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Astrocyte remodeling in the beneficial effects of long-term voluntary exercise in Alzheimer’s disease

Authors
  • Belaya, Irina1
  • Ivanova, Mariia1
  • Sorvari, Annika1
  • Ilicic, Marina2
  • Loppi, Sanna1
  • Koivisto, Hennariikka1
  • Varricchio, Alessandra1
  • Tikkanen, Heikki1
  • Walker, Frederick R.2
  • Atalay, Mustafa1
  • Malm, Tarja1
  • Grubman, Alexandra3, 4, 3
  • Tanila, Heikki1
  • Kanninen, Katja M.1
  • 1 University of Eastern Finland, Kuopio, FI-70211, Finland , Kuopio (Finland)
  • 2 The University of Newcastle, University Dr, Callaghan, NSW, 2308, Australia , Callaghan (Australia)
  • 3 Monash University, Melbourne, Australia , Melbourne (Australia)
  • 4 Monash Biomedicine Discovery Institute, Melbourne, Australia , Melbourne (Australia)
Type
Published Article
Journal
Journal of Neuroinflammation
Publisher
Springer (Biomed Central Ltd.)
Publication Date
Sep 15, 2020
Volume
17
Issue
1
Identifiers
DOI: 10.1186/s12974-020-01935-w
Source
Springer Nature
Keywords
License
Green

Abstract

BackgroundIncreased physical exercise improves cognitive function and reduces pathology associated with Alzheimer’s disease (AD). However, the mechanisms underlying the beneficial effects of exercise in AD on the level of specific brain cell types remain poorly investigated. The involvement of astrocytes in AD pathology is widely described, but their exact role in exercise-mediated neuroprotection warrant further investigation. Here, we investigated the effect of long-term voluntary physical exercise on the modulation of the astrocyte state.MethodsMale 5xFAD mice and their wild-type littermates had free access to a running wheel from 1.5 to 7 months of age. A battery of behavioral tests was used to assess the effects of voluntary exercise on cognition and learning. Neuronal loss, impairment in neurogenesis, beta-amyloid (Aβ) deposition, and inflammation were evaluated using a variety of histological and biochemical measurements. Sophisticated morphological analyses were performed to delineate the specific involvement of astrocytes in exercise-induced neuroprotection in the 5xFAD mice.ResultsLong-term voluntary physical exercise reversed cognitive impairment in 7-month-old 5xFAD mice without affecting neurogenesis, neuronal loss, Aβ plaque deposition, or microglia activation. Exercise increased glial fibrillary acid protein (GFAP) immunoreactivity and the number of GFAP-positive astrocytes in 5xFAD hippocampi. GFAP-positive astrocytes in hippocampi of the exercised 5xFAD mice displayed increases in the numbers of primary branches and in the soma area. In general, astrocytes distant from Aβ plaques were smaller in size and possessed simplified processes in comparison to plaque-associated GFAP-positive astrocytes. Morphological alterations of GFAP-positive astrocytes occurred concomitantly with increased astrocytic brain-derived neurotrophic factor (BDNF) and restoration of postsynaptic protein PSD-95.ConclusionsVoluntary physical exercise modulates the reactive astrocyte state, which could be linked via astrocytic BDNF and PSD-95 to improved cognition in 5xFAD hippocampi. The molecular pathways involved in this modulation could potentially be targeted for benefit against AD.

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