Across the pulmonary epithelial barrier: Integration of physicochemical properties and human cell models to study pulmonary drug formulations

Recent advances in cell-based in vitro models for predicting drug permeability across brain, intestinal, and pulmonary barriers

INTRODUCTION

Recent years have witnessed remarkable progress in the development of cell-based in vitro models aimed at predicting drug permeability, particularly focusing on replicating the barrier properties of the blood-brain barrier (BBB), intestinal epithelium, and lung epithelium.

AREA COVERED

This review provides an overview of 2D in vitro platforms, including monocultures and co-culture systems, highlighting their respective advantages and limitations. Additionally, it discusses tools and techniques utilized to overcome these limitations, paving the way for more accurate predictions of drug permeability. Furthermore, this review delves into emerging technologies, particularly microphysiological systems (MPS), encompassing static platforms such as organoids and dynamic platforms like microfluidic devices. Literature searches were performed using PubMed and Google Scholar. We focus on key terms such as in vitro permeability models, MPS, organoids, intestine, BBB, and lungs.

EXPERT OPINION

The potential of these MPS to mimic physiological conditions more closely offers promising avenues for drug permeability assessment. However, transitioning these advanced models from bench to industry requires rigorous validation against regulatory standards. Thus, there is a pressing need to validate MPS to industry and regulatory agency standards to exploit their potential in drug permeability prediction fully. This review underscores the importance of such validation processes to facilitate the translation of these innovative technologies into routine pharmaceutical practice.

Hyaluronic acid modified nanocarriers for aerosolized delivery of verteporfin in the treatment of acute lung injury

Verteporfin (VER), a photosensitizer used in macular degeneration therapy, has shown promise in controlling macrophage polarization and alleviating inflammation in acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). However, its hydrophobicity, limited bioavailability, and side effects hinder its therapeutic potential. In this study, we aimed to enhance the therapeutic potential of VER through pulmonary nebulized drug delivery for ALI/ARDS treatment. We combined hydrophilic hyaluronic acid (HA) with an oil-in-water system containing a poly(lactic acid-co-glycolic acid) (PLGA) copolymer of VER to synthesize HA@PLGA-VER (PHV) nanoparticles with favorable surface characteristics to improve the bioavailability and targeting ability of VER. PHV possesses suitable electrical properties, a narrow size distribution (approximately 200 nm), and favorable stability. In vitro and in vivo studies demonstrated the excellent biocompatibility, safety, and anti-inflammatory responses of the PHV by suppressing M1 macrophage polarization while inducing M2 polarization. The in vivo experiments indicated that the treatment with aerosolized nano-VER (PHV) allowed more drugs to accumulate and penetrate into the lungs, improved the pulmonary function and attenuated lung injury, and mortality of ALI mice, achieving improved therapeutic outcomes. These findings highlight the potential of PHV as a promising delivery system via nebulization for enhancing the therapeutic effects of VER in ALI/ARDS.

Algal Phycocolloids: Bioactivities and Pharmaceutical Applications

Seaweeds are abundant sources of diverse bioactive compounds with various properties and mechanisms of action. These compounds offer protective effects, high nutritional value, and numerous health benefits. Seaweeds are versatile natural sources of metabolites applicable in the production of healthy food, pharmaceuticals, cosmetics, and fertilizers. Their biological compounds make them promising sources for biotechnological applications. In nature, hydrocolloids are substances which form a gel in the presence of water. They are employed as gelling agents in food, coatings and dressings in pharmaceuticals, stabilizers in biotechnology, and ingredients in cosmetics. Seaweed hydrocolloids are identified in carrageenan, alginate, and agar. Carrageenan has gained significant attention in pharmaceutical formulations and exhibits diverse pharmaceutical properties. Incorporating carrageenan and natural polymers such as chitosan, starch, cellulose, chitin, and alginate. It holds promise for creating biodegradable materials with biomedical applications. Alginate, a natural polysaccharide, is highly valued for wound dressings due to its unique characteristics, including low toxicity, biodegradability, hydrogel formation, prevention of bacterial infections, and maintenance of a moist environment. Agar is widely used in the biomedical field. This review focuses on analysing the therapeutic applications of carrageenan, alginate, and agar based on research highlighting their potential in developing innovative drug delivery systems using seaweed phycocolloids.

Inhalable microparticles as drug delivery systems to the lungs in a dry powder formulations

Inhalation-administrated drugs remain an interesting possibility of addressing pulmonary diseases. Direct drug delivery to the lungs allows one to obtain high concentration in the site of action with limited systemic distribution, leading to a more effective therapy with reduced required doses and side effects. On the other hand, there are several difficulties in obtaining a formulation that would meet all the criteria related to physicochemical, aerodynamic and biological properties, which is the reason why only very few of the investigated systems can reach the clinical trial phase and proceed to everyday use as a result. Therefore, we focused on powders consisting of polysaccharides, lipids, proteins or natural and synthetic polymers in the form of microparticles that are delivered by inhalation to the lungs as drug carriers. We summarized the most common trends in research today to provide the best dry powders in the right fraction for inhalation that would be able to release the drug before being removed by natural mechanisms. This review article addresses the most common manufacturing methods with novel modifications, pros and cons of different materials, drug loading capacities with release profiles, and biological properties such as cytocompatibility, bactericidal or anticancer properties.

Dissolution and Absorption of Inhaled Drug Particles in the Lungs

Dry powder inhalation therapy has been effective in treating localized lung diseases such asthma, chronic obstructive pulmonary diseases (COPD), cystic fibrosis and lung infections. In vitro characterization of dry powder formulations includes the determination of physicochemical nature and aerosol performance of powder particles. The relationship between particle properties (size, shape, surface morphology, porosity, solid state nature, and surface hydrophobicity) and aerosol performance of an inhalable dry powder formulation has been well established. However, unlike oral formulations, there is no standard dissolution method for evaluating the dissolution behavior of the inhalable dry powder particles in the lungs. This review focuses on various dissolution systems and absorption models, which have been developed to evaluate dry powder formulations. It covers a summary of airway epithelium, hurdles to developing an in vitro dissolution method for the inhaled dry powder particles, fine particle dose collection methods, various in vitro dissolution testing methods developed for dry powder particles, and models commonly used to study absorption of inhaled drug.

[Establishment of a culture system for human nasal mucosa organoids with controllable differentiation]

OBJECTIVE

To establish a culture system for human nasal mucosal organoids with controllable differentiation to reproduce the structure and function of the source tissue through staged expansion-differentiation culture.

