Fig. 6From: Size and surface modification of silica nanoparticles affect the severity of lung toxicity by modulating endosomal ROS generation in macrophagesNOX2 inhibition suppressed endosomal ROS generation and chemokine induction by silica NPs in vitro. A-B. Intracellular levels of ROS signals in Raw264.7 cells that endocytosed silica-NPs. Raw264.7 cells incubated with silica-NPs for 6 h were stained with DCFDA (intracellular ROS indicator), and signals were quantified by flowcytometry. A. Representative histography of fluorescent intensity of RAW cells by DCFDA assay. DCFDA(−) represents vehicle treated cells without staining with DCFDA (negative control). B. The graph shows relative levels of intracellular ROS normalized by signals in untreated cells. C-E. Chemokine gene expression in RAW264.7 cells incubated with silica-NPs in the presence of N-acetylcysteine (NAC). Total RNA was isolated from RAW264.7 cells 6 h after silica-NPs exposure with or without addition of 10 mM of NAC, and gene expression of proinflammatory cytokine genes (MIP1α (C), MIP2 (E), and TNF-α (F)) was determined by qRT-PCR. F-G. Assessment of endosomal ROS levels in RAW264.7 cells with different silica-NPs using OxyBURST. Cells were incubated with silica-NPs (50 nm-plain, 50 nm-NH2) for 2 h or PMA for 30 min as a positive control. Some experiments were done with cells pre-treated with gp91ds-tat, a specific inhibitor of NOX2. F. Representative images obtained by confocal microscopy. Scale bars = 10 μm G. Average number of puncta indicating the signals of endosomal compartment with increased ROS level per cell. (# p = 0.0001 vs vehicle, 50 nm-NH2, PMA + gp91ds-tat, 50 nm-plain + gp91ds-tat, and 50 nm-NH2 + gp91ds-tat groups, respectively by one-way ANOVA with Tukey’s multiple comparison test) H-J. Induction of proinflammatory cytokines in Raw264.7 cells treated with silica-NPs was suppressed by treatment with gp91ds-tat, a specific inhibitor of NOX2 activation. For Figs. B, C, D, E, H, I, and J, * p < 0.05, **p < 0.01, ***p < 0.001, and ****p < 0.0001 by one-way ANOVA with Tukey’s multiple comparison testsBack to article page