Immune Netw.  2013 Jun;13(3):94-101. 10.4110/in.2013.13.3.94.

Immunostimulatory Effects of Silica Nanoparticles in Human Monocytes

• Yang EJ
• Choi IH

• KMID: 2150772
• DOI: http://doi.org/10.4110/in.2013.13.3.94

Abstract

Amorphous silica particles, whose applications are increasing in many biomedical fields, are known to be less toxic than crystalline silica. In this study, the inflammatory effects of amorphous silica nanoparticles were investigated using 30-nm amorphous silica nanoparticles and human peripheral blood mononuclear cells (PBMCs) or purified monocytes. As a result, production of IL-1beta and IL-8 were increased. In addition, the mitochondrial reactive oxygen species (ROS) was detected, which may lead to mitochondrial membrane disruption. Most importantly, inflammasome formation was observed. Therefore, these results provide immunological information about amorphous silica nanoparticles and suggest that amorphous silica nanoparticles can evoke innate immune reactions in human monocytes through production of IL-1beta and IL-8.

Keyword

Silica nanoparticles; Human monocytes; Cytokine; Inflammasome; Mitochondrial membrane

MeSH Terms

Crystallins
Humans
Interleukin-8
Mitochondrial Membranes
Monocytes
Nanoparticles
Reactive Oxygen Species
Silicon Dioxide
Crystallins
Interleukin-8
Reactive Oxygen Species
Silicon Dioxide

Figure

• 

  Figure 1 Cytotoxicity and production of cytokines in PBMCs. (a) PBMCs were treated with 30-nm amorphous silica nanoparticles for 6 h and cytotoxicity was determined by CCK-8 assay. (b, c) PBMCs were treated with silica nanoparticles for 6 h and supernatant levels of IL-1β (b) and IL-8 (c) were assessed by ELISA. LPS (25 ng/ml) was pretreated for 3 h before nanoparticle exposure. Data represent means±S.D. of three independent experiments. One-way ANOVA analysis shows significance (p<0.0001) (b, c) and student's t-test between certain pairs (b, c) was used for statistical analysis.

• 

  Figure 2 Production of mitochondria ROS in blood monocytes. Monocytes were treated with silica nanoparticles or silver nanoparticles for 40 min. Cells were stained with 2.5µM MitoSOX (for mitochondrial superoxide) for 15 min and analyzed by flow cytometry. MI, mean intensity. Data shown here are representative results from three independent experiments.

• 

  Figure 3 Assessment of mitochondrial membrane integrity. Monocytes were treated with 125µg/ml of 30 nm silica nanoparticles for 1 h, 1.5 h, and 2 h. After exposure for the indicated time, JC-1 (2µM) staining was performed to evaluate disturbance of mitochondrial membranes. Cells stained as red (intact mitochondria) were determined by flow cytometry. Data shown here are representative results from three independent experiments. MI, mean intensity.

• 

  Figure 4 Inflammasome formation of caspase-1 and NLRP3 in monocytes. To analyze oligomerization of NLRP3 and caspase-1, monocytes were treated with silica nanoparticles (125µg/ml) for 15 min. Oligomerization of NLRP3 and caspase-1 was assessed by confocal microscopy after staining with anti-NLRP3 and anti-caspase-1 antibodies. White arrows indicate oligomerization of each molecule, which are not observed in controls.

• 

  Figure 5 TEM images of monocytes after exposure to silica nanoparticles. Monocytes were treated with silica nanoparticles (125µg/ml) for 30 min. After 30 nm silica nanoparticle exposure, (a) double membrane structures (white arrows) suggesting autophagy-like structures and (b) presence of silica nanoparticles were observed inside endosome.

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