attenuation of the lysosomal death pathway by lysosomal cholesterol accumulation
TRANSCRIPT
Poster Presentations P2 S375
by increased caspase activity and accordingly, not affected by z-VAD-fmk.
Instead, the PARP-1 inhibitor 3-ABA almost completely prevented H2O2 in-
duced-death by reducing both apoptosis and necrosis, in elderly as well as
young individuals. Conclusions: H2O2-induced death of human lympho-
cytes displays both apoptotic and necrotic features, is highly PARP-1-depen-
dent but independent of caspase activation. Aging is associated with an
increase in apoptotic death. Understanding the mechanisms of cell death
might have implications for the study of neurodegenerative and proliferative
disorders.
P2-208 NEUROPROTECTIVE EFFECT OF A BLOOD BRAIN
PERMEABLE TRIAZINE DERIVATIVE THROUGH
INHIBITION OF NF-kB AND HSP-90 ALONG WITH
ACTIVATION OF NRF2 SIGNALING
Fariba Khodagholi, Niloufar Ansari, Solaleh Khoramian Tusi,
Mohsen Amini, Azim Dehghan Amirabad, Neuroscience Research Center,
Shahid Beheshti University of Medical Sciences, Tehran, Islamic Republic of
Iran. Contact e-mail: [email protected]
Background: Increased oxidative stress is a widely accepted factor in the de-
velopment and progression of Alzheimer’s disease (AD) and the ability of
cells to control the balance between the generation and quenching of reactive
oxygen species is important in combating its potentially damaging effects.
Moreover, in order for drugs to be effective in the treatment of neurodegen-
erative diseases, they must be capable of penetrating the blood-brain barrier
(BBB), whereas more than 98% of all potential CNS drugs don’t cross.
Methods: Here we wished to examine whether 3-thioethyl-5,6-(dichloro-
phenyl)-1,2,4-triazine has neuroprotective effect and the ability of penetrat-
ing the BBB. Using NGF-differentiated PC12 cells, the levels of Nrf2, NF-
kB, Caspase-3 and antioxidant enzymes were determined after stress (H2O2
and/or LPS) in the presence and/or absence of this compound. Results: In
H2O2 and/or LPS-induced cells, Nrf2, GSH, SOD and CAT were decreased
compared to control significantly. In the same time, NF-kB, HSP-90, cas-
pase-3 and MDA were increased. Pretreatment with this 1,2,4-triazine deriv-
ative caused a significant increase in the level of Nrf2, HO-1, g-GCS, GSH,
SOD and CAT in H2O2 and/or LPS-induced cells. Concomitantly NF-kB,
HSP-90, caspase-3 and MDA levels were decreased which shows its neuro-
protective effect through its ability to initiate phase 2 gene, concomitantly,
increase of GSH level, CAT and SOD activities and decrease of MDA level
and inhibition of NF-kB. Moreover, ANN result showed this compound has
good permeability value (0.93) comparing with logBB<-8.0 of impermeable
compounds that indicate this compound has the ability of penetrating the
BBB. Conclusions: This compound can be suitable candidates for AD be-
cause of 1) Its neuroprotective effect. 2) Ability to pass BBB.
P2-209 CONTRIBUTION OF GAMMA-SECRETASE TO
CALCIUM-MEDIATED CELL DEATH
Dong-Gyu Jo, A-Ryeong Gwon, Jong-Sung Park, Sungkyunkwan
University, Suwon, Republic of Korea. Contact e-mail: [email protected]
Background: Presenilins are the catalytic subunit of the large g-secretase
complex, that promotes intramembranous proteolysis of the beta-amyloid
precursor protein (APP), resulting in the production of beta-amyloid (Ab).
Mutant presenilin causes early-onset familial Alzheimer’s disease (FAD),
is related to abnormal Ca2+ signaling, and render cells vulnerable to cell
death. Methods: g-secretase activity was determined using the fluorescent
transfer of peptides containing the APP g-secretase cleavage site (R&D Sys-
tems). The level of secretase activity was proportional to the fluorometric re-
action, and the data were expressed as the fold-increase in fluorescence over
that of the background controls (reactions in the absence of cell lysates). g-
secretase inhibitors (DAPT, Compound E and L-685.458), thapsigargin,
A23187, staurosporin, tunicamycin and z-VAD were purchased from Cal-
biochem. Results: In the present study, we demonstrated that Ca2+-mediated
cell death is functionally associated with g-secretase activity. We found that
g-secretase activity was elevated during Ca2+-mediated cell death. Using se-
lective g-secretase inhibitors, we examined the role of g-secretase in cell
death triggered by increased intracellular Ca2+. Indeed, treatment with the se-
lective g-secretase inhibitors, compound E, DAPT, or L-685.458 signifi-
cantly decreased Ca2+-triggered cell death with that of the controls, but did
not affect staurosporin or tunicamycin-mediated cell death. Conclusions:
Our results suggest that g-secretase plays an important role in inducing
Ca2+-mediated cell death. The fact that g-secretase inhibitors reduced
Ca2+-mediated cell death might highlight a need to treat AD and ischemic
stroke patients with g-secretase inhibitors. Further studies are needed linking
g-secretase activity to Ca2+-triggered cell death.
