Orally administered phosphatidic acids and lysophosphatidic acids ameliorate aspirin-induced stomach mucosal injury in mice.

BACKGROUND: Recent investigations revealed that lysophosphatidic acid (LPA), a phospholipid with a growth factor-like activity, plays an important role in the integrity of the gastrointestinal tract epithelium. AIM: This paper attempts to clarify the effect of orally administered phosphatidic acid (PA) and LPA on aspirin-induced gastric lesions in mice. MATERIALS AND METHODS: Phospholipids, a free fatty acid, a diacylglycerol and a triglyceride at 1 mM (5.7 µmol/kg body weight) or 0.1 mM were orally administered to mice 0.5 h before oral administration of aspirin (1.7 mmol/kg). The total length of lesions formed on the stomach wall was measured as a lesion index. Formation of LPA from PA in the mouse stomach was examined by in vitro (in stomach lavage fluid), ex vivo (in an isolated stomach) and in vivo (in the stomach of a living mouse) examinations of phospholipase activity. RESULTS: Palmitic acid, dioleoyl-glycerol, olive oil and lysophosphatidylcholine did not affect the aspirin-induced lesions. In contrast, phosphatidylcholine (1 mM), LPA (1 mM) and PA (0.1, 1 mM) significantly reduced the lesion index. Evidence for formation of LPA from PA in the stomach by gastric phospholipase A2 was obtained by in vitro, ex vivo and in vivo experiments. An LPA-specific receptor, LPA2, was found to be localized on the gastric surface-lining cells of mice. CONCLUSION: Pretreatment with PA-rich diets may prevent nonsteroidal anti-inflammatory drug-induced stomach ulcers.

Intragastrically administered lysophosphatidic acids protect against gastric ulcer in rats under water-immersion restraint stress.

BACKGROUND AND AIM: Lysophosphatidic acid exerts important physiological effects on many types of animal cells through its specific binding to several G protein-coupled receptors. In particular, its potent wound-healing effect has attracted much attention. To determine whether lysophosphatidic acids in a foodstuff and Chinese medicine are effective in protecting against gastric ulcer, we subjected rats to water-immersion restraint stress. METHODS AND RESULTS: Three direct administrations of a solution of lysophosphatidic acid with a C18 fatty acyl group to the rat stomach in a concentration range of 0.001-0.1 mM resulted in a significant reduction in the number of gastric ulcers induced during water-immersion restraint stress, and the potencies were as follows: linoleoyl species=α-linolenoyl species>oleoyl species. Intragastric administrations of a solution of highly purified lysophosphatidic acid from soybean lecithin significantly protected against the stress-induced gastric ulcers at lower concentrations than partially purified lysophosphatidic acid from soybean lecithin did. In addition, administration of a decocted solution of antyu-san, and lysophosphatidic acid-rich Chinese medicine, to the stomach was more effective in protecting against stress-induced ulcer than decoctations of antyu-san lacking the corydalis tuber component that is rich in lysophosphatidic acid. CONCLUSIONS: These results clearly show that lysophosphatidic acid is the effective component of soybean lecithin and antyu-san in protection against stress-induced gastric ulcer in the rat model, and suggest that daily intake of lysophosphatidic acid-rich foods or Chinese medicines may be beneficial for prevention of stress-induced gastric ulcer in human subjects.

A clean-up technology for the simultaneous determination of lysophosphatidic acid and sphingosine-1-phosphate by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry using a phosphate-capture molecule, Phos-tag.

Lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) are growth factor-like lipids having a phosphate group. The concentrations of these mediator lipids in blood are considered to be potential biomarkers for early detection of cancer or vascular diseases. Here, we report a method for simultaneous determination of LPA and S1P using Phos-tag, a zinc complex that specifically binds to a phosphate-monoester group. Although both LPA and S1P are hydrophilic compounds, we found that they acquire hydrophobic properties when they form complexes with Phos-tag. Based on this finding, we developed a method for the enrichment of LPA and S1P from biological samples. The first partition in a two-phase solvent system consisting of chloroform/methanol/water (1:1:0.9, v/v/v) is conducted for the removal of lipids. LPA and S1P are specifically extracted as Phos-tag complexes at the second partition by adding Phos-tag. The Phos-tag complexes of LPA and S1P are detectable by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) and quantifiable based on the relative intensities of ions using 17:0 LPA and C17 S1P as internal standards. The protocol was validated by analyses of these mediator lipids in calf serum, a rat brain and a lung. The clean-up protocol is rapid, requires neither thin-layer chromatography (TLC) nor liquid chromatography (LC), and is applicable to both blood and solid tissue samples. We believe that our protocol will be useful for a routine analysis of LPA and S1P in many clinical samples.

