title: Environmental Enrichment Potently Prevents Microglia-Mediated Neuroinflammation by Human Amyloid β-Protein Oligomers.
abstract: Microglial dysfunction is increasingly recognized as a key contributor to the pathogenesis of Alzheimer's disease (AD). Environmental enrichment (EE) is well documented to enhance neuronal form and function, but almost nothing is known about whether and how it alters the brain's innate immune system. Here we found that prolonged exposure of naive wild-type mice to EE significantly altered microglial density and branching complexity in the dentate gyrus of hippocampus. In wild-type mice injected intraventricularly with soluble Aβ oligomers (oAβ) from hAPP-expressing cultured cells, EE prevented several morphological features of microglial inflammation and consistently prevented oAβ-mediated mRNA changes in multiple inflammatory genes both in vivo and in primary microglia cultured from the mice. Microdialysis in behaving mice confirmed that EE normalized increases in the extracellular levels of the key cytokines (CCL3, CCL4, TNFα) identified by the mRNA analysis. Moreover, EE prevented the changes in microglial gene expression caused by ventricular injection of oAβ extracted directly from AD cerebral cortex. We conclude that EE potently alters the form and function of microglia in a way that prevents their inflammatory response to human oAβ, suggesting that prolonged environmental enrichment could protect against AD by modulating the brain's innate immune system.
  
  
  
  Environmental enrichment (EE) is a potential therapy to delay Alzheimer's disease (AD). Microglial inflammation is associated with the progression of AD, but the influence of EE on microglial inflammation is unclear. Here we systematically applied in vivo methods to show that EE alters microglia in the dentate gyrus under physiological conditions and robustly prevents microglial inflammation induced by human Aβ oligomers, as shown by neutralized microglial inflammatory morphology, mRNA changes, and brain interstitial fluid cytokine levels. Our findings suggest that EE alters the innate immune system and could serve as a therapeutic approach to AD and provide new targets for drug discovery. Further, we propose that the therapeutic benefits of EE could extend to other neurodegenerative diseases involving microglial inflammation.
authors: Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115.
authors: Huixin
authors: 0000-0003-4190-4244
authors: H
authors: Xu
authors: Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115.
authors: Eilrayna
authors: 0000-0003-2474-7806
authors: E
authors: Gelyana
authors: Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115.
authors: Molly
authors: 0000-0003-0234-4272
authors: M
authors: Rajsombath
authors: Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115.
authors: Ting
authors: T
authors: Yang
authors: Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115.
authors: Shaomin
authors: S
authors: Li
authors: Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115 dselkoe@rics.bwh.harvard.edu.
authors: Dennis
authors: D
authors: Selkoe
mesh_terms: D000544:Alzheimer Disease / Q000473:pathology*; D016229:Amyloid beta-Peptides / Q000235:genetics / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000235:genetics; D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D015214:Antigens, Differentiation, Myelomonocytic / Q000378:metabolism; D016466:CHO Cells; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002478:Cells, Cultured; D003412:Cricetulus; D016207:Cytokines / Q000378:metabolism; D018891:Dentate Gyrus / Q000473:pathology* / Q000503:physiopathology; D003857:Deoxyuridine / Q000031:analogs & derivatives / Q000378:metabolism; D000089622:Doublecortin Domain Proteins; D004660:Encephalitis / Q000473:pathology*; D004777:Environment; D006801:Humans; D017774:Long-Term Potentiation / Q000187:drug effects / Q000235:genetics; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D017551:Microdialysis; D008840:Microfilament Proteins / Q000378:metabolism; D017628:Microglia / Q000378:metabolism*; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D009479:Neuropeptides / Q000378:metabolism; D010587:Phagocytosis / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D014162:Transfection; D000097382:CD68 Molecule
chemical_list: D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D002135:Calcium-Binding Proteins; D016207:Cytokines; D003857:Deoxyuridine; D000089622:Doublecortin Domain Proteins; D008840:Microfilament Proteins; D008869:Microtubule-Associated Proteins; D009479:Neuropeptides; D012333:RNA, Messenger; C491049:Aif1 protein, mouse; C081026:CD68 protein, mouse; D000097382:CD68 Molecule; C031086:5-ethynyl-2'-deoxyuridine
keywords: Alzheimer's disease; brain inflammation; environmental enrichment; microglia; oligomeric amyloid beta