NMM3/1,05,53-64,12gs
2/10/03 11:15 AM
Page 53
NeuroMolecular Medicine Copyright © 2003 Humana Press Inc. All rights of any nature whatsoever reserved. ISSN1535-1084/03/03:53–64/$20.00
ORIGINAL RESEARCH
Presenilin-1 Mutation Sensitizes Oligodendrocytes to Glutamate and Amyloid Toxicities, and Exacerbates White Matter Damage and Memory Impairment in Mice Kirk Pak,1 Sic L. Chan,1 and Mark P. Mattson*,1,2 1
Laboratory of Neurosciences, National Institute on Aging Gerontology Research Center, 5600 Nathan Shock Drive, Baltimore, MD 21224; 2Department of Neuroscience, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205 Received October 25, 2002; Accepted November 15, 2002
Abstract Damage to white matter occurs in the brains of patients with Alzheimer’s disease (AD), but it is not known if and how oligodendrocytes are affected in AD, nor whether white matter alterations contribute to the cognitive dysfunction in this disease. Mutations in the gene encoding presenilin-1 (PS1) cause some cases of early-onset inherited AD. These mutations may promote neuronal degeneration by increasing the production of neurotoxic forms of amyloid β-peptide and by perturbing cellular calcium homeostasis. Damage to oligodendrocytes induced by a demyelinating agent is enhanced, and spatial learning is impaired in PS1 mutant knockin mice. Oligodendrocytes from PS1 mutant knockin mice are more vulnerable to being killed by glutamate and amyloid β-peptide, and exhibit an abnormality in calcium regulation which is responsible for their death. These findings demonstrate an adverse effect of a disease-causing PS1 mutation in oligodendrocytes, and suggest a mechanism responsible for white matter damage in AD and a contribution of such damage to cognitive impairment. Index Entries: Alzheimer ’s disease; amyloid beta-peptide; apoptosis; axons; calcium; cognitive; excitotoxicity; white matter.
Introduction
pocampus and functionally related regions of cerebral cortex (DeKosky, 2001). Most studies of AD pathogenesis have therefore focused on Aβ production and deposition, and the mechanisms that result in the dysfunction and death of neurons (Mattson, 1997). A less-studied abnormality in AD is
Alzheimer’s disease (AD) involves the progressive deposition of amyloid β-peptide (Aβ) and associated degeneration of neurons in brain regions involved in learning and memory, including the hip-
*Author to whom all correspondence and reprint requests should be addressed. E-mail:
[email protected]
NeuroMolecular Medicine
53
Volume 3, 2003
NMM3/1,05,53-64,12gs
2/10/03 11:15 AM
Page 54
54 damage to white matter which has been documented in examinations of postmortem tissue from AD patients (Brun, 1989) and MRI studies of living patients (Bronge, 2002). White matter consists of axons, oligodendrocytes, and astrocytes. Oligodendrocytes play a critical role in brain function by myelinating axons and thereby increasing axonal conduction velocity; they also provide trophic support to the axons (Byravan et al., 1994; Vabnick and Shrager, 1998; Wilkins et al., 2001). It is not known if oligodendrocytes are damaged in AD. Mutations in the gene encoding presenilin-1 (PS1) cause some cases of early-onset dominantly inherited familial AD (FAD) (Price et al., 1998). The PS1 mutations alter the proteolytic processing of the amyloid precursor protein in a manner that increases the production of Aβ, particularly the long 42 amino acid form (Aβ1-42). In addition, PS1 mutations perturb cellular calcium homeostasis by increasing the amount of calcium released from the endoplasmic reticulum (Guo et al., 1997, 1999a). Studies of cultured cells overexpressing mutant PS1 and of PS1 mutant knockin mice have shown that PS1 mutations render neurons vulnerable to excitotoxic and metabolic insults by a mechanism involving perturbed calcium regulation (Guo et al., 1999a, 1999b). The expression of PS1 is not limited to neurons, it is also expressed in astrocytes (Weggen et al., 1998; Miake et al., 1999) and microglia (Xia et al., 1998). In the present study we show that PS1 mutations adversely affect oligodendrocytes by perturbing cellular calcium homeostais and increasing the vulnerability of the cells to death induced by glutamate and Aβ1-42. These findings suggest a mechanism for white matter damage in AD.
Materials and Methods Mice and Cuprizone Model of Demyelination The generation and characterization of PS1 mutant (M146V) knockin (PS1mutKI) mice is described in our previous studies (Guo et al., 1999a, 1999b). Eight-wk-old male PS1mutKI mice and littermate wild-type mice were fed either normal mouse chow or chow containing 0.15% cuprizone (oxalic bis(cyclohexylidenehydrazide; Sigma, St.
NeuroMolecular Medicine
Pak, Chan, and Mattson Louis, MO) by weight for 6 wk to induce demyelination (Hiremath et al., 1998).
