailable substrates through microbial communities associated with health and disease. A major limitation to the growth of the field is the dearth of biologically relevant "heavy" labeled substrates. Mucin glycoproteins, for example, comprise an abundant source of carbon in the gut, oral cavity, respiratory tract, and other mucosal surfaces but are not commercially available. Here, we describe a method to incorporate a ¹³C-labeled monosaccharide into MUC5AC, a predominant mucin in both gastrointestinal and airway environments. Using the lung adenocarcinoma cell line, Calu-3, polarized cell cultures grown in ¹³C-labeled d-glucose resulted in liberal mucin production on the apical surface. Mucins were isolated by size-exclusion chromatography, and O-linked glycans were released by β-elimination, permethylated, and analyzed by electrospray ionization tandem mass spectrometry (ESI-MS/MS) and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) techniques. We demonstrate a 98.7% incorporation of ¹³C in the heterogeneous O-linked oligosaccharides that make up >80% of mucin dry weight. These "heavy" labeled glycoproteins represent a valuable tool for probing in vivo activity of host-associated bacterial communities and their interactions with the mucosal barrier. The continued expansion of labeled substrates for use in SIP will eventually allow bacterial taxa that degrade host compounds to be identified, with long-term potential for improved health and disease management.

Contribution of the Alkylquinolone Quorum-Sensing System to the Interaction of Pseudomonas aeruginosa With Bronchial Epithelial Cells

Pseudomonas aeruginosa causes infections in patients with compromised epithelial barrier function. Multiple virulence factors produced by P. aeruginosa are controlled by quorum sensing (QS) via 2-alkyl-4(1H)-quinolone (AQ) signal molecules. Here, we investigated the impact of AQs on P. aeruginosa PAO1 infection of differentiated human bronchial epithelial cells (HBECs). The pqsA-E operon is responsible for the biosynthesis of AQs including the 2-alkyl-3-hydroxy-4-quinolones, 4-hydroxy-2-alkylquinolines, and 4-hydroxy-2-alkylquinoline N-oxides as exemplified by pseudomonas quinolone signal (PQS), 2-heptyl-4-hydroxyquinoline (HHQ), and 2-heptyl-4-hydroxyquinoline N-oxide (HQNO), respectively. PQS and HHQ both act as QS signal molecules while HQNO is a cytochrome inhibitor. PqsE contributes both to AQ biosynthesis and promotes virulence in a PQS-independent manner. Our results show that PQS, HHQ, and HQNO were produced during PAO1 infection of HBECs, but no differences in growth or cytotoxicity were apparent when PAO1 and an AQ-negative ΔpqsA mutant were compared. Both strains promoted synthesis of inflammatory cytokines TNF-α, interleukin (IL)-6, and IL-17C by HBECs, and the provision of exogenous PQS negatively impacted on this response without affecting bacterial growth. Expression of pqsE and the PQS-independent PqsE-regulated genes mexG and lecA was detected during HBEC infection. Levels were reduced in the ΔpqsA mutant, that is, in the absence of PQS, and increased by exogenous PQS. These results support an AQ-independent role for PqsE during initial infection of HBEC by P. aeruginosa and for PQS as an enhancer of PqsE and PqsE-controlled virulence determinants and as an immunomodulator.

In vitro Models and On-Chip Systems: Biomaterial Interaction Studies With Tissues Generated Using Lung Epithelial and Liver Metabolic Cell Lines

In vitro models are very important in medicine and biology, because they provide an insight into cells' and microorganisms' behavior. Since these cells and microorganisms are isolated from their natural environment, these models may not completely or precisely predict the effects on the entire organism. Improvement in this area is secured by organ-on-a-chip development. The organ-on-a-chip assumes cells cultured in a microfluidic chip. The chip simulates bioactivities, mechanics and physiological behavior of organs or organ systems, generating artificial organs in that way. There are several cell lines used so far for each tested artificial organ. For lungs, mostly used cell lines are 16HBE, A549, Calu-3, NHBE, while mostly used cell lines for liver are HepG2, Hep 3B, TPH1, etc. In this paper, state of the art for lung and liver organ-on-a-chip is presented, together with the established in vitro testing on lung and liver cell lines, with the emphasis on Calu-3 (for lung cell lines) and Hep-G2 (for liver cell lines). Primary focus in this review is to discuss different researches on the topics of lung and liver cell line models, approaches in determining fate and transport, cell partitioning, cell growth and division, as well as cell dynamics, meaning toxicity and effects. The review is finalized with current research gaps and problems, stating potential future developments in the field.

