Wednesday, January 21, 2009

Silica Nanoparticles

Toxicology LettersVolume 184, Issue 1, 10 January 2009, Pages 18-25

Oxidative stress and pro-inflammatory responses induced by silica nanoparticles in vivo and in vitro

Eun-Jung Parka and Kwangsik Park, a,
aCollege of Pharmacy, Dongduk Women's University, 23-1 Wolgok-dong, Seongbuk-gu, Seoul 136-714, Republic of Korea
Received 27 June 2008;

Oxidative stress and inflammatory responses induced by silica nanoparticles were evaluated both in mice and in RAW264.7 cell line. Single treatment of silica nanoparticles (50 mg/kg, i.p.) led to the activation of peritoneal macrophages, the increased blood level of IL-1β and TNF-α, and the increased level of nitric oxide released from the peritoneal macrophages. mRNA expressions of inflammation-related genes such as IL-1, IL-6, TNF-α, iNOS, and COX-2 were also elevated in the cultured peritoneal macrophages harvested from the treated mice. When the viability of splenocytes from the mice treated with silica nanoparticles (50 mg/kg, 100 mg/kg, and 250 mg/kg, i.p.) was measured, the viability of splenocytes was significantly decreased in the higher dose-treated groups (100 mg/kg, 200 mg/kg i.p.). However, cell proliferation without cytotoxicity was shown in group treated with relatively low dose of 50 mg/kg i.p. When leukocyte subtypes of mouse spleen were evaluated using flow cytometry analysis, it was found that the distributions of NK cells and T cells were increased to 184.8% and 115.1% of control, respectively, while that of B cells was decreased to 87.7%. To elucidate the pro-inflammatory mechanism of silica nanoparticles in vivo, in vitro study using RAW 264.7 cell line which is derived from mouse peritoneal macrophage was done. Treatment of silica nanoparticles to the cultured RAW264.7 cells led to the reactive oxygen species (ROS) generation with a decreased intracellular GSH. In accordance with ROS generation, silica nanoparticles increased the level of nitric oxide released from the cultured macrophage cell line. These results suggested that silica nanoparticles generate ROS and the generated ROS may trigger the pro-inflammatory responses both in vivo and in vitro.
BrooklynDodger(s) comment(s): This is a bit of a hazard identification project: injected silica "nanoparticles" (nature unspecified in the abstract) cause inflammation and some immune system changes. This is toxic potential. It's disappointing not to have a comparison with non-nano silica particles to examine different potency of nano v non-nano. That would provide an aspect of exposure-response assessmnt.

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