Lymphocytes as cell model to study apoptosis in Alzheimer's disease: vulnerability to programmed cell death appears to be altered

Impaired electro-genesis in skeletal muscle fibers of transgenic Alzheimer mice

Alzheimer's disease (AD) is characterized by memory decline, but is often associated with non-cognitive symptoms, including muscular dysfunction. In the majority of cases these motor disturbances are seen when other neuro-degenerative disorders such as Parkinson's disease overlap dementia, however these can also be directly related to AD itself. Although the patho-mechanism remains largely unclear, β-amyloid peptide (βAP) is thought to be a key role-player in both the brain and periphery. Here we studied the electro-genesis of skeletal muscle fibers in a mouse transgenic AD model. Membrane potential was recorded by standard electro-physiological techniques. Compared to wild-type rodents, AD mice show severe disturbances in skeletal muscle electro-genesis manifested by significant depolarization of myo-fibers. These changes are not affected by short-term βAP treatment, the mark of a chronic degenerative process in the periphery directly related to AD whereby ion pumps on muscle membranes exhibit reduced activity. This phenomenon may explain ionic imbalance and cellular dysfunction both in the neuro-muscular system and in the brain. The observed motor disturbances might play a key role in impaired activities of daily living, and addressing the muscular patho-physiology could improve quality of life in AD.

Modulation of cholesterol, farnesylpyrophosphate, and geranylgeranylpyrophosphate in neuroblastoma SH-SY5Y-APP695 cells: impact on amyloid beta-protein production

There is keen interest in the role of the isoprenoids farnesylpyrophosphate (FPP) and geranylgeranylpyrophosphate (GGPP) in protein prenylation and cell function in Alzheimer's disease (AD). We recently reported elevated FPP and GGPP brain levels and increased gene expression of FPP synthase (FPPS) and GGPP synthase (GGPPS) in the frontal cortex of AD patients. Cholesterol levels and gene expression of 3-hydroxy-3-methylglutaryl-coenzyme A reductase were similar in AD and control samples, suggesting that homeostasis of FPP and GGPP but not cholesterol is specifically targeted in brain tissue of AD patients (Neurobiol Dis 2009 35:251-257). In the present study, it was determined if cellular levels of FPP, GGPP, and cholesterol affect beta-amyloid (Abeta) abundance in SH-SY5Y cells, expressing human APP695. Cells were treated with different inhibitors of the mevalonate/isoprenoid/cholesterol pathway. FPP, GGPP, cholesterol, and Abeta(1-40) levels were determined, and activities of farnesyltransferase and geranylgeranyltransferase I were measured. Inhibitors of different branches of the mevalonate/isoprenoid/cholesterol pathway as expected reduced cholesterol and isoprenoid levels in neuroblastoma cells. Abeta(1-40) levels were selectively reduced by cholesterol synthesis inhibitors but not by inhibitors of protein isoprenylation, indicating that changes in cholesterol levels per se and not isoprenoid levels account for the observed modifications in Abeta production.

Can peripheral leukocytes be used as Alzheimer's disease biomarkers?

Alzheimer's disease (AD) is the leading cause of dementia in elderly populations throughout the world and its incidence is on the rise. Current clinical diagnosis of AD requires intensive examination that includes neuropsychological testing and costly brain imaging techniques, and a definitive diagnosis can only be made upon postmortem neuropathological examination. Additionally, antemortem clinical AD diagnosis is typically administered following onset of cognitive and behavioral symptoms. As these symptoms emerge relatively late in disease progression, therapeutic intervention occurs after significant neurodegeneration, thereby limiting efficacy. The identification of noninvasive diagnostic biomarkers of AD is becoming increasingly important to make diagnosis more widely available to clinics with limited access to neuropsychological testing or state-of-the-art brain imaging, reduce the cost of clinical diagnosis, provide a biological measure to track the course of therapeutic intervention, and most importantly, allow for earlier diagnosis--possibly even during the prodromal phase--with hopes of therapeutic intervention prior to appreciable neurodegeneration. Circulating leukocytes are attractive candidate AD biomarkers as they can be obtained in a minimally invasive manner and are easily analyzed by widely available flow cytometry techniques. In this review, we critically analyze the potential utility of peripheral leukocytes as biological markers for AD.

