Project description:Understanding toxicity pathways of engineered nanomaterials (ENM) has recently been brought forward as a key step in 21st century ENM risk assessment. Molecular mechanisms linked to phenotypic end points is a step towards the development of toxicity tests based on key events, which may allow for grouping of ENM according to their mechanisms of action. This study identified molecular mechanisms underlying mitochondrial dysfunction in human bronchial epithelial BEAS 2B cells following exposure to one of the most studied multi-walled carbon nanotubes (MWCNTs; Mitsui-7). Asbestos was used as a positive control and a non-carcinogenic glass wool material was included as a negative fibre control. Decreased mitochondrial membrane potential (MMP↓) was observed for MWCNTs at a biologically relevant dose (0.25 μg/cm2) and for asbestos at 2 μg/cm2, but not for glass wool. Extensive temporal transcriptomic and microRNA expression analyses identified a 330-gene signature related to MWCNT- and asbestos-induced MMP↓. Fourty-nine of the MMP↓-associated genes showed highly similar expression patterns over time (six time points) and the majority was found to be regulated by two transcription factors strongly involved in mitochondrial homeostasis, APP and NRF1. In addition, four miRNAs were associated with MMP↓ and one of them, miR-1275, was found to negatively correlate with a large part of the MMP↓-associated genes. Cellular processes such as gluconeogenesis, glucose metabolism, mitochondrial LC-fatty acid β-oxidation and spindle microtubule function were enriched among the MMP↓-associated genes and miRNAs. These results are expected to be useful in the identification of key events in ENM-related toxicity pathways for the development of molecular screening techniques. BEAS 2B cells were exposed to 0.25 and 2 μg/cm2 of MWCNT, asbestos and glass wool (MMVF10) for 1, 4, 6, 12, 24 and 48 hours. Three independent experiments were performed to obtain a total of 3 replicates for each experimental condition. Non-exposed cells for each time point were used as controls. Three samples failed to give adequate quality RNA and a total of 123 samples were hybridized to Agilent miRNA arrays.

Project description:Understanding toxicity pathways of engineered nanomaterials (ENM) has recently been brought forward as a key step in 21st century ENM risk assessment. Molecular mechanisms linked to phenotypic end points is a step towards the development of toxicity tests based on key events, which may allow for grouping of ENM according to their mechanisms of action. This study identified molecular mechanisms underlying mitochondrial dysfunction in human bronchial epithelial BEAS 2B cells following exposure to one of the most studied multi-walled carbon nanotubes (MWCNTs; Mitsui-7). Asbestos was used as a positive control and a non-carcinogenic glass wool material was included as a negative fibre control. Decreased mitochondrial membrane potential (MMP↓) was observed for MWCNTs at a biologically relevant dose (0.25 μg/cm2) and for asbestos at 2 μg/cm2, but not for glass wool. Extensive temporal transcriptomic and microRNA expression analyses identified a 330-gene signature related to MWCNT- and asbestos-induced MMP↓. Fourty-nine of the MMP↓-associated genes showed highly similar expression patterns over time (six time points) and the majority was found to be regulated by two transcription factors strongly involved in mitochondrial homeostasis, APP and NRF1. In addition, four miRNAs were associated with MMP↓ and one of them, miR-1275, was found to negatively correlate with a large part of the MMP↓-associated genes. Cellular processes such as gluconeogenesis, glucose metabolism, mitochondrial LC-fatty acid β-oxidation and spindle microtubule function were enriched among the MMP↓-associated genes and miRNAs. These results are expected to be useful in the identification of key events in ENM-related toxicity pathways for the development of molecular screening techniques. BEAS 2B cells were exposed to 0.25 and 2 μg/cm2 of MWCNT, asbestos and glass wool (MMVF10) for 1, 4, 6, 12, 24 and 48 hours. Three independent experiments were performed to obtain a total of 3 replicates for each experimental condition. Non-exposed cells for each time point were used as controls. Three samples failed to give adequate quality RNA and a total of 123 samples were hybridized to Affymetrix GeneChip U133 Plus 24-array plates.

Project description:Human mesothelial cells (LP9/TERT-1) were exposed to low and high (15 and 75 μm2/cm2 dish) equal surface area concentrations of crocidolite asbestos, nonfibrous talc, fine titanium dioxide (TiO2), or glass beads for 8 or 24 h. RNA was then isolated for Affymetrix microarrays, GeneSifter analysis and QRT-PCR. Gene changes by asbestos were concentration- and time-dependent. At low nontoxic concentrations, asbestos caused significant changes in mRNA expression of 29 genes at 8 h and 205 genes at 24 h, whereas changes in mRNA levels of 236 genes occurred in cells exposed to high concentrations of asbestos for 8 h. Human primary pleural mesothelial cells also showed the same patterns of increased gene expression by asbestos. Nonfibrous talc at low concentrations in LP9/TERT-1 mesothelial cells caused increased expression of 1 gene Activating Transcription Factor 3 (ATF3) at 8 h and no changes at 24 h, whereas expression levels of 30 genes were elevated at 8 h at high talc concentrations. Fine TiO2 or glass beads caused no changes in gene expression. In human ovarian epithelial (IOSE) cells, asbestos at high concentrations elevated expression of 2 genes (NR4A2, MIP2) at 8 h and 16 genes at 24 h that were distinct from those elevated in mesothelial cells. Since ATF3 was the most highly expressed gene by asbestos, its functional importance in cytokine production by LP9/TERT-1 cells was assessed using siRNA approaches. Results reveal that ATF3 modulates production of inflammatory cytokines (IL-1β, IL-13, G-CSF) and growth factors (VEGF and PDGF-BB) in human mesothelial cells. Microarrays were performed on samples from 3 independent experiments. All cell types, time points, and mineral types and concentrations were included in all 3 experiments. For each experiment, n=3 dishes were pooled into one sample per treatment group. Each of the pooled samples was analyzed on a separate array, i.e., n=3 arrays per condition (3 independent biological replicates). We tested the hypothesis that alteration in gene expression in human cells correlate with mineral pathogenicity. We used GeneSifter program to analyze our data and pairwise analysis showed that number of gene changes correlate with toxicity of pathogenic minerals. While non-pathogenic minerals glass beads and fine TiO2 treatment to cell resulted in no gene change, crocidolite asbestos caused maximum number of gene changes followed by talc.

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Extensive temporal transcriptome and microRNA analyses identify molecular mechanisms underlying mitochondrial dysfunction induced by multi-walled carbon nanotubes in human lung cells (miRNA)

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