Behavioral Analyses Spatial learning was evaluated in a Morris water maze using methods similar to those described previously (Janus et al., 2000). Briefly, the apparatus consisted of a 1.5 m diameter swimming pool with a 10-cm diameter (non-visible) platform (goal) submerged 1.5 cm below the surface of the water. Objects were placed on the walls of the pool to provide spatial reference cues to the mice. Mice were subjected to a training session on each of five consecutive days; each session consisted of four trials in which the mouse was placed in the pool and the time it took to locate the submerged platform was recorded. Following the training session on d 3, a probe test was performed in which the platform was removed and the percentage of time the mouse spent in the quadrant of the pool where the platform had been located was determined. Mice were videotaped and their swim paths were recorded on a computer and analyzed using Columbus Instruments water maze software; swim speed, path length and percentage of time spent in each quadrant were determined using the software. Goal latency was measured using a hand-held timer.
Histological Analyses Mice were perfused transcardially with cold PBS followed by 4% paraformaldehyde in PBS. Brains were removed, postfixed overnight in 4% paraformaldehyde in PBS, cryoprotected in a 30% sucrose solution, and 30 µm thick coronal sections were cut using a freezing microtome. Sections throughout the rostro-caudal extent of corpus collosum were saved. Sections were immunostained with an antibody against CNPase (2′,3′-cyclic nucleotide-3′-phosphodiesterase) as follows. Free floating sections were treated with 0.6% H2O2 in Tris-buffered saline (TBS; pH 7.5) to block endogenous peroxidases. The sections were incubated in TBS/0.1% Triton X-100/5% horse serum (TBS-TS) for 30 min, and incubated with primary mouse antiCNPase antibody (Sigma; 1000 dilution), a marker for oligodendrocytes (Kim et al., 1984) in TBS-TS overnight at 4°C. Sections were further processed
Volume 3, 2003
NMM3/1,05,53-64,12gs
2/10/03 11:15 AM
Page 55
Presenilin, Amyloid, and Oligodendrocyte Damage using a biotinylated horse anti-mouse IgG antibody (Vector Laboratories, 1200), avidin-peroxidase complex, and diaminobenzidine. To determine the extent of demyelination induced by cuprizone, CNPase-stained coronal sections at 7 different rostrocaudal levels spaced evenly from the front to the back of the corpus collosum were evaluated. Sections were assigned a score from 0 to 4 based upon the area and intensity of CNPase immunoreactivity (0, no immunoreactivity; 1, weak; 2, moderate; 3, strong; 4, intense). Additional brain sections were stained with either Luxol Fast-Blue to label myelin (Scholtz, 1977) or cresyl violet to stain neurons.
Oligodendrocyte Cultures and Cell Survival Analysis Dissociated cultures of cortical oligodendrocytes were established from postnatal d 1 mice using methods similar to those described in our previous studies (Bruce-Keller et al., 1999). Cells were plated into polyethyleneimine-coated 35-mm diameter plastic culture dishes or 22 mm2 glass coverslips in minimum essential medium with Earle’s salts supplemented with 10% heat-inactivated fetal bovine serum, 2 mM L-glutamine, 1 mM pyruvate, 20 mM KCl, 10 mM sodium bicarbonate, and 1 mM HEPES (pH 7.2). Following cell attachment (3–6 h after plating), the culture medium was replaced with Neurobasal medium with B27 supplements (Life Technologies, Gaithersburg, MD). Cells were maintained in a 6% CO2/94% room air humidified atmosphere at 37°C. Experiments were performed in 7-d-old cultures; the cultures contained 70–80% oligodendrocytes (CNPase positive), 20–30% astrocytes (GFAP positive) and no neurons (MAP-2 or NeuN positive). Aβ1-42 (Bachem) was prepared as a 1 mM stock in water and allowed to aggregate overnight prior to addition to cultures. Glutamate (Sigma) was prepared as a 10 mM stock in culture medium. BAPTA-AM (Calbiochem), nimodipine (Sigma), and dantrolene (Sigma) were prepared as 500X stocks in dimethylsulfoxide. To quantify oligodendrocyte cell survival, photographs of designated microscope fields were taken prior to treatment and at specified post-treatment timepoints. The number of undamaged oligodendrocytes in each field was determined from photographic neg-
NeuroMolecular Medicine
55 atives; oligodendrocytes with intact cell bodies and processes were considered viable. Counts were performed by an investigator who was unaware of the genotype or treatment history of the cultures.
