Nilsson Ulrika K, Andersson Rolf G G, Ekeroth Johan, Hallin Elisabeth C, Konradsson Peter, Lindberg Jan, Svensson Samuel P S
Division of Pharmacology, Department of Medicine and Care, Faculty of Health Sciences, Linköpings Universitet, SE-581 85 Linköping, Sweden.
Lipids. 2003 Oct;38(10):1057-64. doi: 10.1007/s11745-006-1161-2.
Lysophosphatidic acid (LPA) is a lipid mediator that, among several other cellular responses, can stimulate cells to mobilize calcium (Ca2+). LPA is known to activate at least three different subtypes of G protein-coupled receptors. These receptors can then stimulate different kinds of G proteins. In the present study, LPA and LPA analogs were synthesized from (R)- and (S)-glycidol and used to characterize the ability to stimulate Ca2+ mobilization. The cytosolic Ca2+ concentration ([Ca2+]i) was measured in fura-2-acetoxymethylester-loaded human erythroleukemia (HEL) cells. Furthermore, a reverse transcriptase polymerase chain reaction was used to characterize LPA receptor subtypes expressed in HEL cells. The results show that HEL cells mainly express LPA1 and LPA2, although LPA3 might possibly be expressed as well. Moreover, LPA and its analogs concentration-dependently increased [Ca2+]i in HEL cells. The response involved both influx of extracellular Ca2+ and release of Ca2+ from intracellular stores. This is the first time the unnatural (S)-enantiomer of LPA, (S)-3-O-oleoyl-1-O-phosphoryl-glycerol, has been synthesized and studied according to its ability to activate cells. The results indicate that this group of receptors does not discriminate between (R)- and (S)-enantiomers of LPA and its analogs. When comparing ether analogs having different hydrocarbon chain lengths, the tetradecyl analog (14 carbons) was found to be the most effective in increasing [Ca2+]i. Pertussis toxin treatment of the HEL cells resulted in an even more efficient Ca2+ mobilization stimulated by LPA and its analogs. Furthermore, at repeated incubation with the same ligand no further increase in [Ca2+]i was obtained. When combining LPA with the ether analogs no suppression of the new Ca2+ signal occurred. All these findings may be of significance in the process of searching for specific agonists and antagonists of the LPA receptor subtypes.
溶血磷脂酸（LPA）是一种脂质介质，在多种细胞反应中，它能刺激细胞动员钙离子（Ca2+）。已知LPA可激活至少三种不同亚型的G蛋白偶联受体。这些受体随后可刺激不同种类的G蛋白。在本研究中，LPA及其类似物由（R）-和（S）-缩水甘油合成，并用于表征刺激Ca2+动员的能力。在负载呋喃-2-乙酰氧基甲酯的人红白血病（HEL）细胞中测量胞质Ca2+浓度（[Ca2+]i）。此外，使用逆转录聚合酶链反应来表征HEL细胞中表达的LPA受体亚型。结果表明，HEL细胞主要表达LPA1和LPA2，尽管LPA3也可能表达。此外，LPA及其类似物在HEL细胞中浓度依赖性地增加[Ca2+]i。该反应涉及细胞外Ca2+的内流和细胞内储存的Ca2+释放。这是首次根据其激活细胞的能力合成并研究LPA的非天然（S）-对映体，即（S）-3-O-油酰基-1-O-磷酰甘油。结果表明，这组受体不会区分LPA及其类似物的（R）-和（S）-对映体。比较具有不同烃链长度的醚类似物时，发现十四烷基类似物（14个碳）在增加[Ca2+]i方面最有效。用百日咳毒素处理HEL细胞导致LPA及其类似物刺激的Ca2+动员更有效。此外，在与相同配体重复孵育时，[Ca2+]i没有进一步增加。当将LPA与醚类似物结合时，没有出现新Ca2+信号的抑制。所有这些发现可能在寻找LPA受体亚型的特异性激动剂和拮抗剂的过程中具有重要意义。
