Neurite-promoting effect of alpha 2-macroglobulin in rat cerebral cortex is mainly associated with alpha 2-macroglobulin receptor

Fetal Neuroprotective Mechanism of Maternal Magnesium Sulfate: Proteomic Analysis

Mg supplementation has been shown to protect preterm fetuses from white and gray matter damage, but the mechanism is unclear. The purpose of this study was to study the effect of maternal inflammation on the overall protein panel of the fetal rat brain, as well as the neuroprotective effect of magnesium-sulfate (MG). Pregnant rats at e20 (n = 6, 18 total) received injections of i.p. lipopolysaccharide (LPS) 500 ug/kg or control saline (SAL) at time 0. Dams were randomized to treatment with s.c. MG (270 mg/kg loading followed by 27 mg/kg q20 min) or saline (SAL) from -2 to +2 h, followed by an additional injection of MG (270 mg/kg) at +2 h. At 4 h after LPS administration, fetal brains were collected from the 3 treatment groups (LPS/SAL, LPS/MG, SAL/SAL) and analyzed by proteomic technique. LPS significantly decreased fetal brain complement C3, alpha-1-antiproteinase, metallothionein-3, alpha-2-macroglobulin, neurosecretory protein VGF, glutathione S-transferase mu 2, fam91a1, cnot7, mitogen-activated protein kinase levels, and significantly increased fetal brain Hbg1, while MG treatment normalized these measures to normal values. Maternal inflammation may cause brain injury via pathways other than the activation of neurotoxic cytokines; this effect could be due to increased/decreased production of certain proteins associated with securing oligodendrocytes, encouraging neuronal growth in the brain, or protecting against cerebral ischemia. MG's neuroprotective activity may be achieved by modifying the effect of LPS on proteins involved in early brain development.

A meta-analysis of microarray-based gene expression studies of olfactory bulb-derived olfactory ensheathing cells

Genome wide transcriptional profiling and large scale proteomics have emerged as two powerful methods to dissect the molecular properties of specific neural tissues or cell types on a global scale. Several genome-wide transcriptional profiling and proteomics studies have been published on cultured olfactory ensheathing cells (OEC). In this article we present a meta-analysis of all five published and publicly available micro-array gene expression datasets of cultured early-passage-OB-OEC with other cell types (Schwann cells, late-passage-OB-OEC, mucosa-OEC, an OEC cell line, and acutely dissected OEC). The aim of this meta-analysis is to identify genes and molecular pathways that are found in multiple instead of one isolated study. 454 Genes were detected in at least three out of five microarray datasets. In this "Top-list", genes involved in the biological processes "growth of neurites", "blood vessel development", "migration of cells" and "immune response" were strongly overrepresented. By applying network analysis tools, molecular networks were constructed and Hub-genes were identified that may function as key genes in the above mentioned interrelated processes. We also identified 7 genes (ENTPD2, MATN2, CTSC, PTHLH, GLRX1, COL27A1 and ID2) with uniformly higher or lower expression in early-passage-OB-OEC in all five microarray comparisons. These genes have diverse but intriguing roles in neuroprotection, neurite extension and/or tissue repair. Our meta-analysis provides novel insights into the molecular basis of OB-OEC-mediated neural repair and can serve as a repository for investigators interested in the molecular biology of OEC. This article is part of a Special Issue entitled: Understanding olfactory ensheathing glia and their prospect for nervous system repair.

alpha 2-Macroglobulin exposure reduces calcium responses to N-methyl-D-aspartate via low density lipoprotein receptor-related protein in cultured hippocampal neurons

There is increasing evidence that the low-density lipoprotein receptor-related protein (LRP) can function as a signaling link in the central nervous system. To investigate the pathophysiological role of LRP in the central nervous system, we examined the effects of activated alpha(2)-macroglobulin (alpha2M*), a ligand of LRP, on intracellular calcium signaling in cultured rat hippocampal neurons. Neuronal effects of alpha2M* (50 nm) were assessed by a comparison of calcium signals produced in control and alpha2M*-pretreated neurons by N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid. alpha2M* pretreatment significantly decreased the calcium signals to NMDA, whereas little change was observed for the signals to alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid. Native alpha2M, which is not a ligand for LRP, did not affect signals to NMDA. The receptor-associated protein prevented alpha2M*-induced decrease of calcium responses to NMDA, suggesting that alpha2M* exerted its effects through an LRP-mediated pathway. Experiments changing calcium sources demonstrated that alpha2M* pretreatment altered calcium responses to NMDA by primarily changing extracellular calcium influx and subsequently affecting calcium release from intracellular calcium stores. Immunoblot analysis demonstrated that alpha2M* caused a reduction in the levels of the NMDA receptor subunit, NMDAR1. These results suggest that alpha2M* can alter the neuronal response to excitatory neurotransmitters and that alpha2M* pretreatment selectively reduced the calcium responses to NMDA by down-regulating the NMDA receptor.