Quantification of Intracellular Calcium Levels Intracellular free calcium concentrations were measured using fluorescence ratio imaging of the calcium indicator dye fura-2 as described previously (Guo et al., 1999a). For these experiments, cells were plated into polyethyleneimine-coated glassbottomed 35 mm dishes. Cells were loaded with fura-2 (30 min incubation in the presence of 10 µM fura-2 acetoxymethyl ester), and then washed with Locke’s solution (mM): NaCl, 154; KCl, 5.6; CaCl2, 2.3; MgCl2, 1.0; NaHCO3, 3.6; glucose, 10; HEPES buffer, 5 (pH 7.2). Cultures were transferred to the stage of a Zeiss Axiovert microscope coupled to a CCD camera and a Zeiss AttoFluor calcium imaging system and cellular fluorescence was imaged using a 40× oil immersion objective. The average [Ca2+]i in individual neuronal cell bodies was determined from the ratio of the fluorescence emissions obtained using two different excitation wavelengths (340 nm and 380 nm). The system was calibrated using solutions containing either no Ca 2+ or a saturating level of Ca2+ (1 mM) using the formula: [Ca2+]i = Kd[(R-Rmin)/(Rmax-R)](Fo/Fs).
Results White Matter Damage is Increased and Behavioral Impairment Worsened in Presenilin Mutant Knockin Mice Fed Cuprizone An established model of demyelination resulting from selective damage to oligodendrocytes involves chronic administration of cuprizone to mice (Hiremath et al., 1998; Arnett et al., 2001; Jurevics et al., 2001). We fed PS1 mutant knockin mice and wild-type control mice either normal food or food containing 0.15% cuprizone for 6 wk. Examination of brain sections from each of the four groups of mice that had been immunostained with an anti-
Volume 3, 2003
NMM3/1,05,53-64,12gs
2/10/03 11:15 AM
Page 56
56 body against the oligodendrocyte protein CNPase (Reynolds et al., 1989) revealed a reduction in CNPase immunoreactivity in the corpus callosum, cerebral cortex, striatum and midbrain of cuprizone-treated mice compared to control mice (Fig. 1A). The extent of the decrease in CNPase immunoreactivity was significantly greater in the cuprizone-treated PS1mutKI mice compared to the cuprizone-treated control mice. This difference was particularly prominent at intermediate rostrocaudal levels of the brain (Fig. 1B). A similar exacerbation of cuprizone-induced white matter damage was observed in brain sections (adjacent to those used for CNPase immunostaining) that were stained with the myelin stain Luxol fast blue (data not shown). Because cognitive impairment is the most prominent clinical abnormality in AD, including cases caused by PS1 mutations (Rosselli et al., 2000), and PS1 mutations exacerbate memory deficits in transgenic mice (Holcomb et al., 1999), we tested spatial learning abilities in WT and PS1mutKI mice that had been maintained on control and cuprizonesupplemented diets. Mice were tested in a Morris water maze; the time it took the mice to find the submerged platform (goal latency) was measured on five consecutive days (four trials per day) and a probe trial was performed on test day three. The goal latency times for WT and PS1mutKI mice on the normal diet decreased progressively between test d 1 and 4, with no significant differences between these two groups of mice (Fig. 2A). The performance of WT mice that had been fed cuprizone was not significantly different than that of mice not treated with cuprizone. In contrast to the other three groups, the goal latencies of PS1mutKI mice given cuprizone did not decrease during the first three days of testing, indicating an impaired learning ability of these mice (Fig. 2A). The results of the probe trial test revealed a significant impairment in the ability of cuprizone-treated PS1mutKI mice to remember the location of the platform compared to each of the other three groups (Fig. 2B). Swim speeds among the four groups of mice were not significantly different, nor did the goal latencies differ when the platform was raised above the water level so that it was visible (data not shown), indicating that cuprizone did not adversely affect motor function or vision in this study.
NeuroMolecular Medicine
Pak, Chan, and Mattson Examination of brain sections stained with cresyl violet revealed no evidence of neuronal loss in cuprizone-treated WT or PS1mutKI mice in any brain region examined including hippocampus, cerebral cortex, striatum and thalamus (Fig. 2C and data not shown).
PS1 Mutation Increases the Vulnerability of Cultured Oligodendrocytes to Glutamate and Amyloid β-Peptide Toxicities In order to more directly examine the impact of PS1 mutations on oligodendrocytes and to explore the underlying mechanisms, we established oligodendrocyte cell cultures from the cerebral cortices of WT and PS1mutKI mice. CNPase immunoreactive oligodendrocytes in cultures established from WT and PS1mutKI mice were also immunoreactive with an antibody against PS1 (Fig. 3A). The PS1 immunoreactivity was most intense in perinuclear cytoplasmic regions consistent with a localization in the endoplasmic reticulum, a site where PS1 is concentrated in neurons (Guo et al., 1999a). CNPase immunoreactivity was present at high levels in the processes of the oligodendrocytes, consistent with it being membrane-associated (Fig. 3A). Aβ and excessive activation of glutamate receptors are believed to play roles in the degeneration of neurons in AD (Mattson et al., 1992; Mark et al., 1997). Because oligodendrocytes are also vulnerable to being killed by glutamate (Yoshioka et al., 1996), we determined whether mutant PS1 affects the vulnerability of oligodendrocytes to death induced by glutamate and Aβ1-42. Oligodendrocytes from PS1mutKI mice exhibited significant increases in vulnerability to both glutamate and Aβ1-42 during a 24-h exposure period compared to oligodendrocytes from wild-type mice (Fig. 3B,C).
