Abstract
Background
Accumulating evidence indicates that iron oxide nanoparticles modulate immune responses, and induce oxidative stress in macrophages. It was recently reported that iron oxide nanoparticles attenuated antigen-specific immunity in vivo, though the underlying mechanism remains elusive. The present study investigates the direct effect of iron oxide nanoparticles on antigen-specific cytokine expression by T cells, and potential underlying mechanisms.
Methods
Ovalbumin-primed splenocytes were exposed to iron oxide nanoparticles, followed by restimulation with ovalbumin. Cell viability, cytokine production, and cellular levels of glutathione and reactive oxygen species were measured.
Results
The splenocyte viability and the production of interleukin-2 and interleukin-4 were unaffected, whereas interferon-γ production was markedly attenuated by iron oxide nanoparticles (10–100 μg iron/mL) in a concentration-dependent manner. Iron oxide nanoparticles also transiently diminished the intracellular level of glutathione, with a peak response at 6 hours posttreatment. The effects of iron oxide nanoparticles on interferon-γ and glutathione were attenuated by the presence of N-acetyl-L-cysteine, a precursor of glutathione. However, iron oxide nanoparticles did not influence the generation of reactive oxygen species.
Conclusion
Iron oxide nanoparticles induced a differential effect on antigen-specific cytokine expression by T cells, in which the T helper 1 cytokine IFN-γ was sensitive, whereas the T helper 2 cytokine interleukin-4 was refractory. In addition, the suppressive effect of iron oxide nanoparticles on interferon-γ was closely associated with the diminishment of glutathione.
Acknowledgments
This work was supported by grants NSC98-2320-B-002-036-MY3 from the National Science Council, Executive Yuan, Taiwan. The authors thank the Consulting Center of Statistics and Bioinformatics in the College of BioResources and Agriculture, National Taiwan University, for help in statistical analysis.
Disclosure
The authors report no conflicts of interest in this work.