Expression and functional profiling of neprilysin, insulin-degrading enzyme, and endothelin-converting enzyme in prospectively studied elderly and Alzheimer’s brain

Authors

  • Suqing Wang,

    1. Department of Pathology and Laboratory Medicine, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin, USA
    2. Department of Nutrition and Food Health, School of Public Health, Wuhan University, Wuhan, China
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    • These authors contributed equally.

  • Rui Wang,

    1. Department of Pathology and Laboratory Medicine, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin, USA
    2. Department of Pharmaceutical Sciences, School of Pharmacy, East China University of Science and Technology, Shanghai, China
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    • These authors contributed equally.

  • Lang Chen,

    1. Department of Pathology and Laboratory Medicine, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin, USA
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  • David A. Bennett,

    1. Rush Alzheimer’s Disease Center, Rush University Medical Center, Chicago, Illinois, USA
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  • Dennis W. Dickson,

    1. Department of Pathology (Neuropathology) and Neuroscience, Mayo Clinic College of Medicine, Jacksonville, Florida, USA
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  • Deng-Shun Wang

    1. Department of Pathology and Laboratory Medicine, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin, USA
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Address correspondence and reprint requests to Deng-Shun Wang, MD, PhD, Department of Pathology and Laboratory Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA. E-mail: dwang6@wisc.edu

Abstract

J. Neurochem. (2010) 115, 47–57.

Abstract

The brain steady state level of β-amyloid (Aβ) is determined by the balance between its production and removal, the latter through egress across blood and CSF barriers as well as Aβ degradation. The major Aβ-degrading enzymes are neprilysin (NEP), insulin-degrading enzyme (IDE), and endothelin-converting enzyme (ECE-1). Although evidence suggests that NEP is down-regulated in Alzheimer’s disease (AD), the role of IDE and ECE in the Aβ accumulation in aging and dementia remains less certain. In this study, we examined mRNA and protein expression, as well as biological activity of NEP, IDE, and ECE-1 in human frontal cortex by real-time RT-PCR for mRNA, immunoblotting for protein, and highly sensitive and specific fluorescence assays for activity. The relationships between Aβ-degrading enzymes and pathologic measures and clinical features were also assessed. The results showed that NEP mRNA, protein level, and activity were decreased in AD compared with normal controls with no cognitive impairment (NCI). In contrast, IDE activity was unchanged, but there was higher expression of IDE mRNA, indicating a possible compensatory reaction because of deficits in activity. ECE-1 expression in AD brain showed no significant difference compared with age-matched controls. Correlation analyses suggested that NEP expression was correlated with Aβ accumulation and clinical diagnosis, being lower in AD than in no cognitive impairment. In contrast, neither IDE nor ECE-1 correlated with Aβ or clinical diagnosis. These findings provide additional support for NEP as the major protease involved in Aβ degradation and suggest its possible therapeutic targeting in AD.

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