Browsing by Author "von Bernhardi, R"

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    Expression of scavenger receptors in glial cells - Comparing the adhesion of astrocytes and microglia from neonatal rats to surface-bound beta-amyloid
    (AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC, 2005) Alarcon, R; Fuenzalida, C; Santibanez, M; von Bernhardi, R
    Astrocytes and microglia associate to amyloid plaques, a pathological hallmark of Alzheimer disease. Microglia are activated by and can phagocytose beta-amyloid ( A beta). Scavenger receptors ( SRs) are among the receptors mediating the uptake of fibrillar A beta in vitro. However, little is known about the function of the astrocytes surrounding the plaques or the nature of their interaction with A beta. It is unknown whether glial cells bind to nonfibrillar A beta and if binding of astrocytes to A beta depends on the same Scavenger receptors described for microglia. We determined the binding of glia to A beta by an adhesion assay and evaluated the presence of scavenger receptors in glial cells by immunocytochemistry, immunohistochemistry of brain sections, and immunoblot. We found that astrocytes and microglia from neonatal rats adhered in a concentration-dependent manner to surfaces coated with fibrillar A beta or nonfibrillar A beta. Fucoidan and poly( I), known ligands for SR-type A, inhibited adhesion of microglia and astrocytes to A beta and also inhibited A beta phagocytosis. In contrast, a ligand for SR-type B like low density lipoprotein, did not compete glial adhesion to A beta. Microglia presented immunodetectable SR-BI, SR-AI/AII, RAGE, and SR-MARCO ( macrophage receptor with collagenous structure, a member of the SR-A family). Astrocytes presented SR-BI and SR-MARCO. To our knowledge, this is the first description of the presence of SR-MARCO in astrocytes. Our results indicate that both microglia and astrocytes adhere to fibrillar and nonfibrillar A beta. Adhesion was mediated by a fucoidan-sensitive receptor. We propose that SR-MARCO could be the Scavenger receptor responsible for the adhesion of astrocytes and microglia to A beta.
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    Expression of α2-macroglobulin receptor/low density lipoprotein receptor-related protein (LRP) in rat microglial cells
    (2000) Marzolo, MP; von Bernhardi, R; Bu, GJ; Inestrosa, NC
    Low density lipoprotein receptor-related protein (LRP) participates in the uptake and degradation of several ligands implicated in neuronal pathophysiology including apolipoprotein E (apoE), activated alpha(2)-macroglobulin (alpha(2)M*) and beta-amyloid precursor protein (APP). The receptor is expressed in a variety of tissues. in the brain LRP is present in pyramidal-type neurons in cortical and hippocampal regions and in astrocytes that are activated as a result of injury or neoplasmic transformation. As LRP is expressed in the monocyte/macrophage cell system, we were interested in examining whether LRP is expressed in microglia. We isolated glial cells from the brain of neonatal rats and LRP was immunodetected both in microglial cells and in astrocytes expressing glial fibrillar acidic protein (GFAP). Microglial cells were able to bind and internalize LRP-specific ligand, alpha(2)M*. The internalization was inhibitable by RAP, with a Kd of 1.7 nM. The expression of LRP was upregulated by dexamethasone, and down-regulated by lipopolysaccharide (LPS), gamma interferon (IFN-gamma) or a combination of both. LRP was less sensitive to dexamethasone in activated astrocytes than in microglia. We provided the first analysis of LRP expression and regulation in microglia. Our results open the possibility that microglial cells could be related to the participation of LRP and its ligands in different pathophysiological states in brain. (C) 2000 Wiley-Liss, Inc.
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    Microglial reactivity to β-amyloid is modulated by astrocytes and proinflammatory factors
    (2004) von Bernhardi, R; Eugenín, J
    The brains of Alzheimer's disease (AD) patients present activated glial cells, amyloid plaques and dystrophic neurites. The core of amyloid plaques is composed of aggregated amyloid peptide (A), a peptide known to activate glial cells and to have neurotoxic effects. We evaluated the capability of glial cells to mediate Abeta(1-42) cytotoxicity in hippocampal cultures. Conditioned media obtained from microglial cultures exposed to Abeta induced apoptosis of hippocampal cells. This pro-apoptotic effect was not observed in hippocampal cultures exposed to conditioned media obtained from mixed glial (astrocytes and microglia) cultures that had been exposed to Abeta. Microglia exposed to Abeta responded with reactive morphological changes, induction of NOS, elevated nitric oxide production and decreased reductive metabolism. All these responses were attenuated by the presence of astrocytes. This astrocyte modulation was however, not observed when glial cells were exposed to proinflammatory factors (LPS+Interferon-gamma) alone or in combination with Abeta. Our results suggest that astrocytes and proinflammatory molecules are determining factors in the response of microglia to A. (C) 2004 Elsevier B.V All rights reserved.
