Hexadecanamide alleviates Staphylococcus aureus-induced mastitis in mice by inhibiting inflammatory responses and restoring blood-milk barrier integrity

by Lijuan Bao, Hao Sun, Yihong Zhao, Lianjun Feng, Keyi Wu, Shan Shang, Jiawen Xu, Ruping Shan, Shiyu Duan, Min Qiu, Naisheng Zhang, Xiaoyu Hu, Caijun Zhao, Yunhe Fu

Subacute ruminal acidosis (SARA) has been demonstrated to promote the development of mastitis, one of the most serious diseases in dairy farming worldwide, but the underlying mechanism is unclearn. Using untargeted metabolomics, we found hexadecanamide (HEX) was significantly reduced in rumen fluid and milk from cows with SARA-associated mastitis. Herein, we aimed to assess the protective role of HEX in Staphylococcus aureus (S. aureus)- and SARA-induced mastitis and the underlying mechanism. We showed that HEX ameliorated S. aureus-induced mastitis in mice, which was related to the suppression of mammary inflammatory responses and repair of the blood-milk barrier. In vitro, HEX depressed S. aureus-induced activation of the NF-κB pathway and improved barrier integrity in mouse mammary epitheial cells (MMECs). In detail, HEX activated PPARα, which upregulated SIRT1 and subsequently inhibited NF-κB activation and inflammatory responses. In addition, ruminal microbiota transplantation from SARA cows (S-RMT) caused mastitis and aggravated S. aureus-induced mastitis, while these changes were reversed by HEX. Our findings indicate that HEX effectively attenuates S. aureus- and SARA-induced mastitis by limiting inflammation and repairing barrier integrity, ultimately highlighting the important role of host or microbiota metabolism in the pathogenesis of mastitis and providing a potential strategy for mastitis prevention.