Defects of immune regulation in the presenilin-1 mutant knockin mouse

Mutations in the presenilin-1 (PS1) gene are causally linked to early-onset Alzheimer's disease (AD). Studies of neurons suggest that PS1 mutations result in a gain-of-function, which perturbs calcium regulation and increases cell vulnerability to apoptosis. Alterations in immune cell function have also been demonstrated in AD, and a role for PS1 in immune regulation has been suggested recently. We now report that splenocytes from PS1-mutant (M146V) knockin mice exhibit increased caspase activity, abnormal calcium regulation and aberrant mitochondrial function. Isolated splenic T cells from PS1-mutant mice respond poorly to proliferative signals and have downregulated cluster designation 3 and interleukin (IL)- 2-receptor expression necessary for a normal T-cell immune response. Thus, adverse effects of a mutation that causes AD on immune function that involves perturbed calcium regulation and cytokine signaling in lymphocytes, and associated sensitivity of lymphocytes to apoptosis are demonstrated. These findings suggest that abnormalities in immune function might play major roles in the pathogenesis of AD.

All-or-nothing type biphasic cytokine production of human lymphocytes after exposure to Alzheimer's beta-amyloid peptide

BACKGROUND

Neuro-inflammation, triggered by beta-amyloid peptide, is implicated as one of the primary contributors to Alzheimer's disease (AD) pathogenesis, and several cytokines were identified as key instigating factors.

METHODS

To reveal the inflammatory response of lymphocytes to the neuro-toxic beta-amyloid peptide, we evaluated the release of several cytokines from peripheral blood mononuclear cells with immuno-assays (ELISA). From hyper-acute to chronic effects of beta-amyloid peptide were assessed at a wide range of concentrations.

RESULTS

The pro-inflammatory interleukin (IL)-1beta, tumor necrosis factor-alpha, monocyte chemotactic protein-1, and Rantes (acronym for regulated on activation, normal T-cell expressed and secreted) as well as the pleiotropic IL-6 showed a biphasic release pattern over time in both low and high doses of amyloid treatment: after an initial increase, their concentration gradually fell to the baseline. The suppressors IL-4 and IL-10 had a sinus-like secretion panel: an acute increase in their levels turned to a depression and later followed by their over-secretion. Interestingly, beta-amyloid below 10(-8) mol/L produced no effect at all, but any molarity above this threshold caused the very same cytokine secretion pattern, the mark of an all-or-nothing response of beta-amyloid peptide.

CONCLUSIONS

These results delineate a highly organized pro- and anti-inflammatory response of cells to the neuro-toxic peptide. This is the first study to describe how the beta-amyloid-induced inflammatory processes in Alzheimer's dementia are regulated.

Enhanced apoptosis, oxidative stress and mitochondrial dysfunction in lymphocytes as potential biomarkers for Alzheimer's disease

Alzheimer's disease (AD) is the most common progressive neurodegenerative disease. Today, AD affects millions of people worldwide and the number of AD cases will increase with increased life expectancy. The AD brain is marked by severe neurodegeneration like the loss of synapses and neurons, atrophy and depletion of neurotransmitter systems in the hippocampus and cerebral cortex. Recent findings suggest that these pathological changes are causally induced by mitochondrial dysfunction, increased oxidative stress and elevated apoptosis. Until now, AD cannot be diagnosed by a valid clinical method or a biomarker before the disease has progressed so far that dementia is present. Furthermore, no valid method is available to determine which patient with mild cognitive impairment (MCI) will progress to AD. Therefore, a correct diagnosis in the early stage of AD is not only of importance considering that early drug treatment is more effective but also that the psychological burden of the patients and relatives could be decreased. In this review, we discuss the potential role of elevated apoptosis, increased oxidative stress and mitochondrial dysfunction as biomarker for AD in a peripheral cell model, the lymphocytes.

