Lysophosphatidic acid (LPA) is a water soluble phospholipid derivative.The structure of the compound is shown in figure 1. It is the considered to be the simplest form of the glycerophospholipids that are discovered in vivo (1). The compound is a well-known important potent extracellular signaling molecule. LPA reacts with G protein-coupled receptors also known as GPCR, as a result of which it is found to alter many different cellular responses. It is found to change the dynamics of cell survival operational procedure in the cell proliferation, cytoskeletal changes, and calcium influx and in many more cellular activities (2, 3). The pharmacologically active LPA was initially isolated from brain extracts in 1961 by KIRSCHNER. H. and VOGT. W. (4). Since then, 7696 full-text journal articles related to LPA have already been published on NCBI and 3875 articles among them were supported by NIH grant.
In the current times, there are multiple LPA receptors that are found to be discovered and reported. Th most prominent are the LPA1, LPA2, and LPA3. These are also known as EDG2, EDG4, and EDG7 respectively. The recently identified LPA receptors include LPA4 they include P2RY9, GPR23. Apart from these compounds the LPA5 and LPA6 are found in the systems. These are otherwise known as GPR92 and P2RY5, GPR87. These studies have revealed that LPA binds to its receptors, the heterotrimeric G proteins, and includes Gi/o, G12/13, Gq, and Gs. They are found to mediate effects in numerous cell types and model systems. These are also found to be similar in vitro and in vivo. There is the gain- and loss-of-function study. That has led to physiological and pathophysiological influences on almost every organ system and developmental stage of every organism (5).
The secretory phospholipase A2 (PS-PLA2) and phosphatidylserine-specific phospholipase A1 (PS-PLA1) produce Lysophospholipids are in active platelets. In plasma, it is observed that lecithin-cholesterol acyltransferase (LCAT) and in PLA1-like enzyme is found to produce LPC (6-7). In the second major pathway, diacylglycerol kinase first converts diacylglycerol to phosphatidic acid (PA) or phospholipase D converted phospholipids D to PA. The compound PA is converted directly to LPA by the actions of either PLA1 or PLA2 (8). LPA is present in all eukaryotic tissues that have ever been tested. The most common form of LPA used in laboratory are the compounds 18:1 oleoyl-LPA which is also known as 1-acyl-2-hydroxy-sn-glycero-3-phosphate. However, there are more forms of LPA in different biological systems that have been discovered (9). The observed LPA in various biological systems spans from low Nano molar to micro molar levels. And serum is known to contain micro molar concentrations of LPA which is much higher than in plasma. It is to be noted that the, LPA concentrations in plasma are found to range from 0.1 ìM. These are much higher than the apparent Nano molar Kd of LPA 1-6 (10, 11).