Pharmaceutical applications of the Calu-3 lung epithelia cell line

Dynamic monitoring of a 3D-printed airway tissue model using an organic electrochemical transistor

Assessing the transepithelial resistance to ion flow in the presence of an electric field enables the evaluation of the integrity of the epithelial cell layer. In this study, we introduce an organic electrochemical transistor (OECT) interfaced with a 3D living tissue, designed to monitor the electrical resistance of cellular barriers in real-time. We have developed a non-invasive, tissue-sensing platform by integrating an inkjet-printed large-area OECT with a 3D-bioprinted multilayered airway tissue. This unique configuration enables the evaluation of epithelial barrier integrity through the dynamic response capabilities of the OECT. Our system effectively tracks the formation and integrity of 3D-printed airway tissues in both liquid-liquid and air-liquid interface culture environments. Furthermore, we successfully quantified the degradation of barrier function due to influenza A (H1N1) viral infection and the dose-dependent efficacy of oseltamivir (Tamiflu®) in mitigating this degradation. The tissue-electronic platform offers a non-invasive and label-free method for real-time monitoring of 3D artificial tissue barriers, without disturbing the cellular biology. It holds the potential for further applications in monitoring the structures and functions of 3D tissues and organs, significantly contributing to the advancement of personalized medicine.

Insights into Inhalation Drug Disposition: The Roles of Pulmonary Drug-Metabolizing Enzymes and Transporters

The past five decades have witnessed remarkable advancements in the field of inhaled medicines targeting the lungs for respiratory disease treatment. As a non-invasive drug delivery route, inhalation therapy offers numerous benefits to respiratory patients, including rapid and targeted exposure at specific sites, quick onset of action, bypassing first-pass metabolism, and beyond. Understanding the characteristics of pulmonary drug transporters and metabolizing enzymes is crucial for comprehending efficient drug exposure and clearance processes within the lungs. These processes are intricately linked to both local and systemic pharmacokinetics and pharmacodynamics of drugs. This review aims to provide a comprehensive overview of the literature on lung transporters and metabolizing enzymes while exploring their roles in exogenous and endogenous substance disposition. Additionally, we identify and discuss the principal challenges in this area of research, providing a foundation for future investigations aimed at optimizing inhaled drug administration. Moving forward, it is imperative that future research endeavors to focus on refining and validating in vitro and ex vivo models to more accurately mimic the human respiratory system. Such advancements will enhance our understanding of drug processing in different pathological states and facilitate the discovery of novel approaches for investigating lung-specific drug transporters and metabolizing enzymes. This deeper insight will be crucial in developing more effective and targeted therapies for respiratory diseases, ultimately leading to improved patient outcomes.

Liposomes for Inhalation

Inhalation of liposomes formulated with phospholipids similar to endogenous lung surfactants and lipids offers biocompatibility and versatility within the pulmonary medicine field to treat a range of diseases such as lung cancer, cystic fibrosis and lung infections. Manipulation of the physicochemical properties of liposomes enables innovative design of the carrier to meet specific delivery, release and targeting requirements. This delivery system offers several benefits: improved pharmacokinetics with reduced toxicity, enhanced therapeutic efficacy, increased delivery of poorly soluble drugs, taste masking, biopharmaceutics degradation protection and targeted cellular therapy. This section provides an overview of liposomal formulation and delivery, together with their applications for different disease states in the lung.

A Conformable Organic Electronic Device for Monitoring Epithelial Integrity at the Air Liquid Interface

Air liquid interfaced (ALI) epithelial barriers are essential for homeostatic functions such as nutrient transport and immunological protection. Dysfunction of such barriers are implicated in a variety of autoimmune and inflammatory disorders and, as such, sensors capable of monitoring barrier health are integral for disease modelling, diagnostics and drug screening applications. To date, gold-standard electrical methods for detecting barrier resistance require rigid electrodes bathed in an electrolyte, which limits compatibility with biological architectures and is non-physiological for ALI. This work presents a flexible all-planar electronic device capable of monitoring barrier formation and perturbations in human respiratory and intestinal cells at ALI. By interrogating patient samples with electrochemical impedance spectroscopy and simple equivalent circuit models, disease-specific and patient-specific signatures are uncovered. Device readouts are validated against commercially available chopstick electrodes and show greater conformability, sensitivity and biocompatibility. The effect of electrode size on sensing efficiency is investigated and a cut-off sensing area is established, which is one order of magnitude smaller than previously reported. This work provides the first steps in creating a physiologically relevant sensor capable of mapping local and real-time changes of epithelial barrier function at ALI, which will have broad applications in toxicology and drug screening applications.

Toxicological assessment of E-cigarette flavored E-liquids aerosols using Calu-3 cells: A 3D lung model approach

Scientific progress and ethical considerations are increasingly shifting the toxicological focus from in vivo animal models to in vitro studies utilizing physiologically relevant cell cultures. Consequently, we evaluated and validated a three-dimensional (3D) model of the human lung using Calu-3 cells cultured at an air-liquid interface (ALI) for 28 days. Assessment of seven essential genes of differentiation and transepithelial electrical resistance (TEER) measurements, in conjunction with mucin (MUC5AC) staining, validated the model. We observed a time-dependent increase in TEER, genetic markers of mucus-producing cells (muc5ac, muc5b), basal cells (trp63), ciliated cells (foxj1), and tight junctions (tjp1). A decrease in basal cell marker krt5 levels was observed. Subsequently, we utilized this validated ALI-cultured Calu-3 model to investigate the adversity of the aerosols generated from three flavored electronic cigarette (EC) e-liquids: cinnamon, vanilla tobacco, and hazelnut. These aerosols were compared against traditional cigarette smoke (3R4F) to assess their relative toxicity. The aerosols generated from PG/VG vehicle control, hazelnut and cinnamon e-liquids, but not vanilla tobacco, significantly decreased TEER and increased lactate dehydrogenase (LDH) release compared to the incubator and air-only controls. Compared to 3R4F, there were no significant differences in TEER or LDH with the tested flavored EC aerosols other than vanilla tobacco. This starkly contrasted our expectations, given the common perception of e-liquids as a safer alternative to cigarettes. Our study suggests that these results depend on flavor type. Therefore, we strongly advocate for further research, increased user awareness regarding flavors in ECs, and rigorous regulatory scrutiny to protect public health.

SARS-CoV-2 virus-like-particles via liposomal reconstitution of spike glycoproteins

The SARS-CoV-2 virus, implicated in the COVID-19 pandemic, recognizes and binds host cells using its spike glycoprotein through an angiotensin converting enzyme 2 (ACE-2) receptor-mediated pathway. Recent research suggests that spatial distributions of the spike protein may influence viral interactions with target cells and immune systems. The goal of this study has been to develop a liposome-based virus-like particle (VLP) by reconstituting the SARS-CoV-2 spike glycoprotein within a synthetic nanoparticle membrane, aiming to eventually establish tunability in spike protein presentation on the nanoparticle surface. Here we report on first steps to this goal, wherein liposomal SARS-CoV-2 VLPs were successfully produced via detergent mediated spike protein reconstitution. The resultant VLPs are shown to successfully co-localize in vitro with the ACE-2 receptor on lung epithelial cell surfaces, followed by internalization into these cells. These VLPs are the first step toward the overall goal of this research which is to form an understanding of the relationship between spike protein surface density and cell-level immune response, eventually toward creating better vaccines and anti-viral therapeutics.