An Abnormality of Oligodendrocyte Calcium Homeostasis Contributes to the Pathogenic Action of Mutant PS1 Studies of the effects of PS1 mutations on cultured cell lines and primary neurons have established an adverse effect of the mutations on cellular calcium homeostasis (Guo et al., 1999a, 1999b; Leissring et al., 2000). We measured intracellular free
Volume 3, 2003
NMM3/1,05,53-64,12gs
2/13/03 9:35 AM
Page 57
Presenilin, Amyloid, and Oligodendrocyte Damage
57
Fig. 1. Oligodendrocyte damage induced by cuprizone is increased in PS1 mutant knockin mice. (A) Coronal brain sections at the level of the anterior commissure showing CNPase immunoreactivity (an oligodendrocytespecific protein) in wild-type (WT) and PS1mutKI mice that had been maintained for 6 wk on the normal control diet or a diet containing 0.15% cuprizone. Note that the decrease in CNPase immunoreactivity in cuprizonetreated mice is greater in the PS1mutKI mice. (B) Relative amounts of CNPase immunoreactivity were quantified (see Methods) at 7 different rostro-caudal levels in WT and PS1mutKI mice that had been maintained for 6 wk on control or cuprizone-supplemented diets. Values are the mean and SEM (n=5 mice per group). *p<0.05, **p<0.01 compared to the value for group WT/cuprizone (ANOVA with Scheffe posthoc tests). Color image available for viewing at www.humanapress.com
NeuroMolecular Medicine
Volume 3, 2003
NMM3/1,05,53-64,12gs
2/13/03 9:35 AM
58
Page 58
Pak, Chan, and Mattson
Fig. 2. PS1 mutant knockin mice exhibit spatial memory deficits after treatment with the demyelinating agent cuprizone. Wild-type (WT) and PS1 mutant knockin (KI) mice that had been maintained for 6 wk on the normal diet or a diet containing 0.15% cuprizone were tested in the Morris water maze. (A) Values (mean of 5 mice/group) for goal latencies revealed a significant difference between group KI/cuprizone and each of the other groups of mice (p<0.01; ANOVA). (B) Following the goal latency trials on d 3, a probe trial was performed in which the platform was removed and the percentage of time the mouse spent in the target quadrant was determined. Values are the mean and SEM (n=5). **p<0.01 compared to each of the other 3 values (ANOVA with Scheffe post-hoc tests). (C) Cresyl violet-stained brain sections showing hippocampi of WT and PS1mutKI mice that had been fed control or cuprizone-containing diets for 6 wk. No evidence of neuronal loss was observed in WT or PS1mutKI mice fed cuprizone. Color image available for viewing at www.humanapress.com
NeuroMolecular Medicine
Volume 3, 2003
NMM3/1,05,53-64,12gs
2/13/03 9:35 AM
Page 59
Presenilin, Amyloid, and Oligodendrocyte Damage
59
Fig. 3. Oligodendrocytes from PS1 mutant knockin mice exhibit increased vulnerability to death induced by glutamate and amyloid β-peptide. (A) Confocal images showing immunoreactivity of cultured oligodendrocytes from wild-type and PS1mutKI mice with antibodies against PS1 (red) and CNPase (green). Oligodendrocytes exhibit PS1 immunoreactivity predominantly in perinuclear regions and CNPase immunoreactivity in processes. (B) Oligodendrocyte cultures from wild-type (WT) and PS1mutKI mice were exposed to saline (control) or 100 µM glutamate and cell survival was quantified 12 and 24 h later. Values are the mean and SEM of determinations made in 4–6 cultures. **p<0.01 compared to the WT/glutamate value (ANOVA with Scheffe post-hoc tests). (C) Oligodendrocyte cultures from wild-type (WT) and PS1mutKI mice were exposed to saline (control) or 5 µM Aβ1-42 and cell survival was quantified 12 and 24 h later. Values are the mean and SEM of determinations made in 4–6 cultures. *p<0.05, **p<0.01 compared to the WT,Abeta value (ANOVA with Scheffe posthoc tests). Color image also available for viewing at www.humanapress.com
calcium concentrations [Ca2+]i in oligodendrocytes from WT and PS1mutKI mice. Oligodendrocytes from PS1mutKI mice exhibited a significant elevation of resting [Ca2+]i (140 nM) compared to WT oligodendrocytes (70 nM) (Fig. 4A). Exposure of cul-
NeuroMolecular Medicine
tures to Aβ1-42 for 2 h resulted in significant increases in [Ca 2+ ] i in both WT (180 nM) and PS1mutKI (280 nM) oligodendrocytes (Fig. 4A). Glutamate induced a rapid elevation of [Ca2+]i, the magnitude of which was greatest in PS1mutKI
Volume 3, 2003
Fig. 4. Endangering effect of a PS1 mutation in oligodendrocytes results from perturbed cellular calcium homeostasis. (A) Oligodendrocytes from WT and PS1mutKI mice were exposed to saline (control) or 5 µM Aβ1-42 for 2 h. The intracellular free calcium concentration was then measured prior to and during exposure to 10 µM glutamate. Values are the mean and SEM of measurements made in 6 separate cultures (6–10 oligodendrocytes analyzed per culture). (B) Oligodendrocytes were pretreated for 30 min with 5 µM BAPTA-AM, 10 µM nimodipine, 10 µM dantrolene or 0.2% dimethylsulfoxide (control). The cells were then exposed to either 100 µM glutamate or 5 µM Aβ1-42 for 12 h and neuronal survival was quantified. Values are the mean and SEM of determinations made in 4–6 cultures. *p<0.05, ** p<0.01 compared to value for vehicle-treated cultures (ANOVA with Scheffe posthoc tests).