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    Oligodendrocytes damage in Alzheimer's disease
    (2005) Roth, AD; Ramírez, G; Alarcón, R; von Bernhardi, R
    Research on Alzheimer's disease (AD) focuses mainly on neuronal death and synaptic impairment induced by beta-Amyloid peptide (A beta), events at least partially mediated by astrocyte and microglia activation. However, substantial white matter damage and its consequences on brain function warrant the study of oligodendrocytes' compromise in AD and discuss some experimental data indicative of A beta toxicity in culture. We observed that 1 mu M of fibrilogenic A beta peptide damages of astrocytes reduced the A beta-induced damage. This agrees with our previous results showing an astrocyte-mediated protective effect over A beta-induced damage on hippocampal cells and modulation of the activation of microglial cells in culture. Oligodendrocytes protection by astrocytes could be. either by reduction of A beta peptide damages oligodendrocytes in vitro: while pro-inflammatory molecules (1 mu g/ ml LPS + 1 ng/ml IFN gamma) or the presence of astrocytes reduced the A beta-induced damage on hippocampal cells and modulation of the activation of microglial cells in culture. Oligodendrocytes protection by astrocytes could be either by reduction of A beta fibrilogenesis/deposition or prevention of oxidative damage. Likewise, the decrease of A beta-induced damge by proinflammatory molecules could reflect the production of trophic factors by activated oligodendrocytes and/or a metabolic activation as observed during myelination. Considering the association of inflammation with neurodegenerative disease. oligodendrocytes impairement in AD patients could potentiate cell damage under pathological conditions.
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    Protection of rat primary hippocampal cultures from A beta cytotoxicity by pro-inflammatory molecules is mediated by astrocytes
    (ACADEMIC PRESS INC ELSEVIER SCIENCE, 2005) Ramirez, G; Toro, R; Dobeli, H; von Bernhardi, R
    The brain of Alzheimer's disease patients shows abundant dystrophic neurites in close proximity to fibrillar beta-amyloid (A beta) plaques, and activated glial cells. We evaluated the influence of pro-inflammatory molecules (LPS + IFN-gamma) on A beta(1-42) neurotoxicity. 2 mu M A beta(1-42) induced apoptosis of hippocampal cells and LPS + IFN-gamma reduced the apoptosis induced by A beta. However, LPS + IFN-gamma prevented apoptosis only in hippocampal cultures containing astrocytes. Also, LPS + IFN-gamma induced the secretion of TGF beta, a cytokine having neuroprotective effects, only in hippocampal cultures that contained astrocytes. Astrocytes had a regulatory effect over microglial and neuronal responses to A. The results suggest that LPS + IFN-gamma, traditionally considered as pro-apoptotic, reduced apoptosis induced by A beta through the activation of neuroprotective mechanisms mediated by astrocytes. We propose that astrocytes are pivotal in the modulation of inflammation of the CNS. The impairment of the regulatory functions performed by activated astrocytes could represent an important pathogenic mechanism for neurodegenerative diseases. (c) 2005 Elsevier Inc. All rights reserved.
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    Respiratory responses to pH in the absence of pontine and dorsal medullary areas in the newborn mouse in vitro
    (ELSEVIER, 2003) Infante, CD; von Bernhardi, R; Rovegno, M; Llona, I; Eugenin, JL
    The contribution of pons and dorsal medulla in establishing the pattern of fictive respiration and in mediating the respiratory response to acidification was studied using the isolated brainstem-spinal cord preparation from neonatal mouse. About 40% of ponto-medullary preparations (retaining pons) showed spontaneous, but irregular respiratory-like rhythm. In the other 60%, the elimination of the pons often was followed by the initiation of a respiratory-like rhythm. Medullary preparations, derived from either inactive or rhythmic ponto-medullary preparations, showed a regular respiratory-like rhythm, which was also of a higher frequency and a bigger amplitude than that observed in ponto-medullary preparations. In contrast, ventral medullary preparations, derived from medullary preparations by eliminating the dorsal medulla, showed an irregular rhythm with a reduced amplitude of the integrated inspiratory burst. In ponto-medullary and ventral medullary preparations, acidification of the superfusion medium increased the respiratory frequency, while in medullary preparations, it increased the frequency and reduced the amplitude of the inspiratory burst. Our results suggest that pontine structures influence negatively the rate and depth of the respiratory-like rhythm, while dorsal medullary structures influence positively the depth of the rhythm. They also suggest that the pattern of response to pH supported by the ventral medulla is modified by the input provided from pons and dorsal medulla. (C) 2003 Elsevier B.V. All rights reserved.