METHODS

Fresh samples of surgically resected middle turbinate and nasal polyp tissues were collected, from which the nasal mucosa epithelial cells were isolated by enzymatic digestion and filtration for continuous culture at the air-liquid interface for expansion (EO group) or staged culture for expansion and differentiation (DO group). Immunohistochemical staining was used to characterize the structure, cellular composition and ciliary function of nasal mucosal organoids in the two groups. The secretion function of the differentiated nasal mucosal organoids in DO group was evaluated using PAS staining.

RESULTS

Both of the two organoid culture systems yielded vacuolar or solid spherical 3D organoids, and their diameters increased progressively with time. On day 16 of culture, more vacuolar organoids occurred in DO group, while more solid spherical organoids were seen in EO group, and the proportion of vacuoles was significantly greater in DO group than in EO group [(54.67±13.26)% vs (21.67±8.57)%, P < 0.05]. Short tandem repeat (STR) test of the nasal mucosal organoids and the source tissue showed a 100% match between them. On day 21 of culture, scanning and transmission electron microscopy of the nasal mucosal organoids identified ultrastructure of cilia in DO group and short villi structure in most of the organoids in EO group. Immunohistochemical staining showed positivity for P63 (basal cells), β-tubulin (ciliated columnar cells), and MUC5AC (goblet cells) in the organoids. Compared with those in EO group, the organoids in DO group showed significantly greater percentages of ciliated cells [(7.95±1.81)% vs (27.04±5.91)%, P < 0.05] and goblet cells [(14.46±0.93)% vs (39.85±5.43)%, P < 0.05) with a similar percentage of basal cells [(56.91±14.12)% vs (53.42±15.77)%, P > 0.05]. The differentiated nasal mucosal organoids in DO group were positively stained for glycogen.

CONCLUSION

The staged expansion-differentiation culture method allows more stable and prolonged growth of the cultured cells in vitro to produce organoids with controllable differentiation closely resembling the morphological structure and functions (ciliary function and secretory function) of the source tissue.

Pulmonary inflammation caused by cigarette smoke combined with lipopolysaccharide up-regulated OATP2B1 in rat lung tissue and pulmonary epithelial cells

Organic anion transport polypeptide 2B1 (OATP2B1), as an uptake transporter, is involved in the transport of many related substrate drugs and endogenous substances in the lungs. A large amount of data shows that cigarette smoke plays an important role in the occurrence and development of lung diseases such as chronic obstructive pulmonary disease (COPD), asthma and bronchitis. However, the effect of cigarette smoke combined with lipopolysaccharide-induced pulmonary inflammation on the expression of OATP2B1 is not clear. In this study, we used cigarette smoke combined with lipopolysaccharide to establish a lung inflammation model in vivo and in vitro to explore the effect of inflammation on the expression of OATP2B1. Our study found that cigarette smoke combined with lipopolysaccharide-induced pulmonary inflammation upregulated the mRNA and protein expression of OATP2B1 and related inflammatory factors, and the expression level of related proteins was higher with the aggravation of inflammation. The experimental results of animals in vivo were consistent with those of cells in vitro. In summary, these findings provide a model and basis for a follow-up study of the mechanism of OATP2B1 in pulmonary inflammation.

Inhalation delivery of repurposed drugs for lung cancer: Approaches, benefits and challenges

Lung cancer (LC) is one of the leading causes of mortality accounting for almost 25% of cancer deaths throughout the world. The shortfall of affordable and effective first-line chemotherapeutics, the existence of resistant tumors, and the non-optimal route of administration contribute to poor prognosis and high mortality in LC. Administration of repurposed non-oncology drugs (RNODs) loaded in nanocarriers (NCs) via inhalation may prove as an effective alternative strategy to treat LC. Furthermore, their site-specific release through inhalation route using an appropriate inhalation device would offer improved therapeutic efficacy, thereby reducing mortality and improving patients' quality of life. The current manuscript offers a comprehensive overview on use of RNODs in LC treatment with an emphasis on their inhalation delivery and the associated challenges. The role of NCs to improve lung deposition and targeting of RNODs via inhalation are also elaborated. In addition, information about various RNODs in clinical trials for the treatment of LC, possibility for repurposing phytoceuticals against LC via inhalation and the bottlenecks associated with repurposing RNODs against cancer are also highlighted. Based on the reported studies covered in this manuscript, it was understood that delivery of RNODs via inhalation has emerged as a propitious approach. Hence, it is anticipated to provide effective first-line treatment at an affordable cost in debilitating LC from low and middle-income countries (LMIC).

The changes of MRP2 expression in three kinds of pulmonary inflammation models: the downregulation occurred in cigarette smoke extract (CSE) stimulation group and CSE plus LPS stimulation group, unchanged in LPS stimulation group

The transporter multidrug resistance protein 2 (MRP2) can transport some tobacco carcinogens and plays an important role in the transport of mediators related to pulmonary inflammatory diseases. However, it is not fully understood whether the pulmonary inflammation caused by cigarette smoke extract (CSE) and lipopolysaccharide (LPS) is related to the regulation of MRP2. In this study, CSE and LPS were used alone and in combination as stimuli to induce pulmonary inflammation. In addition, the establishment of a pulmonary inflammation model was verified by animal experiments in vivo. We found that compared with those in the control group, the expression of MRP2 protein was downregulated and the expression of inflammatory cytokines was upregulated in pulmonary inflammation in the CSE group and the CSE combined with LPS group. However, there was almost no change in the expression of MRP2 stimulated by LPS alone. Our results show that CSE and CSE combined with LPS downregulate the expression of MRP2 under inflammatory conditions, while LPS has almost no effect on the expression of MRP2 under inflammatory conditions. The in vivo experimental results of CSE combined with LPS were consistent with the cellular results of CSE combined with LPS, which provides a model and basis for other studies of the role of MRP2 in pulmonary inflammation.

Airway-On-A-Chip: Designs and Applications for Lung Repair and Disease

The lungs are affected by illnesses including asthma, chronic obstructive pulmonary disease, and infections such as influenza and SARS-CoV-2. Physiologically relevant models for respiratory conditions will be essential for new drug development. The composition and structure of the lung extracellular matrix (ECM) plays a major role in the function of the lung tissue and cells. Lung-on-chip models have been developed to address some of the limitations of current two-dimensional in vitro models. In this review, we describe various ECM substitutes utilized for modeling the respiratory system. We explore the application of lung-on-chip models to the study of cigarette smoke and electronic cigarette vapor. We discuss the challenges and opportunities related to model characterization with an emphasis on in situ characterization methods, both established and emerging. We discuss how further advancements in the field, through the incorporation of interstitial cells and ECM, have the potential to provide an effective tool for interrogating lung biology and disease, especially the mechanisms that involve the interstitial elements.

