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Nascent Astrocyte Particles Differ from Lipoproteins in CSF
Author(s) -
LaDu M. J.,
Gilligan S. M.,
Lukens J. R.,
Cabana V. G.,
Reardon C. A.,
Van Eldik L. J.,
Holtzman D. M.
Publication year - 1998
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1998.70052070.x
Subject(s) - astrocyte , lipoprotein , apolipoprotein e , apolipoprotein b , cholesterol , chemistry , phospholipid , high density lipoprotein , biochemistry , albumin , lipoprotein particle , centrifugation , very low density lipoprotein , endocrinology , biology , medicine , central nervous system , disease , membrane
Little is known about lipid transport and metabolism in the brain. As a further step toward understanding the origin and function of CNS lipoproteins, we have characterized by size and density fractionation lipoprotein particles from human CSF and primary cultures of rat astrocytes. The fractions were analyzed for esterified and free cholesterol, triglyceride, phospholipid, albumin, and apolipoproteins (apo) E, AI, AII, and J. As determined by lipid and apolipoprotein profiles, gel electrophoresis, and electron microscopy, nascent astrocyte particles contain little core lipid, are primarily discoidal in shape, and contain apoE and apoJ. In contrast, CSF lipoproteins are the size and density of plasma high‐density lipoprotein, contain the core lipid, esterified cholesterol, and are spherical. CSF lipoproteins were heterogeneous in apolipoprotein content with apoE, the most abundant apolipoprotein, localized to the largest particles, apoAI and apoAII localized to progressively smaller particles, and apoJ distributed relatively evenly across particle size. There was substantial loss of protein from both CSF and astrocyte particles after density centrifugation compared with gel‐filtration chromatography. The differences between lipoproteins secreted by astrocytes and present in CSF suggest that in addition to delivery of their constituents to cells, lipoprotein particles secreted within the brain by astrocytes may have the potential to participate in cholesterol clearance, developing a core of esterified cholesterol before reaching the CSF. Study of the functional properties of both astrocyte‐secreted and CSF lipoproteins isolated by techniques that preserve native particle structure may also provide insight into the function of apoE in the pathophysiology of specific neurological diseases such as Alzheimer's disease.