Immunomodulatory effects of different molecular weight sporisorium reilianum polypeptides on LPS-induced RAW264.7 macrophages

Sporisorium reilianum is an edible fungus that contains polysaccharides, proteins, vitamins, and minerals. Although polysaccharides from S. reilianum have been shown to exert anti-inflammatory and anti-tumor effects, studies of other molecules are still scarce. This study was conducted to examine the immunomodulatory effects of different molecular weights of S. reilianum polypeptides (SRP) on lipopolysaccharide (LPS)-induced RAW264.7 macrophages. A neutral protease was used to prepare SRP, which was divided into different components based on their molecular weights (SRP1, SRP2, SRP3, and SRP4). Evaluation of the immunomodulatory effects of SRP on LPS-induced RAW264.7 macrophages showed that SRP enhanced cell viability and phagocytic activity, and effectively decreased the nitric oxide (NO) content. Furthermore, the SRP with the smallest molecular weight, SRP4 (500–1000 Da) exhibited the strongest effects compared to the other groups. Secretion of the pro-inflammatory cytokines tumor necrosis factor (TNF)-α and interleukin (IL)-6 was markedly decreased by SRP4 in a dose-dependent manner. Moreover, the mRNA expression levels of IL-1β, nitric oxide synthase (iNOS), cyclooxygenase (COX)-2, and toll-like receptor (TLR)-9 in RAW264.7 macrophages were also significantly downregulated by SRP4. Taken together, SRP, particularly SRP4, showed good immunomodulatory effects, indicating its potential as an immune-enhancing agent.