Aerosol technology to mimic dry powder inhalation in vitro using pulmonary cell models

Inhaled therapy confers key advantages for the treatment of topical pulmonary diseases and offers potential for systemic delivery of medicines. Dry powder inhalers (DPIs) are generally the preferred devices for pulmonary delivery due to improved stability and satisfactory patient compliance. However, the mechanisms governing drug powder dissolution and availability in the lung and poorly understood. Here, we report a new in vitro system to study epithelial absorption of inhaled dry powders in lung barrier models of the upper and lower airway. The system is based on a CULTEX® RFS (Radial Flow System) cell exposure module joined to a Vilnius aerosol generator and allows the coupling of drug dissolution and permeability assessments. The cellular models recapitulate the barrier morphology and function of healthy and diseased pulmonary epithelium and incorporate the mucosal barrier to enable the investigation of drug powder dissolution in biorelevant conditions. With this system, we found differences in permeability across the airway tree and pinpointed the impact of diseased barriers in paracellular drug transport. Furthermore, we identified a different rank order of permeability for compounds tested in solution or powder form. These results highlight the value of this in vitro drug aerosolization setup for use in research and development of inhaled medicines.

Antiviral properties of trans-δ-viniferin derivatives against enveloped viruses

Over the last century, the number of epidemics caused by RNA viruses has increased and the current SARS-CoV-2 pandemic has taught us about the compelling need for ready-to-use broad-spectrum antivirals. In this scenario, natural products stand out as a major historical source of drugs. We analyzed the antiviral effect of 4 stilbene dimers [1 (trans-δ-viniferin); 2 (11',13'-di-O-methyl-trans-δ-viniferin), 3 (11,13-di-O-methyl-trans-δ-viniferin); and 4 (11,13,11',13'-tetra-O-methyl-trans-δ-viniferin)] obtained from plant substrates using chemoenzymatic synthesis against a panel of enveloped viruses. We report that compounds 2 and 3 display a broad-spectrum antiviral activity, being able to effectively inhibit several strains of Influenza Viruses (IV), SARS-CoV-2 Delta and, to some extent, Herpes Simplex Virus 2 (HSV-2). Interestingly, the mechanism of action differs for each virus. We observed both a direct virucidal and a cell-mediated effect against IV, with a high barrier to antiviral resistance; a restricted cell-mediated mechanism of action against SARS-CoV-2 Delta and a direct virustatic activity against HSV-2. Of note, while the effect was lost against IV in tissue culture models of human airway epithelia, the antiviral activity was confirmed in this relevant model for SARS-CoV-2 Delta. Our results suggest that stilbene dimer derivatives are good candidate models for the treatment of enveloped virus infections.

In Vitro Dissolution and Permeability Testing of Inhalation Products: Challenges and Advances

In vitro dissolution and permeability testing aid the simulation of the in vivo behavior of inhalation drug products. Although the regulatory bodies have specific guidelines for the dissolution of orally administered dosage forms (e.g., tablets and capsules), this is not the case for orally inhaled formulations, as there is no commonly accepted test for assessing their dissolution pattern. Up until a few years ago, there was no consensus that assessing the dissolution of orally inhaled drugs is a key factor in the assessment of orally inhaled products. With the advancement of research in the field of dissolution methods for orally inhaled products and a focus on systemic delivery of new, poorly water-soluble drugs at higher therapeutic doses, an evaluation of dissolution kinetics is proving crucial. Dissolution and permeability testing can determine the differences between the developed formulations and the innovator’s formulations and serve as a useful tool in correlating in vitro and in vivo studies. The current review highlights recent advances in the dissolution and permeability testing of inhalation products and their limitations, including recent cell-based technology. Although a few new dissolution and permeability testing methods have been established that have varying degrees of complexity, none have emerged as the standard method of choice. The review discusses the challenges of establishing methods that can closely simulate the in vivo absorption of drugs. It provides practical insights into method development for various dissolution testing scenarios and challenges with dose collection and particle deposition from inhalation devices for dissolution tests. Furthermore, dissolution kinetic models and statistical tests to compare the dissolution profiles of test and reference products are discussed.

Model exploration for discovering COVID-19 targeted traditional Chinese medicine

In terms of treatment, a particularly targeted drug is needed to combat the COVID-19 pandemic. Although there are currently no specific drugs for COVID-19, traditional Chinese medicine(TCM) is clearly effective. It is recommended that through data analysis and mining of TCM cases (expert experience) and population evidence (RCT and cohort studies), core prescriptions for various efficacy can be obtained. Starting from a multidimensional model of regulating immunity, improving inflammation, and protecting multiple organs, this paper constructs a multidimensional model of targeted drug discovery, integrating molecular, cellular, and animal efficacy evaluation. Through functional activity testing, biophysical detection of compound binding to target proteins, multidimensional pharmacodynamic evaluation systems of cells (Vero E6, Vero, Vero81, Huh7, and caca2) and animals (mice infected with the new coronavirus, rhesus macaques, and hamsters), the effectiveness of effective preparations was evaluated, and various efficacy effects including lung moisturizing, dehumidification and detoxification were obtained. Using modern technology, it is now possible to understand how the immune system is controlled, how inflammation is reduced, and how various organs are protected. Complete early drug characterization and finally obtain effective targeted TCM. This article provides a demonstration resource for the development of new drugs specifically for TCM.

Computational prediction of Calu-3-based in vitro pulmonary permeability of chemicals

Pulmonary is a potential route for drug delivery and exposure to toxic chemicals. The human bronchial epithelial cell line Calu-3 is generally considered to be a useful in vitro model of pulmonary permeability by calculating the apparent permeability coefficient (Papp) values. Since in vitro experiments are time-consuming and labor-intensive, computational models for pulmonary permeability are desirable for accelerating drug design and toxic chemical assessment. This study presents the first attempt for developing quantitative structure-activity relationship (QSAR) models for addressing this goal. A total of 57 chemicals with Papp values based on Calu-3 experiments was first curated from literature for model development and testing. Subsequently, eleven descriptors were identified by a sequential forward feature selection algorithm to maximize the cross-validation performance of a voting regression model integrating linear regression and nonlinear random forest algorithms. With applicability domain adjustment, the developed model achieved high performance with correlation coefficient values of 0.935 and 0.824 for cross-validation and independent test, respectively. The preliminary results showed that computational models could be helpful for predicting Calu-3-based in vitro Pulmonary Permeability of Chemicals. Future works include the collection of more data for further validating and improving the model.

Tailoring functional spray-dried powder platform for efficient donepezil nose-to-brain delivery

Shortcomings of oral donepezil administration in the treatment of Alzheimer's disease have paved the way for ongoing investigations towards more efficient and safe donepezil nose-to-brain delivery. Herein we present the development of advantageous powder platform for donepezil nose-to-brain delivery, coupling careful design of chitosan and mannitol-based carrier matrix with spray-drying technology advantages and early consideration of adequate nasal administration mode, employing QbD approach. Unprecedentedly, ultrasonic nozzle was used to atomise the drying feed in response to size-related requirements for nasal aerosol particles. The optimised spray-drying process resulted in free-flowable dry powder with a great majority of particles larger than 10 µm, ensuring localised nasal deposition upon aerosolization, as evidenced by using 3D-printed nasal cavity model. QbD approach coupling formulation, process and administration parameters enabled optimisation of drug deposition profile reaching tremendously high 65.5 % of the applied dose deposited in the olfactory region. The leading formulation exhibited favourable swelling, mucoadhesion, drug release and permeation-enhancing properties, suiting the needs for efficient brain-targeted delivery. Results of in vitro biocompatibility and physico-chemical stability studies confirmed the leading formulation potential for safe and efficient donepezil nose-to-brain delivery. The obtained results encourage extending the study to an appropriate in vivo model needed for the final proof-of-concept.

