Biomedical subjects

S A Frautschy

Publications and source records attributed to S A Frautschy.

At least 19 recordsLinked to original sources

PubMed2005

Apolipoprotein J (clusterin) activates rodent microglia in vivo and in vitro.

Apolipoprotein J (apoJ; also known as clusterin and sulfated glycoprotein (SGP)-2) is associated with senile plaques in degenerating regions of Alzheimer's disease brains, where activated microglia are also prominent. We show a functional link between apoJ and activated microglia by demonstrating that exogenous apoJ activates rodent microglia in vivo and in vitro. Intracerebroventricular infusion of purified human plasma apoJ ( approximately 4 microg over 28 days) activated parenchymal microglia to a phenotype characterized by enlarged cell bodies and processes (phosphotyrosine immunostaining). In vitro, primary rat microglia were also activated by apoJ, with changes in morphology and induction of major histocompatibility complex class II (MHCII) antigen. ApoJ increased the secretion of reactive nitrogen intermediates in a dose-dependent manner (EC(50) 112 nm), which was completely blocked by aminoguanidine (AG), a nitric oxide synthase inhibitor. However, AG did not block the increased secretion of tumor necrosis factor-alpha by apoJ (EC(50) 55 nm). Microglial activation by apoJ was also blocked by an anti-apoJ monoclonal antibody (G7), and by chemical cleavage of apoJ with 2-nitro-5-thiocyanobenzoate. The mitogen-activated protein kinase kinase and protein kinase C inhibitors PD98059 and H7 inhibited apoJ-mediated induction of reactive nitrogen intermediate secretion from cultured microglia. As a functional measure, apoJ-activated microglia secreted neurotoxic agents in a microglia-neuron co-culture model. We hypothesize that ApoJ contributes to chronic inflammation and neurotoxicity through direct effects on microglia.

Animals↗

PubMed2005

Low density lipoprotein receptor-related proteins (LRPs), Alzheimer's and cognition.

This review will focus primarily on the role of the low density lipoprotein receptor-related protein (LRP-1) in neuronal synapse formation and function in Alzheimer's Disease (AD). We review the role that its ligands may have in cognition or AD: apolipoprotein E (ApoE), alpha2-macroglobulin, Transforming Growth Factor-Beta (TGFbeta, Tissue Plasminogen Activator (tPA), insulin growth factor binding protein-3 (IGFBP-3), which all bind LRP-1 and apolipoprotein J (ApoJ), which is a ligand for LRP-2. After reviewing its role as a signaling receptor, we discuss the connection between LRP and the NMDA glutamate receptor via the post synaptic density 95 (PSD-95) neuronal scaffold protein and the implications it may have for memory and cognition. Finally, we discuss the evidence supporting a role for LRP in AD. Although the evidence for LRP as a genetic risk factor is weak, many of its ligands impose genetic risk, and have been implicated in AD pathogenic cascades. We discuss the role of LRP in amyloid precursor protein (APP) processing and production of beta-amyloid (Abeta. We identify LRP ligands that accelerate aggregation of toxic Abeta species. LRP mediates crucial pathways in AD pathogenesis such as Abeta clearance, Abeta uptake, intraneuronal Abeta accumulation and Abeta-associated neuron death. Interestingly, the TGFbeta -V receptor is LRP-1. Data show that one critical ligand TGFbeta2, associated with neurodegeneration in amyloid diseases, induces LRP expression in PC12 cells. Data from rodent infusion models demonstrate the impact of TGFbeta2 in modifying Abeta- induced Long Term Potentiation (LTP) responses, presynaptic proteins, lipid peroxidation, gliosis and staining for neuronal nuclei. The evidence supports a complex and significant role of LRP in cognition and AD.

Alzheimer Disease↗

PubMed2001

The curry spice curcumin reduces oxidative damage and amyloid pathology in an Alzheimer transgenic mouse.

