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Functional deprivation promotes amyloid plaque pathogenesis in Tg2576 mouse olfactory bulb and piriform cortex

Authors

  • Xue-Mei Zhang,

    1. Department of Anatomy, Southern Illinois University School of Medicine, Carbondale, IL 62901, USA
    2. Department of Neurology, The First Hospital of Jilin University, Changchun, Jilin 130021, China
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  • Kun Xiong,

    1. Department of Anatomy and Neurobiology, Central South University Xiangya Medical School, Changsha, Hunan 410013, China
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  • Yan Cai,

    1. Department of Anatomy and Neurobiology, Central South University Xiangya Medical School, Changsha, Hunan 410013, China
    2. Department of Physiology, Southern Illinois University School of Medicine, Carbondale, IL 62901, USA
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  • Huaibin Cai,

    1. Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892, USA
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  • Xue-Gang Luo,

    1. Department of Anatomy and Neurobiology, Central South University Xiangya Medical School, Changsha, Hunan 410013, China
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  • Jia-Chun Feng,

    1. Department of Neurology, The First Hospital of Jilin University, Changchun, Jilin 130021, China
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  • Richard W. Clough,

    1. Department of Anatomy, Southern Illinois University School of Medicine, Carbondale, IL 62901, USA
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  • Peter R. Patrylo,

    1. Department of Anatomy, Southern Illinois University School of Medicine, Carbondale, IL 62901, USA
    2. Department of Physiology, Southern Illinois University School of Medicine, Carbondale, IL 62901, USA
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  • Robert G. Struble,

    1. Department of Neurology & Center for Alzheimer’s disease, Southern Illinois University School of Medicine, Springfield, IL 62794, USA
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  • Xiao-Xin Yan

    1. Department of Anatomy, Southern Illinois University School of Medicine, Carbondale, IL 62901, USA
    2. Department of Anatomy and Neurobiology, Central South University Xiangya Medical School, Changsha, Hunan 410013, China
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Dr X.-X. Yan, as above.
E-mail: xyan@siumed.edu

Abstract

Cerebral hypometabolism and amyloid accumulation are principal neuropathological manifestations of Alzheimer’s disease (AD). Whether and how brain/neuronal activity might modulate certain pathological processes of AD are interesting topics of recent clinical and basic research in the field, and may be of potential medical relevance in regard to both the disease etiology and intervention. Using the Tg2576 transgenic mouse model of AD, this study characterized a promotive effect of neuronal hypoactivity associated with functional deprivation on amyloid plaque pathogenesis in the olfactory pathway. Unilateral naris-occlusion caused β-secretase-1 (BACE1) elevation in neuronal terminals in the deprived relative to the non-deprived bulb and piriform cortex in young adult mice. In parallel with the overall age-related plaque development in the forebrain, locally increased BACE1 immunoreactivity co-occurred with amyloid deposition first in the piriform cortex then within the bulb, more prominent on the deprived relative to the non-deprived side. Biochemical analyses confirmed elevated BACE1 protein levels, enzymatic activity and products in the deprived relative to non-deprived bulbs. Plaque-associated BACE1 immunoreactivity in the bulb and piriform cortex was localized preferentially to swollen/sprouting glutamatergic axonal terminals, with Aβ immunoreactivity occurring inside as well as around these terminals. Together, these findings suggest that functional deprivation or neuronal hypoactivity facilitates amyloid plaque formation in the forebrain in a transgenic model of AD, which operates synergistically with age effect. The data also implicate an intrinsic association of amyloid accumulation and plaque formation with progressive axonal pathology.

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