Validation of a cell integrated next-generation impactor to assess in vitro drug transport of physiologically relevant aerosolised particles

The development of novel inhaled formulations in the pre-clinical stage has been impeded by a lack of meaningful information related to drug dissolution and transport at the lung epithelia due to the absence of physiologically relevant in vitro respiratory models. The objective of the present study was to develop an in vitro experimental model, which combined the next generation impactor (NGI) and two respiratory epithelial cell lines, for examining the aerodynamic performance of dry powder inhalers and the fate of aerosolised drugs following lung deposition. The NGI impaction plates of stage 3 (i.e., a cut-off diameter of 2.82-4.46 µm) and stage 7 (i.e., a cut-off diameter of 0.34-0.55 µm) were modified to accommodate 3 cell cultures inserts. Specifically, Calu-3 cells and H441 cells, which are representative of the bronchial and alveolar epithelia in the lung, respectively, were cultivated at the air-liquid interface on Snapwells^TM with polycarbonate membranes. The aerodynamic particle size distribution of the modified NGI was investigated using resveratrol dry powder formulation (as a model drug). The suitability of such an in vitro model was confirmed by examining the in vitro aerodynamic performance of the model drug as compared to the conventional NGI setup (i.e., without the integrated Snapwell inserts), as well as the effect of experimental conditions (e.g., 60 L/min airflows) on the cells in the integrated Snapwell inserts. After deposition of the aerodynamically fractioned resveratrol, the permeation of the drug across the cell layer to the basolateral chamber of the Snapwell inserts was evaluated over 24 h. Results obtained from the drug transport study showed that the cell-integrated NGI provided realistic drug delivery conditions to the cells that can be used to assess the fate of fractionated aerosol particles. This system enables a better understanding of the in vitro drug deposition in the lungs and allows studies on both aerodynamic characterisation and drug transport (drug biological interactions with the cells) to be performed simultaneously.

Nanoparticle Delivery Platforms for RNAi Therapeutics Targeting COVID-19 Disease in the Respiratory Tract

Since December 2019, a pandemic of COVID-19 disease, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has rapidly spread across the globe. At present, the Food and Drug Administration (FDA) has issued emergency approval for the use of some antiviral drugs. However, these drugs still have limitations in the specific treatment of COVID-19, and as such, new treatment strategies urgently need to be developed. RNA-interference-based gene therapy provides a tractable target for antiviral treatment. Ensuring cell-specific targeted delivery is important to the success of gene therapy. The use of nanoparticles (NPs) as carriers for the delivery of small interfering RNA (siRNAs) to specific tissues or organs of the human body could play a crucial role in the specific therapy of severe respiratory infections, such as COVID-19. In this review, we describe a variety of novel nanocarriers, such as lipid NPs, star polymer NPs, and glycogen NPs, and summarize the pre-clinical/clinical progress of these nanoparticle platforms in siRNA delivery. We also discuss the application of various NP-capsulated siRNA as therapeutics for SARS-CoV-2 infection, the challenges with targeting these therapeutics to local delivery in the lung, and various inhalation devices used for therapeutic administration. We also discuss currently available animal models that are used for preclinical assessment of RNA-interference-based gene therapy. Advances in this field have the potential for antiviral treatments of COVID-19 disease and could be adapted to treat a range of respiratory diseases.

Hybrid Lipid/Polymer Nanoparticles to Tackle the Cystic Fibrosis Mucus Barrier in siRNA Delivery to the Lungs: Does PEGylation Make the Difference?

Inhaled siRNA therapy has a unique potential for treatment of severe lung diseases, such as cystic fibrosis (CF). Nevertheless, a drug delivery system tackling lung barriers is mandatory to enhance gene silencing efficacy in the airway epithelium. We recently demonstrated that lipid-polymer hybrid nanoparticles (hNPs), comprising a poly(lactic-co-glycolic) acid (PLGA) core and a lipid shell of dipalmitoyl phosphatidylcholine (DPPC), may assist the transport of the nucleic acid cargo through mucus-covered human airway epithelium. To study in depth the potential of hNPs for siRNA delivery to the lungs and to investigate the hypothesized benefit of PEGylation, here, an siRNA pool against the nuclear factor-κB (siNFκB) was encapsulated inside hNPs, endowed with a non-PEGylated (DPPC) or a PEGylated (1,2-distearoyl-sn-glycero-3-phosphoethanolamine-poly(ethylene glycol) or DSPE-PEG) lipid shell. Resulting hNPs were tested for their stability profiles and transport properties in artificial CF mucus, mucus collected from CF cells, and sputum samples from a heterogeneous and representative set of CF patients. Initial information on hNP properties governing their interaction with airway mucus was acquired by small-angle X-ray scattering (SAXS) studies in artificial and cellular CF mucus. The diffusion profiles of hNPs through CF sputa suggested a crucial role of lung colonization of the corresponding donor patient, affecting the mucin type and content of the sample. Noteworthy, PEGylation did not boost mucus penetration in complex and sticky samples, such as CF sputa from patients with polymicrobial colonization. In parallel, in vitro cell uptake studies performed on mucus-lined Calu-3 cells grown at the air-liquid interface (ALI) confirmed the improved ability of non-PEGylated hNPs to overcome mucus and cellular lung barriers. Furthermore, effective in vitro NFκB gene silencing was achieved in LPS-stimulated 16HBE14o- cells. Overall, the results highlight the potential of non-PEGylated hNPs as carriers for pulmonary delivery of siRNA for local treatment of CF lung disease. Furthermore, this study provides a detailed understanding of how distinct models may provide different information on nanoparticle interaction with the mucus barrier.

Applicability of RPMI 2650 and Calu-3 Cell Models for Evaluation of Nasal Formulations

The RPMI 2650 and Calu-3 cell lines have been previously evaluated as models of the nasal and airway epithelial barrier, and they have demonstrated the potential to be used in drug permeation studies. However, limited data exist on the utilization of these two cell models for the assessment of nasal formulations. In our study, we tested these cell lines for the evaluation of in vitro permeation of intranasally administered drugs having a local and systemic effect from different solution- and suspension-based formulations to observe how the effects of formulations reflect on the measured in vitro drug permeability. Both models were shown to be sufficiently discriminative and able to reveal the effect of formulation compositions on drug permeability, as they demonstrated differences in the in vitro drug permeation comparable to the in vivo bioavailability. Good correlation with the available bioavailability data was also established for a limited number of drugs formulated as intranasal solutions. The investigated cell lines can be applied to the evaluation of in vitro permeation of intranasally administered drugs with a local and systemic effect from solution- and suspension-based formulations.

