Amyloid-β Reduces Exosome Release from Astrocytes by Enhancing JNK Phosphorylation.

Exosomes are small extracellular vesicles secreted by variety of cell types such as neurons, astrocytes, and oligodendrocytes. It is suggested that exosomes play essential role in the maintenance of the neuronal functions and also in the clearance of amyloid-β (Aβ) from the brain. Aβ is well known to cause neuronal cell death, whereas little is known about its effect on astrocytes.

Phosphatidylcholine protects neurons from toxic effects of amyloid β-protein in culture.

Amyloid β-protein (Aβ) is the major component of extracellular plaques in the brains of patients with Alzheimer's disease. It has been suggested that the interaction of Aβ with membrane cholesterol is essential for Aβ to exert neurotoxicity; however, the effect of phospholipids, another major membrane lipid component, on Aβ-induced neurotoxicity remains unclarified. Here we report the protective effect of phosphatidylcholine (PC) on primary cultured neurons against Aβ1-42-induced damage.

Feeder cells support the culture of induced pluripotent stem cells even after chemical fixation.

Chemically fixed mouse embryonic fibroblasts (MEFs), instead of live feeder cells, were applied to the maintenance of mouse induced pluripotent stem (miPS) cells. Formaldehyde and glutaraldehyde were used for chemical fixation. The chemically fixed MEF feeders maintained the pluripotency of miPS cells, as well as their undifferentiated state.

Visible light-induced crosslinkable gelatin.

A novel visible light-crosslinkable porcine gelatin was prepared for gelation and micropatterning. The preparation employed a photo-oxidation-induced crosslinking mechanism. First, furfuryl groups were incorporated into the gelatin.

Bioactive TGF-beta can associate with lipoproteins and is enriched in those containing apolipoprotein E3.

Transforming growth factor-beta1 (TGF-beta1) has central functions in development, tissue maintenance, and repair and has been implicated in major diseases. We discovered that TGF-beta1 contains several amphipathic helices and hydrophobic domains similar to apolipoprotein E (apoE), a protein involved in lipoprotein metabolism. Indeed, TGF-beta1 associates with lipoproteins isolated from human plasma, cultured liver cells, or astrocytes, and its bioactivity was highest in high-density lipoprotein preparations.

Surface coating with a thermoresponsive copolymer for the culture and non-enzymatic recovery of mouse embryonic stem cells.

A thermoresponsive substrate based on a triblock copolymer, poly(N-isopropylacrylamide)-block-poly[(R)-3-hydroxybutyrate]-block-poly(N-isopropylacrylamide) (PNIPAAm-PHB-PNIPAAm), co-coated with gelatin, was developed for the culture and non-enzymatic recovery of mouse embryonic stem cells. After culture, the cells could be detached by cooling at 4 degrees C for 20 min without trypsin digestion. The embryonic stem cells remained undifferentiated after culture on the gelatin/copolymer-coated surfaces, similar to standard culture techniques.

Peptide immobilized on gold particles enhances cell growth.

A multivalent ligand of thrombopoietin (TPO) was prepared by immobilization of mimetic peptides on gold particles. An effective peptide ligand containing cysteine was designed to enhance the growth of TPO-sensitive cells. The peptide was then immobilized on gold particles by self assembly.

Resorbable scaffolds from three different techniques: electrospun fabrics, salt-leaching porous films, and smooth flat surfaces.

Nanofibrous scaffolds of poly[(L-lactide)-co-(1,5-dioxepan-2-one)] generated by electrospinning have been compared with porous films obtained by solvent cast/salt leaching and homogeneous films. A comparison between the fibrous materials and the homogeneous solvent-cast films revealed that the surface of the nanofibers was more hydrophobic and that the nanofibers were degraded more rapidly in the presence of proteinase. It was obvious that the strain-to-break was reduced by the nanofiber formation, it decreased from 370% to 130% independent of fiber diameter.