Formation of lysophosphatidic acid, a wound-healing lipid, during digestion of cabbage leaves.

Lysophosphatidic acid (LPA) is a lipid mediator that plays a role in the process of wound healing in animal tissues, including the digestive tract. We determined LPA in several foodstuffs, and found that cabbage leaves were the richest source of LPA. We also found that, at 22 and 195 nmol/g (wet weight), LPA and phosphatidic acid (PA) were respectively formed during mastication of raw cabbage leaves and that the resulting PA was converted to LPA by pancreatic phospholipase A(2). The lipid extract obtained from ground cabbage leaves promoted the proliferation of Swiss 3T3 fibroblasts and the motility of HGC-27 cells, stomach-derived epithelial-like cells, at physiologically relevant concentrations. These activities of cabbage lipids were inhibited by Ki16425, an LPA-receptor antagonist. LPA formed during the digestion of cabbage leaves may be one of the components in the beneficial effect of ingested cabbage on a damaged digestive tract.

Production of bioactive lysophosphatidic acid by lysophospholipase D in hen egg white.

Lysophosphatidic acid (LPA), a lysophospholipid mediator, is produced extracellularly by lysophospholipase D (lysoPLD) secreted in several animal body fluids including blood plasma. Previously, we reported that hen egg white contains polyunsaturated fatty acid-rich LPA. In this study, we examined whether lysoPLD is involved in the production of LPA in hen egg white. LysoPLD activity was measured by determining LPA and choline by mass spectrometric and enzyme-linked fluorometric analyses, respectively. LysoPLD increased with increased dilution of egg white, indicating that one or more components of egg white strongly inhibit its lysoPLD activity. This dilution-dependent increase in the lysoPLD activity was masked by co-incubation of the egg white with lysozyme, a major protein in hen egg white. Furthermore, addition of Zn(2+), Mn(2+), Ni(2+), or Co(2+) to diluted egg white altered preference patterns of lysoPLD toward choline-containing substrates. In particular, the egg white lysoPLD activity was greatly increased when Co(2+) was added. The cation-requirement of lysoPLD activity in hen egg white resembled that of plasma autotaxin (ATX)/lysoPLD. Western blot analysis revealed that egg white contained a protein that was immunostained with anti-ATX antibody. These results suggested that LPA in hen egg white is produced from lysophospholipids, especially LPC, by the action of ATX/lysoPLD, possibly originating from hen oviduct fluid.

A Cleanup Method for Mass Spectrometric Analysis of Sphingosine- and Ceramide-1-Phosphate in Blood and Solid Tissue Using a Phosphate Capture Molecule.

Cleanup technology and mass spectrometric determination of sphingosine-1-phosphate (S1P) using a phosphate capture molecule are shown. The protocol is rapid, requires neither thin-layer chromatography nor liquid chromatography, and is applicable to both blood and solid tissue samples. The mass spectrometric method is also applicable to ceramide-1-phosphate.

Metabolic pathway that produces essential fatty acids from polymethylene-interrupted polyunsaturated fatty acids in animal cells.

Sciadonic acid (20:3 Delta-5,11,14) and juniperonic acid (20:4 Delta-5,11,14,17) are polyunsaturated fatty acids (PUFAs) that lack the Delta-8 double bond of arachidonic acid (20:4 Delta-5,8,11,14) and eicosapentaenoic acid (20:5 Delta-5,8,11,14,17), respectively. Here, we demonstrate that these conifer oil-derived PUFAs are metabolized to essential fatty acids in animal cells. When Swiss 3T3 cells were cultured with sciadonic acid, linoleic acid (18:2 Delta-9,12) accumulated in the cells to an extent dependent on the concentration of sciadonic acid. At the same time, a small amount of 16:2 Delta-7,10 appeared in the cellular lipids. Both 16:2 Delta-7,10 and linoleic acid accumulated in sciadonic acid-supplemented CHO cells, but not in peroxisome-deficient CHO cells. We confirmed that 16:2 Delta-7,10 was effectively elongated to linoleic acid in rat liver microsomes. These results indicate that sciadonic acid was partially degraded to 16:2 Delta-7,10 by two cycles of beta-oxidation in peroxisomes, then elongated to linoleic acid in microsomes. Supplementation of Swiss 3T3 cells with juniperonic acid, an n-3 analogue of sciadonic acid, induced accumulation of alpha-linolenic acid (18:3 Delta-9,12,15) in cellular lipids, suggesting that juniperonic acid was metabolized in a similar manner to sciadonic acid. This PUFA remodeling is thought to be a process that converts unsuitable fatty acids into essential fatty acids required by animals.

