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BackgroundNanomaterials like cerium oxide and barium sulfate are frequently processed in industrial and consumer products and exposure of humans and other organisms is likely. Generally less information is given on health effects and toxicity, especially regarding long-term exposure to low nanoparticle doses. Since inhalation is still the major route of uptake the present study focused on pulmonary effects of CeO2NM-212 (0.1, 0.3, 1.0, 3.0 mg/m3) and BaSO4NM-220 nanoparticles (50.0 mg/m3) in a 90-day exposure setup. To define particle-related effects and potential mechanisms of action, observations in histopathology, bronchoalveolar lavage and immunohistochemistry were linked to pulmonary deposition and clearance rates. This further allows evaluation of potential overload related effects.ResultsLung burden values increased with increasing nanoparticle dose levels and ongoing exposure. At higher doses, cerium clearance was impaired, suggesting lung overload. Barium elimination was extremely rapid and without any signs of overload. Bronchoalveolar lavage fluid analysis and histopathology revealed lung tissue inflammation with increasing severity and post-exposure persistency for CeO2. Also, marker levels for genotoxicity and cell proliferation were significantly increased. BaSO4 showed less inflammation or persistency of effects and particularly affected the nasal cavity.ConclusionCeO2 nanoparticles penetrate the alveolar space and affect the respiratory tract after inhalation mainly in terms of inflammation. Effects at low dose levels and post-exposure persistency suggest potential long-term effects and a notable relevance for human health. The generated data might be useful to improve nanoparticle risk assessment and threshold value generation. Mechanistic investigations at conditions of non-overload and absent inflammation should be further investigated in future studies.

The aim of this study was to investigate the potential cytotoxicity of solid lipid nanoparticles (SLN) for human lung as a suitable drug delivery system (DDS). Therefore we used a human alveolar epithelial cell line (A549) and murine precision-cut lung slices (PCLS) to estimate the tolerable doses of these particles for lung cells. A549 cells (in vitro) and precision-cut lung slices (ex vivo) were incubated with SLN20 (20% phospholipids in the lipid matrix of the particles) and SLN50 (50% phospholipids in the lipid matrix of the particles) in increasing concentrations. The cytotoxic effects of SLN were evaluated in vitro by lactate dehydrogenase (LDH) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Vitality of lung slices was controlled by staining with calcein AM/ethidium homodimer 1 using confocal laser scanning microscopy and followed by quantitative image analysis with IMARIS software. A549 cell line revealed a middle effective concentration (EC(50)) for MTT assay for SLN20 of 4080 microg/ml and for SLN50 of 1520 microg/ml. The cytotoxicity in terms of LDH release showed comparable EC(50) values of 3431 microg/ml and 1253 microg/ml for SLN20 and SLN50, respectively. However, in PCLS we determined only SLN50 cytotoxic values with a concentration of 1500 microg/ml. The lung slices seem to be a more sensitive test system. SLN20 showed lower toxic values in all test systems. Therefore we conclude that SLN20 could be used as a suitable DDS for the lung, from a toxicological point of view.

A wide range of industrial chemicals can induce respiratory allergic reactions. Hence, there is an urgent need for methods identifying and characterizing the biological action of chemicals in the lung. Here, we present an easy, reliable alternative method to measure lung function changes ex vivo after exposure to chemical allergens and compare this to invasive in vivo measurements after sensitization with the industrial chemicals trimellitic anhydride (TMA) and 2,4-dinitrochlorobenzene (DNCB). Female BALB/c mice were sensitized epicutaneously with the respiratory allergen TMA and the contact sensitizer DNCB. The early allergic response to TMA and DNCB was registered in vivo and ex vivo on day 21 after inhalational challenge with dry standardized aerosols or after exposure of precision-cut lung slices (PCLS) to dissolved allergen. Airway hyperresponsiveness (AHR) to increasing doses of methacholine (MCh) was measured on the next day in vivo and ex vivo. Bronchoalveolar lavage (BAL) was performed for immunological characterization of local inflammation. TMA-sensitized mice showed AHR to MCh in vivo (ED(50): 0.06 microg MCh vs. 0.21 microg MCh in controls) and in PCLS (EC(50): 0.24 microM MCh vs. 0.4 microM MCh). TMA-treated animals showed increased numbers of eosinophils (12.8 x 10(4) vs. 0.7 x 10(4)) and elevated eotaxin-2 concentrations (994 pg/ml vs. 167 pg/ml) in BAL fluid 24 h after allergen challenge. In contrast, none of these parameters differed after sensitization with DNCB. The present study suggests that the effects of low molecular weight allergens, like TMA and DNCB, on ex vivo lung functions tested in PCLS reflect the in vivo situation.

BackgroundCarbon black nanoparticles (CBNP) are mainly composed of carbon, with a small amount of other elements (including hydrogen and oxygen). The toxicity of CBNP has been attributed to their large surface area, and through adsorbing intrinsically toxic substances, such as polycyclic aromatic hydrocarbons (PAH). It is not clear whether a PAH surface coating changes the toxicological properties of CBNP by influencing their physicochemical properties, through the specific toxicity of the surface-bound PAH, or by a combination of both.MethodsPrintex®90 (P90) was used as CBNP; the comparators were P90 coated with either benzo[a]pyrene (BaP) or 9-nitroanthracene (9NA), and soot from acetylene combustion that bears various PAHs on the surface (AS-PAH). Oxidative stress and IL-8/KC mRNA expression were determined in A549 and bronchial epithelial cells (16HBE14o-, Calu-3), mouse intrapulmonary airways and tracheal epithelial cells. Overall toxicity was tested in a rat inhalation study according to Organization for Economic Co-operation and Development (OECD) criteria. Effects on cytochrome monooxygenase (Cyp) mRNA expression, cell viability and mucociliary clearance were determined in acute exposure models using explanted murine trachea.ResultsAll particles had similar primary particle size, shape, hydrodynamic diameter and ζ-potential. All PAH-containing particles had a comparable specific surface area that was approximately one third that of P90. AS-PAH contained a mixture of PAH with expected higher toxicity than BaP or 9NA. PAH-coating reduced some effects of P90 such as IL-8 mRNA expression and oxidative stress in A549 cells, granulocyte influx in the in vivo OECD experiment, and agglomeration of P90 and mucus release in the murine trachea ex vivo. Furthermore, P90-BaP decreased particle transport speed compared to P90 at 10 μg/ml. In contrast, PAH-coating induced IL-8 mRNA expression in bronchial epithelial cell lines, and Cyp mRNA expression and apoptosis in tracheal epithelial cells. In line with the higher toxicity compared to P90-BaP and P90-9NA, AS-PAH had the strongest biological effects both ex vivo and in vivo. ConclusionsOur results demonstrate that the biological effect of CBNP is determined by a combination of specific surface area and surface-bound PAH, and varies in different target cells.Electronic supplementary materialThe online version of this article (doi:10.1186/s12989-017-0189-1) contains supplementary material, which is available to authorized users.