Angiotensin-converting enzyme converts amyloid beta-protein 1-42 (Abeta(1-42)) to Abeta(1-40), and its inhibition enhances brain Abeta deposition.

The abnormal deposition of the amyloid beta-protein (Abeta) in the brain appears crucial to the pathogenesis of Alzheimer's disease (AD). Recent studies have suggested that highly amyloidogenic Abeta(1-42) is a cause of neuronal damage leading to AD pathogenesis and that monomeric Abeta(1-40) has less neurotoxicity than Abeta(1-42). We found that mouse and human brain homogenates exhibit an enzyme activity converting Abeta(1-42) to Abeta(1-40) and that the major part of this converting activity is mediated by the angiotensin-converting enzyme (ACE).

Novel action of apolipoprotein E (ApoE): ApoE isoform specifically inhibits lipid-particle-mediated cholesterol release from neurons.

Background: Since the majority of apolipoprotein E (apoE) existing in the cerebrospinal fluid is associated with high-density lipoprotein (HDL), one should focus on the role of the apoE-HDL complex rather than on that of free apoE in cholesterol metabolism in the central nervous system. However, the apoE-isoform-specific effect of apoE-HDL on cholesterol transport remains unclarified.

Results: Here we show that apoE3-HDL induced a marked cholesterol release from neurons, while apoE4-HDL induced little.

Cholesterol-mediated neurite outgrowth is differently regulated between cortical and hippocampal neurons.

The acquisition of neuronal type-specific morphogenesis is a central feature of neuronal differentiation and has important consequences for region-specific nervous system functions. Here, we report that the cell type-specific cholesterol profile determines the differential modulation of axon and dendrite outgrowths in hippocampal and cerebral cortical neurons in culture. The extent of axon and dendrite outgrowths is greater and the polarity formation occurs earlier in cortical neurons than in hippocampal neurons.

Oligomerization of amyloid beta-protein occurs during the isolation of lipid rafts.

Cholesterol- and glycosphingolipid-rich microdomains, called "lipid rafts," are suggested to initiate and promote the pathophysiology of Alzheimer's disease by serving as a platform for generation, aggregation, or degradation of amyloid-beta protein (Abeta). However, methods for biochemical isolation of these microdomains may produce artifacts. In this study, when synthetic Abeta1- 40 monomers were added to the brain fragment at a final concentration of 2.

Altered cholesterol metabolism in Niemann-Pick type C1 mouse brains affects mitochondrial function.

Niemann-Pick type C1 (NPC1) disease is a fatal hereditary disorder characterized by a defect in cholesterol trafficking and progressive neurodegeneration. Although the NPC1 gene has been identified, the molecular mechanism responsible for neuronal dysfunction in brains of patients with NPC1 disease remains unknown. This study demonstrates that the amount of cholesterol within mitochondria membranes is significantly elevated in NPC1 mouse brains and neural cells.

Association of a 5178C-->A (Leu237Met) polymorphism in the mitochondrial DNA with a low prevalence of myocardial infarction in Japanese individuals.

Because mitochondria are the major sources of reactive oxygen species (ROS) in cells, certain alterations in mitochondrial functions can lead to metabolic perturbation in vascular endothelial cells and smooth muscle cells, resulting in vascular dysfunction. We previously demonstrated that a C --> A transversion in mitochondrial DNA (mtDNA) at nucleotide 5178 of the NADH dehydrogenase subunit 2 (ND2) gene, which results in a Lue --> Met substitution at amino acid 237, was found more frequently in Japanese centenarians than in controls. We also demonstrated that this Mt5178C --> A polymorphism has anti-atherosclerotic effects in diabetic subjects.

Modulation of amyloid precursor protein cleavage by cellular sphingolipids.

