| Abstract No.: | C-C3078 |
| Country: | Canada |
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| Title: | DOES HSP27 PROTECT NEURONS AGAINST AMYLOID? |
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| Authors/Affiliations: | 1 Michael King, 1 Clifford Guy, 1 Firrozeh Nafar, 1 Masuma Rahimula, 1 Sherri Rankin, 1 Karen Mearow
1 Memorial University, St. John's, NFLD, Canada |
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| Content: | Neurofibrillary tangles (NFTs) and plaques are considered to be hallmarks of Alzheimer’s disease (AD), although it is still not clear whether these aggregates contribute to disease progress or whether they might even play an initial protective role. A number of studies have shown that the small heat shock protein Hsp27 can afford protection against oxidative stress, growth factor withdrawal or excitotoxicity neuronal cell types. A moderate preconditioning thermal stress (HS) is sufficient to upregulate levels of Hsp27 in cells, and the degree of protection correlates with the level of expression of Hsp27. There are the reports of increased Hsp27 in AD brains and accumulation of Hsps in plaques, NFTs and Lewy bodies. Whether this represents a potentially protective response to the stress or is part of the disease process is not known
Objectives: Our hypothesis is that increased expression of Hsp27 can promote survival and stabilize the axonal cytoskeleton resulting in maintenance of neurite growth and axonal transport in the face of stressors such as amyloid. Our specific aim was to determine whether Hsp27 is important for neuronal survival and neurite growth and maturation in primary cortical neurons in the presence or absence of b-amyloid peptides.
Methods: Cultures of primary rat cortical neurons were subjected to heat stress in an effort to upregulate endogenous Hsp27, while in other experiments Hsp27 was overexpressed in cortical neurons by nucleofection. The potential effects of Hsp27 on neurite growth and survival were assessed using morphological and biochemical analyses. Cells were treated with beta amyloid peptide (25-35, 1-42) and reverse control.
Results: Efforts to upregulate endogenous Hsp27 in cortical neurons were unsuccessful, despite the fact that the neurons do express Hsf1 and increase activation of Hsf1 in response to heat stress. To examine the role of Hsp27, we overexpressed a GFP-Hsp27 fusion protein in the cells at the time of plating. In initial experiments we determined the influence of Hsp27 on neurite growth in comparison to cells transfected with a vectore expressing GFP alone. Our data indicate that cells expressing Hsp27 have greater total neurite growth compared to the empty vector alone. Cultures were then treated with Ab peptides (25-35 or 1-42) or control peptides and survival and growth assessed in Hsp-expressing compared to GFP-expressing neurons. Our preliminary data indicate that at 48-72 hrs after treatment, cells with Hsp27 appeared healthier and had longer neuritic processes than those without. Further experiments are underway to investigate longer exposures and whether survival is also being enhanced.
Conclusions: Our results suggest that the presence of Hsp27 in cortical neurons provides them with a level of protection against beta-amyloid. The mechanisms underlying this protection are under investigation.
Supported by CIHR/RPP funding to KMM.
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