title: Amyloid-β Reduces Exosome Release from Astrocytes by Enhancing JNK Phosphorylation.
abstract: 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. In this study, we examined the effect of Aβ on release of exosomes from astrocytes in culture. We analyzed release of exosomes and apoE, both of which are known to remove/clear Aβ from the brain, in the culture medium of astrocytes. We found that exosome and apoE-HDL were successfully separated by density gradient ultracentrifugation demonstrated by distribution of their specific markers, flotillin and HSP90, and cholesterol, and morphological analysis using electron microscopy. Exosome release was significantly reduced by Aβ1-42 treatment in cultured astrocytes accompanied by an increased JNK phosphorylation. Whereas, apoE-HDL release remained unchanged. A JNK inhibitor restored the decreased levels of exosome release induced by Aβ treatment to levels similar to those of control, suggesting that Aβ1-42 inhibits exosome release via stimulation of JNK signal pathway. Because exosomes are shown to remove Aβ in the brain, our findings suggest that increased Aβ levels in the brain may impair the exosome-mediated Aβ clearance pathway.
authors.affiliation: Department of Biochemistry, Nagoya City University, Mizuho-cyo, Mizuho-ku, Nagoya, Aichi, Japan.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Abdullah
authors.affiliation: Core Laboratory, Graduate School of Medical Sciences, Nagoya City University, Mizuho-cyo, Mizuho-ku, Nagoya, Aichi, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takase
authors.affiliation: Department of Biochemistry, Nagoya City University, Mizuho-cyo, Mizuho-ku, Nagoya, Aichi, Japan.
authors.forename: Mari
authors.initials: M
authors.lastname: Nunome
authors.affiliation: Department of Biochemistry, Nagoya City University, Mizuho-cyo, Mizuho-ku, Nagoya, Aichi, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Enomoto
authors.affiliation: Department of Biochemistry, Nagoya City University, Mizuho-cyo, Mizuho-ku, Nagoya, Aichi, Japan.
authors.forename: Jin-Ichi
authors.initials: J
authors.lastname: Ito
authors.affiliation: Department of Biochemistry, Nagoya City University, Mizuho-cyo, Mizuho-ku, Nagoya, Aichi, Japan.
authors.forename: Jian-Sheng
authors.initials: JS
authors.lastname: Gong
authors.affiliation: Department of Biochemistry, Nagoya City University, Mizuho-cyo, Mizuho-ku, Nagoya, Aichi, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Michikawa
mesh_terms: D016229:Amyloid beta-Peptides / Q000378:metabolism*; D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D001057:Apolipoproteins E / Q000378:metabolism; D001253:Astrocytes / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism; D003470:Culture Media; D055354:Exosomes / Q000187:drug effects / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D048670:MAP Kinase Kinase 4 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism*; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D017207:Rats, Sprague-Dawley
chemical_list: D016229:Amyloid beta-Peptides; D000873:Anthracenes; D001057:Apolipoproteins E; D003470:Culture Media; D018841:HSP90 Heat-Shock Proteins; D008565:Membrane Proteins; D010446:Peptide Fragments; D047428:Protein Kinase Inhibitors; C075222:amyloid beta-protein (1-42); C106354:flotillins; C432165:pyrazolanthrone; D002784:Cholesterol; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D048670:MAP Kinase Kinase 4
keywords: Amyloid-β; JNK; astrocyte; exosome; flotillin