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The Journal of Neuroscience, March 7, 2007, 27(10):2628-2635; doi:10.1523/JNEUROSCI.5053-06.2007
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Neurobiology of Disease
Oligomeric Amyloid Decreases Basal Levels of Brain-Derived Neurotrophic factor (BDNF) mRNA via Specific Downregulation of BDNF Transcripts IV and V in Differentiated Human Neuroblastoma Cells
Diego J. Garzon andMargaret Fahnestock Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, Ontario, Canada L8N 3Z5
Correspondence should be addressed to Dr. Margaret Fahnestock, Department of Psychiatry and Behavioural Neurosciences, McMaster University, 1200 Main Street West, Hamilton, Ontario, Canada L8N 3Z5. Email: fahnest{at}mcmaster.ca
Alzheimer's disease (AD) is a senile dementia characterized by amyloid plaques, neurofibrillary tangles, and synaptic and cell loss. The "amyloid cascade" hypothesis suggests that amyloid-ß (Aß), the peptide deposited as amyloid plaques, is the primary insult in AD. However, debate continues over the mechanism of Aß toxicity and whether fibrillar or oligomeric Aß is the active species of the peptide that ultimately causes the synaptic loss and dementia associated with AD. Brain-derived neurotrophic factor (BDNF) is required for survival and function of cells compromised in AD. Decreased BDNF causes defects in long-term potentiation and memory and correlates with cognitive decline. We previously demonstrated that BDNF reduction occurs early in the course of AD, suggesting that decreased BDNF may promote neuronal dysfunction in AD. We also demonstrated that three of seven human BDNF transcripts are specifically downregulated in AD. What pathological feature(s) of AD leads to the decreased BDNF is unknown.
In this study, we administered both fibrillar and oligomeric conformations of Aß1–42 to differentiated SH-SY5Y, a human neuroblastoma cell line, and measured both phosphorylated cAMP response element-binding protein (CREB), a regulator of BDNF transcription, and BDNF total mRNA. We found that oligomeric but not fibrillar preparations of Aß1–42 significantly decrease both phosphorylated CREB and total BDNF mRNA. Furthermore, oligomeric Aß1–42 decreases BDNF transcripts IV and V in these cells, demonstrating that Aß1–42 downregulates the major BDNF transcript decreased in vivo in the AD brain. Thus, oligomeric Aß1–42 could compromise neuronal function, causing memory loss and cognitive dysfunction by downregulation of BDNF in AD.
Key words: Alzheimer; neurotrophin; exons; real-time RT-PCR; cell culture; CREB
Received May 16, 2006; revised Jan. 26, 2007; accepted Feb. 2, 2007.
Correspondence should be addressed to Dr. Margaret Fahnestock, Department of Psychiatry and Behavioural Neurosciences, McMaster University, 1200 Main Street West, Hamilton, Ontario, Canada L8N 3Z5. Email: fahnest{at}mcmaster.ca
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