Predicting the in vivo pulmonary toxicity induced by acute exposure to poorly soluble nanomaterials by using advanced in vitro methods

BACKGROUND

Animal models remain at that time a reference tool to predict potential pulmonary adverse effects of nanomaterials in humans. However, in a context of reduction of the number of animals used in experimentation, there is a need for reliable alternatives. In vitro models using lung cells represent relevant alternatives to assess potential nanomaterial acute toxicity by inhalation, particularly since advanced in vitro methods and models have been developed. Nevertheless, the ability of in vitro experiments to replace animal experimentation for predicting potential acute pulmonary toxicity in human still needs to be carefully assessed. The aim of the study was to evaluate the differences existing between the in vivo and the in vitro approaches for the prediction of nanomaterial toxicity and to find advanced methods to enhance in vitro predictivity. For this purpose, rats or pneumocytes in co-culture with macrophages were exposed to the same poorly soluble and poorly toxic TiO2 and CeO2 nanomaterials, by the respiratory route in vivo or using more or less advanced methodologies in vitro. After 24 h of exposure, biological responses were assessed focusing on pro-inflammatory effects and quantitative comparisons were performed between the in vivo and in vitro methods, using compatible dose metrics.

RESULTS

For each dose metric used (mass/alveolar surface or mass/macrophage), we observed that the most realistic in vitro exposure method, the air-liquid interface method, was the most predictive of in vivo effects regarding biological activation levels. We also noted less differences between in vivo and in vitro results when doses were normalized by the number of macrophages rather than by the alveolar surface. Lastly, although we observed similarities in the nanomaterial ranking using in vivo and in vitro approaches, the quality of the data-set was insufficient to provide clear ranking comparisons.

CONCLUSIONS

We showed that advanced methods could be used to enhance in vitro experiments ability to predict potential acute pulmonary toxicity in vivo. Moreover, we showed that the timing of the dose delivery could be controlled to enhance the predictivity. Further studies should be necessary to assess if air-liquid interface provide more reliable ranking of nanomaterials than submerged methods.

Site-specific gene expression analysis from archived human intestine samples combining laser-capture microdissection and multiplexed color-coded probes

BACKGROUND

Alterations of site-specific gene expression profiles in disease-relevant networks within the different layers of the intestinal wall may contribute to the onset and clinical course of gastrointestinal disorders. To date, no systematic analysis has assessed and compared sub-regional gene expression patterns in all distinct layers of the gut using fresh frozen human samples. Our aim was to establish an optimized protocol for site-specific RNA isolation in order to achieve maximum RNA quality and amount for subsequent gene expression analysis combining laser-capture microdissection (LCM) with a probe-based technology, the NanoString nCounter Analysis system.

METHODS

Four full-thickness colon samples from patients who underwent surgery due to pathological conditions were processed and separated into epithelium, lamina propria, myenteric plexus, submucosa, and tunica muscularis by LCM. Site-specific marker expression by nCounter technology was performed on total RNA from each sub-region, respectively.

KEY RESULTS

Collecting ~10 mm² (~100 000-250 000 cells) of tissue from the epithelial layer, lamina propria, and myenteric plexus provided sufficient amounts of RNA of appropriate quality for subsequent analyses. In contrast, ~40 mm² (~250 000-650 000 cells) of tissue were dissected from the less cell-rich submucosal and tunica muscularis layer. nCounter analysis revealed a site-specific expression pattern of marker genes in the different layers of the colonic wall which were highly correlating (r > .9).

CONCLUSIONS AND INFERENCES

LCM in combination with nCounter expression analysis enables site-specific, sensitive, reliable detection, and quantification of mRNA from histologically heterogeneous tissues.

