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This Article Full Text Full Text (PDF) All Versions of this Article: 294/2/L358    most recent 00323.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Unfried, K. Articles by Abel, J. Search for Related Content PubMed PubMed Citation Articles by Unfried, K. Articles by Abel, J.

Carbon nanoparticle-induced lung epithelial cell proliferation is mediated by receptor-dependent Akt activation

Toxicology Group, Institut für Umweltmedizinische Forschung, Düsseldorf, Germany

Submitted 14 August 2007 ; accepted in final form 12 December 2007

Treatment of lung epithelial cells with different kinds of nano-sized particles leads to cell proliferation. Because bigger particles fail to induce this reaction, it is suggested that the special surface properties, due to the extremely small size of these kinds of materials, is the common principle responsible for this specific cell reaction. Here the activation of the protein kinase B (Akt) signaling cascade by carbon nanoparticles was investigated with regard to its relevance for proliferation. Kinetics and dose-response experiments demonstrated that Akt is specifically activated by nanoparticulate carbon particles in rat alveolar type II epithelial cells as well as in human bronchial epithelial cells. This pathway appeared to be dependent on epidermal growth factor receptor and β₁-integrins. The activation of Akt by these receptors is known to be a feature of adhesion-dependent signaling. However, intracellular proteins described in this context (focal adhesion kinase pp125^FAK and integrin-linked kinase) were not activated, indicating a specific signaling mechanism. Inhibitor studies demonstrate that nanoparticle-induced proliferation is mediated by phosphoinositide 3-kinases and Akt. Moreover, overexpression of mutant Akt, as well as pretreatment with an Akt inhibitor, reduced nanoparticle-specific ERK1/2 phosphorylation, which is decisive for nanoparticle-induced proliferation. With this report, we describe the activation of a pathway by carbon nanoparticles that was so far known to be triggered by ligand receptor binding or on cell adhesion to extracellular matrix proteins.

nanoparticles; carbon black; protein kinase B; integrins; epidermal growth factor receptor