The Expression of Inflammatory Cytokine and Heme Oxygenase-1 Genes in THP-1 Cells Exposed to Metal Oxide Nanoparticles

The effect of manufactured nanoparticles on the expression of proinflammatory cytokine genes was examined. THP-1 cells differentiated into macrophage cells were exposed to TiO2 and NiO medium dispersions. After 2, 6, 12, or 24 hours exposure, the expression of IL-1β, IL-6, IL-8, TNF-α and HO-1 genes was determined by real-time PCR. TiO2 nanoparticles did not affect cytokine production. In addition, TiO2 nanoparticles did not dissolve in the dispersion. On the other hand, NiO nanoparticles enhanced the expression of all the genes tested. NiO dispersions were composed of 58.3 μg/mL of NiO nanoparticles and 45.8 μg/mL of Ni2+. The release of metal ions from the nanoparticles is associated with their cytotoxicity. Therefore, the effect of an NiCl2 solution containing 45.8 μg/mL of Ni2+ on the expression of cytokine genes was also examined. The effects of NiCl2 were similar to those of the NiO nanoparticles. Furthermore, the effect of ZnO, SiO2-coated ZnO, Sb2O3, and Cr2O3 nanoparticles on the expression of IL-1β, IL-8 and TNF-α genes was examined. Soluble nanoparticles, such as ZnO, SiO2-coated ZnO, and Cr2O3 enhanced the gene expression of cytokines. Sb2O3 nanoparticles showed poor solubility and did not affect the expression of cytokine genes. In conclusion, these results suggest that nanoparticle solubility plays an important role in regulating the expression of proinflammatory cytokines.