An LC-MS/MS method for simultaneous analysis of the cystic fibrosis therapeutic drugs colistin, ivacaftor and ciprofloxacin

Inhaled antibiotics such as colistin and ciprofloxacin are increasingly used to treat bacterial lung infections in cystic fibrosis patients. In this study, we established and validated a new HPLC-MS/MS method that could simultaneously detect drug concentrations of ciprofloxacin, colistin and ivacaftor in rat plasma, human epithelial cell lysate, cell culture medium, and drug transport media. An aliquot of 200 μL drug-containing rat plasma or cell culture medium was treated with 600 μL of extraction solution (acetonitrile containing 0.1% formic acid and 0.2% trifluoroacetic acid (TFA)). The addition of 0.2% TFA helped to break the drug-protein bonds. Moreover, the addition of 0.1% formic acid to the transport medium and cell lysate samples could significantly improve the response and reproducibility. After vortexing and centrifuging, the sample components were analyzed by HPLC-MS/MS. The multiple reaction monitoring mode was used to detect the following transitions: 585.5-101.1 (colistin A), 578.5-101.1 (colistin B), 393.2-337.2 (ivacaftor), 332.2-314.2 (ciprofloxacin), 602.3-101.1 (polymyxin B1 as internal standard (IS)) and 595.4-101.1 (polymyxin B2 as IS). The running time of a single sample was only 6 min, making this a time-efficient method. Linear correlations were found for colistin A at 0.029-5.82 μg/mL, colistin B at 0.016-3.14 μg/mL, ivacaftor at 0.05-10.0 μg/mL, and ciprofloxacin at 0.043-8.58 μg/mL. Accuracy, precision, and stability of the method were within the acceptable range. This method would be highly useful for research on cytotoxicity, animal pharmacokinetics, and in vitro drug delivery.

Evaluation of Calu-3 cell lines as an in vitro model to study the inhalation toxicity of flavoring extracts

This study aimed to evaluate the characteristics of Calu-3 cells as a model to examine the toxicological responses of inhalable substances. Calu-3 cells were grown to the confluence at an air-liquid interface (ALI) using a Transwell^® permeable support system. The ALI resulted in biomimetic native bronchial epithelium displaying pseudostratified columnar epithelium with more microvilli and secretory vesicles. We further characterized and optimized the Calu-3 cell line model using ALI culturing conditions, immunolabeling of protein expression, ultrastructural analysis using scanning electron microscopy (SEM), and transepithelial electrical resistance (TEER) measurements, and then screened for the cytotoxicity of tobacco flavoring extracts. Calu-3 cells displayed dose-dependent responses when treated with the flavoring extract. Within 8-10 days, cell monolayers developed TEER ≥1000 Ω·cm². During this time, Calu-3 cells exposed to flavoring extracts X01 and X06 exhibited a loss of cellular integrity and decreased ZO-1 and E-cadherin protein expression. In conclusion, we investigated the Calu-3 cell line culture conditions, culture time, and barrier integrity and tested the effect of six new synthetic tobacco flavoring extracts. Our data demonstrate that the Calu-3 human bronchial epithelial cell monolayer system is a potential in vitro model to assess the inhalation toxicity of inhalable substances.

Recent advances in human respiratory epithelium models for drug discovery

The respiratory epithelium is intimately associated with the pathophysiologies of highly infectious viral contagions and chronic illnesses such as chronic obstructive pulmonary disorder, presently the third leading cause of death worldwide with a projected economic burden of £1.7 trillion by 2030. Preclinical studies of respiratory physiology have almost exclusively utilised non-humanised animal models, alongside reductionistic cell line-based models, and primary epithelial cell models cultured at an air-liquid interface (ALI). Despite their utility, these model systems have been limited by their poor correlation to the human condition. This has undermined the ability to identify novel therapeutics, evidenced by a 15% chance of success for medicinal respiratory compounds entering clinical trials in 2018. Consequently, preclinical studies require new translational efficacy models to address the problem of respiratory drug attrition. This review describes the utility of the current in vivo (rodent), ex vivo (isolated perfused lungs and precision cut lung slices), two-dimensional in vitro cell-line (A549, BEAS-2B, Calu-3) and three-dimensional in vitro ALI (gold-standard and co-culture) and organoid respiratory epithelium models. The limitations to the application of these model systems in drug discovery research are discussed, in addition to perspectives of the future innovations required to facilitate the next generation of human-relevant respiratory models.

Development and in vitro-in vivo performances of an inhalable indole-3-carboxaldehyde dry powder to target pulmonary inflammation and infection

A tryptophan metabolite of microbial origin, indole-3-carboxaldehyde (3-IAld), has been recently identified as a Janus molecule that, acting at the host-pathogen interface and activating the aryl hydrocarbon receptor, can result as a potential candidate to treat infections as well as diseases with an inflammatory and/or immune component. In this work, an inhaled dry powder of 3-IAld was developed and evaluated for its efficacy, compared to oral and intranasal administration using an aspergillosis model of infection and inflammation. The obtained inhalable dry powder was shown to: i) be suitable to be delivered for pulmonary administration, ii) possess good toxicological safety, and iii) be superior to other administration modalities (oral and intranasal) in reducing disease scores by acting on infection and inflammation. This study supports the use of 3-IAld inhalable dry powders as a potential novel therapeutic tool to target inflammation and infection in pulmonary diseases.

Advanced Nanoparticle-Based Drug Delivery Systems and Their Cellular Evaluation for Non-Small Cell Lung Cancer Treatment

Lung cancers, the number one cancer killer, can be broadly divided into small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC), with NSCLC being the most commonly diagnosed type. Anticancer agents for NSCLC suffer from various limitations that can be partly overcome by the application of nanomedicines. Nanoparticles is a branch within nanomedicine that can improve the delivery of anticancer drugs, whilst ensuring the stability and sufficient bioavailability following administration. There are many publications available in the literature exploring different types of nanoparticles from different materials. The effectiveness of a treatment option needs to be validated in suitable in vitro and/or in vivo models. This includes the developed nanoparticles, to prove their safety and efficacy. Many researchers have turned towards in vitro models that use normal cells or specific cells from diseased tissues. However, in cellular works, the physiological dynamics that is available in the body could not be mimicked entirely, and hence, there is still possible development of false positive or false negative results from the in vitro models. This article provides an overview of NSCLC, the different nanoparticles available to date, and in vitro evaluation of the nanoparticles. Different types of cells suitable for in vitro study and the important precautions to limit the development of false results are also extensively discussed.

Nebulization of Risedronate Sodium Microspheres for Potential Attenuation of Pulmonary Emphysema: a Promising New Insight of Alveolar Macrophage Apoptosis

Risedronate sodium (RS) is a potent nitrogen-containing bisphosphonate which is known to induce osteoclast apoptosis. As a drug repurposing approach, the current work explored the potential of nebulizable RS-chitosan (CS) microspheres to induce alveolar macrophage apoptosis. RS-CS microspheres were assessed for lung deposition, cytotoxicity, and cellular uptake percentage in Calu-3 cells. The potential of nebulizable microspheres for treating elastase-induced emphysema in rats was investigated, compared to RS marketed oral tablets®, with respect to histopathological, immunohistochemical, and flow cytometric studies. The in vitro lung deposition pattern suggested deep alveolar deposition of RS microspheres, with respect to high FPF% and suitable MMAD (66% and 1.506 μm, respectively, at a flow rate of 28.3 L min^-1). No apparent cytotoxicity was observed, with a cell viability > 90%. The inhalation of RS-CS microspheres was suggested to inhibit airspace enlargement and lung rarefaction after elastase instillation and reduce the macrophage accumulation in alveolar parenchyma. Immunohistochemical and cytometric analyses revealed significant low expression levels of CD68 and CD11b surface markers, respectively, with significantly (P < 0.05) lower detected numbers of intact alveolar macrophages following inhalation of RS-CS microspheres. The nebulization of RS-CS microspheres could induce apoptosis in alveolar macrophages and be promisingly adopted for attenuation of pulmonary emphysema.