Prenatal and postnatal exposure to Bisphenol A and Asthma: a systemic review and meta-analysis

Background

Bisphenol A (BPA) is a plasticizer with high production and ubiquitous usage in polycarbonate plastics and epoxy resins. The association between prenatal or postnatal exposure to BPA and childhood wheeze/asthma has not been well established. Our study aimed to provide further justification for the current studies.

Methods

Studies were searched from PubMed, Web of Science, Scopus and Embase from inception until Sep 15, 2020. Meta-analysis was performed to calculate pooled adjusted odds ratios (aOR). The methodological quality of included studies was assessed by using the Newcastle Ottawa Scale (NOS).

Results

Of 2,814 screened articles, 9 studies with 3,885 participants were included in the final analysis. When all studies were pooled, postnatal exposure to BPA was associated with a higher risk of childhood asthma (aOR =1.43; 95% CI: 1.28–1.59) or childhood wheeze (aOR =1.38; 95% CI: 1.18–1.62). Prenatal exposure to BPA had a small but significant increased risk of childhood asthma (aOR =1.17; 95% CI: 1.01–1.34). An increased risk of childhood wheeze was related to prenatal exposure to BPA at 16 weeks’ gestation (aOR =1.29; 95% CI: 1.07–1.55), but not at 26 weeks’ gestation (aOR =1.07; 95% CI: 0.88–1.29) nor at random-time gestation (aOR =1.02; 95% CI: 0.89–1.16).

Conclusions

Prenatal and postnatal exposure to BPA was related to an increased risk of childhood asthma. However, only postnatal and early gestational exposure (at 16 weeks) to BPA could induce the risk of childhood wheeze, but not late gestational exposure (at 26 weeks).

DJ-1 modulates Nrf2-mediated MRP1 expression by activating Wnt3a/β-catenin signalling in A549 cells exposed to cigarette smoke extract and LPS

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is an inflammatory disease characterized by airway obstruction and abnormal inflammatory responses. Multidrug resistance-related protein 1 (MRP1) can reduce lung inflammation and damage by excreting various toxic exogenous substances and certain pro-inflammatory molecules.

AIMS

We studied whether DJ-1 modulates nuclear factor erythroid 2-related factor 2 (Nrf2) by activating the Wnt3a/β-catenin signalling pathway to further regulate MRP1 expression and pulmonary antioxidant defences in alveolar epithelial (A549) cells treated with smoke extract (CSE) and lipopolysaccharide (LPS).

MAIN METHODS

Marker expression was studied by western blot analysis, quantitative real-time PCR and immunofluorescence staining of A549 cells.

KEY FINDINGS

A549 cells exposed to CSE and LPS showed downregulation of DJ-1, Wnt3a, MRP1 and haem oxygenase-1 (HO-1) and upregulation of inflammatory factors. Additionally, Nrf2 protein levels were significantly decreased, while there was no change in Nrf2 mRNA levels. Overexpression of DJ-1 and Wnt3a activated Nrf2 signalling, increased MRP1 and HO-1 levels and decreased IL-6 protein expression, while knockdown of DJ-1 and Wnt3a had the opposite effects. Furthermore, DJ-1 overexpression and DJ-1 knockdown increased and decreased, respectively, the levels of Wnt3a and β-catenin. Interestingly, Nrf2 and Wnt3a deficiency reduced the protective effects of Wnt3a and DJ-1, respectively, in A549 cells. However, the levels of DJ-1 and Wnt3a were not altered by Wnt3a and Nrf2 deletion, respectively.

SIGNIFICANCE

In A549 cells treated with CSE and LPS, DJ-1 regulates Nrf2-mediated MRP1 expression and antioxidant defences by activating the Wnt3a/β-catenin signalling pathway. These findings may provide potential therapeutic targets for COPD intervention.

Advanced therapeutic inhalation aerosols of a Nrf2 activator and RhoA/Rho kinase (ROCK) inhibitor for targeted pulmonary drug delivery in pulmonary hypertension: design, characterization, aerosolization, in vitro 2D/3D human lung cell cultures, and in vivo efficacy

Inhalable nanostructured microparticles of simvastatin, a Nrf2 activator and RhoA/Rho kinase (ROCK) inhibitor, were rationally designed for targeted pulmonary delivery as dry powder inhalers (DPIs) for the treatment of pulmonary hypertension (PH). Advanced particle engineering design technology was employed to develop inhalable dry powders using different dilute feed concentrations and spray drying pump rates. Several analytical techniques were used comprehensively to characterize the physicochemical properties of the resulting powders. Scanning electron microscopy (SEM) was used to visualize particle morphology (shape), surface structure, size, and size distribution. Karl Fischer titration (KFT) was employed to quantify the residual water content in the powders. X-ray powder diffraction (XRPD) was used to determine crystallinity. Hot-stage microscopy (HSM) under cross-polarizing lens was used to observe the presence or absence of birefringence characteristic of crystallinity. Differential scanning calorimetry (DSC) was employed to quantify thermotropic phase behavior. Attenuated total reflectance (ATR)-Fourier-transform infrared (FTIR) spectroscopy and Raman spectroscopy were used to determine the molecular fingerprint of simvastatin powders before and after particle engineering design. In vitro aerosol dispersion performance was performed with three different Food and Drug Administration (FDA)-approved human DPI devices. Cell viability and transepithelial electrical resistance (TEER) were demonstrated using different in vitro human pulmonary cell two and three-dimensional models at the air-liquid interface, and in vivo safety in healthy rats by inhalation. Efficacy was demonstrated in the in vivo lamb model of PH. Four different inhalable powders of simvastatin were successfully produced. They possessed nanostructured surfaces and were in the inhalable size range. Simvastatin retained its crystallinity following particle engineering design. The more dilute feed concentration spray dried at the lower pump rate produced the smallest particles. All powders successfully aerosolized with all three DPI human devices. Inhaled simvastatin as an aerosol restored the endothelial function in the shunt lamb model of PH, as demonstrated by the reduction of pulmonary vascular resistance (PVR) in response to the endothelium-dependent vasodilator acetylcholine.The reviews of this paper are available via the supplemental material section.

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.