NMM3/1,05,53-64,12gs 2/13/03 9:35 AM
60
NeuroMolecular Medicine
Page 60
Pak, Chan, and Mattson
Volume 3, 2003
NMM3/1,05,53-64,12gs
2/10/03 11:15 AM
Page 61
Presenilin, Amyloid, and Oligodendrocyte Damage oligodendrocytes that had been pretreated with Aβ1-42. In an additional experiment, we found that [Ca2+]i responses to thapsigargin, an inhibitor of the endoplasmic reticulum calcium-ATPase, were significantly greater in PS1mutKI oligodendrocytes (peak response, 403 ± 14 nM) compared to WT oligodendrocytes (239 ± 17 nM). To determine whether elevation of [Ca2+]i was a critical event in the death of oligodendrocytes induced by glutamate and Aβ1-42, we treated oligodendrocytes with BAPTA-AM (an intracellular calcium chelator), nimodipine (a blocker of L-type voltage-dependent calcium channels), and dantrolene (an inhibitor of calcium release from ER stores). The survival of oligodendrocytes was significantly increased in cultures treated with BAPTA-AM, nimodipine, and dantrolene (Fig. 4B). These results suggest that calcium influx and release from ER contribute to the endangering effect of the PS1 mutation in oligodendrocytes.
Discussion Although dysfunction and degeneration of neurons is a prominent feature of AD that undoubtedly contributes to the cognitive impairment, abnormalities in glial cells may also play roles in the pathogenesis of AD. Our studies document an adverse effect of a PS1 mutation in oligodendrocytes which increases their vulnerability to death induced by the demyelinating toxin cuprizone, to the excitotoxin glutamate, and to Aβ1-42. The increased oligodendrocyte damage in PS1mutKI mice was associated with impaired spatial learning ability as documented in a water maze test. No deficits in spatial learning were observed in untreated PS1mutKI mice, in agreement with previous studies of PS1 mutant transgenic mice (Janus et al., 2000). We found no evidence of neuronal degeneration in cuprizonetreated PS1mutKI mice, consistent with previous studies of mice subjected to cuprizone in amounts as high or higher than that employed in the present study (Ludwin, 1978; Matsushima and Morrell, 2001). White matter damage has been repeatedly documented in studies of AD patients (Brun, 1989; Bronge, 2002), including a reduction in CNPase immunoreactivity (Vlkolinsky et al., 2001). However, no prior studies have provided evidence that such white matter abnormalities contribute to cog-
NeuroMolecular Medicine
61 nitive dysfunction. Learning and memory deficits can occur in rodents subjected to demyelinating insults that cause little or no neuronal damage, including a mouse model of metachromatic leukodystrophy caused by arylsulfatase A deficiency (D’Hooge et al., 2001) and TNF transgenic mice which exhibit demyelination and impaired performance in the Morris water maze (Aloe et al., 1999). The increased damage to oligodendrocytes in PS1mutKI mice treated with cuprizone may therefore underlie the impaired learning in these mice, although direct damage to synapses and neurons that were undetectable cannot be ruled out. Increased oxidative stress and overactivation of glutamate receptors may promote degeneration of neurons in AD (Mattson, 1997). Previous studies have shown that oligodendrocytes are vulnerable to being damaged and killed by oxidative stress and glutamate (Yoshioka et al., 1996; Back et al., 1998; Vollgraf et al., 2002). Our findings establish an adverse effect of a PS1 mutation in oligodendrocytes that increases their vulnerability to being killed by glutamate and Aβ1-42, suggesting that oligodendrocytes may be vulnerable to dysfunction and degeneration induced by oxidative stress and glutamate in AD (Fig. 5). In AD patients (Behrouz et al., 1990; Uchihara et al., 19953) and in APP/PS1 mutant transgenic mice (Kurt et al., 2001), Aβ is not only deposited in gray matter, but also in cortical and subcortical white matter. We found that oligodendrocytes are sensitive to being damaged and killed by Aβ1-42, consistent with a recent report that an 11 amino acid fragment of Aβ can kill cultured oligodendrocytes (Xu et al., 2001). Previous studies have shown that Aβ damages and kills neurons by a mechanism involving oxidative stress and disruption of calcium homeostasis (Mattson, 1997). We found that disruption of calcium homeostasis plays a major role in the killing of oligodendrocytes by Aβ1-42 (Fig. 4), and that antioxidants such as glutathione and vitamin E can protect oligodendrocytes against Aβ1-42 (data not shown). Collectively, these findings suggest that Aβ exerts adverse effects on oligodendrocytes by a mechanism similar to that by which it damages neurons. As is the case in neurons, high levels of glutamate can kill oligodendrocytes by inducing calcium influx through membrane receptor channels and voltagedependent calcium channels (Yoshioka et al., 1996; Alberdi et al., 2002). The abilities of nimodipine and
Volume 3, 2003
NMM3/1,05,53-64,12gs
2/13/03 9:35 AM
Page 62
62
Pak, Chan, and Mattson
Fig. 5. Model of the mechanisms of white matter damage in Alzheimer’s disease. Color image available for viewing at www.humanapress.com
dantrolene to protect oligodendrocytes against death induced by glutamate suggest a central role for cellular calcium overload in the pathogenic action of mutant PS1 in oligodendrocytes. Previous studies of the pathogenic actions of PS1 mutations in neurons and cultured cell lines have established an abnormality in calcium regulation which results in excessive release of calcium from endoplasmic reticulum stores (Guo et al., 1999a; Leissring et al., 2000). Oligodendrocytes express ryanodine-sensitive endoplasmic reticulum calcium release channels (Simpson et al., 1998), and the ability of dantrolene to protect oligodendrocytes suggests a role for such channels in the pathogenic action of the PS1 mutation in oligodendrocytes. In addition to their role in myelinating axons which increases conduction velocity, oligodendrocytes serve other important functions. For example, they produce neurotrophic factors (Wilkins et al., 2001; Du and Dreyfus, 2002) and modulate ion homeostasis in the local environment of axons
NeuroMolecular Medicine
(Robert and Jirounek, 1994). Adverse effects of Aβ and PS1 mutations on such functions of oligodendrocytes might therefore be expected to promote axonal dysfunction and degeneration. Indeed, axonal degeneration occurs in myelin disorders and in animal models of autoimmune-mediated demyelination (Bjartmar et al., 1999; Onuki et al., 2001). Some of the neurons that degenerate in AD have myelinated axons. For example, among hippocampal neurons, CA1 pyramidal neurons are the most vulnerable in AD (Arriagada et al., 1992) and also exhibit the greatest amount of myelination of their axons (Atkins and Sweatt, 1999). Many of the neurons that degenerate in AD in cortical regions that provide input to the hippocampus also have myelinated axons (Benes, 1989). The adverse effects of a presenilin mutation on oligodendrocytes described in the present study therefore suggest a possible role for oligodendrocyte damage and axonal dysfunction early in the course of the disease process.
Volume 3, 2003
NMM3/1,05,53-64,12gs
2/10/03 11:15 AM
Page 63
Presenilin, Amyloid, and Oligodendrocyte Damage
Acknowledgments We thank J. Mackes for assistance with behavioral analyses and B. Kabbingu for assistance in preparing cell cultures.