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.

A Dry Powder Platform for Nose-to-Brain Delivery of Dexamethasone: Formulation Development and Nasal Deposition Studies

Nasal route of administration offers a unique opportunity of brain targeted drug delivery via olfactory and trigeminal pathway, providing effective CNS concentrations at lower doses and lower risk for adverse reactions compared to systemic drug administration. Therefore, it has been recently proposed as a route of choice for glucocorticoids to control neuroinflammation processes in patients with severe Covid-19. However, appropriate delivery systems tailored to enhance their efficacy yet need to emerge. In this work we present the development of sprayable brain targeting powder delivery platform of dexamethasone sodium phosphate (DSP). DSP-loaded microspheres, optimised employing Quality-by-Design approach, were blended with soluble inert carriers (mannitol or lactose monohydrate). Powder blends were characterized in terms of homogeneity, flow properties, sprayability, in vitro biocompatibility, permeability and mucoadhesion. Nasal deposition studies were performed using 3D printed nasal cavity model. Mannitol provided better powder blend flow properties compared to lactose. Microspheres blended with mannitol retained or enlarged their mucoadhesive properties and enhanced DSP permeability across epithelial model barrier. DSP dose fraction deposited in the olfactory region reached 17.0% revealing the potential of developed powder platform for targeted olfactory delivery. The observed impact of nasal cavity asymmetry highlighted the importance of individual approach when aiming olfactory region.

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.

In vitro evaluation of drug delivery behavior for inhalable amorphous nanoparticle formulations in a human lung epithelial cell model

Respiratory tract infections caused by multidrug-resistant (MDR) Gram-negative bacteria such as Pseudomonas aeruginosa are serious burdens to public health, especially in cystic fibrosis patients. The combination of colistin, a cationic polypeptide antibiotic, and ivacaftor, a cystic fibrosis transmembrane regulator (CFTR) protein modulator, displays a synergistic antibacterial effect against P. aeruginosa. The primary aim of the present study is to investigate the transport, accumulation and toxicity of a novel nanoparticle formulation containing colistin and ivacaftor in lung epithelial Calu-3 cells. The cell viability results demonstrated that ivacaftor alone or in combination with colistin in the physical mixture showed significant toxicity at an ivacaftor concentration of 10 μg/mL or higher. However, the cellular toxicity was significantly reduced in the nanoparticle formulation. Ivacaftor transport into the cells reached a plateau rapidly as compared to colistin. Colistin transport across the Calu-3 cell monolayer was less than ivacaftor. A substantial amount (46-83%) of ivacaftor, independent of dose, was accumulated in the cell monolayer following transport from the apical into the basal chamber, whereas the intracellular accumulation of colistin was relatively low (2-15%). The nanoparticle formulation significantly reduced the toxicity of colistin and ivacaftor to Calu-3 cells by reducing the accumulation of both drugs in the cell and potential protective effects by bovine serum albumin (BSA), which could be a promising safer option for the treatment of respiratory infections caused by MDR P. aeruginosa.

Aerosolization Performance, Antitussive Effect and Local Toxicity of Naringenin-Hydroxypropyl-β-Cyclodextrin Inhalation Solution for Pulmonary Delivery

The aim of present study was to evaluate the feasibility of a naringenin-hydroxypropyl-β-cyclodextrin (naringenin-HPβCD) inhalation solution for pulmonary delivery. Naringenin, a flavanone derived from citrus fruits, has been proven to exhibit excellent peripheral antitussive effect. To address the limitation of its poor oral bioavailability and low local concentration in the lung, a naringenin-HPβCD inhalation solution was prepared for pulmonary delivery. The aerosolization performance of formulation was evaluated by next generation impactor (NGI). Both dose-dependent and time-dependent antitussive effects of naringenin-HPβCD inhalation solution on acute cough induced by citric acid in guinea pigs were investigated. In vitro toxicity of naringenin-HPβCD inhalation solution in pulmonary Calu-3 cells was evaluated by MTS assay, and in vivo local toxicity investigation was achieved by assessing bronchoalveolar lavage (BALF) and lung histology after a 7-day inhalation treatment in guinea pigs. Fine particle fraction (FPF) of the formulation was determined as 53.09%. After inhalation treatment of 15 min, naringenin-HPβCD inhalation solution within the studied range of 0.2-3.6 mg/kg could dose-dependently reduce the cough frequency with the antitussive rate of 29.42-39.42%. Naringenin-HPβCD inhalation solution in concentration range of 100-400 μM did not decrease cell viability of Calu-3 cells, and the maximum effective dose (3.6 mg/kg) was non-toxic during the short-term inhalation treatment for guinea pigs. In conclusion, naringenin-HPβCD inhalation solution was capable for nebulization and could provide rapid response with reduced dose for the treatment of cough.

Optimizations of In Vitro Mucus and Cell Culture Models to Better Predict In Vivo Gene Transfer in Pathological Lung Respiratory Airways: Cystic Fibrosis as an Example

The respiratory epithelium can be affected by many diseases that could be treated using aerosol gene therapy. Among these, cystic fibrosis (CF) is a lethal inherited disease characterized by airways complications, which determine the life expectancy and the effectiveness of aerosolized treatments. Beside evaluations performed under in vivo settings, cell culture models mimicking in vivo pathophysiological conditions can provide complementary insights into the potential of gene transfer strategies. Such models must consider multiple parameters, following the rationale that proper gene transfer evaluations depend on whether they are performed under experimental conditions close to pathophysiological settings. In addition, the mucus layer, which covers the epithelial cells, constitutes a physical barrier for gene delivery, especially in diseases such as CF. Artificial mucus models featuring physical and biological properties similar to CF mucus allow determining the ability of gene transfer systems to effectively reach the underlying epithelium. In this review, we describe mucus and cellular models relevant for CF aerosol gene therapy, with a particular emphasis on mucus rheology. We strongly believe that combining multiple pathophysiological features in single complex cell culture models could help bridge the gaps between in vitro and in vivo settings, as well as viral and non-viral gene delivery strategies.

Contemporary Formulation Development for Inhaled Pharmaceuticals

Pulmonary delivery has gained increased interests over the past few decades. For respiratory conditions, targeted drug delivery directly to the site of action can achieve a high local concentration for efficacy with reduced systemic exposure and adverse effects. For systemic conditions, the unique physiology of the lung evolutionarily designed for rapid gaseous exchange presents an entry route for systemic drug delivery. Although the development of inhaled formulations has come a long way over the last few decades, many aspects of it remain to be elucidated. In particular, a reliable and well-understood method for in vitro-in vivo correlations remains to be established. With the rapid and ongoing advancement of technology, there is much potential to better utilise computational methods including different types of modelling and simulation approaches to support inhaled formulation development. This review intends to provide an introduction on some fundamental concepts in pulmonary drug delivery and inhaled formulation development followed by discussions on some challenges and opportunities in the translation of inhaled pharmaceuticals from preclinical studies to clinical development. The review concludes with some recent advancements in modelling and simulation approaches that could play an increasingly important role in modern formulation development of inhaled pharmaceuticals.