P2-210 A NOVEL TRANSMEMBRANE PROTEIN ADIM IS
DOWNREGULATED IN THE BRAINS OF
ALZHEIMER PATIENTS AND INTERACTS WITH
HLA-B-ASSOCIATED TRANSCRIPT 3 (BAT3)
Qing Yan Liu1,2, Joy Lei1, Sara Bahnam1,2, 1National Research Council of
Canada, Ottawa, ON, Canada; 2Faculty of Medicine, University of Ottawa,
Ottawa, ON, Canada. Contact e-mail: [email protected]
Background: Molecular changes in multiple biological processes contribute
to the development of chronic neurodegeneration such as late onset Alzheim-
er’s disease (LOAD). To discover these changes reflected on the levels of
gene expression, we used a proprietary subtractive hybridization procedure
to identify genes that have altered expression levels in the brains of AD pa-
tients. Among the genes altered their expression levels, one encodes a novel
protein, ADIM, that contains a typical signal peptide at the N-terminus and
two transmembrane domains in the middle of the sequence. Here we exam-
ined its biochemical properties and putative roles in neurodegeneration.
Methods: Changes of gene expression were accessed by quantitative RT-
PCR and Western analyses. The responses of ADIM to stress conditions
were analyzed by gene manipulations in NT2 and N2a cells. The interaction
of BAT3 and ADIM was discovered by yeast two-hybrid screening and con-
firmed by co-immunoprecipitation assay. Results: ADIM protein was ubiq-
uitously detected in human and mouse tissues with higher levels in brain,
muscle, heart and reproductive organs. Analyses of its transcript and protein
levels revealed that ADIM is more abundant in neurons, less in astrocytes and
other cell types. Analysis of AD and control post-mortem human brains
showed that ADIM transcript was indeed significantly down regulated in
the cortex of all AD brains (N ¼ 19). In NT2 neurons, this gene was also
highly responsive to cell death-inducing injuries. The ADIM transcript
was significantly down-regulated 2 h after oxygen-glucose deprivation
(OGD), and had not only recovered by 16 h after, but also appeared signif-
icantly up-regulated compared to untreated NT2 neurons. Overexpression
of ADIM in N2a cells reduced cell death and it’s downregulation accelerated
cells’ response to injurious insults. Yeast two-hybrid screening and co-im-
munoprecipitation approaches revealed, both in vitro and in vivo, an interac-
tion between ADIM and BAT3, known for its role in apoptosis.
Conclusions: Taken together, we have identified a small membrane protein,
which is down regulated in AD brains and very responsive in neuronal cells
exposed to OGD treatment. It contains two transmembrane domains and in-
teracts with BAT3 suggesting that it might play a role in promoting brain cell
survival against injurious insults.
P2-211 ATTENUATION OF THE LYSOSOMAL DEATH
PATHWAY BY LYSOSOMAL CHOLESTEROL
ACCUMULATION
Hanna Appelqvist1, Cathrine Nilsson1, Brett Garner2, Andrew Brown3,
Katarina Kagedal1, Karin Ollinger1, 1Linkoping University, Linkoping,
Sweden; 2Prince of Wales Medical Research Institute, Randwick, Australia;3School of Biotechnology and Biomolecular Sciences, Sydney, Australia.
