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Multiwalled carbon nanotubes induce altered morphology and loss of barrier function in human bronchial epithelium at noncytotoxic doses

Authors Snyder RJ, Hussain S, Rice A, Garantziotis S

Received 8 April 2014

Accepted for publication 1 June 2014

Published 25 August 2014 Volume 2014:9(1) Pages 4093—4105


Checked for plagiarism Yes

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Peer reviewer comments 3

Ryan J Snyder, Salik Hussain, Annette B Rice, Stavros Garantziotis

Clinical Research Unit, National Institute of Environmental Health Sciences/National Institutes of Health, Research Triangle Park, NC, USA

Abstract: Multiwalled carbon nanotubes (MWCNTs) have seen increasing application in consumer products over the past decade, resulting in an increasing risk of human exposure. While numerous toxicological studies have been performed using acute high doses of various carbonaceous nanomaterials, the effects of longer-term, low doses of MWCNTs remain relatively unexplored. This study examined bronchoscopy-derived healthy human bronchial epithelial cells exposed in submerged culture to noncytotoxic doses of MWCNTs over 7 days. Under these conditions, doses as low as 3 µg/mL caused altered cell morphology, superficially resembling fibroblasts. Electrical impedance of the epithelial monolayer was greatly reduced following MWCNT exposure. However, Western blot and polymerase chain reaction showed no elevated expression of the fibroblast markers, vimentin, α-smooth muscle actin, or fibronectin, indicating that a mechanism other than epithelial–mesenchymal transition may be responsible for the changes. Phalloidin and tubulin immunostaining showed disruption of the cytoskeleton, and confocal imaging showed a reduction of the tight junction proteins, zona occludens 1 and occludin. We propose that MWCNTs interfere with the cytoskeleton of the lung epithelium, which can result in a harmful reduction in barrier function over time, even at noncytotoxic doses.

Keywords: multiwalled carbon nanotubes, bronchial epithelium, transepithelial electrical resistance, cytoskeleton, morphology, human

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