N-acetyl cysteine reverts the proinflammatory state induced by cigarette smoke extract in lung Calu-3 cells

Chronic obstructive pulmonary disease (COPD) and cystic fibrosis (CF) are lethal pulmonary diseases. Cigarette consumption is the main cause for development of COPD, while CF is produced by mutations in the CFTR gene. Although these diseases have a different etiology, both share a CFTR activity impairment and proinflammatory state even under sterile conditions. The aim of this work was to study the extent of the protective effect of the antioxidant N-acetylcysteine (NAC) over the proinflammatory state (IL-6 and IL-8), oxidative stress (reactive oxygen species, ROS), and CFTR levels, caused by Cigarette Smoke Extract (CSE) in Calu-3 airway epithelial cells. CSE treatment (100 µg/ml during 24 h) decreased CFTR mRNA expression and activity, and increased the release of IL-6 and IL-8. The effect on these cytokines was inhibited by N-acetyl cysteine (NAC, 5 mM) or the NF-kB inhibitor, IKK-2 (10 µM). CSE treatment also increased cellular and mitochondrial ROS levels. The cellular ROS levels were normalized to control values by NAC treatment, although significant effects on mitochondrial ROS levels were observed only at short times (5´) and effects on CFTR levels were not observed. In addition, CSE reduced the mitochondrial NADH-cytochrome c oxidoreductase (mCx I-III) activity, an effect that was not reverted by NAC. The reduced CFTR expression and the mitochondrial damage induced by CSE could not be normalized by NAC treatment, evidencing the need for a more specific reagent. In conclusion, CSE causes a sterile proinflammatory state and mitochondrial damage in Calu-3 cells that was partially recovered by NAC treatment.

A slippery slope: On the origin, role and physiology of mucus

The mucosa of the gastrointestinal tract, eyes, nose, lungs, cervix and vagina is lined by epithelium interspersed with mucus-secreting goblet cells, all of which contribute to their unique functions. This mucus provides an integral defence to the epithelium against noxious agents and pathogens. However, it can equally act as a barrier to drugs and delivery systems targeting epithelial passive and active transport mechanisms. This review highlights the various mucins expressed at different mucosal surfaces on the human body, and their role in creating a mucoid architecture to protect epithelia with specialized functions. Various factors compromising the barrier properties of mucus have been discussed, with an emphasis on how disease states and microbiota can alter the physical properties of mucus. For instance, Akkermansia muciniphila, a bacterium found in higher levels in the gut of lean individuals induces the production of a thickened gut mucus layer. The aims of this article are to elucidate the different physiological, biochemical and physical properties of bodily mucus, a keen appreciation of which will help circumvent the slippery slope of challenges faced in achieving effective mucosal drug and gene delivery.

In vitro lung epithelial cell transport and anti-interleukin-8 releasing activity of liposomal ciprofloxacin

As a promising long-acting inhaled formulation, liposomal ciprofloxacin (Lipo-CPFX) was characterized in the in vitro human lung epithelial Calu-3 cell monolayer system, compared to ciprofloxacin in solution (CPFX). Its modulated absorptive transport and uptake, and sustained inhibitory activity against induced pro-inflammatory interleukin-8 (IL-8) release were examined. The absorptive transport and uptake kinetics for Lipo-CPFX and CPFX were determined at 0.1-50 mg/ml in the Transwell system. The Lipo-CPFX transport was then challenged for mechanistic exploration via cell energy depletion, a reduced temperature, endocytosis and/or lipid fusion inhibition, and addition of excess non-loaded liposomes. The inhibitory activities of Lipo-CPFX and CPFX against lipopolysaccharide (LPS)-induced IL-8 release were assessed in a co-incubation or pre-incubation mode. In the tight Calu-3 cell monolayers, Lipo-CPFX yielded 15-times slower ciprofloxacin flux of absorptive transport and 5-times lower cellular drug uptake than CPFX. Its transport appeared to be transcellular; kinetically linear, proportional to encapsulated ciprofloxacin concentration; and consistent with the cell energy-independent lipid bilayer fusion mechanism. Lipo-CPFX was equipotent to CPFX in the anti-IL-8 releasing activity upon 24 h co-incubation with LPS. Additionally, Lipo-CPFX, but not CPFX, retained the anti-IL-8 releasing activity even 24 h after pre-incubation. In conclusion, Lipo-CPFX enabled slower absorptive lung epithelial cell transport and uptake of ciprofloxacin, apparently via the lipid bilayer fusion mechanism, and the sustained inhibitory activity against LPS-induced IL-8 release, compared to CPFX.

