Plasmalogen-Mediated Activation of GPCR21 Regulates Cytolytic Activity of NK Cells against the Target Cells.

It is widely known that the immune system becomes slower to respond among elderly people, making them more susceptible to viral infection and cancer. The mechanism of aging-related immune deficiency remained mostly elusive. In this article, we report that plasmalogens (Pls), special phospholipids found to be reduced among the elderly population, critically control cytolytic activity of human NK cells, which is associated with activation of a cell surface receptor, G protein-coupled receptor 21 (GPCR21). We found the extracellular glycosylation site of GPCR21, which is conserved among the mammalian species, to be critically important for the activation of NK cells by Pls. The Pls-GPCR21 signaling cascade induces the expression of Perforin-1, a cytolytic pore-forming protein, via activation of STAT5 transcription factor. Inhibition of STAT5 abrogates GPCR21-mediated cytolytic activation of NK cells against the target cancer cells. In addition, oral ingestion of Pls inhibited cancer growth in SCID mice and inhibited the systemic spread of murine CMV in adult C57BL/6J mice. These findings advocate that Pls-GPCR21 signaling could be critical in maintaining NK cell function, and that the age-related reduction of this signaling cascade could be one of the factors behind immune deficiency in mammals, including humans.

Biological Functions of Plasmalogens.

Plasmalogens (Pls) are one kind of phospholipids enriched in the brain and other organs. These lipids were thought to be involved in the membrane bilayer formation and anti-oxidant function. However, extensive studies revealed that Pls exhibit various beneficial biological activities including prevention of neuroinflammation, improvement of cognitive function, and inhibition of neuronal cell death. The biological activities of Pls were associated with the changes in cellular signaling and gene expression. Membrane-bound GPCRs were identified as possible receptors of Pls, suggesting that Pls might function as ligands or hormones. Aging, stress, and inflammatory stimuli reduced the Pls contents in cells, and addition of Pls inhibited inflammatory processes, which could suggest that reduction of Pls might be one of the risk factors for the diseases associated with inflammation. Oral ingestion of Pls showed promising health benefits among Alzheimer's disease (AD) patients, suggesting that Pls might have therapeutic potential in other neurodegenerative diseases.

Therapeutic Efficacy of Plasmalogens for Alzheimer's Disease, Mild Cognitive Impairment, and Parkinson's Disease in Conjunction with a New Hypothesis for the Etiology of Alzheimer's Disease.

It has been reported in recent years that blood levels of plasmalogens (Pls) are decreased in various diseases. None of those reports, however, conducted any clinical trials to examine the effect of Pls on those diseases. This article describes our recent report on a therapeutic efficacy of orally administered Pls in mild cognitive impairment (MCI), mild to severe Alzheimer's disease (AD), and Parkinson's disease (PD). A 24-week, multicenter, randomized, double-blind, placebo-controlled trial was performed in patients with MCI (n = 178) and mild AD (n = 98). The study design for moderate AD (n = 57) and severe AD (n = 18) was 12-week open-labeled, and the design for patients with PD (n = 10) was 24-week open-labeled. They showed a significant improvement in cognitive function and other clinical symptoms with elevation of the blood Pls levels. No adverse events were reported. The baseline levels of plasma ethanolamine plasmalogen and erythrocyte ethanolamine plasmalogen in MCI, AD, and PD were significantly lower than those of normal aged. The degree of reduction in the blood Pls levels was in the order of MCI â‰º mild AD ≺ moderate AD ≺ severe AD ≺ PD. The findings suggest that the blood levels of Pls may be a beneficial biomarker for assessing AD severity. Based on these results, we have proposed a new hypothesis for the etiology of AD and other neuropsychiatric disorders.

Complete genome sequence of Lentilactobacillus buchneri subsp. silagei MGR2-32 isolated from guinea grass silage in Okinawa, Japan.

The genome sequence of Lentilactobacillus buchneri subsp. silagei MGR2-32, isolated from guinea grass silage, is 2,540,137 bp, has a GC content of 44%, and contains 2,393 predicted protein-coding genes. Pairwise average nucleotide identity and digital DNA-DNA hybridization values between MGR2-32 and the type strain were 99.75% and 99.90%, respectively.

Plasmalogens inhibit neuroinflammation and promote cognitive function.

