Immunoenhancement Function of the Novel Hexapeptide (LVVLGH) from Thick-Shelled Mussel (Mytilus coruscus) on Immunodeficient Mice by Activating the NF-κB/MAPK Pathway

A novel hexapeptide LVVLGH (LH-6) from the thick-shelled mussel (<i>Mytilus coruscus</i>) demonstrated potent immune-enhancing effects in RAW264.7 cells in vitro, but its immunological activity in vivo is unclear. As a result, the present study was designed to investigate the in vivo effects of LH-6 on cyclophosphamide-induced immunodeficient mice. The results demonstrate that LH-6 promoted the growth and development of immunodeficient mice in a concentration-dependent manner, remarkably elevated the immune organ index, and relieved the pathological characteristics of the spleen and thymus. Additional experiments also revealed that LH-6 effectively promoted the multiplication of splenic lymphocytes and natural killer activity, enhanced the function of abdominal macrophages, and apparently recovered delayed-type hypersensitivity in immunodeficient mice. The secretion of IgA, IgG, IgM, TNF-α, IL-1β, IL-6, and serum hemolysin were remarkably improved by LH-6, suggesting that LH-6 can synergistically strengthen cellular and humoral immunity. In addition, LH-6 promoted the phosphorylation of IκBα and nuclear translocation of p65, which correspondingly increased the phosphorylation levels of p38, JNK, and ERK; activated the NF-κB and MAPK pathways; and exerted in vivo immunomodulatory activities. Docking results show that LH-6 has favorable binding energies to candidate proteins in the NF-κB and MAPK pathways. To summarize, this research further demonstrated that LH-6 possesses in vivo immunomodulatory activity, which provides a possibility for the subsequent development of immune-enhancing functional foods.