Proteomic analysis reveals the molecular mechanism of Hippophae rhamnoides polysaccharide intervention in LPS-induced inflammation of IPEC-J2 cells in piglets

Early weaning can cause intestinal disorders and dysfunction in piglets, and may induce intestinal diseases. Hippophae rhamnoides polysaccharide (HRP) has anti-inflammatory and immune promotion function. However, few studies have explored the change of differentially protein expression by lipopolysaccharide (LPS)-induced porcine intestinal epithelial cell (IPEC-J2) after HRP pre-treatment. In this study, proteomic analysis was used to explore the essential proteins and immune-related pathways that can be regulated by LPS-induced IPEC-J2 cells after HRP pre-treatment. The results indicate that by searching the Sus scrofa database, a total of 18,768 proteins was identified. Among recognized proteins, there are 2052 (1720 up-regulated and 332 down-regulated), 358 (262 up-regulated and 96 down-regulated) and1532 (314 up-regulated and 1218 down-regulated) proteins expressed differently in C vs. L, C vs. H6-L and L vs. H6-L, respectively. The Cluster of Orthologous Groups (COG) analysis divided the identified proteins into 23 categories. Gene Ontology (GO) enrichment analysis revealed that cellular process, cell, cell part, organelle and binding were the most enriched pathways for differentially expressed proteins. KEGG enrichment analysis indicated that the top 20 pathways in the L-vs-H6-L group related to immunity were the Tight junction, MAPK signaling pathway, PI3K-Akt signaling pathway, rap1 signaling pathway, HIF-1 signaling pathway, Ras signaling pathway and Fc gamma R-mediated phagocytosis. Moreover, we also found 42 key proteins related to these immune pathways in this study. Additionally, western blotting analyses confirmed that LPS reduced the levels of claudin2 (CLDN2), insulin-like growth factor 2 (IGF2) and increased phosphorylated mitogen-activated protein kinase 7 (MAPK7), phosphorylated transcription factor p65 (RELA), phosphorylated nuclear factor NF-kappa-B p105 subunit (NF-κB1) and phosphorylated nuclear factor of kappa light polypeptide gene enhancer in B-cells 2 (NF-κB2). Pre-treatment with HRP increased the levels of CLDN2, IGF2 and reduced the levels of the phosphorylated MAPK7, phosphorylated RELA, phosphorylated NF-κB1 and phosphorylated NF-κB2 in cells. These results also showed that HRP alleviated LPS-induced inflammation in IPEC-J2 cells by inhibiting the MAPK/NF-κB signaling pathway and its related differentially expressed proteins.