¹College of Veterinary Medicine, Inner Mongolia Agricultural University, Key Laboratory of Clinical Diagnosis and Treatment Technology in Animal Disease, Ministry of Agriculture and Rural Affairs, Hohhot, 010011, Inner Mongolia Autonomous Region, P. R. CHINA DOI : 10.9775/kvfd.2023.29103 This study aimed to investigate the effect of the cell wall component lipoteichoic acid (LTA) of Staphylococcus aureus on mammary alveolar tight junctions (TJs) proteins including claudin-1, occludin and zonula occluden (ZO)-1. Primary bovine mammary epithelial cells were grown on Transwell inserts for 108 hours. The integrity and tightness of the growing epithelial cell layer were evaluated by measuring transepithelial electrical resistance. The permeability of bovine mammary epithelial cells (BMECs) was assessed by measuring horseradish peroxidase transmission. The mRNA levels of BMECs TJ components were measured with quantitative real-time polymerase chain reaction. In LTA-induced mastitis of mouse model, the protein expression of TJs (claudin-1, occludin and ZO-1) were determined by western blot analysis. Our results showed that LTA increased barrier permeability of BMECs. Treatment with LTA decreased mRNA and protein levels of occludin and ZO-1 in vivo and in vitro, however, the expression of claudin-1 did not change. The results suggested that disruption of mammary epithelial barrier integrity is caused by the alteration of occludin and ZO-1. Keywords : Lipoteichoic acid, Mammary, Tight junctions