Antimicrobial Peptide CPP-C3M4 Attenuates Salmonella-Induced Liver Inflammation and Oxidative Stress in Lambs

In this study, we investigated the protective effects of CPP-C3M4 against Salmonella-induced hepatic injury in lambs. Thirty 72-day-old Hu sheep were randomly divided into five groups: the control group (CON), the Salmonella-infected group (ST), and three CPP-C3M4 pretreatment groups at low, medium and high doses (CPP-C3M4-L, CPP-C3M4-M, and CPP-C3M4-H). The results showed that administration of CPP-C3M4 via duodenal fistula significantly alleviated liver enlargement and histopathological damage caused by Salmonella infection. CPP-C3M4 improved liver function by reducing alanine aminotransferase (ALT), aspartate aminotransferase (AST), and triglyceride (TG) levels. It enhanced the liver antioxidant capacity by increasing glutathione peroxidase (GSH-Px), catalase (CAT), and superoxide dismutase (SOD) activities. It also alleviated inflammatory responses by downregulating the mRNA expression of interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), interleukin-2 (IL-2), toll-like receptor 2 (TLR2), and toll-like receptor 9 (TLR9). Transcriptomic Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis further confirmed that CPP-C3M4 exerts its protective effects by suppressing multiple inflammatory pathways, with the interleukin-17 (IL-17) signaling axis being a key target of regulation. These results indicate that CPP-C3M4 is a promising alternative antimicrobial substance for preventing and alleviating Salmonella-induced liver injury in lambs.