In vitro organ culture models of asthma

Engineered aluminum nanoparticle induces mitochondrial deformation and is predicated on cell phenotype

The main role of mitochondria is to generate the energy necessary for the cell to survive and adapt to different environmental stresses. Energy demand varies depending on the phenotype of the cell. To efficiently meet metabolic demands, mitochondria require a specific proton homeostasis and defined membrane structures to facilitate adenosine triphosphate production. This homeostatic environment is constantly challenged as mitochondria are a major target for damage after exposure to environmental contaminants. Here we report changes in mitochondrial structure profiles in different cell types using electron microscopy in response to particle stress exposure in three different representative lung cell types. Endpoint analyses include nanoparticle intracellular uptake; quantitation of mitochondrial size, shape, and ultrastructure; and confirmation of autophagosome formation. Results show that low-dose aluminum nanoparticles exposure (1 ppm; 1 µg/mL; 1.6 × 1 0^-7µg/cell)) to primary and asthma cells incurred significant mitochondrial deformation and increases in mitophagy, while cancer cells exhibited only slight changes in mitochondrial morphology and an increase in lipid body formation. These results show low-dose aluminum nanoparticle exposure induces subtle changes in the mitochondria of specific lung cells that can be quantified with microscopy techniques. Furthermore, within the lung, cell type by the nature of origin (i.e. primary vs. cancer vs. asthma) dictates mitochondrial morphology, metabolic health, and the metabolic stress response of the cell.

The Biological Effects of Complete Gasoline Engine Emissions Exposure in a 3D Human Airway Model (MucilAirTM) and in Human Bronchial Epithelial Cells (BEAS-2B)

The biological effects induced by complete engine emissions in a 3D model of the human airway (MucilAirTM) and in human bronchial epithelial cells (BEAS-2B) grown at the air-liquid interface were compared. The cells were exposed for one or five days to emissions generated by a Euro 5 direct injection spark ignition engine. The general condition of the cells was assessed by the measurement of transepithelial electrical resistance and mucin production. The cytotoxic effects were evaluated by adenylate kinase (AK) and lactate dehydrogenase (LDH) activity. Phosphorylation of histone H2AX was used to detect double-stranded DNA breaks. The expression of the selected 370 relevant genes was analyzed using next-generation sequencing. The exposure had minimal effects on integrity and AK leakage in both cell models. LDH activity and mucin production in BEAS-2B cells significantly increased after longer exposures; DNA breaks were also detected. The exposure affected CYP1A1 and HSPA5 expression in MucilAirTM. There were no effects of this kind observed in BEAS-2B cells; in this system gene expression was rather affected by the time of treatment. The type of cell model was the most important factor modulating gene expression. In summary, the biological effects of complete emissions exposure were weak. In the specific conditions used in this study, the effects observed in BEAS-2B cells were induced by the exposure protocol rather than by emissions and thus this cell line seems to be less suitable for analyses of longer treatment than the 3D model.

A critical assessment of the scientific basis, and implementation, of regulations for the safety assessment and marketing of innovative tobacco-related products

