Immune Netw.  2012 Dec;12(6):296-300. 10.4110/in.2012.12.6.296.

The Effects of Silica Nanoparticles in Macrophage Cells

• Kim S
• Jang J
• Kim H
• Choi H
• Lee K
• Choi IH

• KMID: 2150763
• DOI: http://doi.org/10.4110/in.2012.12.6.296

Abstract

Silica nanoparticles, which are applicable in many industrial fields, have been reported to induce cellular changes such as cytotoxicity in various cells and fibrosis in lungs. Because the immune system is the primary targeting organ reacting to internalized exogenous nanoparticles, we tried to figure out the immunostimulatory effect of silica nanoparticles in macrophages using differently sized silica nanoparticles. Using U937 cells we assessed cytotoxicity by CCK-8 assay, ROS generation by CM-H2DCFDA, intracellular Ca++ levels by staining with Fluo4-AM and IL-8 production by ELISA. At non-toxic concentration, the intracellular Ca++ level has increased immediately after exposure to 15 nm particles, not to larger particles. ROS generation was detected significantly in response to 15 nm particles. However, all three different sizes of silica nanoparticles induced IL-8 production. 15 nm silica nanoparticles are more stimulatory than larger particles in cytotoxicity, intracellular Ca++ increase and ROS generation. But IL-8 production was induced to same levels with 50 or 100 nm particles. Therefore, IL-8 production induced by silica nanoparticles may be dependent on other mechanisms rather than intracellular Ca++ increase and ROS generation.

Keyword

Silica nanoparticles; Macrophages; Intracellular Ca++ level; ROS; IL-8

MeSH Terms

Enzyme-Linked Immunosorbent Assay
Fibrosis
Immune System
Interleukin-8
Lung
Macrophages
Nanoparticles
Silicon Dioxide
Sincalide
U937 Cells
Interleukin-8
Silicon Dioxide
Sincalide

Figure

• 

  Figure 1 Characterization of silica nanoparticles. (A) TEM images of silica nanoparticles show 15 nm, 50 nm or 100 nm particles are relatively uniform in sizes. (B) DLS analysis shows that the mean size is 15.2 nm for 15 nm silica nanoparticles, 62.9 nm for 50 nm particles and 101.4 nm for 100 nm particles by number. Silica nanoparticles dispersed in RPMI 1640 medium containing 10% FBS for DLS analysis. Images shown are representatives of three independent trials.

• 

  Figure 2 Cytotoxicity of silica nanoparticles. U937 cells were treated with different sizes of silica nanoparticles for 24 h and cytotoxicity was determined by CCK-8 assay. Student's t-test was used for statistical analysis. **p<0.01, ***p<0.001.

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  Figure 3 U937 cells were treated with silica nanoparticles and supernatant levels of IL-8 were assessed by ELISA. Data represent means±S.D. of three independent experiments. Student's t-test was used for statistical analysis. *p<0.05, ***p<0.001.

• 

  Figure 4 Detection of intracellular Ca++ level. U937 cells were pre-stained with Fluo4-AM for 30 min and treated with silica nanoparticles. Cells were monitored using a Victor X4 multi label plate reader and measured every 5 sec. Data shown here are representative results from two independent experiments. (A) HBSS with Ca++, (B) HBSS without Ca++.

• 

  Figure 5 Production of ROS. U937 cells were treated with silica nanoparticles for 30 min. Cells were stained with CM-H2DCFDA for 30 min and analyzed by fluorometry. Data represent means±S.D. of three independent experiments. Student's t-test was used for statistical analysis. ***p<0.001.

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