Lamin B1 regulates somatic mutations and progression of B-cell malignancies

Somatic hypermutation (SHM) is a pivotal process in adaptive immunity that occurs in the germinal centre and allows B cells to change their primary DNA sequence and diversify their antigen receptors. Here, we report that genome binding of Lamin B1, a component of the nuclear envelope involved in epigenetic chromatin regulation, is reduced during B-cell activation and formation of lymphoid germinal centres. Chromatin immunoprecipitation-Seq analysis showed that kappa and heavy variable immunoglobulin domains were released from the Lamin B1 suppressive environment when SHM was induced in B cells. RNA interference-mediated reduction of Lamin B1 resulted in spontaneous SHM as well as kappa-light chain aberrant surface expression. Finally, Lamin B1 expression level correlated with progression-free and overall survival in chronic lymphocytic leukaemia, and was strongly involved in the transformation of follicular lymphoma. In summary, here we report that Lamin B1 is a negative epigenetic regulator of SHM in normal B-cells and a 'mutational gatekeeper', suppressing the aberrant mutations that drive lymphoid malignancy.

Attosecond physics at the nanoscale

Recently two emerging areas of research, attosecond and nanoscale physics, have started to come together. Attosecond physics deals with phenomena occurring when ultrashort laser pulses, with duration on the femto- and sub-femtosecond time scales, interact with atoms, molecules or solids. The laser-induced electron dynamics occurs natively on a timescale down to a few hundred or even tens of attoseconds (1 attosecond  =  1 as  =  10^-18 s), which is comparable with the optical field. For comparison, the revolution of an electron on a 1s orbital of a hydrogen atom is  ∼152 as. On the other hand, the second branch involves the manipulation and engineering of mesoscopic systems, such as solids, metals and dielectrics, with nanometric precision. Although nano-engineering is a vast and well-established research field on its own, the merger with intense laser physics is relatively recent. In this report on progress we present a comprehensive experimental and theoretical overview of physics that takes place when short and intense laser pulses interact with nanosystems, such as metallic and dielectric nanostructures. In particular we elucidate how the spatially inhomogeneous laser induced fields at a nanometer scale modify the laser-driven electron dynamics. Consequently, this has important impact on pivotal processes such as above-threshold ionization and high-order harmonic generation. The deep understanding of the coupled dynamics between these spatially inhomogeneous fields and matter configures a promising way to new avenues of research and applications. Thanks to the maturity that attosecond physics has reached, together with the tremendous advance in material engineering and manipulation techniques, the age of atto-nanophysics has begun, but it is in the initial stage. We present thus some of the open questions, challenges and prospects for experimental confirmation of theoretical predictions, as well as experiments aimed at characterizing the induced fields and the unique electron dynamics initiated by them with high temporal and spatial resolution.

Creation of a bovine herpes virus 1 (BoHV-1) quantitative particle standard by transmission electron microscopy and comparison with established standards for use in real-time PCR

Standards are pivotal for pathogen quantification by real-time PCR (qPCR); however, the creation of a complete and universally applicable virus particle standard is challenging. In the present study a procedure based on purification of bovine herpes virus type 1 (BoHV-1) and subsequent quantification by transmission electron microscopy (TEM) is described. Accompanying quantitative quality controls of the TEM preparation procedure using qPCR yielded recovery rates of more than 95% of the BoHV-1 virus particles on the grid used for virus counting, which was attributed to pre-treatment of the grid with 5% bovine albumin. To compare the value of the new virus particle standard for use in qPCR, virus counter based quantification and established pure DNA standards represented by a plasmid and an oligonucleotide were included. It could be shown that the numbers of virus particles, plasmid and oligonucleotide equivalents were within one log10 range determined on the basis of standard curves indicating that different approaches provide comparable quantitative values. However, only virus particles represent a complete, universally applicable quantitative virus standard that meets the high requirements of an RNA and DNA virus gold standard. In contrast, standards based on pure DNA have to be considered as sub-standard due to limited applications.

