Effect of ceria nanoparticles on activity of DSS-induced colitis in mice by eliminating active oxygen species

Objective·To investigate the effect of ceria nanoparticles-polyethylene glycol (CeNP-PEG) on scavenging reactive oxygen species (ROS) and alleviating disease activity in dextran sulphate sodium (DSS)-induced colitis mice.Methods·CeNP was synthesized with the hydrates of cerium acetate, oleamine, and xylene, which was modified with polyethylene glycol-stearyl phosphatidylethanolamine (mPEG-DPSE) to obtain CeNP-PEG. Then CeNP-PEG was purified. The particle size and zeta potential of CeNP-PEG were measured by using transmission electron microscopy (TEM) and dynamic light scattering (DLS). Mouse macrophages (Raw264.7) were cultured in vitro and induced to a pro-inflammatory phenotype (M1 phenotype). M1 macrophages were treated with 0.5 µg/mL and 1.0 µg/mL CeNP-PEG, respectively, and then Western blotting was used to detect the expression changes of the proteins related with nuclear factor-κB (NF-κB) signaling pathway. DSS-induced colitis mice models were constructed, and CeNP-PEG (1.0 mg/mL) was intravenously administrated for 3 times via tail vein during the modeling period. Meanwhile, the body weight, fecal characteristics, and frequency of rectal bleeding in mice were monitored in the normal control group (Normal group), the model group (DSS group), and the CeNP-PEG treatment group. The disease activity index (DAI) was calculated to evaluate the intestinal inflammation. The level of ROS in mouse intestinal tissues was detected by dihydroethidine (DHE) staining and the mRNA expression levels of inflammatory cytokines interferon-γ (Ifn-γ), interleukin-6 (Il-6), Il-1β and tumor necrosis factor-α (Tnf-α) were detected by real-time quantitative PCR (RT-qPCR).Results·The hydrated particle size of synthesized CeNP-PEG was (6.96±0.27) nm, and the average zeta potential was (-6.02±1.31) mV. Western blotting results showed that the expression of p-P65 increased in the pro-inflammatory macrophages compared with the control group. The expression of NF-κB inhibitor-α (IκB-α) decreased, and their expressions tended to recover after the intervention of different concentrations of CeNP-PEG. In the DSS-induced colitis models, mice in the CeNP-PEG treatment group lost less weight than those in the DSS group (P=0.000) and had lower DAI scores (P=0.000). The RT-qPCR results of intestinal tissues showed that the mRNA levels of Ifn-γ, Il-1β, Il-6 and Tnf-α in the DSS group were significantly up-regulated compared with those in the Normal group (P=0.000), and all of them significantly decreased in the CeNP-PEG treatment group. The results of DHE staining showed that the fluorescence intensity of intestinal tissues in the DSS group was significantly enhanced than that in the Normal group, and the fluorescence intensity decreased in the CeNP-PEG treatment group.Conclusion·CeNP-PEG can inhibit the expression of intestinal inflammatory factors and the activation of NF-κB-related inflammatory pathway of pro-inflammatory macrophages, eliminate intestinal ROS, improve the intestinal inflammatory microenvironment, and alleviate the disease activity of DSS-induced colitis in mice.