Dataset Information

Free radical scavenging and formation by multi-walled carbon nanotubes in cell free conditions and in human bronchial epithelial cells.

ABSTRACT:

Background

Certain multi-walled carbon nanotubes (MWCNTs) have been shown to elicit asbestos-like toxicological effects. To reduce needs for risk assessment it has been suggested that the physicochemical characteristics or reactivity of nanomaterials could be used to predict their hazard. Fibre-shape and ability to generate reactive oxygen species (ROS) are important indicators of high hazard materials. Asbestos is a known ROS generator, while MWCNTs may either produce or scavenge ROS. However, certain biomolecules, such as albumin - used as dispersants in nanomaterial preparation for toxicological testing in vivo and in vitro - may reduce the surface reactivity of nanomaterials.

Methods

Here, we investigated the effect of bovine serum albumin (BSA) and cell culture medium with and without BEAS 2B cells on radical formation/scavenging by five MWCNTs, Printex 90 carbon black, crocidolite asbestos, and glass wool, using electron spin resonance (ESR) spectroscopy and linked this to cytotoxic effects measured by trypan blue exclusion assay. In addition, the materials were characterized in the exposure medium (e.g. for hydrodynamic size-distribution and sedimentation rate).

Results

The test materials induced highly variable cytotoxic effects which could generally be related to the abundance and characteristics of agglomerates/aggregates and to the rate of sedimentation. All carbon nanomaterials were found to scavenge hydroxyl radicals (•OH) in at least one of the solutions tested. The effect of BSA was different among the materials. Two types of long, needle-like MWCNTs (average diameter >74 and 64.2 nm, average length 5.7 and 4.0 ?m, respectively) induced, in addition to a scavenging effect, a dose-dependent formation of a unique, yet unidentified radical in both absence and presence of cells, which also coincided with cytotoxicity.

Conclusions

Culture medium and BSA affects scavenging/production of •OH by MWCNTs, Printex 90 carbon black, asbestos and glass-wool. An unidentified radical is generated by two long, needle-like MWCNTs and these two CNTs were more cytotoxic than the other CNTs tested, suggesting that this radical could be related to the adverse effects of MWCNTs.

SUBMITTER: Nymark P

PROVIDER: S-EPMC3933237 | biostudies-literature | 2014 Jan

REPOSITORIES: biostudies-literature

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Publications

Free radical scavenging and formation by multi-walled carbon nanotubes in cell free conditions and in human bronchial epithelial cells.

Nymark Penny P Jensen Keld Alstrup KA Suhonen Satu S Kembouche Yahia Y Vippola Minnamari M Kleinjans Jos J Catalán Julia J Norppa Hannu H van Delft Joost J Briedé Jacob Jan JJ

Particle and fibre toxicology 20140118

<h4>Background</h4>Certain multi-walled carbon nanotubes (MWCNTs) have been shown to elicit asbestos-like toxicological effects. To reduce needs for risk assessment it has been suggested that the physicochemical characteristics or reactivity of nanomaterials could be used to predict their hazard. Fibre-shape and ability to generate reactive oxygen species (ROS) are important indicators of high hazard materials. Asbestos is a known ROS generator, while MWCNTs may either produce or scavenge ROS. H ...[more]

PMID: 24438343

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Project description:BackgroundMulti-walled carbon nanotubes (MWCNT) are currently under intense toxicological investigation due to concern on their potential health effects. Current in vitro and in vivo data indicate that MWCNT exposure is strongly associated with lung toxicity (inflammation, fibrosis, granuloma, cancer and airway injury) and their effects might be comparable to asbestos-induced carcinogenesis. Although fibrosis is a multi-origin disease, epithelial-mesenchymal transition (EMT) is recently recognized as an important pathway in cell transformation. It is known that MWCNT exposure induces EMT through the activation of the TGF-?/Smad signalling pathway thus promoting pulmonary fibrosis, but the molecular mechanisms involved are not fully understood. In the present work we propose a new mechanism involving a TGF-?-mediated signalling pathway.MethodsHuman bronchial epithelial cells were incubated with two different MWCNT samples at various concentrations for up to 96 h and several markers of EMT were investigated. Quantitative real time PCR, western blot, immunofluorescent staining and gelatin zymographies were performed to detect the marker protein alterations. ELISA was performed to evaluate TGF-? production. Experiments with neutralizing anti-TGF-? antibody, specific inhibitors of GSK-3? and Akt and siRNA were carried out in order to confirm their involvement in MWCNT-induced EMT. In vivo experiments of pharyngeal aspiration in C57BL/6 mice were also performed. Data were analyzed by a one-way ANOVA with Tukey's post-hoc test.ResultsFully characterized MWCNT (mean length?<?5 ?m) are able to induce EMT in an in vitro human model (BEAS-2B cells) after long-term incubation at sub-cytotoxic concentrations. MWCNT stimulate TGF-? secretion, Akt activation and GSK-3? inhibition, which induces nuclear accumulation of SNAIL-1 and its transcriptional activity, thus contributing to switch on the EMT program. Moreover, a significant increment of nuclear ?-catenin - due to E-cadherin repression and following translocation to nucleus - likely reinforces signalling for EMT promotion. In vivo results supported the occurrence of pulmonary fibrosis following MWCNT exposure.ConclusionsWe demonstrate a new molecular mechanism of MWCNT-mediated EMT, which is Smad-independent and involves TGF-? and its intracellular effectors Akt/GSK-3? that activate the SNAIL-1 signalling pathway. This finding suggests potential novel targets in the development of therapeutic and preventive approaches.

Project description:The studies focusing on magnesium oxychloride cement (MOC) composites have recently become fairly widespread because of MOC's excellent mechanical properties and environmental sustainability. Numerous fillers, admixtures and nano-dopants were studied in order to improve the overall performance of MOC-based derivatives. Some of them exhibited specific flaws, such as a tendency to aggregate, increase in porosity, aeration of the composite matrix, depreciation in water resistance and mechanical strength, etc. In this manuscript, MOC-based composites doped by multi-walled carbon nanotubes (MWCNTs) are designed and tested. In order to modify the final properties of composites, diatomite was admixed as partial substitution of MgO, which was used in the composition of the researched material in excess, i.e., the majority of MgO constituted part of MOC and the rest served as fine filler. The composites were subjected to the broad experimental campaign that covered SEM (scanning electron microscopy), EDS (energy dispersive spectroscopy), HR-TEM (high-resolution transmission electron microscopy), XRD (X-ray diffraction), OM (optical microscopy) and STA-MS (simultaneous thermal analysis with mass spectroscopy). For 28 days hardened samples, macrostructural and microstructural parameters, mechanical properties, hygric and thermal characteristics were experimentally assessed. The incorporation of MWCNTs and diatomite resulted in the significant enhancement of composites' compactness, mechanical strength and stiffness and reduction in water absorption and rate of water imbibition. The thermal properties of the enriched MOC composites yielded interesting values and provided information for future modification of thermal performance of MOC composites with respect to their specific use in practice, e.g., in passive moderation of indoor climate. The combination of MWCNTs and diatomite represents a valuable modification of the MOC matrix and can be further exploited in the design and development of advanced building materials and components.

Dataset Information

Free radical scavenging and formation by multi-walled carbon nanotubes in cell free conditions and in human bronchial epithelial cells.

Background

Methods

Results

Conclusions

Publications

Free radical scavenging and formation by multi-walled carbon nanotubes in cell free conditions and in human bronchial epithelial cells.

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