Serum amyloid A (SAA)-induced remodeling of CSF-HDL.

Inflammation is a risk factor for Alzheimer's disease. Serum amyloid A (SAA) is an acute phase protein that dissociates apolipoprotein AI (apoAI) from plasma HDL. In cerebrospinal fluid (CSF), the SAA concentration is much higher in subjects with Alzheimer's disease than in controls. CSF-HDL is rich in apoE, which plays an important role as a ligand for lipoprotein receptors in the central nervous system (CNS). To clarify whether SAA dissociates apoE from CSF-HDL, we added recombinant SAA to CSF and determined the apoE distribution in the CSF using native two-dimensional gel electrophoresis. We found that SAA dissociated apoE from CSF-HDL in a dose-dependent manner. This effect was more evident in apoE4 carriers than in apoE3 or apoE2 carriers. After a 24-h incubation at 37 degrees C, SAA continuously dissociated apoE from CSF-HDL. Amyloid beta (Abeta) fragments (1-42) were bound to large CSF-HDL but not to apoE dissociated by SAA. In conclusion, SAA dissociates apoE from CSF-HDL. We postulate that inflammation in the CNS may impair Abeta clearance due to the loss of apoE from CSF-HDL.

Effect of apolipoprotein E (apoE) phenotype on the apoE content of CSF-HDL in children.

BACKGROUND: The majority of the lipoprotein in cerebrospinal fluid (CSF) is apolipoprotein E (apoE)-containing HDL. Since neuronal cells express lipoprotein receptors which recognize apoE, apoE in CSF-HDL is believed to be important for the development of central nervous system (CNS) in children. In adults, the apoE phenotype affects the plasma apoE concentration and the epsilon 4 allele is a risk factor for Alzheimer's disease. Due to the requirement for CNS development, we examined whether the apoE phenotype affects the composition and concentration of CSF-HDL in children. METHODS: We determined the apoE phenotype in 107 neurologically normal subjects, including 67 children (<20 years), by isoelectronic focusing. We also measured apoE, total cholesterol (TC), and phospholipid (PL) concentrations in the CSF. RESULTS: The respective frequencies of apoE4/3, E3/3 and E3/2 were 16.4%, 77.6%, and 6.0%. The allele frequencies of epsilon 4, epsilon 3, and epsilon 2 were 0.082, 0.888, and 0.030, respectively. There were no significant differences in the CSF-apoE, TC, or PL concentrations or the apoE/PL ratio among the apoE phenotypes. However, the CSF-apoE/PL ratio was significantly higher in children than in adults. CONCLUSION: The apoE phenotype does not affect the composition or concentration of CSF-HDL in children. We speculate that an apoE4 carrier is prevented in childhood from the impaired development of central nervous system by CSF-HDL enriched with apoE.

Remodelling of cerebrospinal fluid lipoproteins after subarachnoid hemorrhage.

Lipoprotein particles (Lps) in normal human cerebrospinal fluid (CSF) are distinct from those found in plasma and include unique apolipoprotein E (apoE indicates protein; APOE, gene) containing lipoproteins rarely seen in human plasma. Less favourable neurological recovery after subarachnoid hemorrhage (SAH) has been observed in patients who possess the APOE epsilon4 allele raising the possibility that apoE influences neuronal survival after brain injury. We analysed Lps from control and SAH CSF testing the hypotheses that following brain injury CSF Lps undergo remodelling and apoE containing Lps are selectively depleted from brain injury CSF. Lipoproteins were fractionated using CSF from six control pools and six patients with SAH on a sepharose 6HR 10/30 size exclusion column. Fractions were assayed for total cholesterol (TC), free cholesterol (FC), phospholipid, triglyceride (TG), apoE, apolipoprotein B (apoB), and apolipoprotein AI (apoAI). Compared to control CSF there were significant (P<0.05) increases in TC, FC, TG, and apoAI in SAH CSF. Plasma sized apoB-containing lipoproteins and a very small apoAI-containing Lps were identified in the SAH CSF, which were not present in controls. However, despite the release of plasma lipoproteins into the subarachnoid space, there was no significant increase in CSF apoE. These data provide novel indirect evidence suggesting that after SAH CSF Lps undergo remodelling and apoE containing Lps are selectively reduced in brain injury CSF. The remodelling of CSF Lps and selective reduction of apoE containing lipoproteins may reflect an important response of the human brain to injury.

The levels of soluble amyloid beta in different high density lipoprotein subfractions distinguish Alzheimer's and normal aging cerebrospinal fluid: implication for brain cholesterol pathology?