HMG-CoA reductase inhibitor simvastatin inhibits cell cycle progression at the G1/S checkpoint in immortalized lymphocytes from Alzheimer's disease patients independently of cholesterol-lowering effects

Recent work has suggested that statins may exert beneficial effects on patients suffering from Alzheimer's disease (AD). The pharmacological effects of statins extend beyond their cholesterol-lowering properties. Based on the antineoplastic and apoptotic effects of statins in several cell types, we hypothesized that statins may be able to protect neurons by controlling the regulation of cell cycle. A growing body of evidence indicates that neurodegeneration involves the activation of cell cycle machinery in postmitotic neurons. We and others have presented direct evidence to support the hypothesis that the failure of cell cycle control is not restricted to neurons in AD patients, but that it occurs in peripheral cells as well. For these reasons, we found it worthy to study the role of simvastatin on cell proliferation in immortalized lymphocytes from AD patients. We report here that simvastatin (SIM) inhibits the serum-mediated enhancement of cell proliferation in AD by blocking the events critical for G(1)/S transition. SIM induces a partial blockade of retinoblastoma protein phosphorylation and inhibition of cyclin E/cyclin-dependent kinase (CDK)2 activity associated with increased levels of the CDK inhibitors p21(Cip1) and p27(kip1). These effects of SIM on AD lymphoblasts are dependent on inhibition of the proteasome-mediated degradation of p21 and p27 proteins. The antiproliferative effect of this natural statin may provide a therapeutic approach for AD disease.

Beta-amyloid toxicity and reversal in embryonic rat septal neurons

Alzheimer's disease is characterized mainly by loss of neurons from the septal nucleus. In this study, neurons from the septal nucleus of the embryonic day 16 (E16) rat were grown in culture with a plane of astrocytes from the embryonic rat and in a defined medium in the absence of serum. Neurons were treated with beta-amyloid (Abeta: 0.1, 1 and 10 microM) on day in vitro (DIV) 1 and DIV 4 and fluorescent microscopy was used to measure survival and apoptosis following exposure of the treated cells on DIV 7. Reversal of neurotoxicity was studied using the potentially neuroprotective agents nerve growth factor (NGF, 100 ng/ml), basic fibroblast growth factor (bFGF, 5 ng/ml), insulin-like growth factors (IGF1 and IGF2, 10 ng/ml) and estrogen (10 nM), administered on DIV 4 and DIV 5, that is, subsequent to the Abeta (10 microM)-induced neurotoxicity. Abeta caused a significant decrease in survival at 10 microM, and a significant increase in apoptosis at 0.1 and 10 microM. IGF1, IGF2 and bFGF all caused a reversal of the Abeta-induced neurotoxic effect on survival while NGF and estrogen did not under these experimental conditions.

Proteomic analysis of peripheral leukocytes in Alzheimer's disease patients treated with divalproex sodium

The molecular profiling of peripheral tissues, including circulating leukocytes, may hold promise in the discovery of biomarkers for diagnosing and treating neurodegenerative diseases, including Alzheimer's disease (AD). As a proof-of-concept, we performed a proteomics study on peripheral leukocytes from patients with AD both before and during treatment with divalproex sodium. Using two-dimensional gel electrophoresis and MALDI-TOF mass spectrometry, we identified 10 differentially expressed proteins: two up-regulated proteins, 14-3-3 protein epsilon and peroxiredoxin 2; and eight down-regulated proteins, actin-interacting protein, mitogen activated protein kinase 1, beta actin, annexin A1, glyceraldehyde 3-phosphate dehydrogenase, transforming protein RhoA, acidic leucine-rich nuclear phosphoprotein 32 family member B, and a currently unidentified protein. A subset was validated on both the transcript and protein levels in normal human peripheral blood mononuclear cell cultures treated with valproic acid. These proteins comprise a number of functional classes that may be important to the biology of AD and to the therapeutic action of valproate. These data also suggest the potential of using peripheral leukocytes to monitor pharmaceutical action for neurodegenerative diseases.

