Glutamine protects cow's ruminal epithelial cells from acid-induced injury in vitro

This study was conducted to investigate the effects and mechanisms of glutamine (Gln) on the repair of acid-induced injury in dairy cow ruminal epithelial cells (RECs) in vitro. Dairy cow RECs were cultured in a medium with pH of 5.5 for 3 h and subsequently treated with various concentrations of Gln (4, 8, 12, 32 mmol/l) for 12 h. The messenger ribonucleic acid (mRNA) expression levels of occludin (OCLN), claudin 1 (CLDN1), toll-like receptor 2 (TLR2), toll-like receptor 4 (TLR4) and genes for inflammatory factors were measured using reverse transcription-quantitative real-time PCR (RT-qPCR). The results showed that cellular activity and OCLN expression were significantly highest at 8 mmol/l Gln (P < 0.05). CLDN1 expression was significantly higher at 4 mmol/l Gln compared to the other groups (P < 0.05). The relative expression levels of tumour necrosis factor (TNF), interleukin 1B (IL1B), C-X-C motif chemokine ligand 8 (CXCL8), TLR2 and TLR4 in the acid treatment group were significantly higher than those in the control group (P < 0.05), but they were lower in the Gln-treated groups than in the acid treatment group (P < 0.05). These findings demonstrate that Gln promotes the proliferation of RECs, enhances the expression of epithelial cell junction proteins, and inhibits the expression of inflammatory factors and surface receptors. In conclusion, Gln shows a potential for repairing acid-induced injury in RECs.