核受体LXRα抗奶牛乳腺炎作用机制研究

The severe inflammatory response during the pathogenesis of clinical mastitis in dairy cows often causes serious injury to mammary tissues. To effective control the inflammatory response is essential for the treatment of the disease. LXRα, one of the main members of the nuclear receptor superfamily, has been reported to play important roles in the pathologic process of a variety of diseases. In our preliminary study, we found that activation of LXRα could inhibit LPS-induced mastitis in mice. However, the anti-inflammatory mechanism remains unclear. To further investigate the protective effects and mechanism of LXRα on dairy cattle mastitis, we carried out the following studies: firstly, we validated the anti-inflammatory effects of LXRα in LPS-stimulated bovine mammary epithelial cells in vitro. Secondly, we detected the effects of LXRα on LPS-induced TLR4 oligomerization and translocation of TLR4 to lipid rafts to analysis the effects of LXRα on TLR4 signaling pathway. Thirdly, we investigated the effects of LXRα on ABCA1 and ABCG1 expression, as well as the integrity of lipid rafts. Finally, we clarified the anti-inflammatory mechanism through cholesterol replenishment experiment and knockdown of ABCA1 and ABCG1. These results not only provided novel theoretical base for the treatment of mastitis, but also provided preliminary experimental data and reference in researching drugs for the treatment of mastitis based on the target of LXRα.

奶牛临床型乳腺炎发病过程中剧烈的炎症反应会对乳腺组织造成严重损伤。如何有效控制炎症反应是决定该病临床转归的重要环节。LXRα是核受体超家族成员之一，在多种疾病的发病过程中发挥重要作用。申请人前期研究发现，激活LXRα对LPS诱导的小鼠乳腺炎具有显著的抗炎作用，但机制尚不清楚。为深入探索LXRα抗奶牛乳腺炎作用及机制，本项目展开如下研究：首先验证激活LXRα对LPS刺激奶牛乳腺上皮细胞的抗炎作用；其次检验激活LXRα对LPS诱导的TLR4二聚化及向脂筏募集的影响，分析LXRα对TLR4信号通路的抑制作用；再次研究激活LXRα对ABCA1和ABCG1等胆固醇代谢调节元件及脂筏形成的影响；最后通过胆固醇恢复试验及敲低ABCA1和ABCG1揭示LXRα抗奶牛乳腺炎作用机制。本项目不仅为以LXRα为靶点的抗乳腺炎药物研发提供实验依据及指导，还可为奶牛乳腺炎治疗提供新的思路。

奶牛临床型乳腺炎发病过程中剧烈的炎症反应会对乳腺组织造成严重损伤。如何有效控制炎症反应是决定该病临床转归的重要环节。LXRα是核受体超家族成员之一，在多种疾病的发病过程中发挥重要作用。申请人前期研究发现，激活LXRα对LPS诱导的小鼠乳腺炎具有显著的 抗炎作用，但机制尚不清楚。为深入探索LXRα抗奶牛乳腺炎作用及机制，本项目展开如下研究：首先验证激活LXRα对LPS刺激奶牛乳腺上皮细胞的抗炎作用；其次检验激活LXRα对LPS诱导的TLR4二聚化及向脂筏募集的影响，分析LXRα对TLR4信号通路的抑制作用；再次研究激活LXRα对ABCA1和ABCG1等胆固醇代谢调节元件及脂筏形成的影响；最后通过胆固醇恢复试验及敲低ABCA1和ABCG1揭示LXRα抗奶牛乳腺炎作用机制。结果显示：激活LXRα可以显著抑制LPS诱导的炎性细胞因子产生；同时结果显示激活LXRα对LPS诱导的TLR4表达没有影响，但是激活LXRα可以显著抑制TLR4二聚化及TLR4在脂筏中的表达，结果表明激活LXRα对TLR4信号通路具有抑制作用；再次，结果显示激活LXRα可以上调ABCA1和ABCG1的表达，并可以降低脂筏中胆固醇的含量来扰乱脂筏的形成；最后，我们发现在细胞中添加胆固醇可以阻止LXRα的抗炎效果。结果表明激活LXRα可以上调ABCA1和ABCG1的表达，进而降低脂筏中胆固醇的含量来扰乱脂筏，最终抑制TLR4二聚化及TLR4向脂筏的募集，来发挥抗炎作用。本项目不仅为以LXRα为靶点的抗乳腺炎药物研发提供实验依据及指导，还可为奶牛乳腺炎治疗提供新的思路。