Tea tree oil (TTO) plays an important role in antibacterial activity and alleviating the inflammatory responses. Bovine mammary epithelium and polymorphonuclear leukocytes (PMNL) can actively respond to bovine mastitis infection. However, regulatory effects of TTO extracts on the innate immune response of bovine mammary epithelial cells (BMECs) and PMNL remain not reported. Therefore, aim of the study was to evaluate the effects of TTO extracts on the mRNA levels of the genes involved in the innate immune response of BMECs and PMNL. Our results demonstrated that addition of 0.025% and 0.05% TTO increased the proliferation of BMECs, and significantly enhanced (P < 0.05) the viability of BMECs exposed to Staphylococcus aureus (S. aureus). An inhibitory effect was observed against the growth of S. aureus by TTO incubation. The 0.05% TTO reduced S. aureus biofilm formation, association and invasion of S. aureus to BMECs, and changed the morphological and structural features of S. aureus. The proinflammatory cytokines IL-1β, IL-6, and TNF-α were decreased (P < 0.001) by the incubation of TTO. Interestingly, the expression of IL-8 known for PMNL chemotactic function was elevated (P < 0.05) by 0.05% TTO treatment. Consistently, 0.05% TTO increased the migration of PMNL in S. aureus-exposed BMECs when compared with S. aureus treatment alone (P < 0.05). In addition, PMNL incubated with 0.05% TTO decreased the levels of NFKB inhibitor alpha (NFKBIA) and TNF-α. Our results indicate that use of TTO can relieve the BMECs pro-inflammatory response caused by S. aureus and promote the migration of PMNL to mount the innate immune responses, and it may be novel strategy for the treatment of bovine mastitis caused by S. aureus.

中文翻译：

---

茶树油提取物对牛乳腺上皮细胞和多形核白细胞的保护作用。

茶树油 (TTO) 在抗菌活性和减轻炎症反应中起重要作用。牛乳腺上皮细胞和多形核白细胞 (PMNL) 可以积极应对牛乳腺炎感染。然而，TTO 提取物对牛乳腺上皮细胞 (BMECs) 和 PMNL 的先天免疫反应的调节作用仍未见报道。因此，本研究的目的是评估 TTO 提取物对参与 BMECs 和 PMNL 的先天免疫反应的基因 mRNA 水平的影响。我们的研究结果表明，添加 0.025% 和 0.05% TTO 增加了 BMECs 的增殖，并显着提高了 (P < 0.05) 暴露于金黄色葡萄球菌 (S. aureus) 的 BMECs 的活力。通过 TTO 培养观察到对金黄色葡萄球菌生长的抑制作用。0.05% TTO 降低了 S。金黄色葡萄球菌生物膜的形成、金黄色葡萄球菌对BMECs的结合和侵袭，改变了金黄色葡萄球菌的形态和结构特征。通过 TTO 的孵育，促炎细胞因子 IL-1β、IL-6 和 TNF-α 降低（P < 0.001）。有趣的是，通过 0.05% TTO 处理，已知用于 PMNL 趋化功能的 IL-8 的表达升高（P < 0.05）。与单独处理金黄色葡萄球菌相比，0.05% TTO 增加了 PMNL 在金黄色葡萄球菌暴露的 BMEC 中的迁移（P < 0.05）。此外，与 0.05% TTO 一起孵育的 PMNL 降低了 NFKB 抑制剂 α (NFKBIA) 和 TNF-α 的水平。我们的研究结果表明，使用 TTO 可以缓解金黄色葡萄球菌引起的 BMECs 促炎反应，并促进 PMNL 迁移以产生先天免疫反应，