Contact e-mail: [email protected]
Background: Niemann-Pick type C (NPC) and Alzheimer’s disease (AD)
are both characterized by neurofibrillar tangles, endosomal abnormalities,
and increased generation of b-amyloid, which is interesting for investigation
of the underlying mechanisms of neuronal death. NPC is caused by muta-
tions in the cholesterol transporting proteins NPC1 and NPC2, resulting in
cholesterol accumulation in the endo-lysosomal system and a concomitant
neuronal death. The lysosome is a significant component of the cellular death
machinery. Lysosomal proteases, cathepsins, are released to the cytosol dur-
ing apoptosis, and have proapoptotic functions. It is still unknown how
Poster Presentations P2S376
lysosomal membrane permeabilization is regulated, but the lipid composition
of the lysosomal membrane has a key role for lysosomal stability, and might
influence the susceptibility to lysosomal leakage. The aim of this study was to
investigate the effect of lysosomal cholesterol accumulation on lysosomal
stability and cellular sensitivity to apoptosis. Methods: To mimic the NPC
phenotype in a cell culture model, human fibroblasts and Chinese hamster
ovary (CHO) cells have been treated with 3-b-[2-(diethylamino)ethoxy]an-
drost-5-en-17-one (U18666A), a drug known to interfere with intracellular
cholesterol transport and results in cholesterol accumulation in late endo-
somes and lysosomes. Genetically modified CHO cells (NPC1-/-) was used
to confirm the results. Results: Lysosomal cholesterol accumulation, in-
duced by genetic deficiency of NPC1 or U18666A-treatment, did not affect
cell viability, but was associated with an upregulation of the lysosomal sys-
tem with increased expression cathepsin D and LAMP-2. Cholesterol accu-
mulation rescued cells from apoptosis induced by exposure to staurosporine
or the lyosomotropic detergent O-methyl-serine dodecylamine hydrochlo-
ride (MSDH). Both these inducers are known to promote apoptosis via the
lysosomal death pathway in human fibroblast, and accordingly decreased
sensitivity to apoptosis induction was associated with diminished lysosomal
leakage. The cholesterol content of lysosomes correlated to their susceptibil-
ity to lysosomal membrane permeabilization, suggesting that cholesterol reg-
ulate lysosomal stability. Moreover, APP over expressing CHO cells were
rescued from lysosome-dependent cell death induced by MSDH or ammo-
nium chloride by pretreatment with U18666A, indicating that lysosomal cho-
lesterol accumulation confer significant protection also in an Alzheimer
model. Conclusions: We suggest that cholesterol accumulation in lysosomes
attenuates the lysosomal death pathway by increasing lysosomal membrane
stability.
P2-212 OVEREXPRESSION OF BCL-2 IN APP
TRANSGENIC MICE REDUCES AMYLOID
PATHOLOGY
Wayne W. Poon1, Anthony J. Carlos1, Carl W. Cotman1, Troy T. Rohn2,1Institute for Memory Impairments and Neurological Disorders, UC Irvine,
Irvine, CA, USA; 2Boise State University, Boise, ID, USA.
Contact e-mail: [email protected]
Background: A growing body of evidence demonstrates caspase activation
in the Alzheimer disease brain. Previously, we found that caspases play a crit-
ical role in the initiation and progression of AD pathology. The results sug-
gest that caspase cleavage of tau is a critical step linking amyloid deposition
with neurofibrillary tangle formation. Overexpression of the anti-apoptotic
protein, Bcl-2 in the 3xTg-AD mouse model attenuated APP processing
and subsequent tangle pathology further supporting this notion. A reduction
in pathology corresponded to improved memory retention in the 3xTg-AD
mice. Methods: The current study aimed to test whether Bcl-2 overexpres-
sion in transgenic mice with only amyloid pathology exhibited similar ben-
efits. Results: In TgCRND8 mice, Bcl-2 overexpression decreased plaque
pathology and reduce Abeta42 levels in the hippocampus. Conclusions:
These findings further implicate apoptotic mechanisms in the development
of AD pathology and suggest that therapeutics targeting apoptotic pathways
may prove beneficial in treating AD.
