SNAT2介导E2/P4调控山羊乳腺上皮细胞增殖与分泌的作用及机制

Mammary gland dyslpasia and postpartum lactation disorder can seriously impact the production capacity of dams and the growth of newborns, while hormonal disorders is one of the important factors leading to the above problems. Studies have shown that type-A sodium-dependent neutral amino acid transporter 2 (SNAT2) played an important role in regulating tissue development, and that 17β-estrotial (E2) regulated the expression of SNAT2 in the mammary gland. However, the role of SNAT2 in E2 and progesterone（P4）disoder–mediated dysgalactia is unclear. Here, the goats were exploited in the current study, qRT-PCR, Western blot, Immunofluorescence, Flow cytometry, Electronic speculum and ELISA technologies were applied to firstly clarify the expression pattern of SNAT2 during pregnancy of mammary gland development or the proliferation and lactation of goat mammary epithelial cells (GMECs) with different ratios of E2/P4. Then the knocking-out, RNAi, and over-expression of SNAT2 were carried out to explore the effect of SNAT2 protein level-changes on the proliferation, apoptosis, tight junction, and secretion of GMECs. Further, we would explore whether mTOR signaling pathway played a role in SNAT2 regulating proliferation and secretion of GMECs. The current study would provide new insights and experimental basis for profoundingly analysing mammary gland dysplasia and lactation disorder induced by hormonal disorders.

乳腺发育不良和泌乳障碍严重影响母畜生产能力和新生幼畜生长，而激素水平紊乱是其产生的重要原因之一。研究显示，A型钠离子依赖性中性氨基酸转运体2（SNAT2）在组织发育中有重要作用，17β-雌二醇（E2）调控SNAT2在乳腺组织的表达。然而SNAT2在E2和孕酮（P4）紊乱引发的泌乳障碍中的作用尚不清楚。本项目以山羊为研究对象，应用qRT-PCR、Western blot、免疫荧光、流式细胞术、电镜和ELISA等方法，首先明确生理及紊乱E2/P4条件下山羊妊娠期乳腺发育及山羊乳腺上皮细胞（GMECs）增殖和分泌乳蛋白过程中SNAT2表达规律；通过基因敲除、RNAi和基因过表达等技术探讨SNAT2表达变化对GMECs增殖、紧密连接及分泌乳蛋白的影响；进一步探讨mTOR信号通路在SNAT2调节GMECs增殖与功能中的作用。本项目为深度解析激素紊乱引发的乳腺发育不良及泌乳障碍提供新思路和理论依据。

乳腺发育不良和泌乳障碍严重影响了母畜生产性能和新生幼畜生长，是限制养殖业体质增效的重要原因，而激素水平紊乱是导致母畜产后泌乳障碍的重要原因之一。研究显示，A型钠离子依赖性中性氨基酸转运体2（SNAT2）在组织发育中有重要作用，17β-雌二醇（E2）调控SNAT2在乳腺组织中的表达。由于E2和P4在山羊乳腺发育和泌乳中有重要调控作用，但E2/P4是否通过SNAT2调控乳腺发育和泌乳尚不清楚。.本项目首先应用米非司酮建立了小鼠产后早期缺乳模型，验证了早期缺乳模型小鼠雌激素和孕酮的确实存在异常水平；其次以妊娠和泌乳不同时期山羊和体外培养山羊乳腺上皮细胞为研究对象，探索SNAT2介导E2/P4调控山羊乳腺上皮细胞增殖与分泌的作用及机制。结果发现，SNAT2在妊娠137天（Pd137）和泌乳第四天（Ld4）表达量较妊娠早期和泌乳后期显著提高；体外培养山羊乳腺上皮细胞（GMECs），给予不同浓度E2 和P4，在E2和P4浓度促进细胞增殖最佳水平时，SNAT2表达也有显著提高；随着P4水平升高到生理水平的4倍，紧密连接分子claudin-1, claudin-3, occludin和ZO-1 mRNA和蛋白表达均有显著上升；通过干扰和过表达SNAT2发现，紧密连接蛋白claudin-1和occludin，以及乳蛋白β-lactogobulin的mRNA水平等均有一定程度下降和提高；SNAT2蛋白过表达后，p-mTOR 和p-S6K1蛋白表达水平也有显著提升。以上结果表明，SNAT2介导了E2和P4对山羊乳腺上皮细胞增殖和功能的调控作用，而mTOR信号通路可能是SNAT2介导E2和P4调控山羊乳腺上皮细胞增殖和功能的分子通路。这些研究将有助于深入探讨激素紊乱如何引起母畜乳腺发育不良和泌乳障碍及为解决临床上母畜产后泌乳不足提供理论依据。