Bovine mastitis is a common disease in the dairy industry that causes great economic losses. As the primary pathogen of contagious mastitis, Staphylococcus aureus (S. aureus) can invade bovine mammary epithelial cells, thus evading immune defenses and resulting in persistent infection. Recently, autophagy has been considered an important mechanism for host cells to clear intracellular pathogens. In the current study, autophagy caused by S. aureus was detected, and the correlation between autophagy and intracellular S. aureus survival was assessed. First, a model of intracellular S. aureus infection was established. Then, the autophagy of MAC-T cells was evaluated by confocal microscopy and western blot. Moreover, the activation of the PI3K-Akt-mTOR and ERK1/2 signaling pathways was determined by western blot. Finally, the relationship between intracellular bacteria and autophagy was analyzed by using autophagy regulators (3-methyladenine [3-MA], rapamycin [Rapa] and chloroquine [CQ]). The results showed that S. aureus caused obvious induction of autophagosome formation, transformation of LC3I/II, and degradation of p62/SQSTM1 in MAC-T cells; furthermore, the PI3K-Akt-mTOR and ERK1/2 signaling pathways were activated. The number of intracellular S. aureus increased significantly with autophagy activation by rapamycin, whereas the number decreased when the autophagy flux was inhibited by chloroquine. Therefore, this study indicated that intracellular S. aureus can induce autophagy and utilize it to survive in bovine mammary epithelial cells.

中文翻译：

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细胞内金黄色葡萄球菌诱导的牛乳腺上皮细胞自噬

牛乳腺炎是奶业中的常见疾病，会造成巨大的经济损失。作为传染性乳腺炎的主要病原体，金黄色葡萄球菌（S. aureus）可以侵入牛的乳腺上皮细胞，从而逃避了免疫防御，导致持续感染。最近，自噬被认为是宿主细胞清除细胞内病原体的重要机制。在当前的研究中，检测到由金黄色葡萄球菌引起的自噬，并评估了自噬与细胞内金黄色葡萄球菌存活之间的相关性。首先，细胞内金黄色葡萄球菌的模型确定感染。然后，通过共聚焦显微镜和蛋白质印迹法评估MAC-T细胞的自噬。此外，通过蛋白质印迹确定PI3K-Akt-mTOR和ERK1 / 2信号通路的激活。最后，使用自噬调节剂（3-甲基腺嘌呤[3-MA]，雷帕霉素[Rapa]和氯喹[CQ]）分析细胞内细菌与自噬之间的关系。结果表明，金黄色葡萄球菌在MAC-T细胞中引起明显的自噬体形成诱导，LC3I / II转化和p62 / SQSTM1降解。此外，PI3K-Akt-mTOR和ERK1 / 2信号通路被激活。细胞内金黄色葡萄球菌的数量雷帕霉素激活自噬后，其显着增加，而当氯喹抑制自噬通量时，其数目减少。因此，这项研究表明细胞内金黄色葡萄球菌可以诱导自噬并利用它在牛乳腺上皮细胞中存活。