Multi-walled carbon nanotube exposure alters protein expression in human keratinocytes

Carbon nanotubes have widespread applications, although little is known about their toxicity or interaction with cells. Recent studies in skin and lung reveal that carbon nanoparticles can cause toxicity. To generate a preliminary protein profile of nanotube exposure, we analyzed human epidermal keratinocytes (HEKs) exposed to multi-walled carbon nanotubes (MWCNTs) in cell culture using large-format, two-dimensional (2D) gel electrophoresis and mass spectrometry (MS). Compared with controls, 24 hours of MWCNT exposure altered the expression of 36 proteins (P < .01), whereas 106 were altered at 48 hours. At both time points, roughly 67% of the affected proteins were significantly down-regulated. Peptide mass fingerprinting identified most of the differentially expressed proteins, and the various protein identities reflected a complex cellular response to MWCNT exposure. In addition to proteins associated with metabolism, cell signaling, and stress, we observed a consistent effect on the expression of cytoskeletal elements and vesicular trafficking components. These data clearly show that MWCNTs are capable of altering protein expression in a target epithelial cell that constitutes a primary route of occupational exposure for manufactured nanotubes.