孕期咖啡因暴露所致宫内发育迟缓的胎盘氨基酸转运机制研究

Prenatal caffeine exposure (PCE) is an identified risk factor for intrauterine growth retardation (IUGR). Leucine(Leu) and isoleucine (Ile) are the main ingredients in human’s muscle synthesis. We have previously demonstrated that the expression of Leu and Ile decreased in fetal peripheral blood of IUGR caused by PCE, but the mechanisms remained unclear. Researches showed that the transport function of L-typemino acid transporter 1 (LAT1) mediated Leu and Ile in placenta was related to Hippo signaling pathway, which was regulated by FRMD6. We found that PCE led to decreased expression of adenosine receptor 2a (A2aR) and increased level of acetyltransferase p300. It could be speculated that PCE may promote acetyltransferase p300 expression by antagonism of A2aR, which could activate Hippo signaling pathway by raising the histone acetylation and expression level of placental FRMD6, and eventually contribute to IUGR by down-regulating Leu and Ile expression in fetal peripheral blood through decreasing LAT1 transport function. This project intends to clarify the effects and mechanisms of placental amino acid transport in IUGR by PCE and provides theoretical and experimental basis for exploring the treatment of IUGR at early stage.

孕期咖啡因暴露（PCE）是导致宫内发育迟缓（IUGR）的确切诱因之一。亮氨酸（Leu）和异亮氨酸（Ile）是机体合成肌肉的重要原料。本室前期证实，PCE所致IUGR的子代外周血Leu和Ile含量减少，然而，发生机制尚不明确。文献提示，L型氨基酸转运体1（LAT1）介导Leu和Ile的胎盘转运，其转运功能与Hippo信号通路相关，而Hippo信号通路受FRMD6基因调控。我们发现，PCE可拮抗胎盘腺苷受体2a（A2aR），增加乙酰转移酶p300表达。由此推测，咖啡因通过抑制胎盘A2aR后上调p300表达，引起胎盘FRMD6基因组蛋白乙酰化修饰及表达增加，后者可激活Hippo信号通路，下调胎盘LAT1转运功能，导致子代外周血Leu和Ile含量降低，最终产生 IUGR。本项目为阐明胎盘氨基酸转运在咖啡因致IUGR中的作用及发生机制，探寻PCE所致IUGR的早期干预措施，提供理论和实验依据。

宫内发育迟缓（IUGR）是产科常见的并发症。蛋白质是胚胎发育过程中的三大营养物质之一，氨基酸作为蛋白质的基本单位，是影响胎儿体重增长的关键因素，但氨基酸宫内转运在IUGR的作用和发生机制并不清楚。本项目在建立的孕前咖啡因暴露所致子代大鼠IUGR模型上，发现孕期咖啡因暴露可拮抗胎盘腺苷受体2a（A2aR）表达, 增加胎盘WWC1表达并伴随启动子区组蛋白H3K27ac修饰改变，引起胎盘Hippo信号通路中YAP1/TAZ入核减少，从而下调胎盘氨基酸转运体LAT1，导致子代外周血氨基酸浓度降低，最终产生IUGR；进一步，在体外培养的原代滋养细胞和/或Bewo细胞中，我们发现，不同浓度的咖啡因可直接抑制滋养细胞A2aR表达，上调WWC1表达并伴随基因启动子区H3K27ac乙酰化改变， 抑制Hippo信号通路YAP1/TAZ表达，最终下调转运体LAT1表达，且A2aR的激动剂CGS21680可完全逆转咖啡因所致的WWC1表达上升，Hippo信号通路抑制，氨基酸转运体LAT1表达下调。我们认为，孕期咖啡因暴露所致IUGR通过拮抗A2aR，下调WWC1表达及组蛋白H3K27ac乙酰化水平，抑制Hippo信号通路从而下调胎盘氨基酸转运体LAT1，导致子代外周血氨基酸浓度减少，最终产生IUGR。同时，我们进一步收集了人群IUGR的脐血，母血和胎盘进行验证，本研究为解析IUGR的胎盘氨基酸转运的作用和分子机制，为临床上探寻IUGR早期干预措施，提供了理论和研究依据。本项目待发表SCI论文2篇，还在整理数据中。