Lupane-type saponins from leaves of Acanthopanax sessiliflorus and their inhibitory activity on pancreatic lipase.

Three known saponins, chiisanoside, 11-deoxyisochiisanoside, and isochiisanoside, and one novel saponin, 3,4-seco-4(23),20(29)-lupadiene-3,28-dioic acid 28-O-alpha-l-rhamnopyranosyl (1-->4)-beta-d-glucopyranosyl (1-->6)-beta-d-glucopyranoside, referred to as sessiloside, were isolated from a hot water extract of Acanthopanax sessiliflorus leaves. All of these saponins were lupane-type triterpene triglycosides, and their concentrations were 4.1, 1.0, 0.5, and 0.4% (w/w) of the total extract, respectively. Sessiloside and chiisanoside inhibited pancreatic lipase activity in vitro, and addition of the saponin-rich fraction to a high-fat diet suppressed the body weight gain of mice. The possibility of application of the lupane-type saponins from A. sessiliflorus leaves to the treatment of obesity is discussed.

Production and protein kinase C activation of diacylglycerols containing polymethylene-interrupted PUFA.

Sciadonic acid (20:3, delta-5c,11 c,14c) is a polymethylene-interrupted PUFA (PMI-PUFA) that is present in conifer seeds and known to be incorporated into animal cells and to accumulate in membrane PI as a substitute for arachidonate. In this study, we investigated whether PI having sciadonate could serve as source of DAG that could activate protein kinase C (PKC). When Swiss 3T3 cells cultured with sciadonic acid were stimulated with 100 nM of bombesin, 1-stearoyl-2-sciadonoyl-glycerol (G) and 1-stearoyl-2-arachidonoyl-G were produced. The net increments of these two molecular species of DAG reflected the levels of the two molecular species in the PI in the cells. When cells cultured with juniperonic acid (20:4, delta-5c,11c,14c,17c) were stimulated, 1-stearoyl-2-juniperonoyl-G was produced in proportion to the level of this molecular species in PI in the cells. We also examined PKC activation by synthetic DAG using a partially purified PKC fraction from rat brain and found that both 1-stearoyl-2-sciadonoyl-G and 1-stearoyl-2-juniperonoyl-G could activate PKC comparably to 1 -stearoyl-2-arachidonoyl-G. These results indicate that 1-stearoyl-PI having these C20 PMI-PUFA residues can serve as sources of potential signaling molecules.

Production of 1,2-didocosahexaenoyl phosphatidylcholine by bonito muscle lysophosphatidylcholine/transacylase.

1,2-Didocosahexaenoyl phosphatidylcholine (PC), which has highly unsaturated fatty acid at both sn-1 and sn-2 positions of glycerol, is a characteristic molecular species of bonito muscle. To examine the involvement of a de novo route in its synthesis, the molecular species of phosphatidic acid (PA) were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry using a 1,3-bis[bis(pyridin-2-ylmethyl)amino]propan-2-olato dizinc(II) complex, a novel phosphate-capture molecule. However, 1,2-didocosahexaenoyl species could not be detected. Next, 1,2-didocosahexaenoyl PC synthesis by the cytosolic lysophosphatidylcholine (LPC)/transacylase was examined using endogenous LPC from bonito muscle, in which the 2-docosahexaenoyl species is abundant. The LPC/transacylase synthesized 1,2-didocosahexaenoyl PC as the most abundant molecular species. For further characterization, the LPC/transacylase was purified to homogeneity from the 100,000 x g supernatant of bonito muscle. The isolated LPC/transacylase is a labile glycoprotein with molecular mass of 52 kDa including a 5-kDa sugar moiety. The LPC/transacylase showed a PC synthesis (transacylase activity) below and above the critical micelle concentration of substrate LPC, and fatty acid release (lysophospholipase activity) was always smaller than the transacylase activity, even with a monomeric substrate. These results suggest that the LPC/transacylase is responsible for the synthesis of 1,2-didocosahexaenoyl PC.