Properties of rapamycin solid lipid nanoparticles for lymphatic access through the lungs & part II: the effect of nanoparticle charge

Aim: Lymphangioleiomyomatosis is characterized by smooth muscle-like cells in the lungs that spread to other organs via lymphatic vessels. Oral rapamycin is restricted by low bioavailability approximately 15%. The aim of the present study is to systematically investigate the effect of inhaled rapamycin solid lipid nanoparticles (Rapa-SLN) surface charge on efficacy and penetration into the lymphatics. Materials & methods: Rapa-SLN formulations with different charge: neutral, positive and negative, were produced and assessed for their physicochemical particle characteristics and efficacy in vitro. Results: Negative Rapa-SLNs were significantly faster at entering the lymphatic endothelium and more potent at inhibiting lymphanigiogenesis compared with neutral and positive Rapa-SLNs. Conclusion: Negative Rapa-SLNs showed efficient lymphatic access and should therefore be investigated further as a treatment for targeting extrapulmonary lymphangioleiomyomatosis.

Characterization, in Vitro and in Vivo Evaluation of Naringenin-Hydroxypropyl-ß-Cyclodextrin Inclusion for Pulmonary Delivery

Naringenin, a flavonoid compound which exists abundantly in Citrus fruits, is proven to possess excellent antitussive and expectorant effects. However, the clinical applications of naringenin are restricted by its poor solubility and low local concentration by oral administration. The aim of the present study is to prepare a naringenin-hydroxypropyl-β-cyclodextrin (naringenin-HPβCD) inclusion as an inhalation solution for pulmonary delivery. The naringenin-HPβCD inclusion was characterized by phase solubility study, XRD, differential scanning calorimetry (DSC), proton nuclear magnetic resonance (¹HNMR), and two-dimensional rotating frame Overhauser effect spectroscopy (2D ROESY). The in vitro permeability of the inclusion was evaluated on Calu-3 cells and the pharmacokinetic profile of pulmonary delivery was investigated in Sprague-Dawley (SD) rats. Based on the linear model of phase solubility study, the relationship between naringenin and HPβCD was identified as A^L type with a 1:1 stoichiometry. XRD, DSC, and NMR studies indicated that the entire naringenin molecule is encapsulated into the cavity of HPβCD. HPβCD could increase the concentration of naringenin in the epithelium-lining fluid (ELF) of Calu-3 cells and act as a sustained release system for naringenin. The pharmacokinetic profile of naringenin-HPβCD inclusion showed rapid response and higher local concentration by pulmonary delivery. In conclusion, pulmonary delivery of naringenin-HPβCD inclusion is a promising formulation strategy, which could provide a new possibility for the clinical application of naringenin.

Hyaluronic Acid-Decorated Liposomes as Innovative Targeted Delivery System for Lung Fibrotic Cells

Collagen Tissue Disease-associated Interstitial Lung Fibrosis (CTD-ILDs) and Bronchiolitis Obliterans Syndrome (BOS) represent severe lung fibrogenic disorders, characterized by fibro-proliferation with uncontrolled extracellular matrix deposition. Hyaluronic acid (HA) plays a key role in fibrosis with its specific receptor, CD44, overexpressed by CTD-ILD and BOS cells. The aim is to use HA-liposomes to develop an inhalatory treatment for these diseases. Liposomes with HA of two molecular weights were prepared and characterized. Targeting efficiency was assessed toward CTD-ILD and BOS cells by flow cytometry and confocal microscopy and immune modulation by RT-PCR and ELISA techniques. HA-liposomes were internalized by CTD-ILD and BOS cells expressing CD44, and this effect increased with higher HA MW. In THP-1 cells, HA-liposomes decreased pro-inflammatory cytokines IL-1β, IL-12, and anti-fibrotic VEGF transcripts but increased TGF-β mRNA. However, upon analyzing TGF-β release from healthy donors-derived monocytes, we found liposomes did not alter the release of active pro-fibrotic cytokine. All liposomes induced mild activation of neutrophils regardless of the presence of HA. HA liposomes could be also applied for lung fibrotic diseases, being endowed with low pro-inflammatory activity, and results confirmed that higher MW HA are associated to an increased targeting efficiency for CD44 expressing LFs-derived from BOS and CTD-ILD patients.

Evaluation of co-delivery of colistin and ciprofloxacin in liposomes using an in vitro human lung epithelial cell model

Respiratory tract infections caused by multidrug-resistant Gram-negative bacteria are serious burdens to the public. Our previous findings indicated that co-loading of colistin and ciprofloxacin via liposomes improved in vitro antimicrobial activities against multidrug resistant Pseudomonas aeruginosa as compared to the monotherapies. The current study aims to investigate the transport behavior of colistin and ciprofloxacin in liposomes using the in vitro Calu-3 cell monolayer, which is a lung epithelial model cultured under the air-interfaced condition. The cell viability results demonstrated that there was no obvious toxicity of cells exposed to single or co-administered drugs at the concentration ≤500 μg/mL. Transport of ciprofloxacin into the cells was easier than that of colistin, which reached a plateau rapidly. Colistin was less trapped in the mucus or adhered to the apical cell membrane, and less transported across the cell monolayer than ciprofloxacin. The deposition of ciprofloxacin on the apical side increased over time (from 1 to 4 h). There was no drug-drug interaction observed during the transport of ciprofloxacin and colistin across the cell monolayer, when they were dosed together in the solution form. The amount of drug transported across the cell monolayer was decreased in both agents when loaded in liposomes. Both drugs were more trapped in the mucus or more adhered to the apical side cell membrane of the cell monolayer when they were in liposomes. This study demonstrated that co-delivery of colistin and ciprofloxacin in a single liposome can reduce transport capacity of both drugs across the lung epithelial cell monolayer and enhance drug retention on the lung epithelial surfaces; therefore, it is a promising approach to treat the respiratory infections caused by multidrug resistant Pseudomonas aeruginosa.

Formulation and evaluation of carrier-free dry powder inhaler containing sildenafil

Pulmonary delivery of sildenafil for the treatment of pulmonary arterial hypertension could overcome the limitations of intravenous and oral administration routes, such as poor patient compliance and systemic side effects. In this study, a carrier-free dry powder inhaler (DPI) formulation was developed, using spray drying technique and L-leucine as a dispersibility enhancer. Sildenafil citrate salt and sildenafil free base were evaluated for drug transport using a Calu-3 cell model, and their suitability for DPI production by spray drying was tested. Characteristics of the resultant carrier-free DPI powders were examined, namely crystallinity, morphology, size distribution, density, zeta potential, and aerodynamic performance. A Box-Behnken design was adopted to optimize the formulation and process conditions, including leucine amount, fraction of methanol in spraying solvent, and inlet temperature. While both sildenafil forms exhibited sufficient permeability for lung absorption, only sildenafil base resulted in DPI powders which were stable for 6 months. The introduction of leucine into the formulations effectively enhanced aerodynamic performance of the powders and particles with favorable size, shape, and density were produced. The optimal DPI formulation determined from experimental design possesses excellent aerodynamic performance with 89.39% emitted dose and 80.08% fine particle fraction, indicating the possibility of incorporating sildenafil into carrier-free DPIs for pulmonary delivery.