Neuroinflammation (NF) is defined as the activation of brain glial cells that are found in neurodegenerative diseases including Alzheimer's disease (AD). It has been known that an increase in NF could reduce the memory process in the brain but the key factors, associated with NF, behind the dysregulation of memory remained elusive. We previously reported that the NF and aging processes reduced the special phospholipids, plasmalogens (Pls), in the murine brain by a mechanism dependent on the activation of transcription factors, NF-kB and c-MYC. A similar mechanism has also been found in postmortem human brain tissues with AD pathologies and in the AD model mice. Recent evidence showed that these phospholipids enhanced memory and reduced neuro-inflammation in the murine brain. Pls can stimulate the cellular signaling molecules, ERK and Akt, by activating the membrane-bound G protein-coupled receptors (GPCRs). Therefore, recent findings suggest that plasmalogens could be one of the key phospholipids in the brain to enhance memory and inhibit NF.

Complete Genome Sequence of the Thermophilic Enterococcus faecalis Strain K-4, Isolated from a Grass Silage in Thailand.

The whole-genome sequence of strain K-4, isolated from grass silage in Thailand, which constitutes a chromosome and two plasmids, is 2,914,933 bp long, has a GC content of 37.5%, and contains 2,734 predicted protein-coding genes. Average nucleotide identity based on BLAST+ (ANIb) and digital DNA-DNA hybridization (dDDH) values indicated that the strain K-4 was closely related to Enterococcus faecalis.

Anti-inflammatory/anti-amyloidogenic effects of plasmalogens in lipopolysaccharide-induced neuroinflammation in adult mice.

BACKGROUND: Neuroinflammation involves the activation of glial cells in neurodegenerative diseases such as Alzheimer's disease (AD). Plasmalogens (Pls) are glycerophospholipids constituting cellular membranes and play significant roles in membrane fluidity and cellular processes such as vesicular fusion and signal transduction. METHODS: In this study the preventive effects of Pls on systemic lipopolysaccharide (LPS)-induced neuroinflammation were investigated using immunohistochemistry, real-time PCR methods and analysis of brain glycerophospholipid levels in adult mice. RESULTS: Intraperitoneal (i.p.) injections of LPS (250 µg/kg) for seven days resulted in increases in the number of Iba-1-positive microglia and glial fibrillary acidic protein (GFAP)-positive astrocytes in the prefrontal cortex (PFC) and hippocampus accompanied by the enhanced expression of IL-1ß and TNF-α mRNAs. In addition, ß-amyloid (Aß3-16)-positive neurons appeared in the PFC and hippocampus of LPS-injected animals. The co-administration of Pls (i.p., 20 mg/kg) after daily LPS injections significantly attenuated both the activation of glial cells and the accumulation of Aß proteins. Finally, the amount of Pls in the PFC and hippocampus decreased following the LPS injections and this reduction was suppressed by co-treatment with Pls. CONCLUSIONS: These findings suggest that Pls have anti-neuroinflammatory and anti-amyloidogenic effects, thereby indicating the preventive or therapeutic application of Pls against AD.

Dietary plasmalogen increases erythrocyte membrane plasmalogen in rats.

BACKGROUND: Many disorders with plasmalogen deficiency have been reported. Replenishment or replacement of tissue plasmalogens of these disorders would be beneficial to the patients with these disorders, but effects of dietary plasmalogen on mammals have not been reported. METHODS: Plasmalogens were purified from chicken skin. The purified plasmalogens consisted of 96.4% ethanolamine plasmalogen (PlsEtn), 2.4% choline plasmalogen (PlsCho) and 0.5% sphingomyelin (SM). A diet containing 0.1% the purified plasmalogens (PlsEtn diet) was given to rats. Relative composition of phospholipids was measured by a high performance liquid chromatography (HPLC) method that can separate intact plasmalogens and all other phospholipid classes by a single chromatographic run. RESULTS: The PlsEtn diet given to Zucker diabetic fatty (ZDF) rats for 4 weeks caused decreases of plasma cholesterol and plasma phospholipid as compared to control diet. The other routine laboratory tests of plasma including triacylglycerol, glucose, liver and renal functions, albumin, and body weight were not different. Relative compositions of erythrocyte PlsEtn and phosphatidylethanolamine (PE) increased, and that of phosphatidylcholine (PC) decreased in PlsEtn diet group. The PlsEtn diet given to normal rats for 9 weeks again caused decrease of plasma cholesterol and phospholipid, and it induced increase of relative composition of PlsEtn of the erythrocyte membrane. The other routine laboratory tests of plasma and body weight were not different. CONCLUSIONS: Dietary PlsEtn increases relative composition of PlsEtn of erythrocyte membranes in normal and ZDF rats, and it causes decreases of plasma cholesterol and plasma phospholipids. Dietary PlsEtn for 9 weeks seemingly causes no adverse effect to health of normal rats.