Inflammation in Alzheimer's disease (AD) patients is characterized by increased cytokines and activated microglia. Epidemiological studies suggest reduced AD risk associates with long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs). Whereas chronic ibuprofen suppressed inflammation and plaque-related pathology in an Alzheimer transgenic APPSw mouse model (Tg2576), excessive use of NSAIDs targeting cyclooxygenase I can cause gastrointestinal, liver, and renal toxicity. One alternative NSAID is curcumin, derived from the curry spice turmeric. Curcumin has an extensive history as a food additive and herbal medicine in India and is also a potent polyphenolic antioxidant. To evaluate whether it could affect Alzheimer-like pathology in the APPSw mice, we tested a low (160 ppm) and a high dose of dietary curcumin (5000 ppm) on inflammation, oxidative damage, and plaque pathology. Low and high doses of curcumin significantly lowered oxidized proteins and interleukin-1beta, a proinflammatory cytokine elevated in the brains of these mice. With low-dose but not high-dose curcumin treatment, the astrocytic marker GFAP was reduced, and insoluble beta-amyloid (Abeta), soluble Abeta, and plaque burden were significantly decreased by 43-50%. However, levels of amyloid precursor (APP) in the membrane fraction were not reduced. Microgliosis was also suppressed in neuronal layers but not adjacent to plaques. In view of its efficacy and apparent low toxicity, this Indian spice component shows promise for the prevention of Alzheimer's disease.

Alzheimer Disease↗

PubMed2000

Ibuprofen suppresses plaque pathology and inflammation in a mouse model for Alzheimer's disease.

The brain in Alzheimer's disease (AD) shows a chronic inflammatory response characterized by activated glial cells and increased expression of cytokines and complement factors surrounding amyloid deposits. Several epidemiological studies have demonstrated a reduced risk for AD in patients using nonsteroidal anti-inflammatory drugs (NSAIDs), prompting further inquiries about how NSAIDs might influence the development of AD pathology and inflammation in the CNS. We tested the impact of chronic orally administered ibuprofen, the most commonly used NSAID, in a transgenic model of AD displaying widespread microglial activation, age-related amyloid deposits, and dystrophic neurites. These mice were created by overexpressing a variant of the amyloid precursor protein found in familial AD. Transgene-positive (Tg+) and negative (Tg-) mice began receiving chow containing 375 ppm ibuprofen at 10 months of age, when amyloid plaques first appear, and were fed continuously for 6 months. This treatment produced significant reductions in final interleukin-1beta and glial fibrillary acidic protein levels, as well as a significant diminution in the ultimate number and total area of beta-amyloid deposits. Reductions in amyloid deposition were supported by ELISA measurements showing significantly decreased SDS-insoluble Abeta. Ibuprofen also decreased the numbers of ubiquitin-labeled dystrophic neurites and the percentage area per plaque of anti-phosphotyrosine-labeled microglia. Thus, the anti-inflammatory drug ibuprofen, which has been associated with reduced AD risk in human epidemiological studies, can significantly delay some forms of AD pathology, including amyloid deposition, when administered early in the disease course of a transgenic mouse model of AD.

Alzheimer Disease↗

PubMed1999

Mapping biochemistry to metabolism: FDG-PET and amyloid burden in Alzheimer's disease.

We evaluated the relationship between amyloid-beta protein (A beta) concentration and the metabolic abnormality in an Alzheimer's disease (AD) patient as measured by [18F]fluorodeoxyglucose positron emission tomography (FDG-PET). Across most regions there were significant inverse correlations among FDG-PET intensity values and both insoluble. The temporal lobe samples showed no significant correlation between FDG-PET values and A beta deposition. Findings support A beta as contributing to the hypometabolism in regions of the AD brain that are still relatively viable metabolically; those regions with chronic pathologic damage, such as temporal cortex, may have other factors that contribute to metabolic deficits.

Aged↗

PubMed1999

Lipoprotein effects on Abeta accumulation and degradation by microglia in vitro.

