Gamma-Aminobutyric Acid is Synthesized by Endothelial Cells: Implications in Preeclampsia

摘要 先兆子痫影响3%至6%的孕妇，对母亲和婴儿具有破坏性影响。 然而，没有分子靶点可以推动药物发现走向治疗成功或早期发现。 诊断标志物，可以预测这种综合征的发病之前，发展的症状。我们有 首次观察到γ-氨基丁酸（GABA）是一种中枢抑制性神经递质， 血管内皮细胞合成并释放到体循环中，因此我们的研究结果 解释GABA在体循环中的重要来源。此外，GABA水平在 与非妊娠妇女相比，先兆子痫患者的循环减少，但涉及的机制是 不知道。GABA在内皮细胞中的作用，以及GABA合成和释放的减少是如何引起内皮细胞凋亡的。 GABA发生在先兆子痫中，其在先兆子痫病因学中的意义尚不清楚。初步 实验中，我们观察到从预处理中获得的人脐静脉内皮细胞（HUVEC）， 与正常妊娠的HUVEC相比， 孕妇我们还在先兆子痫的HUVEC中鉴定了L-甲硫氨酰谷氨酸盐（LMG），其抑制了 内皮细胞合成GABA。 基于我们的新观察，我们假设：“内皮合成减少， GABA的释放是内皮功能障碍的原因，并有助于前- 我们的假设将通过以下三个具体目标进行检验。 具体目标1：我们将评估是否从患有先兆子痫的母亲获得HUVEC（PE-HUVEC） 合成和释放较少的GABA时相比，从母亲与正常怀孕。 具体目的2：比较GABA在维持HUVEC正常功能中的作用， 与游离脂肪酸（FFA）氧化，丙酮酸氧化，ATP合成， 调节粘附分子的表达和活性氧（ROS）的产生，以及如何 PE-HUVEC中GABA合成的减少影响这些过程，导致内皮细胞功能障碍。 具体目标3：（a）我们将评估内源性GABA合成抑制剂LMG的作用， 在PE-HUVEC中，对NP-HUVEC和HAEC的一些GABA介导的功能的影响，如在特定的 目的2和（B）我们将定量正常人脐带血和母血中GABA和LMG的水平。 并将其与先兆子痫妊娠中的脐带和母体水平相关联。

Abstract Preeclampsia affects 3 to 6 % of pregnant women with devastating effects on the mother and the baby. However, there are no molecular targets that could drive drug discovery towards therapeutic success or early diagnostic markers that could predict the onset of this syndrome prior to development of symptoms. We have for the first time observed that gamma Aminobutyric acid (GABA) a central inhibitory neurotransmitter is synthesized and released by vascular endothelial cells into the systemic circulation and our findings therefore explain one important source of GABA in the systemic circulation. Furthermore, the level of GABA in the circulation is decreased in preeclampsia compared to non-pregnant women but the mechanism(s) involved is not known. The actions of GABA in the endothelial cells, and how a decrease in synthesis and release of GABA occurs in preeclampsia and its significance in the etiology of preeclampsia is not known. In preliminary experiments, we observed that human umbilical venous endothelial cells (HUVEC) obtained from pre- eclamptic pregnancies synthesize and release less GABA when compared with HUVEC obtained from normal pregnant women. We have also identified L-methionyl glutamate (LMG) in preeclamptic HUVEC which inhibits GABA synthesis by endothelial cells. Based on our novel observations, we HYPOTHESIZE that: “a decrease in endothelial synthesis and release of GABA is responsible for endothelial dysfunction and contributes to the pathogenesis of pre- eclampsia” and our hypothesis will be tested by the following three specific aims. Specific Aim 1: We will assess whether HUVEC obtained from mothers with pre-eclampsia (PE-HUVEC) synthesize and release less GABA when compared to those obtained from mothers with normal pregnancy. Specific Aim 2: We will compare the role of GABA in maintaining the normal functions of HUVEC obtained from normal pregnancies with relation to free fatty acid (FFA) oxidation, pyruvate oxidation, ATP synthesis, regulation of adhesion molecules expression and reactive oxygen species (ROS) generation and how decreased synthesis of GABA in PE-HUVEC affects these processes to cause endothelial cell dysfunction. Specific Aim 3: (a) We will assess the effects of the endogenous GABA synthesis inhibitor LMG, which is high in PE-HUVEC, on some of the GABA mediated functions of NP-HUVEC and HAEC as assessed under specific aim 2 and (b) we will quantify the levels of GABA and LMG in the cord and maternal blood of normal pregnancy and correlate this with the cord and maternal levels in preeclamptic pregnancy.