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    Supplementation of female rats with alpha-linolenic acid or docosahexaenoic acid leads to the same omega-6/omega-3 LC-PUFA accretion in mother tissues and in fetal and newborn brains
    (KARGER, 2004) Valenzuela, A; von Bernhardi, R; Valenzuela, V; Ramirez, G; Alarcon, R; Sanhueza, J; Nieto, S
    Background: Maternal omega-3 fatty acid supplementation has been suggested to provide docosahexaenoic acid (DHA) for the normal brain development during gestation. DHA can be given as such ( preformed) or through the omega-3 precursor alpha-linolenic acid (LNA) which is transformed into DHA by elongation and desaturation reactions. Western diet provides low amounts of LNA and DHA; therefore, supplementation with these omega-3 fatty acids has been suggested for pregnant women. However, the bioequivalence of LNA ingestion to DHA supplementation has not been established. Methods: Recently weaning female Wistar rats were fed a diet containing a small amount of LNA and no DHA. The animals were daily supplemented 40 days before mating, during pregnancy, and until delivery with 60 mg/kg of LNA or 6 mg/kg of DHA dissolved in coconut oil. Fatty acids were given as ethyl ester derivatives. Controls received coconut oil. The fatty acid composition of blood plasma, erythrocytes, liver, visceral adipose tissue, and brain segments (frontal cortex, hippocampus, and cerebellum) was analyzed. Brain segments obtained from 16- and 19-day-old fetuses and from 2- and 21-day- old rats were also analyzed for fatty acid composition. Results: Supplementation with LNA and DHA induced a similar accretion of DHA in plasma, erythrocytes, liver, and brain segments of the mothers. The adipose tissue showed a higher DHA accretion after DHA-supplementation. The DHA accretion in frontal cortex, hippocampus, and cerebellum obtained from the fetuses and the newborn rats was similar when the mothers were supplemented with LNA and DHA. Our results show that under our experimental conditions a similar accretion of DHA in the different tissues of the mothers and in the brain segments of fetuses and newborn rats is obtained after LNA and DHA supplementation. Conclusion: LNA and DHA, at the amounts given in this study, show a similar bioequivalence for DHA accretion in different tissues of the mother and in brain segments of fetuses and newborn rats. Copyright (C) 2004 S. Karger AG, Basel.
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    Transforming growth factor-beta 1 produced by hippocampal cells modulates microglial reactivity in culture
    (ACADEMIC PRESS INC ELSEVIER SCIENCE, 2005) Herrera Molina, R; von Bernhardi, R
    Activated microglia produce superoxide anion (O-2(center dot-)) and nitric oxide (NO), both of which can be neurotoxic. To identify regulatory mechanisms that might modulate over-activation of microglia, we evaluated the inhibition of microglial activation by factors secreted by hippocampal cells. Supernatants from hippocampal cell cultures (Hippocampal-Cm) prevented microglial O-2(center dot) and NO production. LAP-TGF beta 1 was present in the Hippocampal-Cm as shown by immunoblot and a TGF beta 1-dependent proliferation-inhibition bioassay. LAP-TGF beta 1 and TGF beta activity increased in hippocampal cultures exposed to proinflammatory conditions (LPS and Interferon-gamma). The inhibition of (O-2(center dot-)) and NO production by Hippocampal-Cm was mimicked by the addition of recombinant TGF beta 1. Treating Hippocampal-Cm with an antibody against TGF beta 1 to neutralize its activity eliminated its ability to inhibit O-2(center dot-) and NO production. Our findings suggest that the TGF beta 1 secreted by hippocampal cells modulated microglial activity. We propose that in pathological conditions, impairment of this modulatory mechanism could enhance microglia-mediated neurotoxicity. (c) 2005 Elsevier Inc. All rights reserved.