Invited review: human air-liquid-interface organotypic airway tissue models derived from primary tracheobronchial epithelial cells-overview and perspectives

The lung is an organ that is directly exposed to the external environment. Given the large surface area and extensive ventilation of the lung, it is prone to exposure to airborne substances, such as pathogens, allergens, chemicals, and particulate matter. Highly elaborate and effective mechanisms have evolved to protect and maintain homeostasis in the lung. Despite these sophisticated defense mechanisms, the respiratory system remains highly susceptible to environmental challenges. Because of the impact of respiratory exposure on human health and disease, there has been considerable interest in developing reliable and predictive in vitro model systems for respiratory toxicology and basic research. Human air-liquid-interface (ALI) organotypic airway tissue models derived from primary tracheobronchial epithelial cells have in vivo–like structure and functions when they are fully differentiated. The presence of the air-facing surface allows conducting in vitro exposures that mimic human respiratory exposures. Exposures can be conducted using particulates, aerosols, gases, vapors generated from volatile and semi-volatile substances, and respiratory pathogens. Toxicity data have been generated using nanomaterials, cigarette smoke, e-cigarette vapors, environmental airborne chemicals, drugs given by inhalation, and respiratory viruses and bacteria. Although toxicity evaluations using human airway ALI models require further standardization and validation, this approach shows promise in supplementing or replacing in vivo animal models for conducting research on respiratory toxicants and pathogens.

Advanced spray dried proliposomes of amphotericin B lung surfactant-mimic phospholipid microparticles/nanoparticles as dry powder inhalers for targeted pulmonary drug delivery

The purpose of this study was to design, develop and characterize inhalable proliposomal microparticles/nanoparticles of Amphotericin B (AmB) with synthetic phospholipids, dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG) which are lung surfactant-mimic phospholipids. Organic solutions of AmB and phospholipids, were co-spray dried using an advanced closed-mode system and a high performance cyclone. Scanning electron microscopy (SEM) was employed to visualize the surface structure, morphology, and particles size. The residual water content of the proliposomes was quantified by Karl Fisher coulometric titration (KFT). Degree of crystallinity/non-crystallinity was measured by X-ray powder diffraction (XRPD). Phase behavior was measured by differential scanning calorimetry. The chemical composition by molecular fingerprinting was established using attenuated total reflectance (ATR)-Fourier-transform infrared (FTIR) spectroscopy. The amount of AmB loaded into the proliposomes was quantified using UV-VIS spectroscopy. The in vitro aerosol dispersion performance was conducted using the Next Generation Impactor (NGI) and the human dry powder inhaler (DPI) (Handihaler®) that is FDA-approved. Different human lung cell lines were employed to demonstrate in vitro safety as a function of dose and formulation. Smooth, spherical microparticles/nanoparticles were formed at medium and high spray drying pump rates and had low residual water content. A characteristic peak in the XRPD diffraction pattern as well as an endotherm in DSC confirmed the presence of the lipid bilayer structure characteristic in the DPPC/DPPG proliposomal systems. Superior in vitro aerosol performance was achieved with engineered microparticles/nanoparticles demonstrating suitability for targeted pulmonary drug delivery as inhalable dry powders. The in vitro cellular studies demonstrated that the formulated proliposomes are safe. These AmB proliposomes can be a better option for targeted treatment of severe pulmonary fungal infections.

Modifying and Integrating in vitro and ex vivo Respiratory Models for Inhalation Drug Screening

For the past 50 years, the route of inhalation has been utilized to administer therapies to treat a variety of respiratory and pulmonary diseases. When compared with other drug administration routes, inhalation offers a targeted, non-invasive approach to deliver rapid onset of drug action to the lung, minimizing systemic drug exposure and subsequent side effects. However, despite advances in inhaled therapies, there is still a need to improve the preclinical screening and the efficacy of inhaled therapeutics. Innovative in vitro models of respiratory physiology to determine therapeutic efficacy of inhaled compounds have included the use of organoids, micro-engineered lung-on-chip systems and sophisticated bench-top platforms to enable a better understanding of pulmonary mechanisms at the molecular level, rapidly progressing inhaled therapeutic candidates to the clinic. Furthermore, the integration of complementary ex vivo models, such as precision-cut lung slices (PCLS) and isolated perfused lung platforms have further advanced preclinical drug screening approaches by providing in vivo relevance. In this review, we address the challenges and advances of in vitro models and discuss the implementation of ex vivo inhaled drug screening models. Specifically, we address the importance of understanding human in vivo pulmonary mechanisms in assessing strategies of the preclinical screening of drug efficacy, toxicity and delivery of inhaled therapeutics.

Spatial mapping of VOC exhalation by means of bronchoscopic sampling

Breath analysis holds promise for non-invasive in vivo monitoring of disease related processes. However, physiological parameters may considerably affect profiles of exhaled volatile organic substances (VOCs). Volatile substances can be released via alveoli, bronchial mucosa or from the upper airways. The aim of this study was the systematic investigation of the influence of different sampling sites in the respiratory tract on VOC concentration profiles by means of a novel experimental setup. After ethical approval, breath samples were collected from 25 patients undergoing bronchoscopy for endobronchial ultrasound or bronchoscopic lung volume reduction from different sites in the airways. All patients had total intravenous anaesthesia under pressure-controlled ventilation. If necessary, respiratory parameters were adjusted to keep P_ETCO₂ = 35-45 mm Hg. 30 ml gas were withdrawn at six sampling sites by means of gastight glass syringes: S1 = Room air, S2 = Inspiration, S3 = Endotracheal tube, S4 = Trachea, S5 = Right B6 segment, S6 = Left B6 segment (S4-S6 through the bronchoscope channel). 10 ml were used for VOC analysis, 20 ml for PCO₂ determination. Samples were preconcentrated by solid-phase micro-extraction (SPME) and analysed by gas chromatography-mass spectrometry (GC-MS). PCO₂ was determined in a conventional blood gas analyser. Statistically significant differences in substance concentrations for acetone, isoprene, 2-methyl-pentane and n-hexane could be observed between different sampling sites. Increasing substance concentrations were determined for acetone (15.3%), 2-methyl-pentane (11.4%) and n-hexane (19.3%) when passing from distal to proximal sampling sites. In contrast, isoprene concentrations decreased by 9.9% from proximal to more distal sampling sites. Blank bronchoscope measurements did not show any contaminations. Increased substance concentrations in the proximal respiratory tract may be explained through substance excretion from bronchial mucosa while decreased concentrations could result from absorption or reaction processes. Spatial mapping of VOC profiles can provide novel insights into substance specific exhalation kinetics and mechanisms.

Properties of rapamycin solid lipid nanoparticles for lymphatic access through the lungs & part I: the effect of size

Background: Lymphangioleiomyomatosis (LAM) is characterized by growth of smooth muscle-like cells in the lungs that spread to other organs via lymphatic vessels. Current oral rapamycin treatment is limited by low bioavailability of approximately 15%. Aim: The effect of inhaled rapamycin solid lipid nanoparticles (Rapa-SLNs) size on its penetration through the lymphatics. Method: Three Rapa-SLN formulations (200-1000 nm) were produced and assessed for particle characteristics and further for toxicity and performance in vitro. Results: Rapa-SLNs of 200 nm inhibited proliferation in TSC2-negative mouse embryonic fibroblast cells and penetrated the respiratory epithelium and lymphatic endothelium significantly faster compared with free rapamycin and larger Rapa-SLNs. Conclusion: Rapa-SLN approximately 200 nm allows efficient entry of rapamycin into the lymphatic system and is therefore a promising treatment for LAM patients.

