Progressive severe lung injury by zinc oxide nanoparticles; the role of Zn2+ dissolution inside lysosomes

Background: Large production volumes of zinc oxide nanoparticles (ZnONP) might be anticipated to pose risks, of accidental inhalation in occupational and even in consumer settings. Herein, we further investigated the pathological changes induced by ZnONP and their possible mechanism of action.Methods: Two doses of ZnONP (50 and 150 cm(2)/rat) were intratracheally instilled into the lungs of rats with assessments made at 24 h, 1 wk, and 4 wks after instillation to evaluate dose- and time-course responses. Assessments included bronchoalveolar lavage (BAL) fluid analysis, histological analysis, transmission electron microscopy, and IgE and IgA measurement in the serum and BAL fluid. To evaluate the mechanism, alternative ZnONP, ZnONP-free bronchoalveolar lavage exudate, and dissolved Zn2+ (92.5 mu g/rat) were also instilled to rats. Acridine orange staining was utilized in macrophages in culture to evaluate the lysosomal membrane destabilization by NP.Results: ZnONP induced eosinophilia, proliferation of airway epithelial cells, goblet cell hyperplasia, and pulmonary fibrosis. Bronchocentric interstitial pulmonary fibrosis at the chronic phase was associated with increased myofibroblast accumulation and transforming growth factor-beta positivity. Serum IgE levels were up-regulated by ZnONP along with the eosinophilia whilst serum IgA levels were down-regulated by ZnONP. ZnONP are rapidly dissolved under acidic conditions (pH 4.5) whilst they remained intact around neutrality (pH 7.4). The instillation of dissolved Zn2+ into rat lungs showed similar pathologies (eg., eosinophilia, bronchocentric interstitial fibrosis) as were elicited by ZnONP. Lysosomal stability was decreased and cell death resulted following treatment of macrophages with ZnONP in vitro.Conclusions: We hypothesise that rapid, pH-dependent dissolution of ZnONP inside of phagosomes is the main cause of ZnONP-induced diverse progressive severe lung injuries

Comparative absorption, distribution, and excretion of titanium dioxide and zinc oxide nanoparticles after repeated oral administration

Background The in vivo kinetics of nanoparticles is an essential to understand the hazard of nanoparticles. Here, the absorption, distribution, and excretion patterns of titanium dioxide (TiO2) and zinc oxide (ZnO) nanoparticles following oral administration were evaluated. Methods Nanoparticles were orally administered to rats for 13 weeks (7 days/week). Samples of blood, tissues (liver, kidneys, spleen, and brain), urine, and feces were obtained at necropsy. The level of Ti or Zn in each sample was measured using inductively coupled plasma-mass spectrometry. Results TiO2 nanoparticles had extremely low absorption, while ZnO nanoparticles had higher absorption and a clear dose-response curve. Tissue distribution data showed that TiO2 nanoparticles were not significantly increased in sampled organs, even in the group receiving the highest dose (1041.5 mg/kg body weight). In contrast, Zn concentrations in the liver and kidney were significantly increased compared with the vehicle control. ZnO nanoparticles in the spleen and brain were minimally increased. Ti concentrations were not significantly increased in the urine, while Zn levels were significantly increased in the urine, again with a clear dose-response curve. Very high concentrations of Ti were detected in the feces, while much less Zn was detected in the feces. Conclusions Compared with TiO2 nanoparticles, ZnO nanoparticles demonstrated higher absorption and more extensive organ distribution when administered orally. The higher absorption of ZnO than TiO2 nanoparticles might be due to the higher dissolution rate in acidic gastric fluid, although more thorough studies are needed

Predictive value of in vitro assays depends on the mechanism of toxicity of metal oxide nanoparticles

