Abstract:

【Objective】Cow mastitis has been one of the biggest challenges in dairy farming and dairy products industry, which restricts the healthy development of dairy industry. Effective prevention and treatment of cow mastitis can provide a good guarantee for the health of cows and the production of high-quality dairy products. This experiment explored the effects of tea tree oil on LPS-induced mastitis in dairy cows, and explored the feasibility of using tea tree oil instead of antibiotics to treat mastitis in dairy cows. This experiment provides a reference for the treatment of dairy cow mastitis with tea tree oil. 【Methods】The cells in good condition, were selected, which were added 50, 100, 200, 500, and 1 000 μg·mL^-1 LPS respectively in the culture of these cells to detect the relevant indicators. The tea tree oil and LPS were added to the model for co-culture. The model of dairy cow mastitis induced LPS was established by the CCK-8 method, flow cytometry, real-time fluorescence quantification and ELISA assay. Antagonistic effect of tea tree oil on LPS in dairy cow mastitis cell model: 0.0002%, 0.0004%, 0.0006%, 0.0008%, 0.001%, 0.002%, 0.004%, 0.006%, 0.008% and 0.01% tea tree oil were added to the dairy cow mastitis cell model induced by 200 μg·mL^-1 LPS for 12 hours to detect the related indexes. 【Result】CCK-8 method was used to detect the cell proliferation activity. The results showed that under the condition of 100 μg·mL^-1 LPS poisoning, the activity of the cells began to decline in varying degrees. There was not a large number of apoptosis in 100 μg·mL^-1 LPS after 12 hours of induction, while about 46% of the cells showed early and late apoptosis in 200 μg·mL^-1 LPS. 200 μg·mL^-1 LPS induced for 12 hours was the best condition for the establishment of mastitis model. The results also showed that when tea tree oil concentration was 0.0004%, 0.0006% and 0.0008%, the apoptosis rate of the cells decreased. Among them, when tea tree oil concentration was 0.0006%, the protection effect was the most obvious. The proportion of living cells was 71.95%, the proportion of early apoptotic cells was 22.15%, and the proportion of late apoptotic cells was 5.11%; compared with the living cells, the proportion of the mastitis model group of tree oil increased by about 22%. After that, the expression of cytokines and apoptotic factors were detected by qPCR in the three groups with protective effect. With the increase of the concentration of tea tree oil, the expression of TNF-α was down regulated more, the expression of IL-6 was down regulated less (P< 0.01), and the expression of STAT1 was up regulated slightly when 0.0004% tea tree oil was added, while down regulated slightly when 0.0006% and 0.0008% tea tree oil were added, and the expression of tea tree oil with 0.0006% concentration was the lowest (P< 0.05). The expression of NF-κB, MAPK and caspase-3 was significantly reduced in the three groups of tea tree oil adding concentration. Among them, the expression of inflammatory response protein in 0.0006% tea tree oil group was the lowest, about 50% of that in the blank control group. The protein expression was almost the same, about 55% of the blank control group (P< 0.05).【Conclusion】Tea tree oil had a certain antagonistic effect on LPS within the appropriate concentration range, which could reduce the proportion of apoptosis, improve the survival proportion of normal cells, and down regulate the expression of inflammatory factors, apoptosis factors and corresponding proteins.

Key words: tea tree oil, cow, LPS, mastitis, effect mechanism