College of Veterinary Medicine, Shandong Agricultural University, Tai'an, China.
China Animal Health and Epidemiology Center, Qingdao, China.
Front Immunol. 2020 May 5;11:746. doi: 10.3389/fimmu.2020.00746. eCollection 2020.
In dairy herds, mastitis caused by is difficult to completely cure on the account that can invade bovine mammary epithelial cells (BMECs) and result in persistent infection in the mammary gland. Recent studies have demonstrated that autophagy can participate in cell homeostasis by eliminating intracellular microorganisms. The aim of the study was to investigate why can evade autophagy clearance and survive in BMECs. The intracellular infection model was first constructed; then, the bacteria in autophagosome was detected by transmission electron microscopy. The autophagy flux induced by the was also evaluated by immunoblot analysis and fluorescent labeling method for autophagy marker protein LC3. In addition, lysosomal alkalization and degradation ability were assessed using confocal microscopy. Results showed that, after infection, a double-layer membrane structure around the was observed in BMECs, indicating that autophagy occurred. The change in autophagy marker protein and fluorescent labeling of autophagosome also confirmed autophagy. However, as time prolonged, the autophagy flux was markedly inhibited, leading to obvious autophagosome accumulation. At the same time, the lysosomal alkalization and degradation ability of BMECs were impaired. Collectively, these results indicated that could escape autophagic degradation by inhibiting autophagy flux and damaging lysosomal function after invading BMECs.
在奶牛群体中，由 引起的乳腺炎很难完全治愈，因为 可以侵入奶牛乳腺上皮细胞（BMEC），导致乳腺持续感染。最近的研究表明，自噬可以通过清除细胞内微生物来参与细胞内稳态。本研究旨在探讨 为何能逃避自噬清除并在 BMEC 中存活。首先构建了细胞内感染模型，然后通过透射电子显微镜检测自噬体中的细菌。通过免疫印迹分析和自噬标记蛋白 LC3 的荧光标记法评估 诱导的自噬流。此外，还通过共聚焦显微镜评估溶酶体碱化和降解能力。结果表明，感染后，在 BMEC 中观察到 周围有双层膜结构，表明发生了自噬。自噬标记蛋白的变化和自噬体的荧光标记也证实了自噬的发生。然而，随着时间的延长，自噬流明显受到抑制，导致自噬体明显积累。同时，BMEC 的溶酶体碱化和降解能力受损。综上所述，这些结果表明， 侵入 BMEC 后，可以通过抑制自噬流和破坏溶酶体功能来逃避自噬降解。