Fibroblast-derived HGF drives acinar lung cancer cell polarization through integrin-dependent RhoA-ROCK1 inhibition

The formation of lumens in epithelial tissues requires apical-basal polarization of cells, and the co-ordination of this individual polarity collectively around a contiguous lumen. Signals from the Extracellular Matrix (ECM) instruct epithelia as to the orientation of where basal, and thus consequently apical, surfaces should be formed. We report that this pathway is normally absent in Calu-3 human lung adenocarcinoma cells in 3-Dimensional culture, but that paracrine signals from MRC5 lung fibroblasts can induce correct orientation of polarity and acinar morphogenesis. We identify HGF, acting through the c-Met receptor, as the key polarity-inducing morphogen, which acts to activate β1-integrin-dependent adhesion. HGF and ECM-derived integrin signals co-operate via a c-Src-dependent inhibition of the RhoA-ROCK1 signalling pathway via p190A RhoGAP. This occurred via controlling localization of these signalling pathways to the ECM-abutting surface of cells in 3-Dimensional culture. Thus, stromal derived signals can influence morphogenesis in epithelial cells by controlling activation and localization of cell polarity pathways.

Epigenetic Landscape during Coronavirus Infection

Coronaviruses (CoV) comprise a large group of emerging human and animal pathogens, including the highly pathogenic severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV) strains. The molecular mechanisms regulating emerging coronavirus pathogenesis are complex and include virus–host interactions associated with entry, replication, egress and innate immune control. Epigenetics research investigates the genetic and non-genetic factors that regulate phenotypic variation, usually caused by external and environmental factors that alter host expression patterns and performance without any change in the underlying genotype. Epigenetic modifications, such as histone modifications, DNA methylation, chromatin remodeling, and non-coding RNAs, function as important regulators that remodel host chromatin, altering host expression patterns and networks in a highly flexible manner. For most of the past two and a half decades, research has focused on the molecular mechanisms by which RNA viruses antagonize the signaling and sensing components that regulate induction of the host innate immune and antiviral defense programs upon infection. More recently, a growing body of evidence supports the hypothesis that viruses, even lytic RNA viruses that replicate in the cytoplasm, have developed intricate, highly evolved, and well-coordinated processes that are designed to regulate the host epigenome, and control host innate immune antiviral defense processes, thereby promoting robust virus replication and pathogenesis. In this article, we discuss the strategies that are used to evaluate the mechanisms by which viruses regulate the host epigenome, especially focusing on highly pathogenic respiratory RNA virus infections as a model. By combining measures of epigenome reorganization with RNA and proteomic datasets, we articulate a spatial-temporal data integration approach to identify regulatory genomic clusters and regions that play a crucial role in the host’s innate immune response, thereby defining a new viral antagonism mechanism following emerging coronavirus infection.

A translational cellular model to study the impact of high-frequency oscillatory ventilation on human epithelial cell function

High-frequency oscillatory ventilation (HFOV) has been proposed as gentle ventilation strategy to prevent lung injury in the preterm infant. High-frequency jet ventilation leads to dimensional and mechanical airway deformation in animal airway models, which is consistent with translational studies demonstrating the impact of oxygen and biophysical stresses on normal airway cellular function. There is an overall paucity of clinical and cellular data on the impact of HFOV on the conducting airway. We developed an innovative method to test the impact of the clinical HFO Ventilator (SensorMedics 3100A) on human epithelial cell function. In this translational model, we were able to study the differential effects of biophysical stress due to HFOV independently and in combination with hyperoxia on a direct cellular level of the conducting airway system. Additionally, we could demonstrate that hyperoxia and pressure by HFOV independently resulted in significant cell dysfunction and inflammation, while the combination of HFOV and hyperoxia had a synergistic effect, resulting in greater cell death.

NEW & NOTEWORTHY

Traditionally, large-animal models are used to analyze the impact of clinical ventilators on lung cellular function. In our dual-chamber model, we interface high-frequency oscillatory ventilation (HFOV) directly with airway cells to study the effects of HFOV independently and combined with hyperoxia. Therefore, it is possible to study the preclinical impact of interventional factors without the high cost of animal models, thus reducing staff, time, as well as animal sparing.

A paper-based in vitro model for on-chip investigation of the human respiratory system

Culturing cells at the air-liquid interface (ALI) is essential for creating functional in vitro models of lung tissues. We present the use of direct-patterned laser-treated hydrophobic paper as an effective semi-permeable membrane, ideal for ALI cell culture. The surface properties of the paper are modified through a selective CO₂ laser-assisted treatment to create a unique porous substrate with hydrophilic regions that regulate fluid diffusion and cell attachment. To select the appropriate model, four promising hydrophobic films were compared with each other in terms of gas permeability and long-term strength in an aqueous environment (wet-strength). Among the investigated substrates, parchment paper showed the fastest rate of oxygen permeability (3 times more than conventional transwell cell culture membranes), with the least variation in its dry and wet tensile strengths (124 MPa and 58 MPa, remaining unchanged after 7 days of submersion in PBS).The final paper-based platform provides an ideal, robust, and inexpensive device for generating monolayers of lung epithelial cells on-chip in a high-throughput fashion for disease modelling and in vitro drug testing.

