Fig. 5

CeO₂NPs promote NO generation in various cells by NOS-like activity. Cultured HUVEC cells and Raw 264.7 cells are exposed to varying concentrations of CeO₂NPs for a 24 h period, with cells exposed to saline serving as a control group. Cell viability is assessed via the CCK8 assay (n = 6), as shown in (A) and (C), and the concentration of NO in the cell supernatant is measured in (B) and (D) (n = 6), along with the expression levels of the two isoforms of intracellular NO synthase (eNOS and iNOS). (E) In an experiment conducted on Raw 264.7 cells, the effect of treatment with varying concentrations of CeO₂NPs for 24 h is evaluated for the presence of NO concentration (n = 3). Additionally, the survival rate of these cells post-treatment with either L-Arg at various concentrations or a combination of L-Arg and 100 µM CeO₂NPs is determined via CCK8 assay (F) (n = 3), while the NO concentration in the supernatant is assessed using nitric oxide kits (G) (n = 3). In vitro study to evaluate the effect of 500 µM CeO₂NPs on THP-1 and Raw 264.7 cells. The cells are exposed to CeO₂NPs for 24 h, and the supernatant is collected subsequently. The levels of interleukin-4 (IL-4) (H), tumor necrosis factor-α (TNF-α) (I), and nitric oxide (NO) (J) in the supernatant are quantified by the enzyme-linked immunosorbent assay kits (ELISA) and nitric oxide kits, respectively. Data is shown as mean ± SD. *p < 0.05;**p < 0.01; ***p < 0.001