An inflammatory response involving activated microglia in neuritic beta-amyloid plaques is found in Alzheimer's disease (AD) brain. Because HDL lipoproteins have been shown to carry the beta-amyloid peptide (Abeta) in plasma and CSF, we have investigated the influence of plasma high-density lipoprotein (HDL) and lipidated ApoE and ApoJ particles on the interaction of cultured rat microglia with Abeta1-42. Microglia degraded Abeta via a pathway sensitive to cytochalasin D and the scavenger receptor inhibitor, fucoidan. HDL increased the degradation of Abeta and the ratio of multimeric/monomeric Abeta in a dose-dependent manner. In contrast, lipidated ApoJ and ApoE decreased the degradation of Abeta, and the effects were ApoE isoform-dependent. Immuno-electron microscopy revealed internalized Abeta in endosomes and lysosomes as well as cell-associated Abeta in deep invaginations, which may be related to caveolae and surface-connected compartments. These data suggest that lipoprotein-dependent Abeta trafficking to microglia could be relevant to plaque pathogenesis in AD.

Amyloid beta-Peptides↗

PubMed1999

Role of apolipoprotein E and estrogen in mossy fiber sprouting in hippocampal slice cultures.

A role for apolipoprotein E is implicated in regeneration of synaptic circuitry after neural injury. The in vitro mouse organotypic hippocampal slice culture system shows Timm's stained mossy fiber sprouting into the dentate gyrus molecular layer in response to deafferentation of the entorhinal cortex. We show that cultures derived from apolipoprotein E knockout mice are defective in this sprouting response; specifically, they show no sprouting in the dorsal region of the dentate gyrus, yet retain sprouting in the ventral region. Dorsal but not ventral sprouting in cultures from C57B1/6J mice is increased 75% by treatment with 100 pM 17beta-estradiol; this response is blocked by both progesterone and tamoxifen. These results show that neuronal sprouting is increased by estrogen in the same region where sprouting is dependent on apolipoprotein E. Sprouting may be stimulated by estrogen through its up-regulation of apolipoprotein E expression leading to increased recycling of membrane lipids for use by sprouting neurons. Estrogen and apolipoprotein E may therefore interact in their modulation of both Alzheimer's disease risk and recovery from CNS injury.

Animals↗

PubMed1998

Effects of transforming growth factor-beta (isoforms 1-3) on amyloid-beta deposition, inflammation, and cell targeting in organotypic hippocampal slice cultures.

The transforming growth factor-beta (TGF-beta) family consists of three isoforms and is part of a larger family of cytokines regulating differentiation, development, and tissue repair. Previous work from our laboratory has shown that TGF-beta1 can increase amyloid-beta protein (Abeta) immunoreactive (Abetair) plaque-like deposits in rat brain. The aim of the current study was to evaluate all three isoforms of TGF-beta for their ability to affect the deposition and neurotoxicity of Abeta in an organotypic, hippocampal slice culture model of Abeta deposition. Slice cultures were treated with Abeta either with or without one of the TGF-beta isoforms. All three isoforms can increase Abeta accumulation (over Abeta treatment alone) within the slice culture, as determined by ELISA. However, there are striking differences in the pattern of Abetair among the three isoforms of TGF-beta. Isoforms 1 and 3 produced a cellular pattern of Abeta staining that colocalizes with GS lectin staining (microglia). TGF-beta2 produces dramatic Abeta staining of pyramidal neurons in layers CA1-CA2. In addition to cellular Abeta staining, plaque-like deposits are increased by all of the TGF-betas. Although no gross toxicity was observed, morphological neurodegenerative changes were seen in the CA1 region when the slices were treated with Abeta plus TGF-beta2. Our results demonstrate important functional differences among the TGF-beta isoforms in their ability to alter the cellular distribution and degradation of Abeta. These changes may be relevant to the pathology of Alzheimer's disease (AD).

Amyloid beta-Peptides↗

PubMed1998

Protease inhibitor coinfusion with amyloid beta-protein results in enhanced deposition and toxicity in rat brain.

