The peptidergic antidementia drug cerebrolysin increases neurogenesis in the adult rat dentate gyrus and improves spatial learning and memory

s42

Poster

pi%J

THE PEPTIDERGIC ANTIDEMENTIA DRUG CEREBROLYSIN INCREASES NEUROGENESIS IN THE ADULT RAT DENTATE GYRUS AND IMPROVES SPATIAL LEARNING AND MEMORY

Yoshitaka

Tatebayashi,

Basic

Rrsearch

Moon

H Lee. Khalid

in Developmental

Iqbal,

Disabilities,

Inge Grundke-lqbal,

Staten

Island,

NYS Instffv

NY

role of neurogenesis in the adult dentate gyms and Alzheimer’s disease (AD) is poorly understood. Recent evidence indicates the possibility that the suppressed neurogenesis may associate with cognitive and memory impairment as well as depression. Here we show that Cerebrolysin, the peptidergic drug used for the treatment of dementia in European countries, increases neurogenesis in the adult rat dentate gyms with significant improvement of spatial learning performance in Morris water maze. BrdU labeling over I2 days with or without Cerebrolysin showed over 200% increase in numbers of both total and neuronal (NeuN positive) dividing cells in the dentate gyms of Cerebrolysin-treated rats. Consistent with these findings, studies on cultured adult rat hippocampal progenitor cells revealed that Cerebrolysin increased the cell numbers and decreased the number of TUNEL positive cells. Western blot analysis further revealed that Cerebrolysin increased (or induced) MAP2 and decreased phosphorylated tau expression by counteracting FGF-2, a strong stimulant for axonal sprouting as well as a negative regulator of MAP2 expression for the progenitors, resulting in the induction of more mature neuronal phenotypes. These data indicate the possibility: I) that Cerebrolysin improves cognitive impairment and mood partly by increasing neurogenesis in the dentate gyms in AD patients; 2) that in the early phase of AD, abnormality in the dentate gyms may exist probably due to the deleterious reciprocal interaction with the perforant path, causing somehow reversible cognitive impairment and depression; and 3) that FGF-2 may play a role in this abnormality since its levels are elevated significantly in this area of AD brain. The

THE ROLE OF PRESENILIN Alexander Dranovs@,

L Schwarzman,

and Women’s Brook.

Nandita

SUNY at Stony Brook, Hosp.

Boston.

MA;

Singh,

1 IN INTERCELLULAR Yelena Talalayrva.

Stony Brook. Dmitq

Victor

NY; Jie Shen, Xudong

Goldgaber,

State

ADHESION Romanov,

Ala

Yang. Brigham

Univ of New

Presentation:

Molecular

and

Cellular

Biology

invastigated the Ca*‘-influx activity of APP,_,,, in a neuronal cell culture system. leading to cell death. A similar result was observed in APP, ~40induced &+-influx, the presence of Ca*+ ionophore (A23187). Furthermore, the Ca’+ influx induced by APP,.,o was significantly inhibited by a monoclonal antibody raised against the amino-terminal region of APP, Tris, and Zn’+. In conclusion, this study strongly suggests that APP,.,, forms Ca’+ permeable channels in vitro and allow Ca2+ diffusion through plasma membrane. Such calcium exchanges could destabilize cellular calcium homeostasis and lead the neuronal cell toxicity.

piJ

HOMOCYSTEINE ELICITS A DNA DAMAGE RESPONSE IN NEURONS: MECHANISM OF INCREASED RISK FOR ALZHEIMER’S DISEASE?

I. I Kruman,

National

on Aging,

Baltimore.

Baltimore,

MD

Institute MD:

on Aging.

S. L Chun,

Baltimore, M.

P Mattson,

MD;

C. Culmsre.

Nutional

Nationul

Institute

lnst

on Aging,

Elevated circulating levels of the sulfur-containing amino acid homocysteine increase risk for cardiovascular disease, birth defects of the nervous system, and possibly Alrheimer’s disease. Levels of circulating homocysteine increase with age and are dependent on dietary factors such as folic acid intake. The mechanism(s) by which homocysteine may contribute to AD is unknown. We now report that homocysteine induces apoptosis in primary hippocampal neurons which is mediated by DNA strand breaks, PARP activation, p53 up-regulation, and NAD+ depletion. The latter events were followed by mitochondrial dysfunction and caspase activation. zVAD-fmk, a general caspase inhibitor, accelerated NAD+ depletion and loss of mitochondrial potential, and shifted the mode of cell death to necrosis suggesting the importance of PARP/NAD+ in homocysteine-induced mitochondrial dysfunction and cell death. Homocysteine markedly increased neuronal vulnerability to excitotoxic and oxidative insults in vitro and in viva. Our data identify a possible mechanism whereby homocysteine contributes to the pathogenesis of neurodegeneratwe disorders such as AD.

