Kleppa Marc-Jens, Erlenwein Sarah-Vanessa, Darashchonak Natallia, von Kaisenberg Constantin S, von Versen-Höynck Frauke
Department of Obstetrics and Gynecology, Hannover Medical School, Hannover, Germany.
PLoS One. 2014 Jun 5;9(6):e99217. doi: 10.1371/journal.pone.0099217. eCollection 2014.
Anticoagulants, e.g. low-molecular weight heparins (LMWHs) and acetylsalicylic acid (ASA) are prescribed to women at risk for pregnancy complications that are associated with impaired placentation and placental hypoxia. Beyond their role as anticoagulants these compounds exhibit direct effects on trophoblast but their impact on placental function is unknown. The amino acid transport systems A and L, which preferably transfer essential amino acids, are well-described models to study placental nutrient transport. We aimed to examine the effect of hypoxia, LMWHs and ASA on the activity of the placental amino acid transport systems A and L and associated signalling mechanisms.
The uptake of C14-MeAIB (system A) or H3-leucin (system L) was investigated after incubation of primary villous fragments isolated from term placentas. Villous tissue was incubated at 2% O2 (hypoxia), 8% O2 and standard culture conditions (21% O2) or at 2% O2 and 21% O2 with dalteparin or ASA. Activation of the JAK/STAT or mTOR signalling pathways was determined by Western analysis of total and phosphorylated STAT3 or Raptor.
Hypoxia decreased system A mediated MeAIB uptake and increased system L mediated leucine uptake compared to standard culture conditions (21% O2). This was accompanied by an impairment of STAT3 and a stimulation of Raptor signalling. System L activity increased at 8% O2. Dalteparin treatment reduced system A and system L activity under normoxic conditions and ASA (1 mM) decreased system A and L transporter activity under normoxic and hypoxic conditions.
Our data underline the dependency of placental function on oxygen supply. LMWHs and ASA are not able to reverse the effects of hypoxia on placental amino acid transport. These findings and the uncovering of the signalling mechanisms in more detail will help to understand the impact of LMWHs and ASA on placental function and fetal growth.
对于有妊娠并发症风险的女性，会开具抗凝剂，如低分子量肝素（LMWHs）和乙酰水杨酸（ASA），这些并发症与胎盘形成受损和胎盘缺氧有关。除了作为抗凝剂的作用外，这些化合物对滋养层细胞有直接影响，但其对胎盘功能的影响尚不清楚。氨基酸转运系统A和L，主要转运必需氨基酸，是研究胎盘营养物质转运的经典模型。我们旨在研究缺氧、低分子量肝素和乙酰水杨酸对胎盘氨基酸转运系统A和L活性及相关信号机制的影响。
从足月胎盘分离出初级绒毛片段进行孵育后，研究C14 - 甲基氨基异丁酸（系统A）或H3 - 亮氨酸（系统L）的摄取情况。绒毛组织在2%氧气（缺氧）、8%氧气及标准培养条件（21%氧气）下孵育，或在2%氧气和21%氧气条件下与达肝素或乙酰水杨酸一起孵育。通过对总STAT3或Raptor以及磷酸化STAT3或Raptor进行蛋白质印迹分析来确定JAK/STAT或mTOR信号通路的激活情况。
与标准培养条件（21%氧气）相比，缺氧降低了系统A介导的甲基氨基异丁酸摄取，并增加了系统L介导的亮氨酸摄取。这伴随着STAT3的受损和Raptor信号的刺激。在8%氧气条件下系统L活性增加。达肝素治疗在常氧条件下降低了系统A和系统L的活性，而乙酰水杨酸（1 mM）在常氧和缺氧条件下均降低了系统A和L转运体的活性。
我们的数据强调了胎盘功能对氧气供应的依赖性。低分子量肝素和乙酰水杨酸无法逆转缺氧对胎盘氨基酸转运的影响。这些发现以及对信号机制更详细的揭示将有助于理解低分子量肝素和乙酰水杨酸对胎盘功能和胎儿生长的影响。