Several previous studies reported the association of the soluble form of amyloid beta (sA beta) protein, a major constituent of amyloid deposits in Alzheimer's disease (AD), with normal blood, cerebrospinal fluid (CSF) and central nervous system high density lipoproteins (HDLs). The present report aimed to elucidate the pattern of sA beta and apolipoprotein (apo) distribution in AD CSF-HDL subfractions. We studied AD CSF-HDL subfractions by SDS/PAGE and immunoblot analysis after CSF fractionation via density flotation ultracentrifugation. AD CSF was characterized by (i) increased sA beta and apo content of the HDL(1), and (ii) sA beta association with apoE and apoJ in HDL(2), HDL(3) and very high density lipoproteins. The finding supports our proposed hypothesis that upregulation of brain cholesterol dynamics is a fundamental event in the pathophysiology of AD and that sA beta binding to apo and lipid may have important structure-functional consequences.

[Beta amyloid in blood and cerebrospinal fluid is associated with high density lipoproteins]. / Amiloid beta v plazme krovi i spinnomozgovoi zhidkosti assotsiirovan s lipoproteinami vysokoi plotnosti.

Cerebrovascular and parenchymal amyloid deposits found in brains of Alzheimer's disease, Down's syndrome and normal aging are mainly composed of aggregated amyloid beta protein (A beta), a unique peptide 39 to 44 amino acids long. A similar but soluble A beta (s A beta) has been identified in plasma, cerebrospinal fluid (CSF) and cell supernatants, indicating that it is a normal protein. We report here that s A beta in normal human plasma and CSF is complexed to high density lipoprotein (HDL) 3 and very high density lipoprotein (VHDL). Biotinylated synthetic peptide A beta 1-40 was traced in normal human plasma in in vitro experiments. Both tracer biotin-labeled A beta 1-40 and native s A beta were specifically recovered in HDL3 and VHDL as it was assessed in immunoprecipitation experiments of purified plasma lipoproteins and lipoprotein depleted plasma. This fact prompted us to ascertain whether the interaction of s A beta with HDL does occur in normal human CSF in vivo. For this purpose normals human CSF was fractionated by means of sequential flotation ultracentrifugation. The presence of s A beta in the resulting lipoprotein fractions as well as in the lipoprotein depleted CSF was analysed by immunoblot analysis, electron and immune-electron microscopy and native size exclusion chromatography. Immunoblot analysis with 6E10 monoclonal anti-A beta antibodies revealed s A beta association with all HDL subspecies of CSF, primarily HDL3 and VHDL and immunoelectron microscopy confirmed an association of s A beta with CSF-HDL particles of 16.8 + 3.2 nm. Native size exclusion chromatography followed by immunoblot analysis with antibodies against A beta and different apoliproproteins indicated an association of s A beta with HDL complexes of approximately 200 kDa molecular weight. Soluble A beta association with HDL3 and VHDL may be involved in maintaining the solubility of A beta in biological fluids and points to a possible role of lipoproteins and lipoprotein lipid in the biology of aminoloidogenic peptides.

Biochemical characterization of Alzheimer's soluble amyloid beta protein in human cerebrospinal fluid: association with high density lipoproteins.

The soluble form of Alzheimer's amyloid beta protein (sA beta) is associated with high density lipoproteins (HDL) in normal human plasma (BBRC, 1994, 205, 1164-1171). Since sA beta is also present in cerebrospinal fluid (CSF) and the lipoprotein pattern of CSF is different from that of plasma, it was of interest to ascertain whether the interaction of sA beta with HDL also occurs in CSF. Normal human CSF lipoproteins were obtained by sequential flotation ultracentrifugation and analyzed for the presence of sA beta via immunoblot, size-exclusion chromatography, immunoelectron microscopy, N-terminal sequence and mass-spectrometry analyses. Soluble A beta was associated with CSF-HDL particles of 16.8 +/- 3.2 nm in diameter and approximately 200 kDa of relative molecular mass. A approximately 4.3 kDa component purified by HPLC was immunoreactive with anti-A beta antibodies and exhibited an N-terminal sequence identical to the A beta peptide with a mass of 4325.1 Da, indicating that the main sA beta specie associated with CSF-HDL is A beta 1-40.

Isotachophoresis of CSF proteins in gel tubes especially gammaglobulins. An analytical and preparative technique for high-separation of CSF proteins.

An isotachophoretic method using polyacrylamide gel (PAG-ITP) in a simple disc electrophoretic equipment with plastic tubes containing the gels, was elaborated and especially designed for studying the gammaglobulins in CSF and serum from control subjects and patients with neurological disorders, especially known or probable MS. The device and the ITP system used, including leading and terminating electrolytes and spacer substances, dividing the gammaglobulins in a reproducible way, are described. No cooling of the gel tubes was needed. The sample volumes varied between 5--500 microliters, and the separation time was 1.5--3.0 h. CSF from patients with verified or probable MS revealed characteristic, increased low-mobility gammaglobulin fractions. Using other ITP systems, such as other spacer compositions, the anodic proteins can also be studied in more detail. PAG-ITP in gel tubes is a simple and inexpensive technique which can be used for both analytical and preparative procedures for biological material such as CSF, serum and extractions from nervous tissues.