References Alberdi E., Sanchez-Gomez M. V., Marino A., and Matute C. (2002) Ca(2+) influx through AMPA or kainate receptors alone is sufficient to initiate excitotoxicity in cultured oligodendrocytes. Neurobiol. Dis. 9, 234–243. Aloe L., Properzi F., Probert L., et al. (1999) Learning abilities, NGF and BDNF brain levels in two lines of TNF-alpha transgenic mice, one characterized by neurological disorders, the other phenotypically normal. Brain Res. 840, 125–137. Arnett H. A., Mason J., Marino M., et al. (2001) TNF alpha promotes proliferation of oligodendrocyte progenitors and remyelination. Nat. Neurosci. 4, 1116–1122. Arriagada P. V., Marzloff K., and Hyman B. T. (1992) Distribution of Alzheimer-type pathologic changes in nondemented elderly individuals matches the pattern in Alzheimer’s disease. Neurology 42, 1681–1688. Atkins C.M. and Sweatt J. D. (1999) Reactive oxygen species mediate activity-dependent neuron-glia signaling in output fibers of the hippocampus. J. Neurosci. 19, 7241–7248. Back S. A., Gan X., Li Y., Rosenberg P. A., and Volpe J. J. (1998) Maturation-dependent vulnerability of oligodendrocytes to oxidative stress-induced death caused by glutathione depletion. J. Neurosci. 18, 6241–6253. Behrouz N., Defossez A., Delacourte A., and Mazzuca M. (1990) Alzheimer’s disease: the beta amyloid protein A4 is also present in the cortical white matter. C. R. Acad. Sci. III. 310, 539–544. Benes F. M. (1989) Myelination of cortical-hippocampal relays during late adolescence. Schizophr. Bull. 15, 585–593. Bjartmar C., Yin X., and Trapp B. D. (1999) Axonal pathology in myelin disorders. J. Neurocytol. 28, 383–395. Bronge L. (2002) Magnetic resonance imaging in dementia. A study of brain white matter changes. Acta. Radiol. Suppl. 428, 1–32. Bruce-Keller A. J., Geddes J. W., Knapp P. E., et al. (1999) Anti-death properties of TNF against meta-
NeuroMolecular Medicine
63 bolic poisoning: mitochondrial stabilization by MnSOD. J. Neuroimmunol. 93, 53–71. Brun A. (1989) Structural changes in ageing and dementia of Alzheimer’s type with special reference to recent etiologic and therapeutic theories. Prog. Clin. Biol. Res. 317, 285–293. Byravan S., Foster L. M., Phan T., et al. (1994) Murine oligodendroglial cells express nerve growth factor. Proc. Natl. Acad. Sci. USA 91, 8812–8816. D’Hooge R., Van Dam D., Franck F., et al. (2001) Hyperactivity, neuromotor defects, and impaired learning and memory in a mouse model for metachromatic leukodystrophy. Brain Res. 907, 35–43. DeKosky S. T. (2001) Epidemiology and pathophysiology of Alzheimer’s disease. Clin. Cornerstone 3, 15–26. Du Y. and Dreyfus C. F. (2002) Oligodendrocytes as providers of growth factors. J. Neurosci. Res. 68, 647–654. Guo Q., Sopher B. L., Furukawa K., et al. (1997) Alzheimer ’s presenilin mutation sensitizes neural cells to apoptosis induced by trophic factor withdrawal and amyloid beta-peptide: involvement of calcium and oxyradicals. J. Neurosci. 17, 4212–4222. Guo Q., Fu W., Sopher B. L., et al. (1999a) Increased vulnerability of hippocampal neurons to excitotoxic necrosis in presenilin-1 mutant knock-in mice. Nat. Med. 5, 101–106. Guo Q., Sebastian L., Sopher B. L., et al. (1999b) Neurotrophic factors [activity-dependent neurotrophic factor (ADNF) and basic fibroblast growth factor (bFGF)] interrupt excitotoxic neurodegenerative cascades promoted by a PS1 mutation. Proc. Natl. Acad. Sci. USA 96, 4125–4130. Hiremath M. M., Saito Y., Knapp G. W., et al. (1998) Microglial/macrophage accumulation during cuprizone-induced demyelination in C57BL/6 mice. J. Neuroimmunol. 92, 38–49. Holcomb L. A., Gordon M. N., Jantzen P., et al. (1999) Behavioral changes in transgenic mice expressing both amyloid precursor protein and presenilin-1 mutations: lack of association with amyloid deposits. Behav. Genet. 29, 177–185. Janus C., D’Amelio S., Amitay O., et al. (2000) Spatial learning in transgenic mice expressing human presenilin 1 (PS1) transgenes. Neurobiol. Aging 21, 541–549. Jurevics H., Hostettler J., Muse E. D., et al. (2001) Cerebroside synthesis as a measure of the rate of remyeli-
Volume 3, 2003
NMM3/1,05,53-64,12gs
2/10/03 11:15 AM
Page 64