Amyloid beta-protein, Abeta, is normally produced in brain and is cleared by unknown mechanisms. In Alzheimer's disease (AD), Abeta accumulates in plaque-like deposits and is implicated genetically in neurodegeneration. Here we investigate mechanisms for Abeta degradation and Abeta toxicity in vivo, focusing on the effects of Abeta40, which is the peptide that accumulates in apolipoprotein E4-associated AD. Chronic intraventricular infusion of Abeta40 into rat brain resulted in limited deposition and toxicity. Coinfusion of Abeta40 with the cysteine protease inhibitor leupeptin resulted in increased extracellular and intracellular Abeta immunoreactivity. Analysis of gliosis and TUNEL in neuron layers of the frontal and entorhinal cortex suggested that leupeptin exacerbated Abeta40 toxicity. This was supported further by the neuronal staining of cathepsin B in endosomes or lysosomes, colocalizing with intracellular Abeta immunoreactivity in pyknotic cells. Leupeptin plus Abeta40 caused limited but significant neuronal phospho-tau immunostaining in the entorhinal cortex. Intriguingly, Abeta40 plus leupeptin induced intracellular accumulation of the more toxic Abeta, Abeta42, in a small group of septal neurons. Leupeptin infusion previously has been reported to interfere with lysosomal proteolysis and to result in the accumulation of lipofuscin, dystrophic neurites, tau- and ubiquitin-positive inclusions, and structures resembling paired helical filaments. Coinfusion of Abeta40 with the serine protease inhibitor aprotinin also increased diffuse extracellular deposition but reduced astrocytosis and TUNEL and was not associated with intracellular Abeta staining. Collectively, these data suggest that an age or Alzheimer's-related defect in lysosomal/endosomal function could promote Abeta deposition and DNA fragmentation in neurons and glia similar to that found in Alzheimer's disease.

Alzheimer Disease↗

PubMed1998

Effect of chloroquine and leupeptin on intracellular accumulation of amyloid-beta (A beta) 1-42 peptide in a murine N9 microglial cell line.

Murine N9 microglia accumulated A beta from media containing 0.67 microM A beta within 6 h. In N9 and in primary rat microglia, chloroquine, which disrupts lysosomal pH, increased A beta-induced accumulation of A beta, particularly A beta1-42. Leupeptin similarly enhanced A beta accumulation. The scavenger receptor antagonist fucoidan did not affect acute chloroquine-dependent A beta1-42 accumulation, demonstrating uptake of non-aggregated A beta. After prolonged incubations, chloroquine enhanced A beta multimer (8-12 kDa) accumulation, an effect inhibited by fucoidan. Disruptions of the lysosomal system enhance A beta and its multimer formation. Despite negligible effects of fucoidan on initial A beta uptake, chronic exposure inhibits multimer accumulation, demonstrating a role for scavenger receptor in multimer accumulation.

Amyloid beta-Peptides↗

PubMed1998

Spiral intercellular calcium waves in hippocampal slice cultures.

Complex patterns of intercellular calcium signaling occur in the CA1 and CA2 regions of hippocampal slice organotypic cultures from neonatal mice. Spontaneous localized intercellular Ca2+ waves involving 5-15 cells propagate concentrically from multiple foci in the stratum oriens and s. radiatum. In these same regions, extensive Ca2+ waves involving hundreds of cells propagate as curvilinear and spiral wavefronts across broad areas of CA1 and CA2. Ca2+ waves travel at rates of 5-10 mu m/s, are abolished by thapsigargin, and do not require extracellular Ca2+. Staining for astrocytes and neurons indicates that these intercellular waves occur primarily in astrocytes. The frequency and amplitude of Ca2+ waves increase in response to bath application of N-methyl-D-aspartate (NMDA) and decrease in response to removal of extracellular Ca2+ or application of tetrodotoxin. This novel pattern of intercellular Ca2+ signaling is characteristic of the behavior of an excitable medium. Networks of glial cells in the hippocampus may behave as an excitable medium whose spatial and temporal signaling properties are modulated by neuronal activity.

Animals↗

PubMed1998

Microglial response to amyloid plaques in APPsw transgenic mice.

