Immunomodulatory effect of rice bran peptides on RAW264.7 cells

Immunodeficiency represents a burgeoning health concern, and modulating the immune response via dietary intervention is regarded as a novel strategy to improve immune function. In this research, rice bran peptides (RBPs) were prepared via enzymatic hydrolysis combined with fermentation by Lactobacillus plantarum. Compositional analysis revealed that the soluble protein content of RBPs increased from 6.73% to 74.24%, and the peptide fraction with a molecular weight less than 1.0 kDa increased from 0.67% to 6.92%. RBPs had no impact on the viability of RAW264.7 cells; however, they significantly elevated the phagocytosis rate of RAW264.7 cells (P < 0.01). Morphological examination demonstrated that RBPs could alter the cell morphology. Flow cytometry indicated that the expression of CD80 and CD86 on the surface of RAW264.7 cells was upregulated after treatment with RBPs. The DCFH-DA probe assay showed that RBPs could enhance the production of reactive oxygen species (ROS) in RAW264.7 cells. RBPs significantly enhanced the activity of acid phosphatase (ACP) in RAW264.7 cells (P < 0.01). They also facilitated the secretion of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-10 (IL-10), and significantly increased the content of toll-like receptor 4 (TLR4). These findings suggest that RBPs have the potential to serve as a natural food-derived immunomodulatory factor.