Beta-amyloid toxicity in embryonic rat astrocytes

The senile plaques of Alzheimer's disease contain a high concentration of beta-amyloid (betaA) protein, which may affect the glial population in the septal nucleus, an area of increased risk in AD. BetaA toxicity was measured in septal glia, via a dose-response experiment, by quantifying the effects of three different doses (0.1, 1, and 10 microM) of betaA on cell survival. Astrocytes from embryonic day-16 rats were grown in serum-free media in a single layer culture. Cells were treated on day in vitro (DIV)1 and survival was determined on DIV3 to ascertain which concentration was most toxic. In a separate set of experiments, an attempt was made to protect glial cells from the degenerative effects of betaA, with treatments of growth factors and estrogen. BetaA (10 microM) treatment was administered on DIV1, on DIV2 the cells were treated with estrogen (EST, 10 nM), insulin-like growth factors (IGF1 and IGF2, each 10 ng/ml), basic fibroblast growth factor (bFGF, 5 ng/ml) or nerve growth factor (NGF, 100 ng/ml), and on DIV3 the cells were visualized and quantified by fluorescence microscopy with DAPI (4,6-diamidino-2-phenylindole). In addition to dose-response and glial protection, experiments were also conducted to determine whether toxic effects were due to apoptosis. Our results suggest that the survival of glial populations is significantly affected in all three concentrations (0.1, 1.0, and 10 microM) of betaA. Glial protection was evident in the presence of NGF, for it showed the significantly highest survival rate relative to the betaA treatment alone. Furthermore, toxic effects of betaA appear to be due primarily to apoptosis. Significant reversal of betaA-induced apoptosis was seen with bFGF and IGF1.

Changes in the immune system in depression and dementia: causal or coincidental effects?

Epidemiological studies show that there is a correlation between chronic depression and the likelihood of demential in later life. There is evidence that inflammatory changes in the brain are pathological features of both depression and dementia. This suggests that an increase in inflammation-induced apoptosis, together with a reductin in the synthesis of neurotrophic factors caused by a rise in brain glucocorticoids, may play a role in the pathology of these disorders. A reduction in the neuroprotective components of the kynurenine pathway, such as kynurenic acid, and an increase in the neurodegenerative components, 3-hydroxykynurenine and quinolinic acid, contribute to the pathological changes. Such changes are postulated t cause neuronal damage, and thereby predispose chronically depressed patients to demential.

Biomarkers for apoptosis in Alzheimer's disease

Alzheimer's disease (AD) affects millions of people worldwide and the number of AD cases will increase with increased life expectancy. Today there is no cure for this devastating and always lethal disease and therefore it is of great interest for patients, relatives and societies to find new drugs that can hinder the disease process. During the progression of AD a substantial amount of neurons degenerate in the brain. The mechanisms of cell death involved in AD have not been fully elucidated. However, there are several reports showing that neurons die partly by apoptosis in the AD brain. Drugs blocking apoptosis could therefore be potentially useful for early prevention of neuronal cell death. Biomarkers for apoptosis should be important tools in the evaluation of drug effects and in the diagnostics of AD. Here we review the current knowledge in the field and discuss potential biomarkers for apoptosis in AD.