Current Status of Alginate in Drug Delivery

Alginate is one of the natural polymers that are often used in drug- and protein-delivery systems. The use of alginate can provide several advantages including ease of preparation, biocompatibility, biodegradability, and nontoxicity. It can be applied to various routes of drug administration including targeted or localized drug-delivery systems. The development of alginates as a selected polymer in various delivery systems can be adjusted depending on the challenges that must be overcome by drug or proteins or the system itself. The increased effectiveness and safety of sodium alginate in the drug- or protein-delivery system are evidenced by changing the physicochemical characteristics of the drug or proteins. In this review, various routes of alginate-based drug or protein delivery, the effectivity of alginate in the stem cells, and cell encapsulation have been discussed. The recent advances in the in vivo alginate-based drug-delivery systems as well as their toxicities have also been reviewed.

Development of a miniaturized 96-Transwell air-liquid interface human small airway epithelial model

In order to overcome the challenges associated with a limited number of airway epithelial cells that can be obtained from clinical sampling and their restrained capacity to divide ex vivo, miniaturization of respiratory drug discovery assays is of pivotal importance. Thus, a 96-well microplate system was developed where primary human small airway epithelial (hSAE) cells were cultured at an air–liquid interface (ALI). After four weeks of ALI culture, a pseudostratified epithelium containing basal, club, goblet and ciliated cells was produced. The 96-well ALI cultures displayed a cellular composition, ciliary beating frequency, and intercellular tight junctions similar to 24-well conditions. A novel custom-made device for 96-parallelized transepithelial electric resistance (TEER) measurements, together with dextran permeability measurements, confirmed that the 96-well culture developed a tight barrier function during ALI differentiation. 96-well hSAE cultures were responsive to transforming growth factor β1 (TGF-β1) and tumor necrosis factor α (TNF-α) in a concentration dependent manner. Thus, the miniaturized cellular model system enables the recapitulation of a physiologically responsive, differentiated small airway epithelium, and a robotic integration provides a medium throughput approach towards pharmaceutical drug discovery, for instance, in respect of fibrotic distal airway/lung diseases.

Cigarette smoke extract combined with lipopolysaccharide reduces OCTN1/2 expression in human alveolar epithelial cells in vitro and rat lung in vivo under inflammatory conditions

Organic cation transporter 1/2 (OCTN1/2) play important roles in the transport of drugs related to pulmonary inflammatory diseases. Nevertheless, the involvement of inflammation induced by cigarette smoke extract (CSE) combined with lipopolysaccharide (LPS) in the regulation of OCTN1/2 is not fully understood. In this study, CSE combined with LPS was used to establish inflammation models in vitro and in vivo. Our study found that the expression of OCTN1/2 was downregulated in rat lung in vivo and in a human alveolar cell line in vitro after treatment with CSE and LPS compared with the control group, while the expression of inflammatory factors was upregulated. After treatment with ipratropium bromide (IB) or dexamethasone (DEX), the expression of OCTN1/2 was upregulated compared with that in the CSE-LPS model group, while the expression of inflammatory factors was significantly downregulated. After administration of the NF-κB inhibitor PDTC on the basis of the inflammatory status, the expression of OCTN1/2 was upregulated in the treated group compared with the CSE-LPS model group, while the expression of phospho-p65, phospho-IκBα and inflammatory factors was significantly downregulated. We further added the NF-κB agonist HSP70 and found a result that the exact opposite of that observed with PDTC. Our findings show that CSE combined with LPS can downregulate the expression of OCTN1/2 under inflammatory conditions, and that the downregulation of OCTN1/2 expression may partially occur via the NF-κB signaling pathway.

Characterization of ABC Transporters in EpiAirway™, a Cellular Model of Normal Human Bronchial Epithelium

The ATP-binding cassette (ABC) transporters P-glycoprotein (MDR1/ABCB1), multidrug resistance-associated protein 1 (MRP1/ABCC1), and breast cancer resistance protein (BCRP/ABCG2) play a crucial role in the translocation of a broad range of drugs; data about their expression and activity in lung tissue are controversial. Here, we address their expression, localization and function in EpiAirway™, a three-dimensional (3D)-model of human airways; Calu-3 cells, a representative in vitro model of bronchial epithelium, are used for comparison. Transporter expression has been evaluated with RT-qPCR and Western blot, the localization with immunocytochemistry, and the activity by measuring the apical-to-basolateral and basolateral-to-apical fluxes of specific substrates in the presence of inhibitors. EpiAirway™ and Calu-3 cells express high levels of MRP1 on the basolateral membrane, while they profoundly differ in terms of BCRP and MDR1: BCRP is detected in EpiAirway™, but not in Calu-3 cells, while MDR1 is expressed and functional only in fully-differentiated Calu-3; in EpiAirway™, MDR1 expression and activity are undetectable, consistently with the absence of the protein in specimens from human healthy bronchi. In summary, EpiAirway™ appears to be a promising tool to study the mechanisms of drug delivery in the bronchial epithelium and to clarify the role of ABC transporters in the modulation of the bioavailability of administered drugs.

Functional analysis of OCTN2 and ATB0,+ in normal human airway epithelial cells

In human, OCTN2 (SLC22A5) and ATB0,+ (SLC6A14) transporters mediate the uptake of L-carnitine, essential for the transport of fatty acids into mitochondria and the subsequent degradation by β-oxidation. Aim of the present study was to characterize L-carnitine transport in EpiAirway™, a 3D organotypic in vitro model of primary human tracheal-bronchial epithelial cells that form a fully differentiated, pseudostratified columnar epithelium at air-liquid interface (ALI) condition. In parallel, Calu-3 monolayers grown at ALI for different times (8d or 21d of culture) were used as comparison. OCTN2 transporter was equally expressed in both models and functional at the basolateral side. ATB0,+ was, instead, highly expressed and active on the apical membrane of EpiAirway™ and only in early-cultures of Calu-3 (8d but not 21d ALI). In both cell models, L-carnitine uptake on the apical side was significantly inhibited by the bronchodilators glycopyrrolate and tiotropium, that hence can be considered substrates of ATB0,+; ipratropium was instead effective on the basolateral side, indicating its interaction with OCTN2. Inflammatory stimuli, such as LPS or TNFα, caused an induction of SLC6A14/ATB0,+ expression in Calu-3 cells, along with a 2-fold increase of L-carnitine uptake only at the apical side; on the contrary SLC22A5/OCTN2 was not affected. As both OCTN2 and ATB0,+, beyond transporting L-carnitine, have a significant potential as delivery systems for drugs, the identification of these transporters in EpiAirway™ can open new fields of investigation in the study of drug inhalation and pulmonary delivery.