BACKGROUND: Hazard identification for risk assessment of nanoparticles (NPs) is mainly composed of in vitro cell-based assays and in vivo animal experimentation. The rapidly increasing number and functionalizations of NPs makes in vivo toxicity tests undesirable on both ethical and financial grounds, creating an urgent need for development of in vitro cell-based assays that accurately predict in vivo toxicity and facilitate safe nanotechnology. METHODS: In this study, we used 9 different NPs (CeO(2), TiO(2), carbon black, SiO(2), NiO, Co(3)O(4), Cr(2)O(3), CuO, and ZnO). As an in vivo toxicity endpoint, the acute lung inflammogenicity in a rat instillation model was compared with the in vitro toxicity endpoints comprising cytotoxicity, pro-inflammatory cytokine expression, or haemolytic potential. For in vitro assays, 8 different cell-based assays were used including epithelial cells, monocytic/macrophage cells, human erythrocytes, and combined culture. RESULTS: ZnO and CuO NPs acting via soluble toxic ions showed positive results in most of assays and were consistent with the lung inflammation data. When compared in in vitro assays at the same surface area dose (30 cm(2)/mL), NPs that were low solubility and therefore acting via surface reactivity had no convincing activity, except for CeO(2) NP. Cytotoxicity in differentiated peripheral blood mononuclear cells was the most accurate showing 89% accuracy and 11% false negativity in predicting acute lung inflammogenicity. However, the haemolysis assay showed 100% consistency with the lung inflammation if any dose, having statistical significance was considered positivity. Other cell-based in vitro assays showed a poorer correlation with in vivo inflammogenicity. CONCLUSIONS: Based on the toxicity mechanisms of NPs, two different approaches can be applied for prediction of in vivo lung inflammogenicity. Most in vitro assays were good at detecting NPs that act via soluble ions (i.e., ZnO and CuO NP). However, in vitro assays were limited in detecting NPs acting via surface reactivity as their mechanism of toxicity, except for the haemolysis assay

Metal Oxide Nanoparticles Induce Unique Inflammatory Footprints in the Lung: Important Implications for Nanoparticle Testing

BACKGROUND: Metal oxide nanoparticles (NPs) have been widely used in industry, cosmetics, and biomedicine. OBJECTIVES: We examined hazards of several well-characterized high production volume NPs because of increasing concern about occupational exposure via inhalation. METHODS: A panel of well-characterized NPs [cerium oxide (CeO(2)NP), titanium dioxide (TiO(2)NP), carbon black (CBNP), silicon dioxide (SiO(2)NP), nickel oxide (NiONP), zinc oxide (ZnONP), copper oxide (CuONP), and amine-modified polystyrene beads] was instilled into lungs of rats. We evaluated the inflammation potencies of these NPs 24 hr and 4 weeks postinstillation. For NPs that caused significant inflammation at 24 hr, we then investigated the characteristics of the inflammation. All exposures were carried out at equal-surface-area doses. RESULTS: Only CeO(2)NP, NiONP, ZnONP, and CuONP were inflammogenic to the lungs of rats at the high doses used. Strikingly, each of these induced a unique inflammatory footprint both acutely (24 hr) and chronically (4 weeks). Acutely, patterns of neutrophil and eosinophil infiltrates differed after CeO(2)NP, NiONP, ZnONP, and CuONP treatment. Chronic inflammatory responses also differed after 4 weeks, with neutrophilic, neutrophilic/lymphocytic, eosinophilic/fibrotic/granulomatous, and fibrotic/granulomatous inflammation being caused respectively by CeO(2)NP, NiONP, ZnONP, and CuONP. CONCLUSION: Different types of inflammation imply different hazards in terms of pathology, risks, and risk severity. In vitro testing could not have differentiated these complex hazard outcomes, and this has important implications for the global strategy for NP hazard assessment. Our results demonstrate that NPs cannot be viewed as a single hazard entity and that risk assessment should be performed separately and with caution for different NPs

Interferometric Fiber Optic Sensors

Fiber optic interferometers to sense various physical parameters including temperature, strain, pressure, and refractive index have been widely investigated. They can be categorized into four types: Fabry-Perot, Mach-Zehnder, Michelson, and Sagnac. In this paper, each type of interferometric sensor is reviewed in terms of operating principles, fabrication methods, and application fields. Some specific examples of recently reported interferometeric sensor technologies are presented in detail to show their large potential in practical applications. Some of the simple to fabricate but exceedingly effective Fabry-Perot interferometers, implemented in both extrinsic and intrinsic structures, are discussed. Also, a wide variety of Mach-Zehnder and Michelson interferometric sensors based on photonic crystal fibers are introduced along with their remarkable sensing performances. Finally, the simultaneous multi-parameter sensing capability of a pair of long period fiber grating (LPG) is presented in two types of structures; one is the Mach-Zehnder interferometer formed in a double cladding fiber and the other is the highly sensitive Sagnac interferometer cascaded with an LPG pair

