<i>Nypa fruticans</i> Wurmb Extract Recovered Compromised Immune Status Induced by Forced Swimming in a Mouse Model

<i>Nypa fruticans</i> Wurmb is known to contain large amounts of polyphenols and flavonoids with antioxidative and anti-inflammatory effects. However, the biological and physiological functions of <i>N. fruticans</i> have not been scientifically investigated. Thus, we investigated the immunomodulatory effect of <i>N. fruticans</i> hot water extract (YSK-N) in mice using an immune compromised model established by forced swimming (FS). Intensive exercise decreased body weight, organ index, and various immunological parameters in FS mice. However, oral administration of YSK-N significantly restored the FS-induced decreases in body, thymus, and spleen weights, as well as the reduction in the numbers of white blood cells and lymphocytes in the whole blood of mice. Additionally, YSK-N increased splenic cell proliferation in the absence and presence of concanavalin A or lipopolysaccharide stimulation in a concentration-dependent manner. Notably, YSK-N enhanced the cytotoxic activity of natural killer cells against YAC-1 tumor cells under immunosuppressive conditions. Furthermore, YSK-N supplementation reverted the FS-induced downregulation in immunoglobulin production and <i>Il2</i>, <i>Il6</i>, <i>Il12</i>, <i>Ifnγ</i>, <i>Gzmb</i>, and <i>Prf1</i> mRNA expression. Therefore, our observations suggested that YSK-N promotes immune function and has potential as an immunomodulatory agent.