Type 2 lysophosphatidic acid receptor in gastric surface mucous cells: Possible implication of prostaglandin E2 production.

Lysophosphatidic acid (LPA) is a lipid mediator that induces various cell responses via its specific receptors. Recently, we found that orally administered LPA and phosphatidic acid (PA) ameliorate stress- or aspirin-induced stomach injury. However, the mechanisms underlying these effects have not been elucidated yet. In this study, we examined effect of LPA on prostaglandin (PG) E2 production in MKN74 cells, a gastric cell-line expressing type 2 LPA receptor (LPA2). When the cells were treated with LPA, the level of mRNA of COX-2 but not COX-1 was upregulated. The LPA effect was abolished when the cells were pretreated with pertussis toxin (PTX), suggesting the involvement of receptor(s) coupled with Gi. Pretreatment of MKN74 cells with LPA enhanced the PGE2 production triggered by calcium ionophore A23187. Again, PTX abolished the LPA effect. Fluorescent immunohistochemistry using an antibody against LPA2 showed that surface mucous cells (pit cells) in gastric mucosa of mice express LPA2 on the apical side of the plasma membrane. These results suggest that LPA in the diet or its digestion may contribute to the epithelial integrity of stomach mucosa by enhancement of PGE2 production via activation of LPA2.

Lysophosphatidic acid produced by hen egg white lysophospholipase D induces vascular development on extraembryonic membranes.

Lysophosphatidic acid (lysoPtdOH), a lysophospholipid mediator, exerts diverse physiological effects, including angiogenesis, through its specific G-protein-coupled receptors. Previously, we showed that unfertilized hen egg white contains polyunsaturated fatty acid-rich lysoPtdOH and lysophospholipase D (lysoPLD). Here, we examined whether lysoPtdOH was produced by lysoPLD in the presence and absence of a hen fertilized ovum and what the physiological role of lysoPtdOH in hen egg white is. Mass spectrometry showed that fertilized hen egg white contained about 8 µM lysoPtdOH before incubation with an ovum, mainly comprised of 18:1- (12.6 %), 18:2- (37.8 %) and 20:4-molecular species (41.5 %). In an early gestation period, the lysoPtdOH was increased up to 9.6 µM, concomitant with a decrease in the level of polyunsaturated lysophosphatidylcholine (lysoPtdCho). Moreover, lysoPtdOH-degrading activities were found in egg white and the vitelline membrane, showing that these enzymes control lysoPtdOH levels in egg white. In an egg yolk angiogenesis assay, two lysoPtdOH receptor antagonists, Ki16425 and N-palmitoyl serine phosphoric acid (NASP), inhibited blood vessel formation induced by exogenously added 18:1-lysoPtdOH and its precursor lysoPtdCho on the hen yolk sac. Ki16425 and NASP also inhibited blood vessel formation in the chorioallantoic membrane (CAM). Furthermore, the relatively higher levels of LPA1, LPA2, LPA4 and LPA6 mRNA were present in the yolk sac and CAM. These results suggest that lysoPtdOH produced from lysoPtdCho by the action of lysoPLD in hen egg white is involved in the formation of blood vessel networks through several lysoPtdOH receptors on various extraembryonic membranes, including the yolk sac membrane and CAM.

Identification of a sphingolipid-specific phospholipase D activity associated with the generation of phytoceramide-1-phosphate in cabbage leaves.

The structure and biosynthetic route for an unidentified lipid (lipid X) detected by TLC of cabbage (Brassica oleracea) lipids was determined. Lipid X is a phospholipid that is resistant to mild alkali and detectable by MALDI-TOF MS as an adduct with Phos-tag, a phosphate-capture zinc complex. Various α-hydroxy fatty acids (16:0, 22:0, 24:0 and 24:1) were detected by GC-MS of fatty acid methyl esters prepared from lipid X. The deacyl derivative of lipid X was determined to be 4-hydroxysphingenine (dehydrophytosphingosine)-1-phosphate by MALDI-TOF MS with Phos-tag. From these results, lipid X was determined to be phytoceramide-1-phosphate (PC1P) with an α-hydroxy fatty acid. When cabbage homogenates were incubated, PC1P was formed, with a concomitant decrease in the amount of glycosylinositol phosphoceramide (GIPC). The formation of PC1P from GIPC was confirmed by treatment of purified cabbage GIPC with a membrane fraction of cabbage homogenates. Using a partially purified enzyme fraction, we found that the enzyme hydrolyzes GIPC specifically, but not glycerophospholipids and sphingomyelin. Arabidopsis thaliana also had this enzyme activity. From these results, we conclude that a previously uncharacterized phospholipase D activity that specifically hydrolyzes GIPC produces PC1P in brassicaceous plants.