In vitro model for predicting acute inhalation toxicity by using a Calu-3 epithelium cytotoxicity assay

INTRODUCTION

As the current methods to predict the inhalation toxicity of chemicals using animal models are limited, alternative methods are required. We present a new in vitro prediction method for acute inhalation toxicity using the Calu-3 epithelial cytotoxicity assay applicable for water-soluble inhalable chemicals.

METHOD

To confirm the characteristics of the optimal Calu-3 epithelium, tight-junction formation, morphology, and mucus secretion were verified using scanning electron microscopy, transepithelial electrical resistance analysis, and immunofluorescence after growth in an air-liquid interface (ALI). Sixty chemicals, including 38 positive and 22 negative for acute inhalation toxicity, were selected from the European Chemical Agency chemical database. The cell viability of the exposed cells was assessed using an MTT assay to predict the acute inhalation toxicity by calculating the area under the receiver operating characteristic (ROC) curve and accuracy.

RESULTS

When cultivated in an ALI, the epithelium was thicker and secreted more mucin than that under submerged cultivation, characteristic of the in vivo respiratory epithelium. The areas under the ROC curve were 0.75 and 0.78 when exposed to chemicals at concentrations of 2.5 and 5%, respectively. The highest accuracy of the methods was 68 and 78% at cut-off values of 85 and 40% cell viability, respectively.

DISCUSSION

The in vitro model was moderately accurate with good prediction. It is replicable because of its advantages, i.e., the use of cultured cells and the simplicity of the method. Overall, the Calu-3 epithelial cytotoxicity assay may be a useful and simple approach to identify substances that cause acute inhalation toxicity.

TRAIL (CD253) Sensitizes Human Airway Epithelial Cells to Toxin-Induced Cell Death

Ricin toxin is a biothreat agent that is particularly damaging to lung tissue following inhalation. A hallmark of ricin exposure is widespread inflammation and concomitant destruction of the airway epithelium. In this study, we investigated the possible interaction between ricin and known proinflammatory cytokines associated with lung tissue. Using an established human airway epithelial cell line, we demonstrate that epithelial cell killing by ricin is significantly enhanced in the presence of the proinflammatory cytokine known as TRAIL (CD253). Moreover, epithelial cells that are simultaneously exposed to ricin and TRAIL produced large amounts of secondary proinflammatory signals, including IL-6, which in the context of the lung would be expected to exacerbate toxin-induced tissue damage. Our results suggest that therapies designed to neutralize proinflammatory cytokines such as TRAIL and IL-6 may limit the bystander damage associated with ricin exposure.

Inhalation of ricin toxin is associated with the onset of acute respiratory distress syndrome (ARDS), characterized by hemorrhage, inflammatory exudates, and tissue edema, as well as the nearly complete destruction of the lung epithelium. Here we report that the Calu-3 human airway epithelial cell line is relatively impervious to the effects of ricin, with little evidence of cell death even upon exposure to microgram amounts of toxin. However, the addition of exogenous soluble tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL; CD253) dramatically sensitized Calu-3 cells to ricin-induced apoptosis. Calu-3 cell killing in response to ricin and TRAIL exposure was partially inhibited by caspase-8 and caspase-3/7 inhibitors, consistent with involvement of extrinsic apoptotic pathways in cell death. We employed nCounter Technology to define the transcriptional response of Calu-3 cells to ricin, TRAIL, and the combination of ricin plus TRAIL. An array of genes associated with inflammation and cell death were significantly upregulated upon treatment with ricin toxin and were further amplified upon addition of TRAIL. Of particular note was interleukin-6 (IL-6), whose expression in Calu-3 cells increased 300-fold upon ricin treatment and more than 750-fold upon ricin and TRAIL treatment. IL-6 secretion by Calu-3 cells was confirmed by cytometric bead array analysis. On the basis of these finding, we speculate that the severe airway epithelial cell damage observed in animal models following ricin exposure is a result of a positive-feedback loop driven by proinflammatory cytokines such as TRAIL and IL-6.

IMPORTANCE Ricin toxin is a biothreat agent that is particularly damaging to lung tissue following inhalation. A hallmark of ricin exposure is widespread inflammation and concomitant destruction of the airway epithelium. In this study, we investigated the possible interaction between ricin and known proinflammatory cytokines associated with lung tissue. Using an established human airway epithelial cell line, we demonstrate that epithelial cell killing by ricin is significantly enhanced in the presence of the proinflammatory cytokine known as TRAIL (CD253). Moreover, epithelial cells that are simultaneously exposed to ricin and TRAIL produced large amounts of secondary proinflammatory signals, including IL-6, which in the context of the lung would be expected to exacerbate toxin-induced tissue damage. Our results suggest that therapies designed to neutralize proinflammatory cytokines such as TRAIL and IL-6 may limit the bystander damage associated with ricin exposure.

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.

Development and Characterization of Dapsone Cocrystal Prepared by Scalable Production Methods

In this study, the formation of caffeine/dapsone (CAF/DAP) cocrystals by scalable production methods, such as liquid-assisted grinding (LAG) and spray drying, was investigated in the context of the potential use of processed cocrystal powder for pulmonary delivery. A CAF/DAP cocrystal (1:1 M ratio) was successfully prepared by slow evaporation from both acetone and ethyl acetate. Acetone, ethyl acetate, and ethanol were all successfully used to prepare cocrystals by LAG and spray drying. The powders obtained were characterized by X-ray diffractometry (XRD), differential scanning calorimetry (DSC), thermogravimetry (TGA), and Fourier transform infrared spectroscopy (FTIR). Laser diffraction analysis indicated a median particle size (D₅₀) for spray-dried powders prepared from acetone, ethanol, and ethyl acetate of 5.4 ± 0.7, 5.2 ± 0.1, and 5.1 ± 0.0 μm respectively, which are appropriate sizes for pulmonary delivery by means of a dry powder inhaler. The solubility of the CAF/DAP cocrystal in phosphate buffer pH 7.4, prepared by spray drying using acetone, was 506.5 ± 31.5 μg/mL, while pure crystalline DAP had a measured solubility of 217.1 ± 7.8 μg/mL. In vitro cytotoxicity studies using Calu-3 cells indicated that the cocrystals were not toxic at concentrations of 0.1 and of 1 mM of DAP, while an in vitro permeability study suggested caffeine may contribute to the permeation of DAP by hindering the efflux effect. The results obtained indicate that the CAF/DAP cocrystal, particularly when prepared by the spray drying method, represents a possible suitable approach for inhalation formulations with applications in pulmonary pathologies.

Repurposing of statins via inhalation to treat lung inflammatory conditions

Despite many therapeutic advancements over the past decade, the continued rise in chronic inflammatory lung diseases incidence has driven the need to identify and develop new therapeutic strategies, with superior efficacy to treat these diseases. Statins are one class of drug that could potentially be repurposed as an alternative treatment for chronic lung diseases. They are currently used to treat hypercholesterolemia by inhibiting the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, that catalyses the rate limiting step in the mevalonate biosynthesis pathway, a key intermediate in cholesterol metabolism. Recent research has identified statins to have other protective pleiotropic properties including anti-inflammatory, anti-oxidant, muco-inhibitory effects that may be beneficial for the treatment of chronic inflammatory lung diseases. However, clinical studies have yielded conflicting results. This review will summarise some of the current evidences for statins pleiotropic effects that could be applied for the treatment of chronic inflammatory lung diseases, their mechanisms of actions, and the potential to repurpose statins as an inhaled therapy, including a detailed discussion on their different physical-chemical properties and how these characteristics could ultimately affect treatment efficacies. The repurposing of statins from conventional anti-cholesterol oral therapy to inhaled anti-inflammatory formulation is promising, as it provides direct delivery to the airways, reduced risk of side effects, increased bioavailability and tailored physical-chemical properties for enhanced efficacy.

