Molecular responses of alveolar epithelial A549 cells to chronic exposure to titanium dioxide nanoparticles: A proteomic view

Abstract

Our results make possible the identification of new mechanisms that explain TiO2-NP toxicity upon long-term, in vitro exposure of A549 cells. It is the first article describing -omics results obtained with this experimental strategy. We show that this long-term exposure modifies the cellular content of proteins involved in functions including mitochondrial activity, intra- and extracellular trafficking, proteasome activity, glucose metabolism, and gene expression. Moreover we observe modification of content of proteins that activate the p53 pathway, which suggest the induction of a DNA damage response. Technically, our results show that exposure of A549 cells to a high concentration of TiO2-NPs leads to the identification of modulations of the same functional categories than exposure to low, more realistic concentrations. Still the intensity differs between these two exposure scenarios. We also show that chronic exposure to TiO2-NPs induces the modulation of cellular functions that have already been reported in the literature as being impacted in acute exposure scenarios. This proves that the exposure protocol in in vitro experiments related to nanoparticle toxicology might be cautiously chosen since inappropriate scenario may lead to inappropriate and/or incomplete conclusions.

Mass spectrometry-based proteomics for system-level characterization of biological responses to engineered nanomaterials

“…Alterations of key enzyme activities in metabolic pathways could be one mechanism that ENMs exert to affect metabolism. For example, protein abundances of both α-enolase and malate dehydrogenase, two enzymes involved in glucose metabolism, were decreased in human lung epithelial cells under long-term exposure to TiO 2 ENMs [74]. Similarly, glycolysis was observed as most impacted pathway in RAW264.7 macrophage cells exposed to CoO, an ENM inducing a relative high level of ROS [24].…”

“…Proteins involved in key mitochondrial activities, such as electron transfer in the respiratory chain, TCA cycle, and β-oxidation of fatty acid, decreased in abundance upon exposure to ENMs. The down-regulation of mitochondrial enzymes was further confirmed by measuring the membrane potential to indicate the decrease in mitochondrial activity [74,76]. …”

“…For example, a recent proteomics study discovered that the toxicity mechanism of CdTe ENMs involves down-regulation of topoisomerases, suggesting that CdTe ENMs may inhibit cellular DNA repair mechanisms [73]. In another study, the abundance of serine-threonine kinase receptor-associated protein, an activator of P53 for mediating DNA damage response, was observed to be increased in A549 cells exposed to TiO2 ENMs [74]. Alternatively, other ENMs were observed to induce upregulation of proteins in the ubiquitin-proteasome system, a major player in DNA repair [23].…”

SERENADE: safer and ecodesign research and education applied to nanomaterial development, the new generation of materials safer by design

“…We demonstrated upregulation of the genes encoding these pumps in Caco-2 cells exposed to A12. [34][35][36] The approaches used here, i.e. assessing both chronic and acute effects, and using cell lines that are aligned with the expected exposure routes, give a better assessment of potential effects than using less relevant cell lines.…”

Cellular Responses in Titanium Dioxide Nanoparticle Cytotoxicity Studies: Parts of the Map Waiting to be Composed

“…The involvement of tumour suppressor p53 in TNP induced apoptosis has been extensively studied in recent years. DNA damage resulting from TNP induced oxidative stress leads to the activation of p53 [2][3][4][5]29,44,53,54] , which triggers cell cycle arrest to prevent proliferation of cells with damaged DNA and ensure genomic stability [55] . In response to apoptosis inducing stress, p53 rapidly translocates to the mitochondria, where it interacts with the Bcl-2 family members, consequently upreg-DOI: 10.15436/2575-808X.17.1402…”