Plasmalogens, the Vinyl Ether-Linked Glycerophospholipids, Enhance Learning and Memory by Regulating Brain-Derived Neurotrophic Factor.

Plasmalogens (Pls), a kind of glycerophospholipids, have shown potent biological effects but their role in hippocampus-dependent memory remained mostly elusive. Here, we first report Pls can enhance endogenous expression of brain-derived neurotrophic factor (Bdnf) in the hippocampus and promotes neurogenesis associated with improvement of learning and memory in mice. Genomic and proteomic studies revealed that Pls enhanced recruitment of CREB transcription factor onto the murine Bdnf promoter region via upregulating ERK-Akt signaling pathways in neuronal cells. Reduction of endogenous Pls in murine hippocampus significantly reduced learning and memory associated with the reduction of memory-related protein expression, suggesting that Pls can regulate memory-related gene expression in the hippocampus.

Rheological Abnormalities in Human Erythrocytes Subjected to Oxidative Inflammation.

Erythrocytes are oxygen carriers and exposed to redox cycle in oxygenation and deoxygenation of hemoglobin. This indicates that circulating erythrocytes are vulnerable to the oxidative injury occurring under the imbalance of redox homeostasis. In this review article, two topics are presented concerning the human erythrocytes exposed to the oxidative inflammation including septic and sterile conditions. First, we demonstrate rheological derangement of erythrocytes subjected to acute oxidative injury caused by exogenous generators of reactive oxygen species (ROS). Erythrocyte filterability as whole-cell deformability has been estimated by the gravity-based nickel mesh filtration technique in our laboratory and was dramatically impaired in a time-dependent manner after starting exposure to the ROS generators, that is associated with concurrent progression of membrane protein degradation, phospholipid peroxidation, erythrocyte swelling, methemoglobin formation, and oxidative hemolysis. Second, we introduce an impairment of erythrocyte filterability confirmed quantitatively in diabetes mellitus and hypertension of animal models and patients under treatment. Among the cell geometry, internal viscosity, and membrane property as the three major determinants of erythrocyte deformability, erythrocyte membrane alteration is supposed to be the primary cause of this impairment in these lifestyle-related diseases associated with persistent oxidative inflammation. Excessive ROS trigger the inflammatory responses and reduce the erythrocyte membrane fluidity. Oxidative inflammation increasing erythrocyte membrane rigidity underlies the impaired systemic microcirculation, which is observed in diabetic and/or hypertensive patients. On the other hand, elevated internal viscosity caused by sickle hemoglobin polymerization is a primary cause of impaired erythrocyte filterability in sickle cell disease (SCD). However, oxidative inflammation is also involved in the pathophysiology of SCD. The physiologic level of ROS acts as signaling molecules for adaptation to oxidative environment, but the pathological level of ROS induces suicidal erythrocyte death (eryptosis). These findings provide further insight into the ROS-related pathophysiology of many clinical conditions.

ATP8B2-Mediated Asymmetric Distribution of Plasmalogens Regulates Plasmalogen Homeostasis and Plays a Role in Intracellular Signaling.

Plasmalogens are a subclass of glycerophospholipid containing vinyl-ether bond at the sn-1 position of glycerol backbone. Ethanolamine-containing plasmalogens (plasmalogens) are major constituents of cellular membranes in mammalian cells and de novo synthesis of plasmalogens largely contributes to the homeostasis of plasmalogens. Plasmalogen biosynthesis is regulated by a feedback mechanism that senses the plasmalogen level in the inner leaflet of the plasma membrane and regulates the stability of fatty acyl-CoA reductase 1 (Far1), a rate-limiting enzyme for plasmalogen biosynthesis. However, the molecular mechanism underlying the localization of plasmalogens in cytoplasmic leaflet of plasma membrane remains unknown. To address this issue, we attempted to identify a potential transporter of plasmalogens from the outer to the inner leaflet of plasma membrane by focusing on phospholipid flippases, type-IV P-type adenosine triphosphatases (P4-ATPase), localized in the plasma membranes. We herein show that knockdown of ATP8B2 belonging to the class-1 P4-ATPase enhances localization of plasmalogens but not phosphatidylethanolamine in the extracellular leaflet and impairs plasmalogen-dependent degradation of Far1. Furthermore, phosphorylation of protein kinase B (AKT) is downregulated by lowering the expression of ATP8B2, which leads to suppression of cell growth. Taken together, these results suggest that enrichment of plasmalogens in the cytoplasmic leaflet of plasma membranes is mediated by ATP8B2 and this asymmetric distribution of plasmalogens is required for sensing plasmalogens as well as phosphorylation of AKT.

