title: Androgens regulate neprilysin expression: role in reducing beta-amyloid levels.
abstract: Age-related testosterone depletion in men is a risk factor for Alzheimer's disease. Prior studies suggest that androgens affect Alzheimer's disease risk by regulating accumulation of beta-amyloid protein (Abeta) by an undefined mechanism. In this study, we investigated the role of the Abeta-catabolizing enzyme neprilysin (NEP) in this process. First, we observed that androgens positively regulate neural expression of NEP in adult male rats. Next, we investigated androgen regulatory effects on both NEP expression and Abeta levels using cultured hippocampal neurons and neuronally differentiated rat pheochromocytoma cell 12 with or without androgen receptor (AR). Dihydrotestosterone (DHT) induced a time-dependent increase in NEP expression. DHT also significantly decreased levels of Abeta in AR-expressing cells transfected with amyloid precursor protein, but did not affect levels of either full-length or non-amyloidogenic, soluble amyloid precursor protein. Importantly, the DHT induced decrease of Abeta was blocked by pharmacological inhibition of NEP. The DHT-mediated increase in NEP expression and decrease in Abeta levels were (i) not observed in rat pheochromocytoma cell 12 lacking AR and (ii) blocked in AR-expressing cells by the antagonists, cyproterone acetate and flutamide. Together, these findings suggest that androgen regulation of Abeta involves an AR-dependent mechanism requiring up-regulation of the Abeta catabolizing enzyme NEP.
authors.affiliation: Davis School of Gerontology, University of Southern California, Los Angeles, California 90089-0191, USA.
authors.forename: Mingzhong
authors.initials: M
authors.lastname: Yao
authors.forename: Thuy-Vi V
authors.initials: TV
authors.lastname: Nguyen
authors.forename: Emily R
authors.initials: ER
authors.lastname: Rosario
authors.forename: Martin
authors.initials: M
authors.lastname: Ramsden
authors.forename: Christian J
authors.initials: CJ
authors.lastname: Pike
mesh_terms: D016229:Amyloid beta-Peptides / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D000728:Androgens / Q000502:physiology*; D000818:Animals; D001921:Brain / Q000201:enzymology / Q000378:metabolism; D002478:Cells, Cultured; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D006801:Humans; D008297:Male; D015260:Neprilysin / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology; D016716:PC12 Cells; D051381:Rats; D017207:Rats, Sprague-Dawley; D011944:Receptors, Androgen / Q000502:physiology; D015854:Up-Regulation / Q000502:physiology
chemical_list: D016229:Amyloid beta-Peptides; D000728:Androgens; D011944:Receptors, Androgen; D015260:Neprilysin