Plasmalogens brain

Plasmalogens are monoacyl monoalk-l-enyl ether forms of phospholipids. The most common forms of plasmalogens are the choline, ethanolamine, and serine derivatives. They are present in most animal tissues, especially in the mammalian brain. Plasmalogens are stmctural components of membranes. It has been proposed that plasmalogens protect membranes against oxidative stress (9). 

UUen, A., G. Fauler, H. Kofeler, S. Waltl, C. Nusshold, E. Bemhart, H. Reicher et al. 2010. Mouse brain plasmalogens are targets for hypochlorous acid-mediated modification in vitro and in vivo. Free Radir Biol Med49(11) 1655-65. 

These compounds constimte as much as 10% of the phospholipids of brain and muscle. StmcmraUy, the plasmalogens resemble phosphatidylethanolamine but possess an ether link on the sn- carbon instead of the ester link found in acylglycerols. Typically, the alkyl radical is an unsamrated alcohol (Figure 14-10). In some instances, choline, serine, or inositol may be sub-stimted for ethanolamine. 

Ethanol and choline glycerolipids were isolated from calf brain and beef heart lipids by PTLC using silica gel H plates. Pure ethanol amine and choline plasmalogens were obtained with a yield of 80% [74]. Four phosphohpid components in the purple membrane (Bacteriorhodopsin) of Halobacterium halobium were isolated and identified by PTLC. Separated phosphohpids were add-hydrolyzed and further analyzed by GC. Silica gel G pates were used to fractionate alkylglycerol according to the number of carbon atoms in the aliphatic moiety [24]. Sterol esters, wax esters, free sterols, and polar lipids in dogskin hpids were separated by PTLC. The fatty acid composition of each group was determined by GC. 

Inclusion of other molecules of irregular shape within membranes also lowers Tm. However, a molecule of cholesterol can pack into a bilayer with a cross-sectional area of 0.39 nm2, just equal to that of two hydrocarbon chains.49 It tends to harden membranes above Tm but increases mobility of hydrocarbon chains below Tm.97 -100 A complex of cholesterol and phosphatidylcholine may form a separate phase within the membrane.101102 The ether-linked plasmalogens may account for over 30% of the phosphoglycerides of the white matter of the brain and of heart and ether linked phospholipids are the major lipids of many anaerobic bacteria.103 Their Tm values are a few degrees higher than those of the corresponding acyl phospholipids.104... 

Guan Z., Wang Y., Cairns N. J., Lantos P L., Dallner G., and Sindelar P. J. (1999). Decrease and structural modifications of phosphatidylethanolamine plasmalogen in the brain with Alzheimer disease. J. Neuropathol. Exp. Neurol. 58 740-747. 

Latorre E., Collado M. P, Fernandez I., Aragones M. D., and Catalan R. E. (2003). Signaling events mediating activation of brain ethanolamine plasmalogen hydrolysis by ceramide. Eur. 

Yang, H.C., A.A. Farooqui, and L.A. Horrocks. 1996. Characterization of plasmalogen-selective phospholipase A2 from bovine brain. Adv Exp Med Biol 416 309. 

Phospholipid molecules form the lipid bilayer of cell membranes (Appendix 3). Plasmalogens and sphingomyelins are particularly abundant in brain tissue. 

The a,jS-unsaturated fatty ether is an aldehydogenie group because its hydrolysis releases an a -unsaturated primary alcohol that readily tautomerizes to an aldehyde. Choline, ethanolamine, and serine plasmalogens are found in cardiac and skeletal muscle, brain, and liver. The biosynthesis of phosphatidylethanolamine is shown in Figure 19-5. 

Very little is known about the biosynthesis of the three most recently proposed endocannabinoids, 2-AGE, virodhamine and NADA. Regarding 2-AGE (noladin ether), this compound was previously identified in pig brain (Hanus et al. 2001) and in some rat tissues and brain areas (Fezza et al. 2002) by using mass-spectrometric (MS) methods coupled to chromatographic separations. However, a recent study cast some doubt on the actual existence of 2-AGE in mammalian brain tissue (Oka et al. 2003). At the time of this study it was already known that (1) the only acyl ethers to have been detected in animals before the discovery of 2-AGE were 2-acyl ethers (e.g. alkenyl ethers such as platelet activating factor and plasmalogens) (2) there was no evidence for the existence of any enzyme catalysing the formation... 

Ginsberg L, Rafique S, Xuereb JH, Rapoport SI, Gershfeld NL. Disease and anatomic specificity of ethanolamine plasmalogen deficiency in Alzheimer s disease brain. Brain Res 1995 698 223-226. 

Farooqui AA, Rapoport SI, Horrocks LA (1997) Membrane phospholipid alterations in Alzheimer s disease deficiency of ethanolamine plasmalogens. Neurochem Res 22 523-527 Farooqui AA, Horrocks LA (1998) Lipid peroxides in the free radical pathophysiology of brain diseases. Cell Mol Neurobiol 18 599-608... 

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