A cleanup method for mass spectrometry of sphingosine-1-phosphate in blood and solid tissues using a phosphate capture molecule.

Cleanup technology and mass spectrometric determination of sphingosine-1-phosphate using a -phosphate capture molecule are shown. The protocol is rapid, requires neither thin-layer chromatography nor liquid chromatography, and is applicable to both blood and solid tissue samples.

Phosphatidic acid production in the processing of cabbage leaves.

Lysophosphatidic acid (LPA) is a lipid mediator involved in various physiological responses, including wound healing. Evidence of the antiulcer activity of LPA has been reported, and soybean LPA at a concentration of 10 µM is effective in reducing stress-induced gastric ulcer. Because LPA can be formed from phosphatidic acid (PA) by digestive phospholipase A2, dietary PA can be considered a potential antiulcer phospholipid. In this study, PA production in cut processing of cabbage leaves was examined. The amounts of PA in sliced, minced, and homogenized cabbage leaves were 107 ± 5, 134 ± 19, and 286 ± 29 nmol PA/g (wet weight), respectively, all being significantly higher than the amount of PA found in intact leaves. Mixing mayonnaise with sliced cabbage dramatically increased the PA content (1586 ± 393 nmol/3 g), indicating phospholipase D activity leaked raw cabbage produced PA. These results indicate that fine cutting raw cabbage leaves and mixing them with foods rich in phospholipids resulted in an abundant production of PA.

Quantification of phosphatidic acid in foodstuffs using a thin-layer-chromatography-imaging technique.

Apical application of lysophosphatidic acid (LPA), a growth-factor-like phospholipid, was shown to prevent or restore gastrointestinal (GI) disorders, such as diarrhea and stomach ulcer, in experimental animals. Because LPA is formed from phosphatidic acid (PA) by the activity of digestive phospholipase A(2), PA is a potential component for dietary treatment of such GI disorders. Here, we quantified PA contained in 38 foodstuffs and 3 herbs by a thin-layer-chromatography-imaging technique. Vegetables belonging to Brassicaceae, such as cabbage leaves (700 nmol/g of wet weight) and Japanese radish leaves (570 nmol/g), contained higher amounts of PA than other foodstuffs. Amounts of PA in fruits, cereals, and starchy root vegetables were below 300 nmol/g. Animal foodstuffs contained low amounts of PA (<60 nmol/g). Interestingly, leaves of Mallotus japonicas, a Japanese edible herb used for treatment of stomach ulcer, had the highest PA (1410 nmol/g) among those examined. The data shown here will be useful for the development of dietary treatment for a damaged GI tract.

S1P3-mediated cardiac fibrosis in sphingosine kinase 1 transgenic mice involves reactive oxygen species.

AIMS: Sphingosine kinase 1 (SPHK1), its product sphingosine-1-phosphate (S1P), and S1P receptor subtypes have been suggested to play protective roles for cardiomyocytes in animal models of ischaemic preconditioning and cardiac ischaemia/reperfusion injury. To get more insight into roles for SPHK1 in vivo, we have generated SPHK1-transgenic (TG) mice and analysed the cardiac phenotype. METHODS AND RESULTS: SPHK1-TG mice overexpressed SPHK1 in diverse tissues, with a nearly 20-fold increase in enzymatic activity. The TG mice grew normally with normal blood chemistry, cell counts, heart rate, and blood pressure. Unexpectedly, TG mice with high but not low expression levels of SPHK1 developed progressive myocardial degeneration and fibrosis, with upregulation of embryonic genes, elevated RhoA and Rac1 activity, stimulation of Smad3 phosphorylation, and increased levels of oxidative stress markers. Treatment of juvenile TG mice with pitavastatin, an established inhibitor of the Rho family G proteins, or deletion of S1P3, a major myocardial S1P receptor subtype that couples to Rho GTPases and transactivates Smad signalling, both inhibited cardiac fibrosis with concomitant inhibition of SPHK1-dependent Smad-3 phosphorylation. In addition, the anti-oxidant N-2-mercaptopropyonylglycine, which reduces reactive oxygen species (ROS), also inhibited cardiac fibrosis. In in vivo ischaemia/reperfusion injury, the size of myocardial infarct was 30% decreased in SPHK1-TG mice compared with wild-type mice. CONCLUSION: These results suggest that chronic activation of SPHK1-S1P signalling results in both pathological cardiac remodelling through ROS mediated by S1P3 and favourable cardioprotective effects.