Air-liquid interface exposure to aerosols of poorly soluble nanomaterials induces different biological activation levels compared to exposure to suspensions

Background

Recently, much progress has been made to develop more physiologic in vitro models of the respiratory system and improve in vitro simulation of particle exposure through inhalation. Nevertheless, the field of nanotoxicology still suffers from a lack of relevant in vitro models and exposure methods to predict accurately the effects observed in vivo, especially after respiratory exposure. In this context, the aim of our study was to evaluate if exposing pulmonary cells at the air-liquid interface to aerosols of inhalable and poorly soluble nanomaterials generates different toxicity patterns and/or biological activation levels compared to classic submerged exposures to suspensions. Three nano-TiO₂ and one nano-CeO₂ were used. An exposure system was set up using VitroCell® devices to expose pulmonary cells at the air-liquid interface to aerosols. A549 alveolar cells in monocultures or in co-cultures with THP-1 macrophages were exposed to aerosols in inserts or to suspensions in inserts and in plates. Submerged exposures in inserts were performed, using similar culture conditions and exposure kinetics to the air-liquid interface, to provide accurate comparisons between the methods. Exposure in plates using classical culture and exposure conditions was performed to provide comparable results with classical submerged exposure studies. The biological activity of the cells (inflammation, cell viability, oxidative stress) was assessed at 24 h and comparisons of the nanomaterial toxicities between exposure methods were performed.

Results

Deposited doses of nanomaterials achieved using our aerosol exposure system were sufficient to observe adverse effects. Co-cultures were more sensitive than monocultures and biological responses were usually observed at lower doses at the air-liquid interface than in submerged conditions. Nevertheless, the general ranking of the nanomaterials according to their toxicity was similar across the different exposure methods used.

Conclusions

We showed that exposure of cells at the air-liquid interface represents a valid and sensitive method to assess the toxicity of several poorly soluble nanomaterials. We underlined the importance of the cellular model used and offer the possibility to deal with low deposition doses by using more sensitive and physiologic cellular models. This brings perspectives towards the use of relevant in vitro methods of exposure to assess nanomaterial toxicity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-016-0171-3) contains supplementary material, which is available to authorized users.

Transfer characteristics of subretinal visual implants: corneally recorded implant responses

PURPOSE

The subretinal Alpha IMS visual implant is a CE-approved medical device for restoration of visual functions in blind patients with end-stage outer retina degeneration. We present a method to test the function of the implant objectively in vivo using standard electroretinographic equipment and to assess the devices' parameter range for an optimal perception.

METHODS

Subretinal implant Alpha IMS (Retina Implant AG, Reutlingen, Germany) consists of 1500 photodiode-amplifier-electrode units and is implanted surgically into the subretinal space in blind retinitis pigmentosa patients. The voltages that regulate the amplifiers' sensitivity (V _gl) and gain (V _bias), related to the perception of contrast and brightness, respectively, are adjusted manually on a handheld power supply device. Corneally recorded implant responses (CRIR) to full-field illumination with long duration flashes in various implant settings for brightness gain (V _bias) and amplifiers' sensitivity (V _gl) are measured using electroretinographic setup with a Ganzfeld bowl in a protocol of increasing stimulus luminances up to 1000 cd/m².

RESULTS

CRIRs are a meaningful tool for assessing the transfer characteristic curves of the electronic implant in vivo monitoring the implants' voltage output as a function of log luminance in a sigmoidal shape. Changing the amplifiers' sensitivity (V _gl) shifts the curve left or right along the log luminance axis. Adjustment of the gain (V _bias) changes the maximal output. Contrast perception is only possible within the luminance range of the increasing slope of the function.

CONCLUSIONS

The technical function of subretinal visual implants can be measured objectively using a standard electroretinographic setup. CRIRs help the patient to optimise the perception by adjusting the gain and luminance range of the device and are a useful tool for clinicians to objectively assess the function of subretinal visual implants in vivo.

