State Key Laboratory of Animal Nutrition, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China; Laboratory of Quality and Safety Risk Assessment for Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China; Key Laboratory of Quality & Safety Control for Milk and Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
State Key Laboratory of Membrane Biology, Tsinghua University-Peking University Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
Int Immunopharmacol. 2021 Dec;101(Pt A):108149. doi: 10.1016/j.intimp.2021.108149. Epub 2021 Oct 8.
Lipopolysaccharide (LPS) can remain in dairy products after the sterilization of milk powder and may pose a threat to the health of infants and young children. There is a large amount of alkaline phosphatase (ALP) in raw milk, which can remove the phosphate bond of LPS, thus, detoxifying it. ALP is regarded as an indicator of the success of milk sterilization due to its strong heat resistance. ALP can alleviate the toxicity of LPS in enteritis and nephritis models, but the mechanism by which oral-intake of ALP protects liver tissue from LPS stimulation is unclear. In this study, an in vivo acute mouse liver injury model was induced by C. sakazakii LPS (200 μg/kg) and used to verify the protective mechanism of ALP (200 U/kg) on mice livers. The related pathways were also verified by in vitro cell culture. Enzyme linked immunosorbent assays (ELISAs), quantitative reverse transcription PCR (RT-qPCR) and western blotting were used to detect the levels of inflammatory factors at the protein level and RNA level, and to confirm the inflammation of liver tissue caused by LPS. ALP was found to alleviate acute liver injury in vitro by activating miR-146a. We found that ALP could up-regulate the level of miR146a and subsequently alleviates the expression of TLR4, TNF-α, matured IL-1β, and NF-κB in mouse liver tissue and hepatocytes; thus, reducing liver inflammation. Herein, we demonstrated for the first time that oral-intake of ALP protected liver tissue by up-regulating the expression of miR-146a and alleviating inflammatory reactions; thus, providing a research basis for the proper processing of milk. This study also suggests that producers should improve the awareness of the protective effects of bioactive proteins in raw milk.
脂多糖（LPS）在奶粉灭菌后仍会残留在乳制品中，可能对婴幼儿的健康构成威胁。生乳中含有大量碱性磷酸酶（ALP），它可以去除 LPS 的磷酸酯键，从而使其解毒。由于 ALP 具有很强的耐热性，因此它被视为牛奶灭菌成功的指标。ALP 可以减轻肠炎和肾炎模型中 LPS 的毒性，但口服 ALP 保护肝脏组织免受 LPS 刺激的机制尚不清楚。在本研究中，通过 C. sakazakii LPS（200μg/kg）诱导体内急性小鼠肝损伤模型，验证了 ALP（200U/kg）对小鼠肝脏的保护机制。还通过体外细胞培养验证了相关途径。酶联免疫吸附测定（ELISA）、定量逆转录 PCR（RT-qPCR）和蛋白质印迹法用于检测蛋白水平和 RNA 水平的炎症因子水平，并证实 LPS 引起的肝组织炎症。ALP 通过激活 miR-146a 在体外减轻急性肝损伤。我们发现 ALP 可以上调 miR146a 的水平，从而减轻小鼠肝组织和肝细胞中 TLR4、TNF-α、成熟的 IL-1β 和 NF-κB 的表达；从而减轻肝脏炎症。在此，我们首次证明口服 ALP 通过上调 miR-146a 的表达并减轻炎症反应来保护肝脏组织；从而为适当处理牛奶提供了研究基础。本研究还表明，生产者应提高对生乳中生物活性蛋白保护作用的认识。