Transient Ca2+ entry by plasmalogen-mediated activation of receptor potential cation channel promotes AMPK activity.

Ethanolamine-containing alkenyl ether glycerophospholipids, plasmalogens, are major cell membrane components of mammalian cells that activate membrane protein receptors such as ion transporters and G-protein coupled receptors. However, the mechanism by which plasmalogens modulate receptor function is unknown. Here, we found that exogenously added plasmalogens activate transient receptor potential cation channel subfamily C member 4 (TRPC4) to increase Ca2+ influx, followed by calcium/calmodulin-dependent protein kinase 2-mediated phosphorylation of AMP-activated protein kinase (AMPK). Upon topical application of plasmalogens to the skin of mice, AMPK activation was observed in TRPC4-expressing hair bulbs and hair follicles. Here, TRPC4 was co-localized with the leucine-rich repeat containing G protein-coupled receptor 5, a marker of hair-follicle stem cells, leading to hair growth. Collectively, this study indicates that plasmalogens could function as gate openers for TRPC4, followed by activating AMPK, which likely accelerates hair growth in mice.

Orally Administered Plasmalogens Alleviate Negative Mood States and Enhance Mental Concentration: A Randomized, Double-Blind, Placebo-Controlled Trial.

Background: Plasmalogens have been shown to improve neurodegenerative pathology and cognitive function. We hypothesized that plasmalogens work in small amounts as a kind of hormone interacting with a G protein-coupled receptor, and then explored the effects of scallop-derived purified plasmalogens on psychobehavioral conditions in a randomized placebo-controlled trial of college athletes in Japan. Methods and materials: Eligible participants were male students aged 18-22 years who belonged to university athletic clubs. They were randomly allocated to either plasmalogen (2 mg per day) or placebo treatment of 4 weeks' duration. The primary outcome was the T-score of the Profile of Mood States (POMS) 2-Adult Short, and the secondary outcomes included the seven individual scales of the POMS 2, other psychobehavioral measures, physical performance, and laboratory measurements. The trial was registered at the Japan Registry of Clinical Trials (jRCTs071190028). Results: Forty participants (20 in the plasmalogen group and 20 in the placebo group) completed the 4-week treatment. The Total Mood Disturbance (TMD) score of the plasmalogen group showed a greater decrease at 4 weeks than that of the placebo group while the between-group difference was marginally significant (p = 0.07). The anger-hostility and fatigue-inertia scores of the POMS 2 decreased significantly in the plasmalogen group, but not in the placebo group, at 4 weeks. Between-group differences in those scores were highly significant (p = 0.003 for anger-hostility and p = 0.005 for fatigue-inertia). The plasmalogen group showed a slight decrease in the Athens Insomnia Scale at 2 weeks, and the between-group difference was near-significant (p = 0.07). The elapsed time in minute patterns on the Uchida-Kraepelin test, which is a marker of mental concentration, revealed significantly greater performance in the plasmalogen group than in the placebo group. There were no between-group differences in physical and laboratory measurements. Conclusion: It is suggested that orally administered plasmalogens alleviate negative mood states and sleep problems, and also enhance mental concentration.

Ethanolamine plasmalogens derived from scallops stimulate both follicle-stimulating hormone and luteinizing hormone secretion by bovine gonadotrophs.

Brain ethanolamine plasmalogens (EPls) are the only known ligands of G-protein-coupled receptor 61, a novel receptor that stimulates follicle-stimulating hormone (FSH), but not luteinizing hormone (LH), secretion by bovine gonadotrophs. We hypothesized that the recently developed neuroprotective EPls extracted from scallop (Pecten yessoensis) (scallop EPls) could stimulate FSH secretion by gonadotrophs. To test this hypothesis, bovine gonadotrophs were cultured for 3.5 days and treated with increasing concentrations of scallop EPls. FSH secretion was stimulated by all tested concentrations of scallop EPls (P < 0.05). Surprisingly, LH secretion was stimulated by both 0.5 (P < 0.05) and 5 (P < 0.01) ng/mL of scallop EPls. To clarify the important differences between bovine brain and scallop EPls, we utilized two-dimensional liquid chromatography-mass spectrometry, which revealed 44 peaks, including 10 large peaks. Among them, eight were scallop-specific EPl molecular species, occupying approximately 58% of the total area percentage of scallop EPls. Almost all large peaks contained 4, 5, or 6 unsaturated double bonds in the carbon chain at the sn-2 position of the glycerol backbone. Our results showed that EPls from scallops, lacking pituitary glands, stimulated both FSH and LH secretion by bovine gonadotrophs.