Lipid rafts and their component, cholesterol, modulate the processing of beta-amyloid precursor protein (APP). However, the role of sphingolipids, another major component of lipid rafts, in APP processing remains undetermined. Here we report the effect of sphingolipid deficiency on APP processing in Chinese hamster ovary cells treated with a specific inhibitor of serine palmitoyltransferase, which catalyzes the first step of sphingolipid biosynthesis, and in a mutant LY-B strain defective in the LCB1 subunit of serine palmitoyltransferase.

Amyloid beta-protein (Abeta)1-40 protects neurons from damage induced by Abeta1-42 in culture and in rat brain.

Previously, we found that amyloid beta-protein (Abeta)1-42 exhibits neurotoxicity, while Abeta1-40 serves as an antioxidant molecule by quenching metal ions and inhibiting metal-mediated oxygen radical generation. Here, we show another neuroprotective action of nonamyloidogenic Abeta1-40 against Abeta1-42-induced neurotoxicity in culture and in vivo. Neuronal death was induced by Abeta1-42 at concentrations higher than 2 microm, which was prevented by concurrent treatment with Abeta1-40 in a dose-dependent manner.

Promotion of tau phosphorylation by MAP kinase Erk1/2 is accompanied by reduced cholesterol level in detergent-insoluble membrane fraction in Niemann-Pick C1-deficient cells.

Niemann-Pick type C (NPC) disease is a cholesterol-storage disease accompanied by neurodegeneration with the formation of neurofibrillary tangles, the major component of which is the hyperphosphorylated tau. Here, we examined the mechanism underlying hyperphosphorylation of tau using mutant Chinese hamster ovary (CHO) cell line defective in NPC1 (CT43) as a tool. Immunoblot analysis revealed that tau was hyperphosphorylated at multiple sites in CT43 cells, but not in their parental cells (25RA) or the wild-type CHO cells.

Amyloid beta-protein affects cholesterol metabolism in cultured neurons: implications for pivotal role of cholesterol in the amyloid cascade.

Recently, we have found that alterations in cellular cholesterol metabolism are involved in promotion of tau phosphorylation (Fan et al. [2001] J. Neurochem.

Gene therapy for mitochondrial disease by delivering restriction endonuclease SmaI into mitochondria.

The restriction endonuclease SmaI has been used for the diagnosis of neurogenic muscle weakness, ataxia and retinitis pigmentosa disease or Leigh's disease, caused by the Mt8993T-->G mutation which results in a Leu156Arg replacement that blocks proton translocation activity of subunit a of F(0)F(1)-ATPase. Our ultimate goal is to apply SmaI to gene therapy for this disease, because the mutant mitochondrial DNA (mtDNA) coexists with the wild-type mtDNA (heteroplasmy), and because only the mutant mtDNA, but not the wild-type mtDNA, is selectively restricted by the enzyme. For this purpose, we transiently expressed the SmaI gene fused to a mitochondrial targeting sequence in cybrids carrying the mutant mtDNA.

A novel function of monomeric amyloid beta-protein serving as an antioxidant molecule against metal-induced oxidative damage.

Aggregated and oligomeric amyloid beta-protein (Abeta) is known to exhibit neurotoxicity. However, the action of Abeta monomers on neurons is not fully understood. We have studied aggregation state-dependent actions of Abeta and found an oligomer-specific effect of Abeta on lipid metabolism in neurons (Michikawa et al.

Apolipoprotein E (ApoE) isoform-dependent lipid release from astrocytes prepared from human ApoE3 and ApoE4 knock-in mice.

We have reported previously (Michikawa, M., Fan, Q.-W.

Cholesterol-dependent modulation of dendrite outgrowth and microtubule stability in cultured neurons.

Microtubule-associated protein 2 (MAP2) is a neuron-specific cytoskeletal protein enriched in dendrites and cell bodies. MAP2 regulates microtubule stability in a phosphorylation-dependent manner, which has been implicated in dendrite outgrowth and branching. We have previously reported that cholesterol deficiency causes tau phosphorylation and microtubule depolymerization in axons (Fan et al.