ID: 106: ALVEOLAR ESCAPE BY BACILLUS ANTHRACIS SPORES DOES NOT REQUIRE A CARRIER CELL AND IS NOT ALTERED BY LETHAL TOXIN

Rationale

The lung is the entry site for Bacillus anthracis in inhalation anthrax, the most deadly form of the disease. B. anthracis spores must escape from the alveolus, pass to the regional lymph nodes, germinate and enter the circulatory system as vegetative bacteria to cause systemic disease. Of the resident lung cells, three have been reported to take up B. anthracis spores: the antigen presenting cells (APC) alveolar macrophages and dendritic cells, and alveolar epithelial cells (AEC). Also, B. anthracis produces the exotoxins lethal factor and protective antigen (PA) which combine to form lethal toxin (LT), a metalloproteinase important in pathogenicity. The roles of carrier cells and the effects of B. anthracis toxins in escape of spores from the alveolus are unclear, especially in humans.

Methods

We employed a human lung organ culture model and a human A549 alveolar epithelial cell culture model, along with fluorescent confocal imaging to quantitate spore partitioning between APC and AEC, and the effects of B. anthracis LT and PA on this process. Cell types were distinguished by positive staining for HLA-DR (APC) and cytokeratin (AEC).

Results

We found that spores progressed through the lung slice over time, and that spore movement was not dependent on cell internalization. Both free and cell-associated spores moved through slices between 2 and 48 hrs of incubation. However, partitioning of spores between AEC, APC, and the extracellular space did not significantly change over this time. After 2 hrs, 4.7% of spores were in APC; 13.8% in AEC; and 81.5% were not cell-associated. By 48 hrs, 2.9% were in APC; 12.7% were in AEC; and 84.4% were not cell-associated. Spores also internalized in a non-uniform manner, with more variable spore internalization into AEC than into APC. At all incubation times, the majority of cell-associated spores were in AEC, not in APC. PA and LT did not affect transit of the spores through the lung tissue or the distribution of spores into AEC and APC. In A549 cells, spore internalization increased significantly after 24 hrs incubation. However, there was no statistically consistent effects of PA or LT on spore internalization in A549 cells.

Conclusions

Overall, our results support a “Jailbreak”-like model of spore escape from the alveolus that involves transient passage of spores, although this occurs through intact AEC. However, subsequent transport of spores by APC from the lung to the lymph nodes may occur.

Pollen-derived nonallergenic substances enhance Th2-induced IgE production in B cells

BACKGROUND

B cells play a central role in IgE-mediated allergies. In damaged airway epithelium, they are exposed directly to aeroallergens. We aimed to assess whether direct exposure of B cells to pollen constituents affects allergic sensitization.

METHODS

B cells from murine splenocytes and from blood samples of healthy donors were incubated for 8 days under Th2-like conditions with aqueous ragweed pollen extracts (Amb-APE) or its constituents. Secreted total IgM, IgG, and IgE was quantified by ELISA. Additionally, birch, grass, or pine-pollen extracts were tested. The number of viable cells was evaluated by ATP measurements. B-cell proliferation was measured by CFSE staining. IgE class switch was analyzed by quantitation of class switch transcripts. In an OVA/Alum i.p.-sensitization mouse model, Amb-APE was intranasally instilled for 11 consecutive days.

RESULTS

Upon Th2 priming of murine B cells, ragweed pollen extract caused a dose-dependent increase in IgE production, while IgG and IgM were not affected. The low-molecular-weight fraction and phytoprostane E1 (PPE1) increased IgE production, while Amb a 1 did not. PPE1 enhanced IgE also in human memory B cells. Under Th1 conditions, Amb-APE did not influence immunoglobulin secretion. The IgE elevation was not ragweed specific. It correlated with proliferation of viable B cells, but not with IgE class switch. In vivo, Amb-APE increased total IgE and showed adjuvant activity in allergic airway inflammation.

CONCLUSIONS

Aqueous pollen extracts, the protein-free fraction of Amb-APE, and the pollen-contained substance PPE1 specifically enhance IgE production in Th2-primed B cells. Thus, pollen-derived nonallergenic substances might be responsible for B-cell-dependent aggravation of IgE-mediated allergies.