Cow placenta peptides ameliorate D-galactose-induced intestinal barrier damage by regulating the TLR/NF-kB pathway

To investigate the protective effects of cow placenta peptides (CPP) against D-galactose (D-gal)-induced intestinal barrier damage in aging mice and its mechanism. Forty-eight 8-week-old ICR male mice were equally divided into four groups: blank control group (Group N), D-gal-induced senescence model group (Group M), CPP-treated group (Group T), and vitamin C (Vitamin C, Vit C) control group (Group P), and Groups T and P were gavaged with CPP (2000 mg/kg/day) and Vit C (100 mg/kg/day), respectively. day), respectively. Meanwhile, group M, T and P were injected intraperitoneally with D-gal (300 mg/kg/day), and group N was injected intraperitoneally with an equal amount of saline once/day for 8 weeks, and serum and intestines were collected. Hematoxylin-eosin (H&E) was used to observe the morphological structure of intestinal tissues, and periodic acid Schiff staining (PAS) was used to observe the changes of intestinal cup cells. Immunofluorescence, immunohistochemistry, enzyme-linked immunosorbent assay and real-time quantitative polymerase chain reaction were used to detect the expression levels of oxidative, inflammatory, and aging markers and tight junction protein-associated proteins in the mouse intestine. Transcriptome sequencing was used to analyze the differential genes and pathways of action of CPP in the protection of intestinal barrier damage, and the expression changes of key pathway proteins were verified by Western blot. The results showed that CPP significantly ameliorated the intestinal morphological and structural damage in D-galactose-induced senescent mice, increased the intestinal villus height and villus-to-cryptic ratio (V/C), and decreased the serum DAO and LPS levels. Meanwhile, CPP significantly attenuated oxidative stress and inflammatory responses in the intestine, restored tight junction protein expression, and enhanced intestinal barrier function. Transcriptome sequencing screened 1396 differential genes related to CPP action, and TLR4, IL-1b and Mmp9 were identified as core effector genes by protein interaction network analysis, and the TLR4/NF-kB signaling pathway was selected for further validation by combining with KEGG and GO enrichment analysis. Western blot results showed that CPP significantly up-regulated TLR4, IKKb, and p-kB signaling pathway in the intestinal tract of mice. , IKKb and p-NF-kB p65 protein expression levels in the mouse intestine. In conclusion, CPP could effectively reduce D-gal-induced intestinal barrier damage in mice by enhancing intestinal antioxidant capacity and inhibiting TLR4/NF-kB signaling pathway to reduce inflammatory response.