Development of a Novel ex vivo Nasal Epithelial Cell Model Supporting Colonization With Human Nasal Microbiota

The nasal mucosa provides first line defense against inhaled pathogens while creating a unique microenvironment for bacterial communities. Studying the impact of microbiota in the nasal cavity has been difficult due to limitations with current models including explant cultures, primary cells, or neoplastic cell lines. Most notably, none have been shown to support reproducible colonization by bacterial communities from human donors. Therefore, to conduct controlled studies of the human nasal ecosystem, we have developed a novel ex vivo mucosal model that supports bacterial colonization of a cultured host mucosa created by immortalized human nasal epithelial cells (NEC). For this model, immortalized NEC established from 5 male and 5 female donors were cultured with an air-interfaced, apical surface on a porous transwell membrane. NEC were grown from nasal turbinate tissues harvested from willed bodies or from discarded tissue collected during sinonasal procedures. Immortalized cells were evaluated through molecular verification of cell type, histological confirmation of tissue differentiation including formation of tight junctions, NEC multilayer viability, metabolism, physiology and imaging of the luminal surface by scanning electron microscopy. Results showed proper differentiation and multilayer formation at seven to 10 days after air interface that was maintained for up to 3 weeks. The optimized mucosal cultures created an environment necessary to sustain colonization by nasal microbiomes (NMBs) that were collected from healthy volunteers, cryogenically preserved and characterized with customized quantitative polymerase chain reaction (qPCR) arrays. Polymicrobial communities of nasal bacteria associated with healthy and inflamed states were consistently reproduced in matured NEC co-cultures by transplant of NMBs from multiple community types. The cultured NMBs were stable after an initial period of bacterial replication and equilibration. This novel ex vivo culture system is the first model that supports controlled cultivation of NMBs, allowing for lab-based causation studies and further experimentation to explore the complexities of host-microbe and microbe-microbe interactions.

Pharmacokinetic and pharmacodynamic modeling of gut hormone peptide YY(3-36) after pulmonary delivery

Peptide YY_(3-36) (PYY_(3-36)) is an endogenous appetite suppressing peptide. The present research was to perform pharmacokinetic/pharmacodynamic (PK/PD) analysis for predicting the concentration- and response-time profiles of PYY_(3-36) after systemic and pulmonary delivery in mice, with the goal of suggesting a potential pulmonary dosing regimen in humans. A PK/PD model was developed to describe PYY_(3-36) plasma concentration - and relative food intake rate ratio (as % of control) - time profiles after intraperitoneal and subcutaneous administration, and inhalation in mice. The absorption of inhaled PYY_(3-36) from the lungs of mice could only be described with a combined slow (absorption rate of 0.147 L/h) and fast (absorption rate of 104.4 L/h) absorption process, presumably related to absorption from the central and peripheral regions of the lungs. The estimates for IC₅₀ and I_max were 6.8 ng/mL and 63.5%, respectively, based on inhibitory E_max model. The PK parameters, such as clearance (CL), volume of distribution at steady state (Vd_ss), and the absorption rates (k_a), were then scaled to human's. The scaled human CL and Vd_ss for obese subjects were 24.8 L/h and 9.0 L, respectively. The model predicted human plasma PYY_(3-36) concentrations agreed reasonably well with placebo-normalized plasma PYY_(3-36) concentrations after short-term infusion and SC injection in literature. An inhalation dose of PYY_(3-36) of about 100 µg was proposed for obese subjects based on simulations. This PK/PD analysis satisfactorily described PYY_(3-36) concentration-time and relative food intake rate ratio- time profiles at all doses and routes. The developed model might facilitate the inhalation dose selection of PYY_(3-36).

Chitosan-based binary dry powder inhaler carrier with nanometer roughness for improving in vitro and in vivo aerosolization performance

Suitable nanometer roughness favors interactions between drugs and carriers, and it is a promising approach to enhance the aerosolization performance of carrier-based dry powder inhalers (DPIs). In this study, by altering the molecular migration rates, chitosan-based binary carriers (CBBCs) with nanometer roughness were fabricated for DPIs. Comprehensive physicochemical characterizations were conducted to elucidate the formation mechanism of the CBBCs. It was hypothesized that different constituent ratios in the formulations would result in different assembling of the particles and diverse roughness scales. The fine particle fractions (FPF, approximately 40~60%) of nanometer roughness CBBC-based DPI formulations were satisfactory, demonstrating the enhancement of the in vitro aerodynamic performance. The positive correlation (R² = 0.9883) between the nanometer roughness and FPF was revealed, and the surface roughness of 20 nm might achieve the best aerosolization performance. CBBCs (optimal formulations) showed no difference in cytotoxicity on A549 and Calu-3 cells (p > 0.05). Additionally, the increased C_max and AUC_0-8h of the formulation with the nanometer roughness (p < 0.05) were observed in pharmacokinetic studies, which resulted from the improved in vivo aerosolization performance. In summary, the CBBCs were a prospective tool to improve the in vitro and in vivo aerosolization performance of DPIs. Graphical abstract ᅟ.

Spray-dried fucoidan microparticles for pulmonary delivery of antitubercular drugs

Pulmonary tuberculosis accounts for 80% of cases and the delivery of antitubercular drugs into the lungs allows targeting the infected organ and, possibly, reducing systemic drug toxicity. This work aimed at using fucoidan as matrix of inhalable microparticles that associate two first-line antitubercular drugs, for an application in pulmonary tuberculosis therapy. Fucoidan is composed of fucose and sulphated sugar residues, moieties described as being recognised by surface receptors of alveolar macrophages, which host mycobacteria. Inhalable fucoidan microparticles loaded with antitubercular drugs were successfully produced with high association efficiencies of either isoniazid (95%) or rifabutin (81%). The microparticles evidenced no cytotoxicity on lung epithelial cells (A549). However, rifabutin-loaded microparticles showed a certain degree of toxicity on macrophage-like cells (THP-1) at the highest tested concentration (1 mg/mL). Furthermore, microparticles showed favourable aerodynamic properties for deep lung delivery (MMAD 2.0-3.8 µm) and, thus, show potential for an application as inhalable tuberculosis therapy.

