Immunomodulatory effects of lotus seed (Nelumbo nucifera Gaertn.) peptides on macrophages in mice

Immunomodulatory effects of lotus seed (Nelumbo nucifera Gaertn.) peptides (LSPs) were studied in this paper. The LSPs were prepared by trypsin enzymatic hydrolysis and were separated by ultrafiltration separation technology. The following four peptide fractions with different molecular weight were obtained: LSP-I (>10 kDa), LSP-II (5-10 kDa), LSP-III (3-5 kDa), and LSP-IV (<3 kDa). Macrophage phagocytosis capacity, NO production and cytokine levels were measured in healthy and immunosuppressed mice to explore the effects of immunomodulatory activity of LSPs. In vitro, among the four peptides, LSP-IV showed the greatest effect on RAW264.7 macrophage phagocytosis. In vivo, LSP-IV had no significant effect on the levels of nitric oxide (NO), interleukin 6 (IL-6) and tumor necrosis factor (TNF-alpha) in healthy mice in a dose-dependent manner, but significantly increased the levels of NO, IL -6 and TNF-alpha secreted by peritoneal macrophages (p < 0.01 and p < 0.001, respectively) in immunosuppressed mice. In particular, high doses of LSP-IV (0.10 g/kg body weight) showed a stronger immunomodulatory potential. Our findings shed light on the potential of low-molecular-weight peptides from lotus seeds as novel natural immunoregulatory dietary factors.