Bioelectric and Morphological Response of Liquid-Covered Human Airway Epithelial Calu-3 Cell Monolayer to Periodic Deposition of Colloidal 3-Mercaptopropionic-Acid Coated CdSe-CdS/ZnS Core-Multishell Quantum Dots

Lung epithelial cells are extensively exposed to nanoparticles present in the modern urban environment. Nanoparticles, including colloidal quantum dots (QDs), are also considered to be potentially useful carriers for the delivery of drugs into the body. It is therefore important to understand the ways of distribution and the effects of the various types of nanoparticles in the lung epithelium. We use a model system of liquid-covered human airway epithelial Calu-3 cell cultures to study the immediate and long-term effects of repeated deposition of colloidal 3-mercaptopropionic-acid coated CdSe-CdS/ZnS core-multishell QDs on the lung epithelial cell surface. By live confocal microscope imaging and by QD fluorescence measurements we show that the QD permeation through the mature epithelial monolayers is very limited. At the time of QD deposition, the transepithelial electrical resistance (TEER) of the epithelial monolayers transiently decreased, with the decrement being proportional to the QD dose. Repeated QD deposition, once every six days for two months, lead to accumulation of only small amounts of the QDs in the cell monolayer. However, it did not induce any noticeable changes in the long-term TEER and the molecular morphology of the cells. The colloidal 3-mercaptopropionic-acid coated CdSe-CdS/ZnS core-multishell QDs could therefore be potentially used for the delivery of drugs intended for the surface of the lung epithelia during limited treatment periods.

Interest of cyclodextrins in spray-dried microparticles formulation for sustained pulmonary delivery of budesonide

To achieve an efficient lung delivery and efficacy, both active ingredient aerosolisation properties and permeability through the lung need to be optimized. To overcome these challenges, the present studies aim to develop cyclodextrin-based spray-dried microparticles containing a therapeutic corticosteroid (budesonide) that could be used to control airway inflammation associated with asthma. The complexation between budesonide and hydroxypropyl-β-cyclodextrin (HPBCD) has been investigated. Production of inhalation powders was carried out using a bi-fluid nozzle spray dryer and was optimized based on a design of experiments. Spray-dried microparticles display a specific "deflated-ball like shape" associated with an appropriate size for inhalation. Aerodynamic assessment show that the fine particle fraction was increased compared to a classical lactose-based budesonide formulation (44.05 vs 26.24%). Moreover, the budesonide permeability out of the lung was shown to be reduced in the presence of cyclodextrin complexes. The interest of this sustained budesonide release was evaluated in a mouse model of asthma. The anti-inflammatory effect was compared to a non-complexed budesonide formulation at the same concentration and attests the higher anti-inflammatory activity reach with the cyclodextrin-based formulation. This strategy could therefore be of particular interest for improving lung targeting while decreasing systemic side effects associated with high doses of corticosteroids. In conclusion, this works reports that cyclodextrins could be used in powder for inhalation, both for their abilities to improve active ingredient aerosolisation properties and further to their dissolution in lung fluid, to decrease permeability out of the lungs leading to an optimized activity profile.

Biocompatibility and Stability of Polysaccharide Polyelectrolyte Complexes Aimed at Respiratory Delivery

Chitosan (CS) and chondroitin sulfate (CHS) are natural polymers with demonstrated applicability in drug delivery, while nanoparticles are one of the most explored carriers for transmucosal delivery of biopharmaceuticals. In this work we have prepared CS/CHS nanoparticles and associated for the first time the therapeutic protein insulin. Fluorescein isothiocyanate bovine serum albumin (FITC-BSA) was also used to enable comparison of behaviors regarding differences in molecular weight (5.7 kDa versus 67 kDa). Nanoparticles of approximately 200 nm and positive zeta potential around +20 mV were obtained. These parameters remained stable for up to 1 month at 4 °C. Proteins were associated with efficiencies of more than 50%. The release of FITC-BSA in PBS pH 7.4 was more sustained (50% in 24 h) than that of insulin (85% in 24 h). The biocompatibility of nanoparticles was tested in Calu-3 and A549 cells by means of three different assays. The metabolic assay MTT, the determination of lactate dehydrogenase release, and the quantification of the inflammatory response generated by cell exposure to nanoparticles have indicated an absence of overt toxicity. Overall, the results suggest good indications on the application of CS/CHS nanoparticles in respiratory transmucosal protein delivery, but the set of assays should be widened to clarify obtained results.