Karahoda Rona, Abad Cilia, Horackova Hana, Kastner Petr, Zaugg Jonas, Cerveny Lukas, Kucera Radim, Albrecht Christiane, Staud Frantisek
Department of Pharmacology and Toxicology, Faculty of Pharmacy in Hradec Kralove, Charles University, Hradec Kralove, Czechia.
Department of Pharmaceutical Chemistry and Pharmaceutical Analysis, Faculty of Pharmacy in Hradec Kralove, Charles University, Hradec Kralove, Czechia.
Front Cell Dev Biol. 2020 Sep 18;8:574034. doi: 10.3389/fcell.2020.574034. eCollection 2020.
L-Tryptophan is an essential amino acid and a precursor of several physiologically active metabolites. In the placenta, the serotonin and kynurenine metabolic pathways of tryptophan metabolism have been identified, giving rise to various molecules of neuroactive or immunoprotective properties, such as serotonin, melatonin, kynurenine, kynurenic acid, or quinolinic acid. Current literature suggests that optimal levels of these molecules in the fetoplacental unit are crucial for proper placenta functions, fetal development and programming. Placenta is a unique endocrine organ that, being equipped with a battery of biotransformation enzymes and transporters, precisely orchestrates homeostasis of tryptophan metabolic pathways. However, because pregnancy is a dynamic process and placental/fetal needs are continuously changing throughout gestation, placenta must adapt to these changes and ensure proper communication in the feto-placental unit. Therefore, in this study we investigated alterations of placental tryptophan metabolic pathways throughout gestation. Quantitative polymerase chain reaction (PCR) analysis of 21 selected genes was carried out in first trimester ( = 13) and term ( = 32) placentas. Heatmap analysis with hierarchical clustering revealed differential gene expression of serotonin and kynurenine pathways across gestation. Subsequently, digital droplet PCR, Western blot, and functional analyses of the rate-limiting enzymes suggest preferential serotonin synthesis early in pregnancy with a switch to kynurenine production toward term. Correspondingly, increased function and/or protein expression of serotonin degrading enzyme and transporters at term indicates efficient placental uptake and metabolic degradation of serotonin. Lastly, gene expression analysis in choriocarcinoma-derived cell lines (BeWo, BeWo b30, JEG-3) revealed dissimilar expression patterns and divergent effect of syncytialization compared to primary trophoblast cells isolated from human term placentas; these findings show that the commonly used placental models are not suitable to study placental handling of tryptophan. Altogether, our data provide the first comprehensive evidence of changes in placental homeostasis of tryptophan and its metabolites as a function of gestational age, which is critical for proper placental function and fetal development.
L-色氨酸是一种必需氨基酸，也是几种生理活性代谢物的前体。在胎盘中，已确定色氨酸代谢的血清素和犬尿氨酸代谢途径，可产生具有神经活性或免疫保护特性的各种分子，如血清素、褪黑素、犬尿氨酸、犬尿喹啉酸或喹啉酸。当前文献表明，这些分子在胎儿-胎盘单位中的最佳水平对于胎盘正常功能、胎儿发育和编程至关重要。胎盘是一个独特的内分泌器官，配备了一系列生物转化酶和转运蛋白，精确地协调色氨酸代谢途径的稳态。然而，由于怀孕是一个动态过程，胎盘/胎儿的需求在整个妊娠期不断变化，胎盘必须适应这些变化并确保胎儿-胎盘单位中的适当沟通。因此，在本研究中，我们调查了整个妊娠期胎盘色氨酸代谢途径的变化。在孕早期（n = 13）和足月（n = 32）胎盘上对21个选定基因进行了定量聚合酶链反应（PCR）分析。通过层次聚类的热图分析揭示了整个妊娠期血清素和犬尿氨酸途径的差异基因表达。随后，数字液滴PCR、蛋白质印迹以及限速酶的功能分析表明，妊娠早期优先合成血清素，足月时转向犬尿氨酸生成。相应地，足月时血清素降解酶和转运蛋白的功能和/或蛋白质表达增加表明胎盘对血清素的有效摄取和代谢降解。最后，绒毛膜癌衍生细胞系（BeWo、BeWo b30、JEG-3）中的基因表达分析显示，与从人类足月胎盘中分离的原代滋养层细胞相比，其表达模式不同，合体化的影响也不同；这些发现表明，常用的胎盘模型不适用于研究胎盘对色氨酸的处理。总之，我们的数据首次全面证明了色氨酸及其代谢物的胎盘稳态随胎龄变化，这对胎盘正常功能和胎儿发育至关重要。
