Intervention of Fish (Perca fluviatilis) Maw Hydrolysate in Cyclophosphamide-Induced Immunosuppressed Mice via NF-κB Pathway.

Immune dysregulation is a critical driver of various pathological processes. Fish maw (FM) serves as a traditional immunomodulatory food. However, the immunomodulatory properties and mechanisms of fish maw hydrolysate (FMH) remain unclear. Here, low-molecular-weight FMH was prepared from Perca fluviatilis, exhibiting a major molecular weight distribution of 73-580 Da (83.89%), enriched in charged and hydrophobic amino acids (28.61% and 67.33%, respectively). Moreover, high-resolution mass spectrometry (HRMS) analysis identified 5 small peptides, including Asp-Leu and Gly-Pro-Ala, alongside 7 collagen-derived polypeptides with characteristic Gly-X-Y repetitive motifs. In cyclophosphamide (CTX)-induced immunosuppressed C57BL/6J mice, FMH significantly ameliorated alterations in peripheral blood cell parameters, regulated cytokine homeostasis, attenuated splenic histopathological lesions, and enhanced splenic lymphocyte proliferation. Mechanistically, thymic transcriptomic profiling identified 2237 DEGs in the CTX vs. CON comparison and 212 DEGs in the CTX+FMH vs. CTX comparison, with the NF-κB signaling pathway significantly enriched. Furthermore, qRT-PCR validated the expression of key NF-κB-related genes, including IκBα, P50, P65, CHUK, IL-1β, and IL-6, while immunohistochemical analysis confirmed reduced PI3K and P65 expression, thereby partly restoring immune homeostasis. These findings support FMH as a potential dietary immunomodulator.