Effects of N-acetyl chitooligosaccharides (NACOS) pretreatment on the production of NO, reactive oxygen species (ROS), gene expression of iNOS and NOX2, and phagocytosis in lipopolysaccharide (LPS)-treated RAW264.7 macrophages. Cells were pretreated with NACOS (100 µg/mL), chitosan oligosaccharides (COS) (100 µg/mL), or lipopolysaccharide (LPS) (1 µg/mL) for 24 h and then co-incubated with LPS. Gene expressions were measured by RT-qPCR. (A) Production of NO following treatment with NACOS for 24 h and LPS for 24 h. (B) Expression of the iNOS gene following treatment with NACOS for 24 h and LPS for 8 h. (C) ROS production following treatment with NACOS for 24 h and LPS for 4 h. (D) Expression of the NOX2 gene following treatment with NACOS for 24 h and LPS for 4 h. (E) Phagocytosis by RAW 264.7 cells, as detected by flow cytometry following treatment with NACOS for 24 h and LPS for 4 h. Phagocytosis of beads was determined by flow cytometry. Only the control (Ctrl), LPS, and NACOS6 + LPS treatments are shown (COS + LPS and NACOS1 to NACOS5 + LPS are presented in Supplementary Figure S4). (F) Histogram of phagocytosis rates following pretreatment of RAW264.7 cells with NACOS. Data were normalized to β-actin and presented as the fold induction, compared with the control group. Values are presented as the mean ± SD (n = 3). * p < 0.05; ** p < 0.01, compared with the only LPS-treated group.