York, Stony

NY

Most cases of familial early-onset Alzheimer’s disease arc caused by mutations in the presenilin I (PSI) gene. However. the cellular functions of PSI are unknown. We showed predominant localization of PSI to cell-cell contacts of the plasma membrane in human prostate epithelial tissue. The results were reproduced in a human epithelial cell line, which was stably transfected with an inducible GFP-PSI construct. To examine if PSI is involved in intercellular adhesion, the interaction between PSI and p-catenin was analyzed. GFP-PSI co-immunoprecipitated with @-cat&n from lyaates of cells stably transfected with the GFP-PS I cDNA. On the contrary, mutant GFP-PSI lacking the PSI p-catenin interaction sltc did not co-immunoprecipitate with p-catenin and was not recruited to the intercellular contacts of transfected epithelial cells. Together, these results suggest that p-catenin mediates the recruitment of PS I into adherence junctions of epithelial cells. Next, we directly examined the role of PSI in intercellular adhesion by using L fibroblaats, which do not form intercellular contacts. L cells transfected with GFP-PSl formed small clusters of adhered cells. Monoclonal antibodies to the N-terminus of PSI (MKAD 3.4) but not anti-GFP antibodies had an inhibitory effect on the cell-cell adhesion. Furthermore, L cells transfected with mutant GFP-PSI constructs, which had a truncated N-terminus of PSI, but contained their p-cat&n interaction site, failed to form intercellular contacts. In primary cultures of mouse cortical neurons, PSI was concentrated on the surface of axonal growth cones and matched contact sites of neurites. Abnormal spreading, branching, and adhesion of growth cones was observed in PSI-deficient primary neuronal cultures. Taken together, our results indicate an important role of PSI in intercellular adhesion of epithelial cells and neurons.

MOLECULAR MECHANISM OF THE NEURONAL INDUCED BY AMYLOID-B-PROTEIN(l-40) Sun Y Park, Seung K Rhee. Yeungnam

Univ.

Kyongsan

South

TOXICITY

Korea

Alzheimer’s disease is commonly associated with two major pathological landmarks, amyloid plaques and intraneuronal neurofibrillary tangles which correlate with ascular and neuronal death. The molecular mechanism underlying neurotoxicity is poorly understood, though a leading element for such neurotoxicity is the amyloid p protein (APP), a proteolytic product of commonly observed amyloid precursor glycoprotein (APP).In this study, we have observed that APP, 40 binds to the plasma membrane surface of neuronal cell-line (IMR-32), using an immune-fluorescent microscopy technique. In addition, APP,~,,-induced cytotoxicity was measured by a MlT assay system. On the other hand, current studies suggest an increased cytoplasmic Ca*+ mediating the APP-induced neurotoxicity, examining the Ca*’ channel actixity ot APP, at, in the reconstitutied phopholipid vesicles. To this end, we

MOLECULAR BIOLOGICAL CHARACTERIZATION OF NICOTINIC RECEPTORS IN BRAIN AND ADRENAL MEDULLA Malahat linsko

T Mousavi, In.% Stockholm

Agneta

Nordberg,

lvan

Bednor,

Ewrr Linstrom-Lindahl.

Kam-

Sweden

In Alrheimer’a diww (AD) and ageing human brain, the number of nicotinic receptors (nAChRs) is decreased. Several studies have ahown that nicotine increases the number of nAChRs in the brain of smokers and rodent and may have protective effects against neurodegenerative diseases like AD. Besides brain, nAChR\ arc also present in several peripheral tissues such as adrenal medulla, which also may be affected by ageing, nicotine and neurodegenerative disorders. Cells m adrenal medulla secret stress hormones, which arc regulated by nAChRs. Thus, the tindmg of the effects of ageing process and nicotine on expression of these receptors in adrenal medulla may lead to the development of more effective but less side effects nAChRs agonists as therapeutic strategy for drug dependence and neurodegenerative disorders. The presence of nAChRs in adrenal medulla from several species has been reported. But which subunits arc assembled in these receptors is not clear. By RT-PCR, we investigated seven nAChR subunits in adrenal medulla from three species. mRNA for alpha 3.4, 5.7 and beta 3,4 in human and alpha3,4,5. 7 and beta2.4 in rat and mice were detected. Preliminary findings showed that mRNA for alpha3, 5, and beta4 are missing in adrenal medulla from an aged individual (79 years) compared with a middle aged (42 years) and fetus (E-IO gestation weeks). The binding of L3H]epibatidine was significantly higher (197%) in fetal compared to human aged adrenal medulla. The genes, alpha3, 5, and beta4 arc tightly clustered, and their encoded proteins make up the predominant receptor subtype in the peripheral nervous system. The tight linkage of the genes suggests that there may be a common regulatory mechanism underlying their expression, which may be disturbed in aged, adrenal medulla. Chronic administration of nicotine to rats for 12 days did not change the number of nAChRs in adrenal medulla,, but quantification of nAChR subunit mRNAs, revealed a significant increase in the level of alpha4, and a slight but not significant increase in beta2. No changes in mRNA for alpha3, 7 or beta4 were detected. Thus the effect of nicotine on nAChRa was different in the rat adrenal medulla compared to brain.