The crux of positive controls - Pro-inflammatory responses in lung cell models

Positive controls are an important feature in experimental studies as they show the responsiveness of the model under investigation. An often applied reagent for a pro-inflammatory stimulus is the endotoxin lipopolysaccharide (LPS), which has been shown to induce a cytokine release by various cell cultures. The effect of LPS in monocultures of 16HBE14o-, a bronchial cell line, and of A549, an alveolar cell line, were compared in submerged and air-liquid interface cultures, as well as in co-cultures of the two epithelial cells with monocyte-derived macrophages and dendritic cells. The protein and mRNA levels of the two most relevant pro-inflammatory mediators, Tumor necrosis factor alpha (TNF) and Interleukin 8 (CXCL8), were measured after 4 h and 24 h exposure. 16HBE14o- cells alone as well as in co-cultures are non-responsive to an LPS stimulus, but an already increased basal expression of both pro-inflammatory mediators after prolonged time in culture was observed. In contrary, A549 in monocultures showed increased CXCL8 production at the gene and protein level after LPS exposure, while TNF-levels were below detection limit. In A549 co-cultured with immune cells both mediators were upregulated. This study shows the importance of a careful evaluation of the culture system used, including the application of positive controls. In addition, the use of co-cultures with immune cells more adequately reflects the inflammatory response upon exposure to toxicants.

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.

Oxidative stress and cell cycle arrest induced by short-term exposure to dustfall PM2.5 in A549 cells

It was reported that in vitro short-term exposure to PM_2.5 caused different lung diseases through inflammatory response, immune toxicity, oxidative stress, and genetic mutations. However, the complex molecular biological mechanism for its toxicity had not been fully elucidated. Therefore, the present study investigated the cytotoxicity, oxidative damage, mitochondria damage, apoptosis, and cell cycle arrest of NX and QH PM_2.5 in A549 cells. Further, cell cycle arrest-related gene levels in PM_2.5-induced A549 cells were also detected. Our results suggested that PM_2.5 reduced the cell viability in A549 cells. Simultaneously, excessive ROS decreased MMP levels and damaged mitochondrial membrane integrity and induced mitochondrial oxidative damage through the oxygen-dependent killer route, resulting in mitochondrial damage and cell apoptosis. Besides, the results also showed that PM_2.5 induced A549 cell cycle alteration in G2/M phase after co-culture for 24 h. G2/M phase arrest was induced by upregulation of p53 and p21 and downregulation of CDK1 mRNA expression. In addition, lncRNA Sox2ot might play an important role as the specific oncogenes and it participated in G2/M phase arrest by regulating the expression of EZH₂.

Inhalable Fucoidan Microparticles Combining Two Antitubercular Drugs with Potential Application in Pulmonary Tuberculosis Therapy

The pulmonary delivery of antitubercular drugs is a promising approach to treat lung tuberculosis. This strategy not only allows targeting the infected organ instantly, it can also reduce the systemic adverse effects of the antibiotics. In light of that, this work aimed at producing fucoidan-based inhalable microparticles that are able to associate a combination of two first-line antitubercular drugs in a single formulation. Fucoidan is a polysaccharide composed of chemical units that have been reported to be specifically recognised by alveolar macrophages (the hosts of Mycobacterium). Inhalable fucoidan microparticles were successfully produced, effectively associating isoniazid (97%) and rifabutin (95%) simultaneously. Furthermore, the produced microparticles presented adequate aerodynamic properties for pulmonary delivery with potential to reach the respiratory zone, with a mass median aerodynamic diameter (MMAD) between 3.6⁻3.9 µm. The formulation evidenced no cytotoxic effects on lung epithelial cells (A549), although mild toxicity was observed on macrophage-differentiated THP-1 cells at the highest tested concentration (1 mg/mL). Fucoidan microparticles also exhibited a propensity to be captured by macrophages in a dose-dependent manner, as well as an ability to activate the target cells. Furthermore, drug-loaded microparticles effectively inhibited mycobacterial growth in vitro. Thus, the produced fucoidan microparticles are considered to hold potential as pulmonary delivery systems for the treatment of tuberculosis.

Mucoadhesive solid lipid microparticles for controlled release of a corticosteroid in the chronic obstructive pulmonary disease treatment

Aim: Therapeutic efficacy of pulmonary diseases is often limited and drug delivery systems offer new solutions to clinical problems. Solid lipid microparticles (SLMs) are suggested as systems for the delivery of therapeutics to the lung as, because of their size, they are able to deposit into secondary bronchi. Materials & methods: Here, we describe two novel different SLMs using chitosan and alginate such as mucoadhesive polymers and we also studied their biocompatibility and their effectiveness compared with the free drug in controlling senescence and inflammatory processes in cigarette smoke extracts. Results: Data reported show that fluticasone propionate (FP)-loaded SLMs are more effective than FP alone in controlling oxidative stress. Conclusion: The therapeutic approach using FP-loaded microparticles could be a promising strategy for the treatment of the chronic inflammatory pulmonary diseases.

Bisphenol A exposure pathways in early childhood: Reviewing the need for improved risk assessment models

Bisphenol A (BPA) is a plasticiser found in a number of household plastics, electronics, and food-packaging materials. Over the past 5 years, several human epidemiological studies have reported a positive association between BPA exposure and adverse health outcomes in children, including obesity, asthma, preterm birth, and neuro-behavioural disturbances. These findings are in conflict with international environmental risk assessment models, which predict daily exposure levels to BPA should not pose a risk to child health. The aim of this review is to provide an overview of the evidence for different exposure sources and potential exposure pathways of BPA in early childhood. By collating the findings from experimental models and exposure associations observed in human bio-monitoring studies, we affirm the potential for non-dietary sources to make a substantial contribution to total daily exposure in young children. Infants and toddlers have distinctive exposure sources, physiology, and metabolism of endocrine-disrupting chemicals. We recommend risk-assessment models implement new frameworks, which specifically address exposure and hazard in early childhood. This is particularly important for BPA, which is present in numerous products in the home and day-care environments, and for which animal studies report contradictory findings on its safety at environmentally relevant levels of exposure.