In situ hybridization for the detection of the apxIV gene in the lungs of pigs experimentally infected with twelve Actinobacillus pleuropneumoniae serotypes

The detection of the apxIV gene in lung tissues from pigs experimentally infected with the 12 major A. pleuropneumoniae serotype (1 to 12) reference strains was studied by in situ hybridization using a non-radioactive digoxigenin-labeled DNA probe. In situ hybridization produced a distinct positive signal in all pigs inoculated with the 12 A. pleuropneumoniae serotypes. Positive hybridization typically exhibited a dark-brown to black reaction product in intracellular and extracellular locations, without background staining. A strong hybridization signal was seen in degenerated alveolar leukocytes (“oat cells”) adjacent to the foci of coagulative necrosis and in the alveolar spaces. The in situ hybridization methodology developed for the detection of the apxIV gene is a valuable tool for the diagnosis of porcine pleuropneumonia caused by A. pleuropneumoniae when only formalin-fixed tissues are submitted for diagnosis.Détection par hybridation in situ du gène apxIV dans les poumons de porcs infectés expérimentalement par douze sérotypes de Actinobacillus pleuropneumoniae. La détection du gène apxIV dans les tissus pulmonaires de porcs infectés expérimentalement par les douze sérotypes majeurs des souches de référence (1 à 12) de Actinobacillus pleuropneumoniae a été effectuée par hybridation in situ utilisant une sonde à ADN non radioactive marquée à la digoxigénine. L'hybridation in situ a produit un signal positif distinct chez tous les porcs inoculés par les douze sérotypes de A. pleuropneumoniae. Un résultat positif d'hybridation entraînait typiquement un produit de réaction marron foncé à noir localisé en intra- et en extra-cellulaire, sans bruit de fond. Un signal fort d'hybridation a été observé dans les leucocytes alvéolaires dégénérés adjacents aux foyers de nécrose et dans les espaces alvéolaires. La méthode d'hybridation in situ développée pour la détection du gène apxIV est un outil précieux pour le diagnostic de la pleuropneumonie porcine causée par A. pleuropneumoniae lorsque seuls les tissus fixés dans le formol sont soumis pour le diagnostic

Zinc oxide nanoparticles trigger autophagy-mediated cell death through activating lysosomal TRPML1 in normal kidney cells

Zinc oxide nanoparticles (ZnO NPs) have been widely used in various materials including sunscreens, cosmetics, over-the-counter topical skin products, and pigments. As traces of the used ZnO NPs have been found in the kidney, it is crucial to uncover their potential risks. The aim of this study is to elucidate detrimental effects of ZnO NPs and the molecular mechanism behind their renal toxicity. Cytotoxic effects were measured by MTT assay after HK2 cells were exposed to ZnO NPs for 24 h and IC50 value was determined. ROS and intracellular Zn2+ levels were detected by flow cytometry, and localization of Zn2+ and lysosome was determined by confocal microscopy. Occurrence of autophagy and detection of autophagic flux were determined by Western blot and confocal microscopy, respectively. We performed unpaired student t test for two groups, and one-way ANOVA with Tukey’s post hoc for over three groups. ZnO NPs induced cell death in human renal proximal tubule epithelial cells, HK2. Cytosolic Zn2+ caused autophagy-mediated cell death rather than apoptosis. Cytosolic Zn2+ processed in lysosome was released by TRPML1, and inhibition of TRPML1 significantly decreased autophagic flux and cell death. The findings of this study suggest that ZnO NPs strongly induce autophagy-mediated cell death in human kidney cells. Controlling TRPML1 can be potentially used to prevent the kidney from ZnO NPs-induced toxicity