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Down‐regulation of serum gonadotropins but not estrogen replacement improves cognition in aged‐ovariectomized 3xTg AD female mice
Author(s) -
Palm Russell,
Chang Jaewon,
Blair Jeffrey,
GarciaMesa Yoelvis,
Lee Hyounggon,
Castellani Rudy J.,
Smith Mark A.,
Zhu Xiongwei,
Casadesus Gemma
Publication year - 2014
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/jnc.12706
Subject(s) - ovariectomized rat , estrogen , endocrinology , medicine , estrogen replacement therapy , menopause , cognition , biology , neuroscience
Development of Alzheimer's disease (AD) has been linked to the de‐regulation of estrogen and gonadotropins such as luteinizing hormone (LH). In this study, we found increases in AD pathology in the hippocampi of aged female 3xTg AD mice after ovariectomy that were unable to be reduced by estrogen therapy or down‐regulation of serum LH levels. Despite the lack of effect of these treatments on AD pathology, down‐regulation of serum LH but not estrogen improved factors associated with neuronal plasticity such as spatial memory, inhibition of glycogen synthase kinase‐3 beta, expression of beta‐catenin, and brain‐derived neurotrophic factor transcription. Contrasting previous studies in younger mice, estrogen replacement was not able to rescue behavioral deficits, reduced glycogen synthase kinase‐3 beta inhibition and increased hippocampal phosphorylation of tau. Of critical importance, serum LH was negatively correlated with brain LH in regions associated with spatial memory, and increases in brain LH correlated with cognitive improvement. This paralleled changes in human female AD brains which showed a significant reduction in brain LH mRNA compared to healthy age‐ and PMI‐matched controls. Taken together, these findings should promote further research into the LH‐dependent mechanisms associated with AD cognitive deficits as well as the effects of estrogen within the aged brain.In the aged triple transgenic Alzheimer's disease (AD) mouse model (3xAD‐Tg), estrogen replacement after ovariectomy does not improve cognitive function, increases phosphorylated Tau levels and decreases inhibition of GSK3 beta. Luprolide acetate rescues ovariectomy‐dependent cognitive function, increases signaling events associated with synaptic plasticity including GSK3 beta inhibition, but does not alter AD pathology. In the human AD female brain, luteinizing hormone (LH) mRNA levels are reduced. In the 3XAD‐tg model, brain LH protein levels are reduced by ovariectomy and normalized by leuprolide acetate treatment. These treatment‐dependent normalization of LH positively correlates with markers of neuroplasticity and cognitive improvement.