Multi-walled carbon nanotubes directly induce epithelial-mesenchymal transition in human bronchial epithelial cells via the TGF-β-mediated Akt-GSK-3β-SNAIL-1 signalling pathwayReportar como inadecuado

Multi-walled carbon nanotubes directly induce epithelial-mesenchymal transition in human bronchial epithelial cells via the TGF-β-mediated Akt-GSK-3β-SNAIL-1 signalling pathway - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Particle and Fibre Toxicology

, 13:27

First Online: 01 June 2016Received: 23 February 2015Accepted: 10 May 2016DOI: 10.1186-s12989-016-0138-4

Cite this article as: Polimeni, M., Gulino, G.R., Gazzano, E. et al. Part Fibre Toxicol 2015 13: 27. doi:10.1186-s12989-016-0138-4


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-β-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-β-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-β production. Experiments with neutralizing anti-TGF-β antibody, specific inhibitors of GSK-3β 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 μm 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-β secretion, Akt activation and GSK-3β 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 β-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-β and its intracellular effectors Akt-GSK-3β that activate the SNAIL-1 signalling pathway. This finding suggests potential novel targets in the development of therapeutic and preventive approaches.

KeywordsEpithelial-mesenchymal transition Lung fibrosis Epithelial cells Carbon nanotubes hazard Fibrogenic potential TGF-β SNAIL-1 signalling pathway Dario Ghigo Deceased.

Electronic supplementary materialThe online version of this article doi:10.1186-s12989-016-0138-4 contains supplementary material, which is available to authorized users.

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Autor: Manuela Polimeni - Giulia Rossana Gulino - Elena Gazzano - Joanna Kopecka - Arianna Marucco - Ivana Fenoglio - Federico Ce


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