Inhibitory effect of juniperonic acid (Delta-5c,11c,14c,17c-20:4, omega-3) on bombesin-induced proliferation of Swiss 3T3 cells.

Juniperonic acid (Delta-5c,11c,14c,17c-20:4, JA) is a polymethylene-interrupted (PMI) fatty acid that occurs in Biota orientalis. In this study, we found that JA has an antiproliferative activity. Swiss 3T3 cells were preloaded with fatty acids before stimulation with bombesin, a mitogenic neuropeptide, and proliferation of the cells was assessed by [(3)H]thymidine incorporation. Preloading of linoleic acid (Delta-9c,12c-18:2) significantly enhanced bombesin-induced proliferation. In contrast, preloading of eicosapentaenoic acid (Delta-5c,8c,11c,14c,17c-20:5, EPA) suppressed proliferation. Likewise, cells preloaded with JA showed a significantly curtailed response to bombesin. The antiproliferative potency of JA was equivalent to that of EPA. Sciadonic acid (Delta-5c,11c,14c-20:3), an omega-6 analogue of JA did not show antiproliferative activity, suggesting the importance of the omega-3 double bond rather than the PMI structure. The EPA-like activity of JA may be involved in the pharmaceutical activity of biota seeds, a psychoactive Chinese traditional medicine.

CGI-58 facilitates lipolysis on lipid droplets but is not involved in the vesiculation of lipid droplets caused by hormonal stimulation.

A lipid droplet (LD)-associated protein, perilipin, is a critical regulator of lipolysis in adipocytes. We previously showed that Comparative Gene Identification-58 (CGI-58), a product of the causal gene of Chanarin-Dorfman syndrome, interacts with perilipin on LDs. In this study, we investigated the function of CGI-58 using RNA interference. Notably, CGI-58 knockdown caused an abnormal accumulation of LDs in both 3T3-L1 preadipocytes and Hepa1 hepatoma cells. CGI-58 knockdown did not influence the differentiation of 3T3-L1 adipocytes but reduced the activity of both basal and cAMP-dependent protein kinase-stimulated lipolysis. In vitro studies showed that CGI-58 itself does not have lipase/esterase activity, but it enhanced the activity of adipose triglyceride lipase. Upon lipolytic stimulation, endogenous CGI-58 was rapidly dispersed from LDs into the cytosol along with small particulate structures. This shift in localization depends on the phosphorylation of perilipin, because phosphorylated perilipin lost the ability to bind CGI-58. During lipolytic activation, LDs in adipocytes vesiculate into micro-LDs. Using coherent anti-Stokes Raman scattering microscopy, we pursued the formation of micro-LDs in single cells, which seemed to occur in cytoplasmic regions distant from the large central LDs. CGI-58 is not required for this process. Thus, CGI-58 facilitates lipolysis in cooperation with perilipin and other factors, including lipases.

Quantitative analysis of lysophosphatidic acid by time-of-flight mass spectrometry using a phosphate-capture molecule.

Lysophosphatidic acid (LPA) is a lipid mediator that may play an important role in wound healing, embryonic development, and progression of cancer. Here, we report a procedure for the quantification of LPA by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The method is based on a characteristic mass shift with total charge change (from -2 to +1) of the phosphate species due to 1:1 complexation of LPA(2-) with a dinuclear zinc (II) complex [1,3-bis[bis(pyridin-2-ylmethyl)amino]propan-2-olato dizinc(II) complex; Zn(2)L(3+)] at physiological pH. The monocationic complex [LPA(2-)-Zn(2)L(3+)](+) was detected in the positive mode, in which no other signal of cation adducts of LPA(2-) was observed. The detection limit of 18:1 LPA by this method was 0.1 pmol on a sample plate. The intensity ratio of [LPA(2-)-Zn(2)L(3+)](+) against an internal standard [17:0 LPA(2-)-Zn(2)L(3+)](+) increased linearly with their molar ratio. Based on the relative intensities of complex ions, we determined the amounts of LPA homologs in an egg white by this method; the results obtained were in good agreement with those by gas liquid chromatography. This sensitive and convenient procedure for LPA-specific detection is useful for the quantification of LPA homologs occurring in biological materials.