Neuronal cells are susceptible to many stresses, which will cause the apoptosis and neurodegenerative diseases.
The precise molecular mechanism behind the neuronal protection against these apoptotic stimuli is necessary for drug discovery. In the present study, we have found that plasmalogens (Pls), which are glycerophospholipids containing vinyl ether linkage at sn-1 position, can protect the neuronal cell death upon serum deprivation.
Interestingly, caspse-9, but not caspase-8 and caspase-12, was cleaved upon the serum starvation in Neuro-2A cells. Pls treatments effectively reduced the activation of caspase-9. Furthermore, cellular signaling experiments showed that Pls enhanced phosphorylation of the phosphoinositide 3-kinase (PI3K)-dependent serine/threoninespecific protein kinase AKT and extracellular-signal-regulated kinases ERK1/2. PI3K/AKT inhibitor LY294002 and MAPK/ERK kinase (MEK) inhibitor U0126 treatments study clearly indicated that Pls-mediated cell survival was dependent on the activation of these kinases. In addition, Pls also inhibited primary mouse hippocampal neuronal cell death induced by nutrient deprivation, which was associated with the inhibition of caspase-9 and caspase-3 cleavages. It was reported that Pls content decreased in the brain of the Alzheimer’s patients, which indicated that the reduction of Pls content could endanger neurons. The present findings, taken together, suggest that Pls have an anti-apoptotic action in the brain. Further studies on precise mechanisms of Pls-mediated protection against cell death may lead us to establish a novel therapeutic approach to cure neurodegenerative disorders.
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.
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.
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-1β and TNF-α mRNAs. In addition, β-amyloid (Aβ3–16)-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 Aβ 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.
These findings suggest that Pls have anti-neuroinflammatory and anti-amyloidogenic effects, thereby indicating the preventive or therapeutic application of Pls against AD.
Katafuchi, M. Ifuku, S. Mawatari, M. Noda, K. Miake, M. Sugiyama, T. Fujino. 2012. Effects of plasmalogens on systemic lipopolysaccharide-induced glial activation and β-amyloid accumulation in adult mice. Ann. N.Y. Acad. Sci., 1262: 85-92.
Neuroinflammation essentially involves an activation of glial cells as the cause/effect of 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 like vesicular fusion and signal transduction. Intraperitoneal (i.p.) injection of lipopolysaccharide (LPS, 250 μg/kg) for 7 days resulted in the morphological changes and increase in number of Iba-1(+) microglia showing neuroinflammation in the adult mouse hippocampus. The LPS-induced activation of glial cells was significantly attenuated by i.p. pretreatment with Pls dissolved in corn oil. In addition, systemic injection of LPS induced Aβ(1-16) (+) neurons in the hippocampus were also abolished by application of Pls. Finally, contents of Pls in the hippocampus decreased after LPS injection, and the reduction was suppressed by administration of Pls. These findings suggest an antiamyloidogenic effect of Pls, implicating a possible therapeutic application of Pls against AD.
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.
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.
The PlsEtn diet given to Zucker diabetic fatty (ZDF) rats for 4 weeks caused decreases in plasma cholesterol and plasma phospholipid compared to those on a 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 a decrease in plasma cholesterol and phospholipid, and it induced an increase in relative composition of PlsEtn of the erythrocyte membrane. The other routine laboratory tests of plasma and body weight were not different.
Dietary PlsEtn increases relative composition of PlsEtn of erythrocyte membranes in normal and ZDF rats, and it causes decreases in plasma cholesterol and plasma phospholipids. Dietary PlsEtn for 9 weeks seemingly causes no adverse effect to health of normal rats.
Shinji Oma , Shiro Mawatari , Kazuyuki Saito , Chikako Wakana , Yoshio Tsuboi , Tatsuo Yamada , Takehiko Fujino. 2012. Changes in Phospholipid Composition of Erythrocyte Membrane in Alzheimer’s Disease. Dement Geriatr Cogn Disord Extra, 2:298-303.
There are several reports indicating a decrease of ethanolamine plasmalogen (pl-PE) in brain tissues and in serum of patients with Alzheimer’s disease (AD). The present study aimed to examine the composition of erythrocyte phospholipids including pl-PE in patients with AD.
A high-performance liquid chromatography (HPLC) method that can separate intact plasmalogens and all other phospholipid classes by a single chromatographic run was used.
The ratios of pl-PE, phosphatidylethanolamine (PE) and phosphatidylserine (PS) to sphingomyelin were low as compared to those of the age-matched controls.
These changes in erythrocyte phospholipids may reflect changes induced by oxidative stress, indicating the presence of high oxidative stress in the peripheral blood of AD patients.
Plasmalogens are a unique subclass of glycerophospholipids characterized by the presence of a vinyl ether bond at the sn-1 position of the glycerol backbone, and they are found in high concentration in cellular membranes of many mammalian tissues. However, separation of plasmalogens as intact phospholipids has not been reported. This article describes a high-performance liquid chromatographic method that can separate intact ethanolamine plasmalogens (pl-PEs) and choline plasmalogens (pl-PCs) as well as all other phospholipid classes usually found in mammalian tissues by a single chromatographic run. The separation was obtained using an HPLC diol column and a gradient of a hexane/isopropanol/water system containing 1% acetic acid and 0.08% triethylamine. The HPLC method allowed a clear separation of plasmalogens from their diacyl analogues. The HPLC method, as applied to the study of peroxidation in human erythrocytes by a hydroperoxide, demonstrated that pl-PEs were targeted twice as much as their diacyl analogues.