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Effects of aromatase inhibition versus gonadectomy on hippocampal complex amyloid pathology in triple transgenic mice.

ABSTRACT: Alzheimer's disease (AD) is the most common form of dementia among the elderly with women exhibiting a higher risk than men for the disease. Due to these gender differences, there is great interest in the role that estrogens play in cognitive impairment and the onset of the classic amyloid and tau lesions in AD. Human and rodent studies indicate a strong association between low brain aromatase, sex hormone levels, and beta amyloid deposition. Therefore, the effects of depleting both circulating and brain estrogen levels, through gonadectomy and/or treatment with the aromatase inhibitor, anastrozole, upon hippocampal AD-like pathology in male and female 3xTgAD mice were evaluated. Liquid chromatography-mass spectrometry revealed anastrozole serum levels of 10.19 ng/mL and for the first time brain levels were detected at 4.7 pg/mL. Densitometric analysis of the hippocampus revealed that anastrozole significantly increased A?- but not APP/A?-immunoreactivity in intact 3xTgAD females compared to controls (p<0.001). Moreover, anastrozole significantly increased the number of A?- compared to APP/A?-positive hippocampal CA1 neurons in intact and gonadectomized female mice. Concurrently, anastrozole significantly reduced the APP/A? plaque load in 9 month old female 3xTgAD mice. These data suggest that anastrozole treatment differentially affects select amyloid species which in turn may play a role in the extraneuronal to intraneuronal deposition of this peptide.

SUBMITTER: Overk CR

PROVIDER: S-EPMC3225601 | biostudies-literature | 2012 Jan

REPOSITORIES: biostudies-literature

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Effects of aromatase inhibition versus gonadectomy on hippocampal complex amyloid pathology in triple transgenic mice.

Overk Cassia R CR Lu Pei-Yi PY Wang Yue-Ting YT Choi Jaewoo J Shaw James W JW Thatcher Gregory R GR Mufson Elliott J EJ

Neurobiology of disease 20110916 1

Alzheimer's disease (AD) is the most common form of dementia among the elderly with women exhibiting a higher risk than men for the disease. Due to these gender differences, there is great interest in the role that estrogens play in cognitive impairment and the onset of the classic amyloid and tau lesions in AD. Human and rodent studies indicate a strong association between low brain aromatase, sex hormone levels, and beta amyloid deposition. Therefore, the effects of depleting both circulating ...[more]

PMID: 21945538

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Project description:Alzheimer's disease (AD) is a progressive neurodegenerative disease manifested by cognitive impairment. As a unique approach to open the blood-brain barrier (BBB) noninvasively and temporarily, a growing number of studies showed that low-intensity focused ultrasound in combination with microbubbles (FUS/MB), in the absence of therapeutic agents, is capable of ameliorating amyloid or tau pathology, concurrent with improving memory deficits of AD animal models. However, the effects of FUS/MB on both the two pathologies simultaneously, as well as the memory behaviors, have not been reported so far. Methods: In this study, female triple transgenic AD (3×Tg-AD) mice at eight months of age with both amyloid-? (A?) deposits and tau phosphorylation were treated by repeated FUS/MB in the unilateral hippocampus twice per week for six weeks. The memory behaviors were investigated by the Y maze, the Morris water maze and the step-down passive avoidance test following repeated FUS/MB treatments. Afterwards, the involvement of A? and tau pathology were assessed by immunohistochemical analysis. Neuronal health and phagocytosis of A? deposits by microglia in the hippocampus were examined by confocal microscopy. Further, hippocampal proteomic alterations were analyzed by employing two-dimensional fluorescence difference gel electrophoresis (2D-DIGE) combined with mass spectrometry. Results: The three independent memory tasks were indicative of evident learning and memory impairments in eight-month-old 3×Tg-AD mice, which developed intraneuronal A?, extracellular diffuse A? deposits and phosphorylated tau in the hippocampus and amygdala. Following repeated FUS/MB treatments, significant improvement in learning and memory ability of the 3×Tg-AD mice was achieved. Amelioration in both A? deposits and phosphorylated tau in the sonicated hemisphere was induced in FUS/MB-treated 3×Tg-AD mice. Albeit without increase in neuron density, enhancement in axonal neurofilaments emerged from the FUS/MB treatment. Confocal microscopy revealed activated microglia engulfing A? deposits in the FUS/MB-treated hippocampus. Further, proteomic analysis revealed 20 differentially expressed proteins, associated with glycolysis, neuron projection, mitochondrial pathways, metabolic process and ubiquitin binding etc., in the hippocampus between FUS/MB-treated and sham-treated 3×Tg-AD mice. Conclusions: Our findings reinforce the positive therapeutic effects on AD models with both A? and tau pathology induced by FUS/MB-mediated BBB opening, further supporting the potential of this treatment regime for clinical applications.

Project description:IntroductionEpidemiological studies show that women have a higher prevalence of Alzheimer's disease (AD) than men. Peripheral estrogen reduction during aging in women is proposed to play a key role in this sex-associated prevalence, however, the underlying mechanism remains elusive. We previously found that transcription factor early growth response-1 (EGR1) significantly regulates cholinergic function. EGR1 stimulates acetylcholinesterase (AChE) gene expression and is involved in AD pathogenesis. We aimed to investigate whether the triple-transgenic AD (3xTg-AD) mice harboring PS1 M146V , APP Swe , and Tau P301L show sex differences in β-amyloid (Aβ) and hyperphosphorylated tau (p-Tau), the two primary AD hallmarks, and how local 17β-estradiol (E2) may regulate the expression of EGR1 and AChE.MethodsWe first sacrificed male and female 3xTg-AD mice at 3-4, 7-8, and 11-12 months and measured the levels of Aβ, p-Tau, EGR1, and AChE in the hippocampal complex. Second, we infected SH-SY5Y cells with lentivirus containing the amyloid precursor protein construct C99, cultured with or without E2 administration we measured the levels of extracellular Aβ and intracellular EGR1 and AChE.ResultsFemale 3xTg-AD mice had higher levels of Aβ compared to males, while no p-Tau was found in either group. In SH-SY5Y cells infected with lentivirus containing the amyloid precursor protein construct C99, we observed significantly increased extracellular Aβ and decreased expression of intracellular EGR1 and AChE. By adding E2 to the culture medium, extracellular Aβ(l-42) was significantly decreased while intracellular EGR1 and AChE expression were elevated.DiscussionThis data shows that the 3xTg-AD mouse model can be useful for studying the human sex differences of AD, but only in regards to Ap. Furthermore, in vitro data shows local E2 may be protective for EGR1 and cholinergic functions in AD while suppressing soluble Aβ(1-42) levels. Altogether, this study provides further in vivo and in vitro data supporting the human epidemiological data indicating a higher prevalence of AD in women is related to changes in brain estrogen levels.

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Effects of aromatase inhibition versus gonadectomy on hippocampal complex amyloid pathology in triple transgenic mice.

Publications

Effects of aromatase inhibition versus gonadectomy on hippocampal complex amyloid pathology in triple transgenic mice.

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