Caragana korshinskii Tannin Attenuates LPS-Induced Sheep Rumen Epithelial Injury via TLR4/MyD88/NF-κB Signaling

The rumen epithelium mediates nutrient absorption and mucosal defense in ruminants, whereas increased exposure to lipopolysaccharide (LPS) under high-concentrate feeding may induce epithelial inflammation and barrier injury. This study investigated whether Caragana korshinskii tannin (CKT) protects against LPS-induced injury in primary sheep rumen epithelial cells and whether TLR4/MyD88/NF-κB signaling is involved. Cells were pretreated with 5 μg/mL CKT for 18 h and then challenged with 5 μg/mL LPS for 6 h. TLR4 knockdown experiments were performed in a sheep rumen epithelial cell line for mechanistic investigation. LPS induced inflammatory cytokine production, oxidative stress, G0/G1 cell-cycle arrest, apoptosis, and reductions in tight-junction-related markers (p < 0.05). CKT pretreatment attenuated these changes, as reflected by lower ROS and MDA levels, increased antioxidant enzyme activities, reduced apoptosis, and improved the expression of selected tight-junction-related proteins (p < 0.05). CKT also suppressed LPS-recognition components and TLR4/MyD88/NF-κB pathway activation (p < 0.05). TLR4 knockdown weakened LPS-induced injury and reduced the additional protective effect of CKT. Overall, CKT may protect rumen epithelial cells against LPS-induced inflammatory injury partly by inhibiting TLR4/MyD88/NF-κB signaling.