beta-Amyloid protein aggregation: its implication in the physiopathology of Alzheimer's disease

beta-Amyloid protein (A beta), a 39-42 residue peptide resulting from the proteolytic processing of a membrane-bound beta-amyloid precursor protein (APP), is one of the major components of the fibrillar deposits observed in Alzheimer patients. A beta fibril formation is a complex process which involves changes in A beta conformation and self-association to form cross-beta pleated sheets, protofibrils, and fibrils. Since the aggregation of soluble A beta peptide into fibrils is viewed as a critical event in the physiopathology of Alzheimer's disease (AD), preventing, altering, or reversing fibril formation may thus be of therapeutic value. This review will focus on the current state of knowledge of A beta fibril formation, with special emphasis on physiological and exogenous inhibitors which may have a therapeutic potential.

The endocytic receptor protein LRP also mediates neuronal calcium signaling via N-methyl-D-aspartate receptors

The low density lipoprotein receptor-related protein (LRP) is an endocytic receptor that is a member of the low density lipoprotein receptor family. We report that the LRP ligand, activated alpha(2)-macroglobulin (alpha(2)M*), induces robust calcium influx in cultured primary neurons, but not in nonneuronal LRP-containing cells in the same culture. The calcium influx is mediated through N-methyl-d-aspartate receptor channels, which explains the neuron specificity of the response. Microapplication of alpha(2)M* leads to a localized response at the site of application that dissipates rapidly, suggesting that the calcium signal is temporally and spatially discrete. Calcium influx to alpha(2)M* is blocked by the physiological LRP inhibitor, receptor-associated protein. Bivalent antibodies to the extracellular domain of LRP, but not Fab fragments of the same antibody, cause calcium influx, indicating that the response is specific to LRP and may require dimerization of the receptor. Thus, LRP is an endocytic receptor with a novel signaling role.

Lipoprotein receptor-related protein in brain and in cultured neurons of mice deficient in receptor-associated protein and transgenic for apolipoprotein E4 or amyloid precursor protein

The role of the receptor-associated protein in controlling the expression of the low-density lipoprotein receptor-related protein was analysed in brain and in cultured neurons of receptor-associated protein - / - mice. In addition, the effect of two important ligands of lipoprotein receptor-related protein in brain, i.e. apolipoprotein E and amyloid precursor protein, was examined by crossing the receptor-associated protein - / - mice with transgenic mice overexpressing these proteins specifically in neurons. The immunohistochemical localization of lipoprotein receptor-related protein and receptor-associated protein in wild-type mouse brain was demonstrated to be congruent over all structures, including the cortex and hippocampus. In primary hippocampal neurons, lipoprotein receptor-related protein was distributed somatodendritically and receptor-associated protein was concentrated perinuclearly. In hippocampal neurons from receptor-associated protein - / - mice, lipoprotein receptor-related protein was redistributed over the cell body at the expense of the dendrites. In the absence of receptor-associated protein, maturation of lipoprotein receptor-related protein is slow, resulting in accumulation of the uncleaved 600,000 mol. wt precursor. Neither the added expression of apolipoprotein E4 nor that of amyloid precursor protein in cultured neurons influenced the maturation of lipoprotein receptor-related protein, in either the presence or absence of receptor-associated protein. This result shows that receptor-associated protein is not needed to allow co-expression of lipoprotein receptor-related protein with these ligands in neurons. Furthermore, the typical ramified neuronal morphology of cultured primary neurons and the histology and architecture of the brain were normal in receptor-associated protein - / - mice and in all of the double transgenic mice. Finally, we demonstrated that the survival of receptor-associated protein - /- hippocampal neurons was normal and unaffected by the genotype of the glial feeder cells, whether they were derived from wild-type mice or from mice deficient in receptor-associated protein or apolipoprotein E. These results show that, despite the dramatic effect on maturation and cellular localization of lipoprotein receptor-related protein, the absence of receptor-associated protein did not result in any notable physiological, functional or morphological effects.