64 nation following cuprizone-induced demyelination in brain. J. Neurochem. 77, 1067–1076. Kim S. U., McMorris F. A., and Sprinkle T. J. (1984) Immunofluorescence demonstration of 2′3′cyclic-nucleotide 3′-phosphodiesterase in cultured oligodendrocytes of mouse, rat, calf and human. Brain Res. 300, 195–199. Kurt M. A., Davies D. C., Kidd M., et al. (2001) Neurodegenerative changes associated with betaamyloid deposition in the brains of mice carrying mutant amyloid precursor protein and mutant presenilin-1 transgenes. Exp. Neurol. 171, 59–71. Leissring M. A., Akbari Y., Fanger C. M., et al. (2000) Capacitative calcium entry deficits and elevated luminal calcium content in mutant presenilin-1 knockin mice. J. Cell Biol. 149, 793–798. Ludwin S. K. (1978) Central nervous system demyelination and remyelination in the mouse: an ultrastructural study of cuprizone toxicity. Lab. Invest. 39, 597–612. Mark R. J., Pang Z., Geddes J. W., et al. (1997) Amyloid beta-peptide impairs glucose transport in hippocampal and cortical neurons: involvement of membrane lipid peroxidation. J. Neurosci. 17, 1046–1054. Matsushima G. K. and Morell P. (2001) The neurotoxicant, cuprizone, as a model to study demyelination and remyelination in the central nervous system. Brain Pathol. 11, 107–116. Mattson M. P. (1997) Cellular actions of β-amyloid precursor protein, and its soluble and fibrillogenic peptide derivatives. Physiol. Rev. 77, 1081–1132. Mattson M. P., Cheng B., Davis D., et al. (1992) betaAmyloid peptides destabilize calcium homeostasis and render human cortical neurons vulnerable to excitotoxicity. J. Neurosci. 12, 376–389. Miake H., Tsuchiya K., Nakamura A., et al. (1999) Glial expression of presenilin epitopes in human brain with cerebral infarction and in astrocytoma. Acta Neuropathol. 98, 337–340. Onuki M., Ayers M. M., Bernard C. C., and Orian J. M. (2001) Axonal degeneration is an early pathological feature in autoimmune-mediated demyelination in mice. Microsc. Res. Tech. 52, 731–739. Price D. L., Tanzi R. E., Borchelt D. R., and Sisodia S. S. (1998) Alzheimer’s disease: genetic studies and transgenic models. Annu. Rev. Genet. 32, 461–493. Reynolds R., Carey E. M., and Herschkowitz N. (1989) Immunohistochemical localization of myelin basic protein and 2′,3′-cyclic nucleotide 3′-phosphohydrolase in flattened membrane expansions pro-
NeuroMolecular Medicine
Pak, Chan, and Mattson duced by cultured oligodendrocytes. Neuroscience 28, 181–188. Robert A. and Jirounek P. (1994) Uptake of potassium by nonmyelinating Schwann cells induced by axonal activity. J. Neurophysiol. 72, 2570–2579. Rosselli M. C., Ardila A. C., Moreno S. C., et al. (2000) Cognitive decline in patients with familial Alzheimer’s disease associated with E280a presenilin-1 mutation: a longitudinal study. J. Clin. Exp. Neuropsychol. 22, 483–495. Scholtz C. L. (1977) Quantitative histochemistry of myelin using Luxol Fast Blue MBS. Histochem. J. 9, 759–765. Simpson P. B., Holtzclaw L. A., Langley D. B., and Russell J. T. (1998) Characterization of ryanodine receptors in oligodendrocytes, type 2 astrocytes, and O-2A progenitors. J. Neurosci. Res. 52, 468–482. Uchihara T., Kondo H., Akiyama H., and Ikeda K. (1995) White matter amyloid in Alzheimer’s disease brain. Acta Neuropathol. 90, 51–56. Vabnick I. and Shrager P. (1998) Ion channel redistribution and function during development of the myelinated axon. J. Neurobiol. 37, 80–96. Vlkolinsky R., Cairns N., Fountoulakis M., and Lubec G. (2001) Decreased brain levels of 2′,3′-cyclic nucleotide-3′-phosphodiesterase in Down syndrome and Alzheimer’s disease. Neurobiol. Aging 22, 547–553. Vollgraf U., Wegner M., and Richter-Landsberg C. (2002) Activation of AP-1 and nuclear factorkappaB transcription factors is involved in hydrogen peroxide-induced apoptotic cell death of oligodendrocytes. J. Neurochem. 73, 2501–2509. Weggen S., Diehlmann A., Buslei R., et al. (1998) Prominent expression of presenilin-1 in senile plaques and reactive astrocytes in Alzheimer ’s disease brain. Neuroreport 9, 3279–3283. Wilkins A., Chandran S., and Compston A. (2001) A role for oligodendrocyte-derived IGF-1 in trophic support of cortical neurons. Glia 36, 48–57. Xia M. Q., Berezovska O., Kim T. W., et al. (1998) Lack of specific association of presenilin 1 (PS-1) protein with plaques and tangles in Alzheimer’s disease. J. Neurol. Sci. 158, 15–23. Xu J., Chen S., Ahmed S. H., et al. (2001) Amyloid-beta peptides are cytotoxic to oligodendrocytes. J. Neurosci. 21, RC118. Yoshioka A., Bacskai B., and Pleasure D. (1996) Pathophysiology of oligodendroglial excitotoxicity. J. Neurosci. Res. 46, 427–437.
Volume 3, 2003