Deposition and transport of linezolid mediated by a synthetic surfactant Synsurf® within a pressurized metered dose inhaler: a Calu-3 model

BACKGROUND

Previous studies in our laboratory demonstrated that a synthetic peptide containing lung surfactant enhances the permeability of chemical compounds through bronchial epithelium. The purpose of this study was to test two formulations of Synsurf® combined with linezolid as respirable compounds using a pressurized metered dose inhaler (pMDI).

METHODS

Aerosolization efficiency of the surfactant-drug microparticles onto Calu-3 monolayers as an air interface culture was analyzed using a Next Generation Impactor™.

RESULTS

The delivered particles and drug dose showed a high dependency from the preparation that was aerosolized. Scanning electron microscopy imaging allowed for visualization of the deposited particles, establishing them as liposomal-type structures (diameter 500 nm to 2 μm) with filamentous features.

CONCLUSION

The different surfactant drug combinations allow for an evaluation of the significance of the experimental model system, as well as assessment of the formulations providing a possible noninvasive, site-specific, delivery model via pMDI.

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.

Inhaled simvastatin nanoparticles for inflammatory lung disease

Aim: Current inhaled treatments are not adequate to treat all lung diseases. In this study, a promising nanotechnology has been developed to deliver a potential anti-inflammatory and muco-inhibitory compound, simvastatin, for treatment of inflammatory lung diseases via inhalation. Materials & methods: Simvastatin nanoparticles (SV-NPs) encapsulated with poly(lactic-co-glycolic) acid were fabricated using the solvent and anti-solvent precipitation method. Results: SV-NPs were found to be stable up to 9 months at 4°C in a freeze-dried form prior to reconstitution. The amount of mucus produced was significantly reduced after SV-NPs treatment on inflammation epithelial cell models and were effective in suppressing the proinflammatory marker expression. Conclusion: This study suggests that SV-NPs nebulization could potentially be used for the treatment of chronic pulmonary diseases.

Flavored little cigar smoke induces cytotoxicity and apoptosis in airway epithelia

Addition of flavors reduces the harsh taste of tobacco, facilitating the initiation and maintenance of addiction among youths. Flavored cigarettes (except menthol) are now banned. However, the legislation on little cigars remains unclear and flavored little cigars are currently available for purchase. Since inhaled tobacco smoke directly exerts toxic effects on the lungs, we tested whether non-flavored and flavored little cigar smoke exposure had the potential for harm in cultured pulmonary epithelia. We cultured Calu-3 lung epithelia on both 96-well plates and at the air–liquid interface and exposed them to smoke from non-flavored Swisher Sweets and flavored (sweet cherry, grape, menthol, peach and strawberry) Swisher Sweets little cigars. Irrespective of flavor, acute little cigar smoke exposure (10×35 ml puffs) significantly increased cell death and decreased the percentage of live cells. Chronic exposure (10×35 ml puffs per day for 4 days) of smoke to Calu-3 cultures significantly increased lactate dehydrogenase release, further indicating toxicity. To determine whether this exposure was associated with increased cell death/apoptosis, a protein array was used. Chronic exposure to smoke from all types of little cigars induced the activation of the two major apoptosis pathways, namely the intrinsic (mitochondrial-mediated) and the extrinsic (death receptor-mediated) pathways. Both flavored and non-flavored little cigar smoke caused similar levels of toxicity and activation of apoptosis, suggesting that flavored and non-flavored little cigars are equally harmful. Hence, the manufacture, advertisement, sale and use of both non-flavored and flavored little cigars should be strictly controlled.

Insight into the relationship between the cell culture model, cell trafficking and siRNA silencing efficiency

Despite research efforts, cell uptake processes determining siRNA silencing efficiency remain unclear. Here, we examine the relationship between in vitro cell culture models, cellular trafficking and siRNA silencing efficiency to provide a mechanistic insight on siRNA delivery system design. Model siRNA-polyplexes, based on chitosan as a ‘classical’ condensing agent, were applied to a panel of lung epithelial cell lines, H1299, A549 and Calu-3 and cell internalization levels, trafficking pathways and gene silencing assessed on exposure to pharmacological inhibitors. The data reveal striking differences in the internalization behaviour and gene silencing efficiency in the tested cell lines, despite their common lung epithelial origins. The model system’s silencing was lower where clathrin internalization pathway predominated in Calu-3, relative to silencing in H1299 cells where a non-clathrin internalization appears dominant. Increased silencing on endosomal disruption was apparent in Calu-3 cells, but absent when cellular internalization was not predominantly clathrin-mediated in A549 cells. This highlights that identifying cell trafficking pathways before incorporation of functional components to siRNA delivery systems (e.g. endosomolytic compounds) is crucial. The study hence stresses the importance of selection of appropriate cell culture model, relevant to in vivo target, to assess the gene silencing efficiency and decide which functionalities the ‘stratified siRNA silencing vector’ requires.

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Relationship between cell type, uptake path and silencing examined to inform siRNA vector design.

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Notable differences observed in cell uptake pathways and silencing despite cells’ common origin.

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Addition of endosomolytic functionality shows no effect when non-clathrin pathways dominate.

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Cell model important to assess silencing and decide which functionalities siRNA vector requires.

The development of a tissue-engineered tracheobronchial epithelial model using a bilayered collagen-hyaluronate scaffold

Today, chronic respiratory disease is one of the leading causes of mortality globally. Epithelial dysfunction can play a central role in its pathophysiology. The development of physiologically-representative in vitro model systems using tissue-engineered constructs might improve our understanding of epithelial tissue and disease. This study sought to engineer a bilayered collagen-hyaluronate (CHyA-B) scaffold for the development of a physiologically-representative 3D in vitro tracheobronchial epithelial co-culture model. CHyA-B scaffolds were fabricated by integrating a thin film top-layer into a porous sub-layer with lyophilisation. The film layer firmly connected to the sub-layer with delamination occurring at stresses of 12-15 kPa. Crosslinked scaffolds had a compressive modulus of 1.9 kPa and mean pore diameters of 70 μm and 80 μm, depending on the freezing temperature. Histological analysis showed that the Calu-3 bronchial epithelial cell line attached and grew on CHyA-B with adoption of an epithelial monolayer on the film layer. Immunofluorescence and qRT-PCR studies demonstrated that the CHyA-B scaffolds facilitated Calu-3 cell differentiation, with enhanced mucin expression, increased ciliation and the formation of intercellular tight junctions. Co-culture of Calu-3 cells with Wi38 lung fibroblasts was achieved on the scaffold to create a submucosal tissue analogue of the upper respiratory tract, validating CHyA-B as a platform to support co-culture and cellular organisation reminiscent of in vivo tissue architecture. In summary, this study has demonstrated that CHyA-B is a promising tool for the development of novel 3D tracheobronchial co-culture in vitro models with the potential to unravel new pathways in drug discovery and drug delivery.