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Poster Presentations P2 S407
levels of CaN and pCREB in their hippocampus. Results: We found that
CaN was increased and pCREB was significantly reduced in the hippocam-
pus and cortex of AD patients and, to a lesser extent in MCI subjects as
compared to non-demented individuals. Indeed there was a significant in-
verse correlation between pCREB levels and MMSE scores among AD pa-
tients, MCI subjects and normal individuals. Furthermore, icv injection of
Ab oligomers that results in memory dysfunction in mice increased CaN
and decreased pCREB, establishing a causal link between Ab-driven cog-
nitive deficits and CaN hyper-activation. Conclusions: Collectively these
results reveal that increased CaN activity may be central to Ab oligo-
mer-induced memory deficits in AD and suggest it as a potential pharma-
cological target.
P2-319 AN Ab TRANSCRIPTION SIGNATURE
Elena M. Ribe1, Richard Killick2, Raya Al-Shawi2, Bilal Malik1,
Claudie Hooper1, Cathy Fernandes1, Alvina W. M. To1, Kuang Lin1,
Simon Furney1, Brian Anderton1, J. Paul Simons2, Simon Lovestone1,1King’s College London, MRC Centre for Neurodegenerative Research,Institute of Psychiatry, London, United Kingdom; 2King’s College London,
MRC Centre for Neurodegenerative Research, Institute of Psychiatry, London,
United Kingdom.
Background: Increasing evidence suggests aberrant wnt signalling to be
a contributory factor to Alzheimer’s disease (AD), not least because wnt
signalling regulates GSK-3 and either though this, or another mechanism,
protects neurons from the neurotoxicity of b-amyloid (Ab). Interestingly,
Dickkopf-1 (Dkk-1), an inhibitor of wnt signalling, has been shown to
be induced by Ab in a p53-dependent manner. Methods: To determine
the effects of Ab on neuronal gene transcription we independently treated
primary neurons with Ab or with recombinant Dkk-1 and examined the ef-
fects of each by microarray analyses. The effects of each of the Dkk family
members and of deletion constructs of Dkk-1 on neuronal gene expression
were examined and siRNA and small molecule inhibitors were employed to
further explore the pathway through which Ab activates the expression of
this gene set. Results: Using whole genome arrays we find that Ab and
Dkk-1 induce a gene expression with a remarkable degree of overlap (p
< 0.0000002). From this whole genome dataset we identified a set of
five common genes upregulated by Ab and Dkk-1. The use of siRNA
knockdown, p53 and JNK inhibitors and deletion constructs of Dkk-1 in-
dicate that the transcriptional effects of Ab are dependent upon the activa-
tion of p53, which once activated is responsible for the upregulation of
Dkk-1. Dkk-1 then acts to drive wnt signalling down the planar cell polar-
ity (PCP)/JNK pathway. JNK1 then drives the expression of the gene set.
Conclusions: We have identified an Ab transcriptional profile set of five
neuronal genes upregulated within hours of Ab treatment, via a p53/
Dkk-1/JNK1-dependent mechanism. As we, and others, have previously
shown that p53 and aberrant wnt signalling can lead to increased tau phos-
phorylation, the elucidation of the above mechanism will help further our
understanding of the molecular mechanism underpinning the amyloid cas-
cade, linking Ab to tau pathology.
P2-320 Ab OLIGOMERS AND FIBRILS INSTIGATE THE
RELEASE OF EXCITATORY AMINO ACIDS FROM
HIPPOCAMPAL NEURONS
Jordano Brito Moreira1, Andrea Cristina Paula Lima2,
Theresa R. Bomfim1, Fabio Figueiredo Oliveira1, Fernando J. Sepulveda3,
Fernando G. de Mello4, Luis G. Aguayo3, Rogerio Panizzutti5,
Sergio Teixeira Ferreira1, 1IBqM - UFRJ, Rio de Janeiro, Brazil;2Universidad de Chile, Santiago, Chile; 3Universidad de Concepcion,
Concepcion, Chile; 4IBCCF - UFRJ, Rio de Janeiro, Brazil; 5ICB - UFRJ,
Rio de Janeiro, Brazil. Contact e-mail: [email protected]
Background: Accumulation of amyloid-b peptide (Ab) aggregates in the
brain is a hallmark of Alzheimer’s disease (AD) and is directly implicated
in mechanisms of pathogenesis. Considerable evidence indicates that the
neurotoxicity of Ab aggregates is, at least in part, due to dysregulation of
glutamate signaling via interference with N-methyl-D-aspartate receptor
(NMDAR) function. Methods: We measured by HPLC the extracellular
concentration of glutamate and D-serine, a co-agonist of NMDARs, in
hippocampal neuronal cultures treated with soluble Ab oligomers
(AbOs) and insoluble Ab fibrils (AbFs). In order to understand the mech-
anism responsible for glutamate accumulation, we treated cultures with
TTX, MK-801, and the removal of Ca2+ from extracellular medium.