P2-213 APPOPTOSIN INTERACTS WITH AMYLOID
PRECURSOR PROTEIN AND MEDIATES
NEURONAL TOXICITY VIA CASPASE DEPENDED
PATHWAY
Han Zhang1, Yunwu Zhang1, Xiumei Huang1, Yaomin Chen2, Huaxi Xu2,1Xiamen University, Xiamen, China; 2Sanford Burnham Insititute for Med-
ical Research, La Jolla, CA, USA. Contact e-mail: [email protected]
Background: An important pathologic feature of Alzheimer’s disease (AD)
is the excessive formation and accumulation of senile plaques in the brain,
whose major components are beta-amyloid (A-beta) peptides which are de-
rived from beta-amyloid precursor protein (APP) through sequential cleav-
ages by beta-secretase and gamma-secretase. Besides the key role of its
proteolytic product, A-beta, plays in Alzheimer’s disease, studies suggest
APP may have many other important physiological and pathological func-
tions, many of those are still not clearly understood. Methods: Yeast two hy-
brid assay was applied to screen APP interacting proteins. Molecular cell
biology and biochemical assays were carried out to indentify appoptosin
and characterize its functions. Results: Overexpression of appotosin injures
mitochondria, induces cytochrome C release and hence caspase activation
and cell death. While silencing of the gene using small RNA interfering pre-
vents Bax/BH3I induced caspase-dependent apoptosis. Moreover, APP was
found a possible mediator of appoptosin induced cell death. Further more,
protein levels of appoptosin were found increased before caspase-3 activa-
tion in primary neurons upon acute neurotoxicity treatment or in rat brains
subjected to ischemia stroke. Knocking down of appoptosin prevents cas-
pase-3 activation and mitochondrial fragmentation in primary neuronal cul-
ture caused by insults such as A-beta or glutamate. Conclusions: Our studies
indentify a novel APP binding protein, appoptosin, and indicate it may be an
important player in the cell death regulation and involved in neuronal cell
death. Thus we provide a probable therapeutic target for neurodegenerative
diseases and cancers.
P2-214 C-ABL KINASE ACTIVATION REGULATES BOTH
THE NEURONAL DEATH AND THE TAU
PHOSPHORYLATION IN ALZHEMIER’S DISEASE
MODELS
Alejandra R. Alvarez, Karen G. Perez de Arce, Gonzalo I. Cancino, Uni-
versidad Catolica de Chile, Santiago, Chile. Contact e-mail: aalvarez@bio.
puc.cl
Background: Amyloid b-protein (Ab) accumulation has been causally im-
plicated in the neuronal dysfunction and neuronal loss that underlies the clin-
ical manifestations of Alzheimer’s disease. However, the signal transduction
pathways involved in this neuronal death and the genesis of the cytoskeleton
alterations are not understood. The c-Abl tyrosine kinase is an important link
in signal transduction pathways that promote cytoskeletal rearrangements
and apoptotic signals. We have previously shown that the amyloid-b-peptide
(Ab) activates c-Abl. Here we show that c-Abl kinase activation in response
to Ab participates in the cell signalling that regulates both the neuronal death,
through TAp73 apoptotic signalling, and the tau phosphorylation, through
Cdk5 activation. Methods: We analyzed the c-Abl/p73 and c-Abl/Cdk5 sig-
nalling in an AD double transgenic animal model, the APPswe/PSEN1DE9
mouse, and in vitro, using hippocampal neurons exposed to Ab peptide. We
modulated the c-Abl signalling using the selective c-Abl inhibitor STI571 or
by down regulation of c-Abl expression with shRNAs. Results: In vitro, the
Ab induced the increase of c-Abl protein levels and its phosphorylated form,
which is associated to its activation. This c-Abl activation was associated
with Tyr-99 phosphorylation of p73, the increase of TAp73 isoform levels
and enhance of its proapoptotic function. All these effects where reduced
by STI571 and the neuronal death was prevented. Furthermore, c-Abl activa-
tion was associated with Tyr15 phosphorylation of Cdk5, the inhibition of c-
Abl expression by shRNA as well as by STI571, prevented tau phosphory-
lation followed as AT8 and PHF1 signals. Furthermore, in APPsw/
PSEN1DE9 mice, the intraperitoneal administration of STI571 rescued the
cognitive decline of animals and decreased; i) the p73 phosphorylation, ii)
tau phosphorylation, iii) phospho-Cdk5 levels and iv) Caspase-3 activation
in the APPsw/PSEN1DE9 mice brains. Conclusions: Together, our evidence
is consistent with a role of the c-Abl signalling pathway in AD neurodegen-
eration, and suggests that c-Abl activation by Ab, promotes a dual signalling
that regulates neuronal death through TAp73 activation and tau phosphory-
lation though Cdk5 activation. Moreover our findings suggest that treatments
with drugs that inhibit c-Abl, such STI571 or similar compounds, could delay
the progression of the neurodegeneration, supporting its use for AD.
P2-215 MOLECULAR ANALYSIS OF APOPTOTIC
PATHWAYS INDUCED BY AMYLOID-b VARIANTS
IN CEREBRAL VASCULAR CELLS
Silvia Fossati, Jorge Ghiso, Agueda Rostagno, NYU School of Medicine,
New York, NY, USA. Contact e-mail: [email protected]
Background: The vascular deposition of amyloid, known as Cerebral Am-
yloid Angiopathy (CAA) is an age-associated condition and a common