Lymphoblastoid cell lines of Rett syndrome patients exposed to oxidative-stress-induced apoptosis

Despite the identification of mutations in the methyl CpG binding protein 2 gene, the pathogenesis of Rett syndrome (RS) is still unknown. In order to clarify the role of apoptosis in this disorder, we studied lymphoblastoid cell lines in five classical RS patients and five controls, incubated with 2-deoxy-d-ribose (dRib), a reducing sugar that induces apoptosis in human cells, through oxidative damage. The apoptotic response was detected by flow cytometric analysis and agarose gel electrophoresis. The cells of RS patients showed a lower percentage of apoptosis in a routine condition than those of controls did, whereas, in the presence of dRib, the percentage of apoptotic cells in RS patients increased with time and reached the same percentage of those of controls at 72 h. The data observed here suggest that RS may have a low susceptibility or an increased resistance to the apoptotic cell death, which may be corrected only in the presence of a strong apoptotic stimulus.

The effect of citalopram on gene expression profile of Alzheimer lymphocytes

Antidepressants are widely used in the treatment of mood disorders associated with dementia, however little information is available on their effect at the molecular level. In certain neurodegenerative disorders, such as in Alzheimer's disease, lymphocytes have been used to assess mirror changes that thought to occur in the brain. Gene expression profiles of lymphocytes from Alzheimer patients have been shown to differ from that seen with controls. To address this issue in light of antidepressant treatment, we used lymphocytes derived from Alzheimer's disease patients and control individuals to assess the impact of the selective serotonine reuptake inhibitor citalopram on gene expression using a cDNA microarray representing 3200 distinct human genes. Sequences that are differentially regulated after treatment with citalopram were identified and categorized based on similarities in biological functions. This analysis revealed that the overexpression of genes in control and Alzheimer white blood cells by citalopram are implicated in cell survival. Apart from this, citalopram did not markedly alter genes involved in other molecular functions in control cells. In contrast, alteration of genes implicated in ionic currents, cell-adhesion, immune mechanism, and adrenergic functions, were also observed in Alzheimer lymphocytes. The expression of genes of Alzheimer lymphocytes by citalopram is modulated differently which may correlate with the pathology.

Effects of homocysteine on apoptosis-related proteins and anti-oxidant systems in isolated human lymphocytes

Homocysteine (Hcy) is a nonprotein-forming sulphur amino acid that plays an important role in remethylation and trans-sulphuration processes. In recent years, it has been suggested that increased levels of plasma Hcy may play a role in the pathogenesis of various diseases, particularly at the cardiovascular level. The pathogenic mechanism of hyperhomocysteinemia, however, has not been clarified. Because oxygen radicals can be generated by the auto-oxidation of this amino acid, it has been suggested that Hcy may cause cellular damage through oxidative mechanisms, ultimately leading to apoptotic cell death. In this study, we sought to investigate the effects of Hcy on oxidative damage and antioxidant agent levels, as well as on apoptosis-related proteins and apoptosis occurrence in human cells. For this purpose, we measured levels of Bcl-2, caspase-3 and caspase-9 activity, Cu/Zn superoxide dismutase, reduced glutathione, lipid peroxidation [malondialdehyde and 4-hydroxy-2 (E)-nonenal concentrations], apoptotic single-stranded DNA and nuclear changes in human isolated lymphocytes exposed to increasing concentrations of Hcy. Incubation with Hcy did not induce significant changes in any of these biomarkers. Therefore, our results do not support the existence of a direct link between increased levels of Hcy and the occurrence of a pro-apoptotic state mediated by enhanced oxidative stress.

Long-term exposition of cells to beta-amyloid results in decreased intracellular calcium concentration

The ubiquitously present beta-amyloid peptide plays an important role in the pathogenesis of Alzheimer's disease. Its neurotoxicity has been blamed on its mal-activity to increase calcium-levels. In the present study, we demonstrate that treatment of fibroblasts with beta-amyloid has, indeed, resulted in a transient rise in the calcium-concentration. Chronic exposition of cultures to the peptide, however, caused a fall in the calcium-level. Apparently, beta-amyloid has biphasic effects: acutely, it increases the calcium-concentration of cells; in contrast, on the long-run, beta-amyloid peptide acts as a calcium-antagonist. Therefore, the idea that beta-amyloid peptide leads to neural degeneration solely by increasing cells' calcium concentration must be replaced with a more complex view of its dual function in intracellular ionic homeostasis.