We also used FM1-43 to label pre-synaptic vesicles and whole-cell
patch-clamp to access spontaneous post-synaptic activity. Results: Our
results show that both Ab aggregates promote extracellular accumulation
of glutamate and D-serine. The increase was blocked by culture treat-
ments above, indicating dependence on excitatory neuronal activity.
AbOs enhanced both the release of pre-synaptic vesicles and spontaneous
post-synaptic activity. Consistent with these results, activation of inhibi-
tory GABAA receptors by taurine blocked the increase in extracellular
glutamate levels instigated by Ab aggregates. Conclusions: These results
reveal a novel mechanism by which Ab aggregates instigate abnormal re-
lease of glutamate and accumulation of excitatory amino acids in hippo-
campal neurons.
P2-321 THE POTENTIAL EFFECT OF PSA-NCAM
EXPRESSION LEVEL ON THE SPATIAL MEMORY
IMPAIRMENTS IN TG2576 AND WORT+GFX
INJECTING ALZHEIMER MODELS
Ziyuan Guo, Dan Liu, Xiong Wang, Jianzhi Wang, Lingqiang Zhu,
Huazhong University of Science and Technology, Wuhan, China.Contact e-mail: [email protected]
Background: The mechanisms of dysfunction in neuronal plasticity in the
adult hippocampus of AD model are still unknown. Age-dependent spatial
memory impairments have been related to a decline in hippocampal plastic-
ity. And the PSA (polysialic acid) level of NCAM molecules has been pro-
posed to mediate neuronal plasticity during learning and memory. Previous
study has demonstrated that increased proliferation and neuronal differenti-
ation detected by PSA-NCAM in the hippocampi of 3 month-old J20 mice
that reverted when animals became older. However, there are still few re-
ports about the expression of PSA-NCAM in hippocampus of other AD
models and its relationship with spatial memory impairment. Methods:
24 male Sprague-Dawley rats were divided randomly into two groups (N
¼ 12) and stereological injected with Wort+GFX and normal saline respec-
tively. The spatial memory retention ability was tested by Morris water
maze. Western blotting, immunohistochemistry and immunofluorescence
were used to detect the immunoactivity of PSA-NCAM and NCAM immu-
noreaction. Results: Immunohistochemical and immunofluorescence
showed that the PSA level of NCAM in APP+/- brains is significantly lower
than APP-/- at CA3 region in hippocampus; while remarkably increased in
CA1 region. Meanwhile, Tg2576 demonstrated the poorer performance than
control group probed by Morris water maze tests, which represented hippo-
campus dependent spatial memory impairment. In addition, we have also ob-
served the weaker performance of rats injected by Wort+GFX to model AD
pathology against control in Morris water maze. Furthermore, we tested the
level of PSA-NCAM in hippocampus of rat brain by Western Blot and found
that the immunoreaction intenstity of PSA-NCAM decreased significantly
after injected by Wort+GFX, following by the decrease of neuronal plastic-
ity function. Conclusions: The decrease of of hippocampus neuronal plas-
ticity marked by the level of PSA-NCAM has a strong relationship with
the impairment of spatial memory retention in Wort+GFX injected and
Tg2576 APP transgenic AD model. However, interestingly, the level of
PSA-NCAM in CA1 of Tg2576 is dramatically increased in contrast of
CA3 region, which suggests although neurogenesis is stimulated by possibly
by the processe of Alzheimer’s disease in CA3, it does not suffice to restore
function.