Decreases of ethanolamine plasmalogen and phosphatidylcholine in erythrocyte are a common phenomenon in Alzheimer's, Parkinson's, and coronary artery diseases.

Decreased plasma levels of plasmalogens in neurodegenerative diseases have been watched with interest. We previously reported the decreases of erythrocyte ethanolamine plasmalogen (PlsPE) of blood not only in Alzheimer's disease (AD) and Parkinson's disease (PD), but also in coronary artery disease (CAD). In the present study, by using the same high-performance liquid chromatography (HPLC) method, we investigated the pattern of changes in the phospholipid composition of erythrocyte membrane in AD, PD and CAD compared with healthy individuals. The common patten of changes among them was as follows: The decrease of erythrocyte PlsPE was accompanied by a decrease of phosphatidylcholine although phosphatidylethanolamine remained unchanged. The decreases of PlsPE and phosphatidylcholine were replaced by an increase of sphingomyelin (SM) in the total phospholipids. The dissociated change between PlsPE and phosphatidylethanolamine (PE) may be caused by the differences in molecular structure or in location in the cell membrane. Such special changes provide another piece of biochemical evidence that these different diseases are caused by identical pathological mechanism, suggesting potential biomarkers for these chronic diseases due to aging.

Identification of plasmalogens in Bifidobacterium longum, but not in Bifidobacterium animalis.

Plasmalogens are glycerophospholipids that contain a vinyl ether bond at the sn-1 position of glycerol backbone instead of an ester bond. Plasmalogens are indicated to have many important functions in mammalian cells. On the other hand, it is suggested that some gut microbiota plays many probiotic functions to human health. Presence of plasmalogens in Clostridium strains in gut microbiota is well-known, but presence of plasmalogens in Bifidobacterium longum (B. longum) strain, one of the most important probiotic gut microbiota, has not been reported. We identified plasmalogens in lipid extract from some B. longum species, but not from Bifidobacterium animalis (B. animalis) species which are another important strain of probiotic bifidobacteria. Major phospholipid classes of plasmalogens in B. longum species were cardiolipin, phosphatidylglycerol and phosphatidic acid. Almost all of the phospholipids from B. longum examined were indicated to be plasmalogens. Although major phospholipid classes of plasmalogens in human brain and major phospholipid classes of plasmalogens in B. longum are different, it is interesting to note that many reported functions of microbiota-gut-brain axis on human neurodegenerative diseases and those functions of plasmalogens on neurodegenerative diseases are overlapped. The presence of plasmalogens in B. longum species may play important roles for many probiotic effects of B. longum to human health.

Improvement of Blood Plasmalogens and Clinical Symptoms in Parkinson's Disease by Oral Administration of Ether Phospholipids: A Preliminary Report.

Introduction. Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease (AD). With the ageing of population, the frequency of PD is expected to increase dramatically in the coming decades. L-DOPA (1,3,4-dihydroxyalanine) is the most effective drug in the symptomatic treatment of PD. Nonmotor symptoms in PD include sleep problems, depression, and dementia, which are not adequately controlled with dopaminergic therapy. Here, we report the efficacy of oral administration of scallop-derived ether phospholipids to some nonmotor symptoms of PD. METHODS: Ten (10) patients received oral administration of 1 mg/day of purified ether phospholipids derived from scallop for 24 weeks. Clinical symptoms and blood tests were checked at 0, 4, 12, 24, and 28 weeks. The blood levels of plasmalogens in patients with PD were compared with those of 39 age-matched normal controls. RESULTS: Initial levels of plasma ethanolamine ether phospholipids in PD and ethanolamine plasmalogen of erythrocyte from PD were lower than those of age-matched normal controls. Oral administration of 1 mg/day of the purified ether phospholipids increased plasma ether phospholipids in PD and increased the relative composition of ether phospholipids of erythrocyte membrane in PD. The levels of ether phospholipids in peripheral blood reached to almost normal levels after 24 weeks. Furthermore, some clinical symptoms of PD improved concomitantly. CONCLUSION: 1 mg/day of oral administration of purified ether phospholipids derived from scallop can increase ether phospholipids in peripheral blood and concomitantly improve some clinical symptoms of PD.

