Potassium octatitanate (K₂O•8TiO₂) fiber is a potent inducer of lung and pleural injury - A comparative study to titanium dioxide nano particles

Abstract

Potassium octatitanate fiber (K₂O•8TiO₂, POT) has been commonly used in various industries as an alternative to asbestos fibers due to good their friction performance. We studied pulmonary and pleural toxicity of POT with reference to non-fiber and short fiber TiO₂ nanoparticles: anatase type (anTiO₂) and rutile type (ruTiO₂).
[Method] Male F344 rats were administered 0.5 ml of 250-μg/ml suspensions of POT, anTiO₂, and ruTiO₂ 8 times (1mg/rat) over a 2-week period by our trans-tracheal intrapulmonary spraying (TIPS) method and killed at 6 hours and 4 weeks after the last dose.
[Results]
Lung: A significant increase in number of alveolar macrophages was observed in all dosed groups. At week 4, the mRNA and protein levels of CCL2 were significantly higher in POT than in the other groups. The mRNA levels of the chemokines CCL2, CCL3, and CCL4 of all dosed groups at week 4 decreased to approximately half that of hour 6.
Visceral pleura: PCNA labeling of visceral mesothelium in all treated groups was significantly higher than controls at hour 6 and week 4.
Pleural cavity lavage fluid: There was a significant increase in levels of LHD protein and total protein in all dosed groups at week 4 over controls.
[Conclusions] Our results indicate that POT fiber is a more potent inducer of lung and pleural cavity inflammatory lesions and mesothelial cell proliferation than anTiO₂ and ruTiO₂. These values were higher in week 4 than hour 6. Our on-going long-term carcinogenicity study will determine the relevance these findings to its carcinogenicity.