Abeta[25-35] peptide and iron promote apoptosis in lymphocytes by an oxidative stress mechanism: involvement of H2O2, caspase-3, NF-kappaB, p53 and c-Jun

The Abeta deposition in the neuritic plaques is one of the major neuropathological hallmarks of the Alzheimer disease (AD). Studies in vitro have demonstrated that the Abeta[25-35] fragment, which contains the cytotoxic functional sequence of the amyloid peptide, induces neurotoxicity and cell death by apoptosis. Despite intense investigations, a complete picture of the precise molecular cascade leading to cell death in a single cellular model is still lacking. In this study, we provide evidence that Abeta[25-35] induce apoptosis either alone or in presence of iron in peripheral blood lymphocytes cells (PBL) in a concentration-dependent fashion by an oxidative stress mechanism involving: (1) the production of hydrogen peroxide (H2O2), reflected by rhodamine-positive fluorescent cells, (2) activation and/or translocation of NF-kappaB, p53 and c-Jun transcription factors showed by immunocytochemical diaminobenzidine positive nuclei, (3) activation of NF-kappaB complex by electrophoretic mobility shift assay/immuno-blotting/and ammonium pyrrolidinedithiocarbamate (PDTC) inhibition, (4) caspase-3 activation, reflected by caspase Ac-DEVD-cho inhibition, (5) mRNA synthesis de novo according to actinomycin D cell death inhibition. These results are consistent with the notion that the Abeta[25-35]/H2O2 generation precede the apoptotic process and that once H2O2 is generated, it is able to trigger a specific cell death signalisation. Thus, taken together these results, we present a well-ordered cascade of the major molecular events leading PBL to apoptosis. These results may contribute to explain the importance of Abeta alone or in the presence of redox-available iron in association with Abeta plaques (and neurofibrillary tangles) in AD brains and the significant role played by H2O2 as a second messenger of death signal in some degenerative diseases linked to oxidative stress stimuli.

Are peripheral blood cells from patients with Alzheimer disease more sensitive to apoptotic stimuli?

One of the reasons for the increased susceptibility to infections in patients with Alzheimer disease may be enhanced apoptotic death of their peripheral leukocytes. If this is the case, the enhanced apoptosis may be due to components in the patients' sera or to an increased sensitivity of the cells to apoptotic stimuli. To examine this possibility, the percentage of apoptotic cells in the peripheral blood mononuclear cells (PBMC) from 12 patients with Alzheimer disease was compared with that of 12 age-matched non-demented persons and 12 middle-aged healthy control subjects. In addition, the effect of sera from subjects in the three groups on the apoptosis, interleukin (IL)-1beta, IL-2, IL-6, IL-10, and tumor necrosis factor (TNF)alpha production by peripheral blood cells from healthy control subjects was examined. It was found that the percentage of apoptotic PBMC from patients with Alzheimer disease was higher than that from the remaining two groups. However, incubation of control cells with sera from patients with Alzheimer disease and non-demented elderly persons did not affect the number of apoptotic cells. Sera from patients with Alzheimer disease and non-demented elderly subjects caused an increase in IL-2 and a decrease in IL-10 production by PBMC from middle-aged control subjects but did not affect IL-1beta, IL-6, and TNFalpha secretion, indicating alterations of the immune system related to aging.

Fibroblasts and lymphocytes from Alzheimer patients are resistant to beta-amyloid-induced increase in the intracellular calcium concentration

A major neuropathological finding in Alzheimer's disease (AD) is the presence of senile plaques in certain regions in the brain. The plaques contain extracellular deposits of beta-amyloid peptide (beta AP). Destabilization of intracellular calcium homeostasis in neurons, caused by beta AP, plays a central role in AD pathogenesis. In the present study, the authors report ionic alterations of lymphocytes and fibroblasts harvested from sporadic AD patients and from age-matched controls. Intracellular free calcium level ([Ca2+]i) of human cells, labeled with Fura-2AM, was determined by dual wavelength spectrofluorimetry. Basal [Ca2+]i appeared to be higher in AD lymphocytes when compared to control ones. Resting [Ca2+]i of AD fibroblasts, however, has proven to be lower than that seen with control cells. Exposure of cells to beta AP resulted in the elevation of the [Ca2+]i in both control cell types, however, that of AD lymphocytes and fibroblasts did not differ considerably.

