Age-associated metabolic risk factor(s) or nutritional imbalances, such as excessive fat and cholesterol intake or hypovitaminosis, are often linked to increased amyloidogenesis, as seen in late-onset sporadic Alzheimer's disease (SAD). Elevated expression of beta-secretase BACE1 is observed in SAD brains. In cultured neuronal models, we show that BACE1 transcription is upregulated through metabolic risk factors. Overexpression of the PPARgamma coactivator (PGC-1) a key metabolic regulator or all-trans retinoid acid (atRA) can reduce the elevated BACE1 expression resulting from inflammation induced by a high fat high cholesterol diet (HFD). Markedly increased RNA and protein levels of BACE1 were also found in the mouse forebrains fed HFD for 2 months;2-months of treatment with atRA restored BACE1 mRNA and expression after HFD feeding. Given the increasingly recognized importance of retinoid signaling in AD and the promise of retinoid-based therapies, our long-term goal is to fully characterize the beneficial effects and the underlying molecular mechanisms of atRA in mitigating neuroinflammation and amyloidogenesis. In this application, we will test the hypotheses first that atRA suppresses BACE1 expression via recruitment of liganded RARs to the promoter, secondly that coregulators including PGC-1 and nuclear corepressors participate in the transcriptional repression and finally that atRA and RARs interfere with the NF-gammaB mediated induction of BACE1.
Two aims are proposed to investigate 1) the molecular mechanism underlying the negative regulation of BACE1 transcription by atRA and 2) the mechanisms by which atRA modulates NF-gammaB activity upon inflammation. We will employ both in vitro cellular (TNFalpha +LPS) as well as animal models representing acute and chronic neuroinflammation (systemic LPS, HFD etc). Given the emerging role of aberrantly activated NF-gammaB in AD pathogenesis, studying atRA's regulation of this molecule is of potential broad impact not only for BACE1 gene regulation but also in large cohorts of NF-gammaB-sensitive genes in AD brains. Although BACE1 regulation has been extensively studied under hypoxic and metabolic stressed conditions including ROS, its upregulation under neuroinflammatory conditions is largely understudied. Hence, our focus of investigating its negative regulation by nuclear receptors upon inflammation is of high novelty. Successful completion of this project will be instrumental for future pursuing potential combination therapy between agents promoting retinoid signaling and insulin- sensitization (PPARgamma agonists etc).

Public Health Relevance

Retinoid-based therapy is emerging as a promising option for preventing and treating AD. This project proposes to further investigate its effect in blunting neuroinflammation as well as the molecular mechanism underlying BACE1 suppression a diet-induced sporadic AD mouse model.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Exploratory/Developmental Grants (R21)
Project #
5R21NS083908-02
Application #
8690189
Study Section
Cellular and Molecular Biology of Neurodegeneration Study Section (CMND)
Program Officer
Corriveau, Roderick A
Project Start
2013-07-01
Project End
2015-06-30
Budget Start
2014-07-01
Budget End
2015-06-30
Support Year
2
Fiscal Year
2014
Total Cost
Indirect Cost
Name
University of Tennessee Health Science Center
Department
Pharmacology
Type
Schools of Medicine
DUNS #
City
Memphis
State
TN
Country
United States
Zip Code
38103
Kim, Eunhee; Wang, Bin; Sastry, Namratha et al. (2016) NEDD4-mediated HSF1 degradation underlies ?-synucleinopathy. Hum Mol Genet 25:211-22
Li, Jing Jing; Wang, Ruishan; Lama, Rati et al. (2016) Ubiquitin Ligase NEDD4 Regulates PPAR? Stability and Adipocyte Differentiation in 3T3-L1 Cells. Sci Rep 6:38550
Tan, Xing-Lin; Xue, Yue-Qiang; Ma, Tao et al. (2015) Partial eNOS deficiency causes spontaneous thrombotic cerebral infarction, amyloid angiopathy and cognitive impairment. Mol Neurodegener 10:24
Wang, Ruishan; Chen, Shaoya; Liu, Yingchun et al. (2015) All-trans-retinoic acid reduces BACE1 expression under inflammatory conditions via modulation of nuclear factor ?B (NF?B) signaling. J Biol Chem 290:22532-42
Li, Jing Jing; Ferry Jr, Robert J; Diao, Shiyong et al. (2015) Nedd4 haploinsufficient mice display moderate insulin resistance, enhanced lipolysis, and protection against high-fat diet-induced obesity. Endocrinology 156:1283-91
Chen, Yupin; Zhang, Dong-qi; Liao, Zhong et al. (2015) Anti-oxidant polydatin (piceid) protects against substantia nigral motor degeneration in multiple rodent models of Parkinson's disease. Mol Neurodegener 10:4
Li, Jing Jing; Dolios, Georgia; Wang, Rong et al. (2014) Soluble beta-amyloid peptides, but not insoluble fibrils, have specific effect on neuronal microRNA expression. PLoS One 9:e90770
Wang, Ruishan; Li, Jing Jing; Diao, Shiyong et al. (2013) Metabolic stress modulates Alzheimer's ?-secretase gene transcription via SIRT1-PPAR?-PGC-1 in neurons. Cell Metab 17:685-94
Zhang, Yun-wu; Chen, Yaomin; Liu, Yun et al. (2013) APP regulates NGF receptor trafficking and NGF-mediated neuronal differentiation and survival. PLoS One 8:e80571