Validation of the 2nd Generation Proteasome Inhibitor Oprozomib for Local Therapy of Pulmonary Fibrosis

Proteasome inhibition has been shown to prevent development of fibrosis in several organs including the lung. However, effects of proteasome inhibitors on lung fibrosis are controversial and cytotoxic side effects of the overall inhibition of proteasomal protein degradation cannot be excluded. Therefore, we hypothesized that local lung-specific application of a novel, selective proteasome inhibitor, oprozomib (OZ), provides antifibrotic effects without systemic toxicity in a mouse model of lung fibrosis. Oprozomib was first tested on the human alveolar epithelial cancer cell line A549 and in primary mouse alveolar epithelial type II cells regarding its cytotoxic effects on alveolar epithelial cells and compared to the FDA approved proteasome inhibitor bortezomib (BZ). OZ was less toxic than BZ and provided high selectivity for the chymotrypsin-like active site of the proteasome. In primary mouse lung fibroblasts, OZ showed significant anti-fibrotic effects, i.e. reduction of collagen I and α smooth muscle actin expression, in the absence of cytotoxicity. When applied locally into the lungs of healthy mice via instillation, OZ was well tolerated and effectively reduced proteasome activity in the lungs. In bleomycin challenged mice, however, locally applied OZ resulted in accelerated weight loss and increased mortality of treated mice. Further, OZ failed to reduce fibrosis in these mice. While upon systemic application OZ was well tolerated in healthy mice, it rather augmented instead of attenuated fibrotic remodelling of the lung in bleomycin challenged mice. To conclude, low toxicity and antifibrotic effects of OZ in pulmonary fibroblasts could not be confirmed for pulmonary fibrosis of bleomycin-treated mice. In light of these data, the use of proteasome inhibitors as therapeutic agents for the treatment of fibrotic lung diseases should thus be considered with caution.

Permeation of Therapeutic Drugs in Different Formulations across the Airway Epithelium In Vitro

BACKGROUND

Pulmonary drug delivery is characterized by short onset times of the effects and an increased therapeutic ratio compared to oral drug delivery. This delivery route can be used for local as well as for systemic absorption applying drugs as single substance or as a fixed dose combination. Drugs can be delivered as nebulized aerosols or as dry powders. A screening system able to mimic delivery by the different devices might help to assess the drug effect in the different formulations and to identify potential interference between drugs in fixed dose combinations. The present study evaluates manual devices used in animal studies for their suitability for cellular studies.

METHODS

Calu-3 cells were cultured submersed and in air-liquid interface culture and characterized regarding mucus production and transepithelial electrical resistance. The influence of pore size and material of the transwell membranes and of the duration of air-liquid interface culture was assessed. Compounds were applied in solution and as aerosols generated by MicroSprayer IA-1C Aerosolizer or by DP-4 Dry Powder Insufflator using fluorescein and rhodamine 123 as model compounds. Budesonide and formoterol, singly and in combination, served as examples for drugs relevant in pulmonary delivery.

RESULTS AND CONCLUSIONS

Membrane material and duration of air-liquid interface culture had no marked effect on mucus production and tightness of the cell monolayer. Co-application of budesonide and formoterol, applied in solution or as aerosol, increased permeation of formoterol across cells in air-liquid interface culture. Problems with the DP-4 Dry Powder Insufflator included compound-specific delivery rates and influence on the tightness of the cell monolayer. These problems were not encountered with the MicroSprayer IA-1C Aerosolizer. The combination of Calu-3 cells and manual aerosol generation devices appears suitable to identify interactions of drugs in fixed drug combination products on permeation.

Inhalable tranexamic acid for haemoptysis treatment

PURPOSE

An inhalable dry powder formulation of tranexamic acid (TA) was developed and tested in a novel high-dose Orbital® multi-breath inhaler. The formulation was specifically intended for the treatment of pulmonary haemorrhage and wound healing associated with haemoptysis.

METHODS

Inhalable TA particles were prepared by spray drying and the powder characterised using laser diffraction, electron microscopy, thermal analysis, moisture sorption and X-ray powder diffraction. The aerosol performance was evaluated using cascade impaction and inline laser diffraction and interaction with epithelia cells and wound healing capacity investigated using Calu-3 air interface model.

RESULTS

The spray dried TA particles were crystalline and spherical with a D0.5 of 3.35 μm. The powders were stable and had limited moisture sorption (0.307%w/w at 90%RH). The Orbital device delivered ca. 38 mg powder per 'inhalation' at 60 l · min(-1) across four sequential shots with an overall fine particle fraction (⩽ 6.4 μm) of 59.3 ± 3.5% based on the emitted mass of ca. 150 mg. The TA particles were well tolerated by Calu-3 bronchial epithelia cells across a wide range of doses (from 1 nM to 10nM) and no increase in inflammatory mediators was observed after deposition of the particles (a decrease in IL-1β, IL-8 and INFγ was observed). Time lapse microscopy of a damaged confluent epithelia indicated that wound closure was significantly greater in TA treated cells compared to control.

CONCLUSION

A stable, high performance aerosol of TA has been developed in a multi-breath DPI device that can be used for the treatment of pulmonary lesions and haemoptysis.

Is the cellular uptake of respiratory aerosols delivered from different devices equivalent?

The study focuses on the application of a cell integrated modified Andersen Cascade Impactor (ACI) as an in vitro lung model for the evaluation of aerosols' behaviour of different formulation devices, containing the same active drug, specifically nebuliser, pressurised metered dose inhaler (pMDI) and dry powder inhaler (DPI). Deposition and transport profiles of the three different inhaled salbutamol sulphate (SS) formulations with clinically relevant doses were evaluated using a modified ACI coupled with the air interface Calu-3 bronchial cell model. Reproducible amounts of SS were deposited on Snapwells for the different formulations, with no significant difference in SS deposition found between the standard ACI plate and modified plate. The transport of SS aerosols produced from pMDI formulation had similar transport kinetics to nebulised SS but significantly higher compared to the DPI, which could have led to the differences in clinical outcomes. Furthermore, drug absorption of different inhaled formulation devices of the same aerodynamic fraction was found not to be equivalent due to their physical chemical properties upon aerosolisation. This study has established an in vitro platform for the evaluation of the different inhaled formulations in physiologically relevant pulmonary conditions.

A lung-on-a-chip array with an integrated bio-inspired respiration mechanism

We report a lung-on-a-chip array that mimics the pulmonary parenchymal environment, including the thin alveolar barrier and the three-dimensional cyclic strain induced by breathing movements. The micro-diaphragm used to stretch the alveolar barrier is inspired by the in vivo diaphragm, the main muscle responsible for inspiration. The design of this device aims not only at best reproducing the in vivo conditions found in the lung parenchyma but also at making the device robust and its handling easy. An innovative concept, based on the reversible bonding of the device, is presented that enables accurate control of the concentration of cells cultured on the membrane by easily accessing both sides of the membranes. The functionality of the alveolar barrier could be restored by co-culturing epithelial and endothelial cells that form tight monolayers on each side of a thin, porous and stretchable membrane. We showed that cyclic stretch significantly affects the permeability properties of epithelial cell layers. Furthermore, we also demonstrated that the strain influences the metabolic activity and the cytokine secretion of primary human pulmonary alveolar epithelial cells obtained from patients. These results demonstrate the potential of this device and confirm the importance of the mechanical strain induced by breathing in pulmonary research.