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.
Xie
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Andrus Gerontology Center and Department of Biological Sciences, University of Southern California, Los Angeles, 90089, USA.
Harris-White
M E
ME
Wals
P A
PA
Frautschy
S A
SA
Finch
C E
CE
Morgan
T E
TE
D000818:Animals; D000831:Animals, Newborn; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology* / Q000187:drug effects; D051152:Clusterin; D015941:Complement Hemolytic Activity Assay / Q000379:methods; D003169:Complement Inactivator Proteins / Q000302:isolation & purification / Q000494:pharmacology*; D003952:Diagnostic Imaging / Q000379:methods; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005419:Flavonoids / Q000494:pharmacology; D006023:Glycoproteins / Q000302:isolation & purification / Q000494:pharmacology*; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D066298:In Vitro Techniques; D007372:Interferons / Q000494:pharmacology; D017628:Microglia / Q000187:drug effects* / Q000378:metabolism; D018832:Molecular Chaperones / Q000302:isolation & purification / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D019000:Phosphotyrosine / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D013861:Thiocyanates / Q000378:metabolism; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
C495242:CLU protein, human; D051152:Clusterin; D003169:Complement Inactivator Proteins; D004791:Enzyme Inhibitors; D005419:Flavonoids; D006023:Glycoproteins; D018832:Molecular Chaperones; D009573:Nitrites; D013861:Thiocyanates; D014409:Tumor Necrosis Factor-alpha; D019000:Phosphotyrosine; D007372:Interferons; C008658:2-nitro-5-thiocyanobenzoic acid; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one