Another endpoint for nano titanium dioxide

BrooklynDodger(s) comment: Continuing to run nano particles through novel test systems. Historically, titanium dioxide is the negative control for lung damage. What's needed is a systematic testing of a spectrum of particles in the same system - full size titanium dioxide, silica (a known human carcinogen), diesel, carbon materials. So that relative potency can be measured.

Toxicology and Applied Pharmacology
Volume 241, Issue 2, 1 December 2009, Pages 182-194

Disturbed mitotic progression and genome segregation are involved in cell transformation mediated by nano-TiO2 long-term exposure

Shing Huang^a, Pin Ju Chueh^a, Yun-Wei Lin^b, Tung-Sheng Shih^c and Show-Mei Chuang^{a, ,}

^aInstitute of Biomedical Sciences, National Chung Hsing University, 250 Kuo-Kuang Road, Taichung 402, Taiwan

^bMolecular Oncology Laboratory, Department of Biochemical Science and Technology, National Chiayi University, Chiayi, Taiwan

^cInstitute of Occupational Safety and Healthy Council of Labor Affairs, Executive Yuan, Taipei 221, Taiwan

Received 9 March 2009;

revised 10 August 2009;

accepted 11 August 2009.

Available online 18 August 2009.

Abstract

Titanium dioxide (TiO2) nano-particles (< 100 nm in diameter) have been of interest in a wide range of applications, such as in cosmetics and pharmaceuticals because of their low toxicity. However, recent studies have shown that TiO2 nano-particles (nano-TiO2) induce cytotoxicity and genotoxicity in various lines of cultured cells as well as tumorigenesis in animal models. The biological roles of nano-TiO2 are shown to be controversial and no comprehensive study paradigm has been developed to investigate their molecular mechanisms. In this study, we showed that short-term exposure to nano-TiO2 enhanced cell proliferation, survival, ERK signaling activation and ROS production in cultured fibroblast cells. Moreover, long-term exposure to nano-TiO2 not only increased cell survival and growth on soft agar but also the numbers of multinucleated cells and micronucleus (MN) as suggested in confocal microscopy analysis. Cell cycle phase analysis showed G2/M delay and slower cell division in long-term exposed cells. Most importantly, long-term TiO2 exposure remarkably affected mitotic progression at anaphase and telophase leading to aberrant multipolar spindles and chromatin alignment/segregation. Moreover, PLK1 was demonstrated as the target for nano-TiO2 in the regulation of mitotic progression and exit. Notably, a higher fraction of sub-G1 phase population appeared in TiO2-exposed cells after releasing from G2/M synchronization. Our results demonstrate that long-term exposure to nano-TiO2 disturbs cell cycle progression and duplicated genome segregation, leading to chromosomal instability and cell transformation