Impaired deformability and association with density distribution of erythrocytes in patients with type 2 diabetes mellitus under treatment.

BACKGROUND: Disturbed microcirculation is related to diabetic complications, and erythrocyte deformability is a critical factor regulating microcirculation. OBJECTIVES: To know the relationship between the impaired deformability and density profile in diabetic erythrocytes. METHODS: We recruited patients with type 2 diabetes (n = 15, diabetic group) and age- and sex-matched non-diabetic subjects (n = 15, control group). Erythrocyte density (ED) profile was obtained by the phthalate ester separation technique. ED distribution was fitted by sigmoidal curve, yielding specific gravity of phthalate ester allowing passage of half erythrocytes population (ED50) and slope factor. Erythrocyte deformability was estimated by our specific filtration technique. RESULTS: Diabetic group showed significantly (p < 0.001) higher HbA1c and fasting blood glucose concentration. Erythrocyte deformability in diabetic group was impaired as compared with that in control group (p < 0.001) and proportional to HbA1c (p = 0.009). However, ED50 and the slope factor in diabetic group did not differ from respective parameters in control group. CONCLUSIONS: This study demonstrated that erythrocyte deformability was impaired in diabetic patients even under treatment. HbA1c up to 7.5% is concluded not to alter the erythrocyte density but to impair the deformability, which might be a warning to clinicians for prevention of diabetic complications.

Simultaneous preparation of purified plasmalogens and sphingomyelin in human erythrocytes with phospholipase A1 from Aspergillus orizae.

A method for the simultaneous purification of plasmalogens and sphingomyelin (SM) in human erythrocytes is described. Treatment of total lipids with n-hexane/acetone (1:1 v/v) resulted in selective precipitation of SM. Both the supernatant and the precipitate fractions were incubated with a phospholipase A(1) (PLA1) from Aspergillus orizae for 3.5 h. The PLA1-treated lipids were extracted with n-hexane/isopropanol, the hexane layer was obtained using a Na(2)SO(4) solution, and the hexane layer was further washed with water. At this step, the relative concentration of the plasmalogens was 92% of the total phospholipids in the supernatant fraction, and that of SM was 97.7% in the precipitate fraction. Each fraction was applied to high performance liquid chromatography (HPLC) for further purification. The plasmalogen and SM obtained were almost free of the other lipids. The purity of the plasmalogens and SM was monitored by HPLC, which can separate intact plasmalogens from their diacyl analogs.

Enzymatic measurement of ether phospholipids in human plasma after hydrolysis of plasma with phospholipase A1.

OBJECTIVES: Ethanolamine ether phospholipids (ePE) and choline ether phospholipid (ePC) are present in human serum or plasma. Decreases in ether phospholipids (plasmalogens) in serum (plasma) have been reported in several diseases such as Alzheimer's disease, Parkinson's disease, metabolic syndrome, schizophrenia. Therefore, need for assay of ether phospholipids in plasma may increase in the future. Nowadays, measurement of the ether phospholipids in human plasma seem to depend on tandem mass spectrometry (LC/MS/MS), but a system for LC/MS/MS is too expensive for most of ordinary clinical laboratories, moreover, use and maintenance of the system are time consuming. DESIGN AND METHODS: Phospholipase A1 (PLA1) hydrolyzes ester (acyl) bond at the sn-1 position of glycerophospholipids, but it does not act on ether bond at the sn-1 position. We confirmed by a HPLC method that treatment of plasma with PLA1 causes complete disappearance of all diacyl phospholipids, but ether phospholipids remain intact. On the basis of these observations, we developed an enzymatic assay method for ePE and ePC in human plasma by use of a fluorescence plate reader. RESULTS: The amount of ePE in human plasma measured by the enzymatic method was well correlated to that by LC/ESI-MS method (R2 > 0.94), but the correlation of ePC between the two methods was bit poorer (R2 > 0.77) than that of ePE. CONCLUSION: The enzymatic method may be applied to assay of ether phospholipids (ePE and ePC) not only in human plasma but also to assay of ePE and ePC in the other tissues.