Our scientific, logistical, ethical and animal welfare-related concerns about the latest US Food and Drug Administration (FDA) regulations for existing and so-called 'new' tobacco products, aimed at reducing harmful exposures, are explained. Such claims for sales in the USA now have to be based on a wide range of information, a key part of which will increasingly be data on safety and risk. One of the pathways to achieve marketing authorisation is to demonstrate substantial equivalence (SE) with benchmark products, called predicates. However, the regulations are insufficiently transparent with regard to: a) a rationale for the cut-off date for 'old' and 'new' products, and for exempting the former from regulation; b) the scientific validity and operation of SE; c) options for product labelling to circumvent SE; d) the experimental data required to support, and criteria to judge, a claim; and e) a strategy for risk assessment/management. Scientific problems related to the traditional animal methods used in respiratory disease and inhalation toxicology, and the use of quantitative comparators of toxicity, such as the No Observed Adverse Effect Level, are discussed. We review the advantages of relevant in vitro, mechanism-based, target tissue-oriented technologies, which an advisory report of the Institute of Medicine of the US National Academy of Sciences largely overlooked. These benefits include: a) the availability, for every major site in the respiratory tract, of organotypic human cell-based tissue culture systems, many of which are already being used by the industry; b) the accurate determination of concentrations of test materials received by target cells; c) methods for exposure to particulate and vapour phases of smoke, separately or combined; d) the ability to study tissue-specific biotransformation; and e) the use of modern, human-focused methodologies, unaffected by species differences. How data extrapolation, for risk assessment, from tissue culture to the whole animal, could be addressed, is also discussed. A cost (to animal welfare)-benefit (to society, including industry and consumers) analysis was conducted, taking into account the above information; the potential for animal suffering; the extensive data already available; the existence of other, less hazardous forms of nicotine delivery; the fact that much data will be generated solely for benchmarking; and that many smokers (especially nicotine-dependents) ignore health warnings. It is concluded that, in common with policies of several tobacco companies and countries, the use of laboratory animals for tobacco testing is very difficult, if not impossible, to justify. Instead, we propose and argue for an integrated testing scheme, starting with extensive chemical analysis of the ingredients and by-products associated with the use of tobacco products and their toxicity, followed by use of in vitro systems and early clinical studies (involving specific biomarkers) with weight-of-evidence assessments at each stage. Appropriate adjustment factors could be developed to enable concentration-response data obtained in vitro, with the other information generated by the strategy, to enable the FDA to meet its objectives. It is hoped that our intentionally provocative ideas will stimulate further debate on this contentious area of regulatory testing and public safety.

Effects of hydrogen peroxide on mucociliary transport in human airway epithelial cells

The effects of environmental pollutants on airway clearance have not been well elucidated. This study examined mucociliary transport using different sized-fluorescent particles on polarized human airway epithelial cells which were maintained in an air-liquid interface (ALI) culture system. The effects of hydrogen peroxide (H2O2) exposure on mucociliary transport were also investigated. The movement of fluorescent particles with diameters of 10-14 and 2.5-4.5 µm was observed by fluorescent microscopy as an index of the mucociliary transport. The mixture of the particles with two different sizes was propelled concentrically on the apical surface by the interaction of ciliary activity and mucus in the control condition, whereas H2O2 exposure for 24 h significantly inhibited the movement of the particles. The particle sizes did not affect their movement after the control or H2O2 exposure. These results suggest that particle tracking on polarized human airway epithelial cells is a useful experimental tool for the evaluation of the effect of environmental pollutants on mucociliary transport. In addition, reactive oxygen species may impair mucociliary transport, leading to the airway damage and exacerbation of respiratory diseases.

Potential of coculture in vitro models to study inflammatory and sensitizing effects of particles on the lung

Exposure to particulate matter (PM) like nanoparticles (NPs) has increased in the last century due to increased combustion processes, road traffic, etc. In addition, the progress in chemical and cosmetic industry led to many new compounds, e.g. fragrances, which humans are exposed to every day. Many chemicals are known to act as contact and some as respiratory sensitizers, causing allergic reactions. Exposure to small particles of less than 100 nm in diameter is linked with an increased risk of respiratory diseases, such as asthma or rhinitis. To date already more than 1000 customer products contain eNPs without knowing much about the health effects. In comparison to chemicals, the mechanisms by which PM and eNPs can cause sensitization are still not fully understood. Validated and regulatory accepted in vitro models to assess this hazard in its full range are still missing. While a huge number of animal studies contributed to our knowledge about sensitization processes, knowledge on involved cellular mechanisms is still limited. In this review relevant in vitro models to study and elucidate these mechanisms in more detail are presented and their potential to serve as part of a tiered testing strategy is discussed.

Animal models of asthma: value, limitations and opportunities for alternative approaches

Asthma remains an area of considerable unmet medical need. Few new drugs have made it to the clinic during the past 50 years, with many that perform well in preclinical animal models of asthma, failing in humans owing to lack of safety and efficacy. The failure to translate promising drug candidates from animal models to humans has led to questions about the utility of in vivo studies and to demand for more predictive models and tools based on the latest technologies. Following a workshop with experts from academia and the pharmaceutical industry, we suggest here a disease modelling framework designed to better understand human asthma, and accelerate the development of safe and efficacious new asthma drugs that go beyond symptomatic relief.