Immune effects of lipids isolated from Oncorhynchus mykiss eggs on cyclophosphamide-induced immunosuppression in mice.

Rainbow trout (Oncorhynchus mykiss) eggs are a rich source of polyunsaturated fatty acids (PUFAs), with levels exceeding those found in fish meat, and are also a notable source of bioactive omega-3 fatty acids, primarily eicosapentaenoic acid (EPA)and docosahexaenoic acid (DHA). However, despite their nutritional advantages, their in vivo immunomodulatory properties remain poorly understood. This study explored the immunomodulatory potential of the lipid extract from O. mykiss eggs combined with PEG6000 (OM-PEG) in a cyclophosphamide (CY)-induced immunosuppressive BALB/c mouse model. Mice were randomly assigned to nine groups (n = 3/group): normal control, CY, CY + ginseng (100 mg/kg), CY + levamisole (40 mg/kg), CY + PEG6000 (10 mg/kg), and four CY + OM-PEG groups (50-200 mg/kg). In CY-treated mice, prophylactic oral administration of OM-PEG (50-200 mg/kg body weight) protected against changes in spleen size and index. It also significantly stimulated splenic immune cells, including T cells, B cells, and natural killer (NK) cells (p < 0.05). Furthermore, cell proliferation, nitric oxide (NO) production, and phagocytic activity were enhanced in peritoneal macrophages (p < 0.05). The mRNA expression of immunostimulatory cytokines and mediators, including interleukin-1β (IL-1β), IL-2, IL-4, IL-6, inducible nitric oxide synthase (iNOS), TNF-α, IFN-γ, and COX-2, was significantly upregulated in both splenic lymphocytes and peritoneal macrophages of CY-treated mice (p < 0.05). Consequently, these results suggest that OM-PEG6000, prepared by incorporating lipids isolated from O. mykiss eggs into PEG6000, contributes to immune system activation and has potential as a functional food ingredient due to its immune-enhancing efficacy.