Microglial activation is central to the inflammatory response in Alzheimer's Disease (AD). A recently described mouse line, Tg(HuAPP695.K670N/M671L)2576, expressing human amyloid precursor protein with a familial AD gene mutation, age-related amyloid deposits, and memory deficits, was found to develop a significant microglial response using Griffonia simplicifolia lectin or phosphotyrosine probe to identify microglia Both Griffonia simplicifolia lectin and phosphotyrosine staining showed increased numbers of intensely labeled, often enlarged microglia clustered in and around plaques, consistent with microglial activation related to beta-amyloid formation. Using quantitative image analysis of coronal phosphotyrosine-immunostained sections, transgene-positive 10- to 16-month-old, hemizygous, hybrid Tg2576 (APPsw) animals showed significantly increased microglial density and size in plaque-forming areas of hippocampus and frontal, entorhinal, and occipital cortex. Quantitative analysis of microglia as a function of distance from the center of plaques (double labeled for A beta peptide and microglia) revealed highly significant, two- to fivefold elevations in microglial number and area within plaques compared with neighboring regions. Tg2576 beta-amyloid-plaque-forming mice should be a useful system for assessing the consequences of the microglial-mediated inflammatory response to beta-amyloid and developing anti-inflammatory therapeutic strategies for Alzheimer's disease. These results provide the first quantitative link between beta-amyloid plaque formation and microglial activation in an animal model with neuritic plaques and memory deficits.

Alzheimer Disease↗

PubMed1998

Antibody to caspase-cleaved actin detects apoptosis in differentiated neuroblastoma and plaque-associated neurons and microglia in Alzheimer's disease.

During apoptosis, activation of a family of cysteine proteases related to interleukin-1beta-converting enzyme (ICE)-related proteases or "caspases" results in endoproteolytic cleavage of multiple substrates at specific aspartate residues. We have sought to develop new antibody probes for the neoepitopes in protein fragments produced by ICE-related proteolytic cleavage as specific markers of events tightly linked to apoptotic mechanisms. Here, we demonstrate that an antibody probe specific for the C terminus of a 32-kd actin fragment produced by ICE-like activity specifically labels apoptotic but not necrotic, differentiated human neuroblastoma cells in culture. Unlike probes for nonspecific DNA strand breaks confined to the nucleus or cell body, this method allows the detection of cytoskeletal fragments in cell processes as well as the perikaryon long before DNA fragmentation and cell death and therefore serves as a novel marker of apoptosis-related events in distal parts of cells such as axons and dendrites. To illustrate this new tool, we show that the antibody detects the processes and cell bodies of degenerating neurons and plaque-associated microglia in Alzheimer's disease. In situ detection of caspase-cleaved actin provides a new means to evaluate the role of caspase activation in pathological and physiological processes.

Actins↗

PubMed1994

Polyclonals to beta-amyloid(1-42) identify most plaque and vascular deposits in Alzheimer cortex, but not striatum.

Alzheimer's beta-peptides (A beta) aggregation rates depend on A beta length. We made synthetic peptide antisera to A beta 34-40 and 37-42. Purified anti-34-40 preferentially recognizes beta 1-40, vascular amyloid and a subset of plaques while purified anti-37-42 recognizes A beta 1-42 and not A beta 1-40 in dot and Western blots and immunoprecipitates; 37-42 precipitates a small percentage of fibroblast secreted A beta and strongly stains all deposits identified by monoclonals to A beta on adjacent sections from frontal cortex, but not in dorsal striatum.

Alzheimer Disease↗

PubMed1994

Monoclonal antibody to the C-terminus of beta-amyloid.

Soluble amyloid beta-protein (A beta) is normally produced, but forms deposits in the brain of Alzheimer's (AD) patients. The length of isolated A beta in SDS-insoluble amyloid from AD brain is reported to vary between plaques and vessels ranging from 28 to 43, with major species being 40 and 42 residues. Because the A beta C-terminus determines aggregation rates, we made an A beta monoclonal antibody distinguishing beta 1-42 from beta 1-40. In AD cortex, the beta 1-42 antibody recognizes all the structures identified by monoclonal to beta 1-40 on adjacent sections: plaque cores, diffuse A beta deposits and vascular amyloid. These antibodies help define variation in A beta length between different deposits, regions and autopsied brains.

