Preparation, unique structural characteristics and immunomodulatory effects of peptides from Antarctic krill (Euphausia superba)

The immunomodulatory potential of marine peptides has gained increasing attention. This study investigated the unique structural characteristics and immunomodulatory effects of Antarctic krill peptides (AKP) using immunosuppression and cell models. AKP could promote spleen lymphocyte proliferation and macrophage phagocytosis, while mitigating cyclophosphamide-induced intestinal damage. The most active peptide fractions of AKP were isolated and purified, leading to the identification of two immunomodulatory peptides, FDYGAN and ESDLYDYPWQ. Molecular docking studies showed that these peptides could effectively interact with the binding sites on TLR4 and MHC-II receptors and the binding energies of both were in the range of −5.0 to −10.0 Kcal/mol. Both peptides significantly activated macrophages, enhancing phagocytic activity and nitric oxide secretion, while modulating cytokine profiles with increased expression of interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-10 (IL-10), and tumor necrosis factor-α (TNF-α) at both mRNA and protein levels. Notably, FDYGAN exhibited the strongest proliferative and phagocytosis effects, with values of 121.34 % and 153.36 % at concentrations of 10 and 200 μg/mL, respectively. This study highlighted the potential of AKP as a functional ingredient for enhancing immune health.