Beta-amyloid-induced increase in the resting intracellular calcium concentration gives support to tell Alzheimer lymphocytes from control ones

Senile plaques containing beta-amyloid peptide (betaAP) comprise the major neuropathological lesions in Alzheimer's disease (AD). In line with ongoing studies investigating alterations of various biochemical processes of cells of peripheral tissues, the authors demonstrate differences in resting intracellular free calcium levels of lymphocytes harvested from sporadic Alzheimer patients and from age-matched controls. Resting intracellular calcium concentration was measured in Fura-2AM-loaded human lymphocytes by dual wavelength spectrofluorimetry. Resting calcium level appeared to be higher in Alzheimer cells when compared to control lymphocytes. After incubating cells in 10(-7)M of beta-amyloid, the resting calcium concentration of the control cells elevated, while that of Alzheimer lymphocytes did not differ considerably.

Functional decline in aging and disease: a role for apoptosis

The process of aging and senescence is associated with a decline in several organ functions and ultimately takes away independence and reduces quality of life. The precariously marginal functional reserves of the immune, pulmonary, and cardiovascular systems are among the most important causes of increased hospitalization in the older population. When complicated by chronic diseases, as is often the case, the problem is magnified. Apoptosis, or programmed cell death, is a process that goes on continuously throughout life. It is involved in embryogenesis for proper organ and tissue development. After birth and through adulthood, it helps eliminate unneeded and damaged cells. There is evidence that advanced age is associated with dysregulation of apoptosis. Several studies have shown age-related changes in the levels of proteins and factors that regulate apoptosis. This could explain the age-associated increased prevalence of cancers, certain autoimmune diseases, and neurodegenerative disorders in older people. More studies are needed to further elucidate the process of apoptosis. With this knowledge, the use of gene therapy and apoptosis modulators may someday have therapeutic value in preventing the functional decline we see in the older population.

Comparative studies on [Ca2+]i-level of fibroblasts from Alzheimer patients and control individuals

The accumulation of the beta-amyloid peptide (betaAP) in the brain, produced from the ubiquitously expressed amyloid precursor protein (APP) is a defining feature of Alzheimer's disease (AD). Consistent with studies demonstrating the importance of skin biopsy in the diagnosis of neurodegenerative disorders, we investigated whether differences in intracellular free calcium levels ([Ca2+]i) of cultured cutaneous fibroblasts derived from sporadic AD patients and from age-matched control individuals might be present. [Ca2+]i was measured in Fura-2AM-loaded human fibroblasts by dual wavelength spectrofluorimetry. AD cells exhibited lower [Ca2+]i as compared to the control cultures. Exposure of fibroblasts to betaAP resulted in increased [Ca2+]i of the control cells, but not of AD fibroblasts. Our test could prove useful in supporting the diagnosis of (sporadic) AD in patients suspected of suffering from the disease.

The amyloid beta peptide abeta (25-35) induces apoptosis independent of p53

Apoptosis of neuronal cells apparently plays a role in Alzheimer's disease (AD). The amyloid beta (Abeta) peptide derived from beta-amyloid precursor protein is found in AD brain in vivo and can induce apoptosis in vitro. While p53 accumulates in cells of AD brain, it is not known if p53 plays an active role in Abeta-induced apoptosis. We show here that inactivation of p53 in two experimental cell lines, either by expression of the papillomavirus E6 protein or by a shift to restrictive temperature, does not affect apoptosis induction by Abeta (25-35), indicating that Abeta induces apoptosis in a p53-independent manner.