Alzheimer Disease↗

PubMed1994

Effects of transforming growth factor beta 1 on scar production in the injured central nervous system of the rat.

In the central nervous system (CNS), nerve regeneration after traumatic injury fails. The formation of a dense fibrous scar is thought to restrict in part the growth of axonal projections, providing one of the many reasons that complete lesions of neural pathways in the adult mammalian CNS are rarely followed by significant functional recovery. In order to determine which mechanisms mediate scar formation in the CNS and to investigate whether they can be modulated in vivo, we have attempted to define the potential role of trophic factors. Our previous studies have shown the focal elevation of transforming growth factor beta 1 (TGF beta 1) expression in lesioned CNS tissue. In the studies described here, we demonstrate that TGF beta 1 participates in the scarring response in the rat brain. First, the elevated protein levels of TGF beta 1 are localized to specific populations of injury-responsive cells in the traumatized CNS. Furthermore, the injection of TGF beta 1 into the brains of injured rats causes a dramatic increase in the scarring response. Conversely, when neutralizing TGF beta 1 antibodies are administered, the deposition of fibrous scar tissue and the formation of a limiting glial membrane that borders the lesion is significantly attenuated, thus establishing a role for the endogenous growth factor in regulation of the non-glial component of the scar. In implicating TGF beta 1 in the scarring response in the CNS, the potential use for TGF beta 1 antagonists as inhibitors of scar formation in the injured mammalian CNS is self-evident.

Animals↗

PubMed1992

Enhanced expression of transforming growth factor beta 1 in the rat brain after a localized cerebral injury.

It is becoming clear that transforming growth factor beta (TGF beta) may be a key factor regulating inflammatory and tissue specific wound responses. Because the formation of a glial-collagen scar at CNS lesion sites is thought to contribute to the pathology associated with penetrating CNS injuries, and because in the periphery TGF beta 1 stimulates fibroblast deposition of scar tissue, we used in situ hybridization and immunohistochemistry to investigate the effect of a defined cerebral lesion on the local expression of TGF beta 1. Induction of TGF beta 1 mRNA and protein is relatively diffuse in the neuropile around the margins of the lesion at 1, 2 and 3 days, but becomes localized to the region of the glial scar at 7 and 14 days. The signal intensity for TGF beta 1 mRNA and protein is maximal between 2 and 3 days and decreases between 7 and 14 days after lesion. The predominant cell types in the neuropile localizing TGF beta 1 mRNA and protein have the morphological characteristics of astrocytes, although macrophages are also detected. An induction of TGF beta 1 mRNA was also observed in endothelial cells of the meninges, hippocampal fissure and choroid plexus, at 2 and 3 days. However, this is dramatically reduced by 7 days and has disappeared by 14 days. These results suggest a role for TGF beta 1, not only in inflammation, but also in the tissue-specific glial scar formation that occurs in the CNS. Furthermore, they suggest a potential therapeutic use of TGF beta 1 antagonists in the CNS to help limit the pathogenesis associated with matrix deposition in the wound.

Animals↗

PubMed1992

Pituitary portal plasma levels of oxytocin during the estrous cycle, lactation, and hyperprolactinemia.

The median eminence receives fibers from both parvocellular and magnocellular OT neurons in the hypothalamus. The OT neuronal terminal in the median eminence is secretory and is the major source of the neuropeptide in the blood of pituitary portal vessels. The OT secretion into pituitary portal plasma increases by ovarian steroids, PRL, and the suckling stimulus. The OT secretion into the blood of pituitary portal vessels changes in parallel with the altered secretion of PRL from the pituitary. Because of correlative association between pituitary portal plasma OT and systemic plasma PRL and much abundant evidence for a direct stimulatory action of OT on PRL release, we propose that the pituitary portal vascular system serves as the window for the central OT neurotransmission to the pituitary lactotropes.

Anesthesia↗