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

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.

Combinatorial approaches to evaluate nanodiamond uptake and induced cellular fate

“…Specifically, previous studies showed that NDs functionalized with O-containing groups (either -OH or -CO 2 H groups) might lead to complex membrane–particle interactions [54] and their non-specific binding or clustering on the cationic sites of the plasma membrane, with subsequent endocytosis through a temperature-, energy-, and clathrin-dependent pathway [54–57]. The uptake of NDs is in contrast with both the uptake of SW- and MWCNTs respectively shown to lead to membrane damage, association with cytoskeleton structures and increased disruption of cellular integrity and organelles upon their translocation [18, 58]. …”

Mechanisms of carbon nanotube‐induced pulmonary fibrosis: a physicochemical characteristic perspective

“…In C57BL6 female mice, SWCNT exposure results in epithelial-derived fibroblasts composing almost half of the fibroblast population in the lung, demonstrating that epithelial-derived fibroblasts contribute significantly to CNT-induced pulmonary fibrosis 50 . In vitro studies of human epithelial cells treated with low doses of MWCNTs demonstrate an altered morphology of epithelial cells towards a mesenchymal cell phenotype 93 . Analysis of epithelial or mesenchymal specific markers E-cadherin, vimentin, α-SMA, and fibronectin protein expression can clarify the extent of differentiation of the epithelial-derived fibroblasts in EMT in human bronchoalveolar cells 93 .…”

Helical Carbon Nanotubes Alter F-Actin and ARP2 Distribution in Macrophages and Inhibit Pseudomonas aeruginosa Phagocytosis in an Intracellular Accumulation-Dependent Manner

“…Prior studies have demonstrated that CNTs may interfere with the cytoskeleton in HeLa, mast, and bronchial epithelial cells by forming bundle with F-actin filaments [20][21][22]. Thus, we examined if exposure to HCNTs altered F-actin and Arp2 distribution in RAW 264.7 macrophages.…”

“…Another study showed that SWCNTs altered the distribution of the actin cytoskeleton and clathrin in mast cells [21]. Furthermore, a separate study showed that multi walled CNTs (MWCNTs) altered both F-actin and tubulin expression and distribution in human bronchial epithelial cells [22]. Collectively, these studies suggest that CNT exposure results in alteration of F-actin distribution and/ or expression but this may be dependent on specific types of purified CNTs and cell lineages used.…”