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The Journal of Neuroscience, March 1, 2002, 22(5):1592-1599
Therapeutic Effects of Coenzyme Q10 and Remacemide in
Transgenic Mouse Models of Huntington's Disease
Robert J.
Ferrante1, 2,
Ole A.
Andreassen3,
Alpaslan
Dedeoglu1, 2,
Kimberly L.
Ferrante5,
Bruce G.
Jenkins4,
Steven
M.
Hersch6, and
M. Flint
Beal5
1 Geriatric Research Education and Clinical Center,
Bedford Veterans Administration Medical Center, Bedford,
Massachusetts 01730, 2 Neurology, Pathology, and Psychiatry
Departments, Boston University School of Medicine, Boston,
Massachusetts 02118, 3 Neurochemistry Laboratory, Neurology
Service, and 4 Department of Radiology, Massachusetts
General Hospital and Harvard Medical School, Boston, Massachusetts
02114, 5 Department of Neurology and Neuroscience, Weill
Medical College of Cornell University, New York Presbyterian Hospital,
New York, New York 10021, and 6 Center for Aging, Genetics
and Neurodegeneration, Neurology Service, Massachusetts General
Hospital and Harvard Medical School, Boston, Massachusetts 02114
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ABSTRACT |
There is substantial evidence that bioenergetic defects and
excitotoxicity may play a role in the pathogenesis of Huntington's disease (HD). Potential therapeutic strategies for neurodegenerative diseases in which there is reduced energy metabolism and
NMDA-mediated excitotoxicity are the administration of the
mitochondrial cofactor coenzyme Q10 and the NMDA antagonist
remacemide. We found that oral administration of either coenzyme
Q10 or remacemide significantly extended survival and
delayed the development of motor deficits, weight loss, cerebral
atrophy, and neuronal intranuclear inclusions in the R6/2 transgenic
mouse model of HD. The combined treatment, using coenzyme
Q10 and remacemide together, was more efficacious than
either compound alone, resulting in a ~32 and 17% increase in
survival in the R6/2 and N171-82Q mice, respectively. Magnetic resonance imaging showed that combined treatment significantly attenuated ventricular enlargement in vivo. These
studies further implicate defective energy metabolism and
excitotoxicity in the R6/2 and N171-82Q transgenic mouse models of HD
and are of interest in comparison with the outcome of a recent clinical
trial examining coenzyme Q10 and remacemide in HD patients.
Key words:
Huntington's disease; excitotoxicity; coenzyme
Q10; remacemide; mitochondria; transgenic
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INTRODUCTION |
The mechanism of neuronal
degeneration in Huntington's disease (HD) remains unknown, despite the
identification of the disease-causing genetic defect as an expansion of
a polyglutamine tract in the protein huntingtin (The Huntington's
Disease Collaborative Research Group, 1993 ). The evidence suggests that
the polyglutamine expansion confers a gain of function that in turn may
be related to effects on gene transcription (Lin et al., 2000 ;
Luthi-Carter et al., 2000 ). The effects on gene transcription may be
linked to energy dysfunction and excitotoxicity, which are implicated
in the pathogenesis of HD (Beal, 2000 ).
There is substantial evidence linking impaired energy metabolism to HD.
Consistent with this, we and others found the following: (1) lactate is
elevated in the cerebral cortex in basal ganglia of patients with HD
(Jenkins et al., 1993 ); (2) the phosphocreatine to inorganic phosphate
ratio is reduced in resting muscle of HD patients (Koroshetz et al.,
1997 ); (3) mitochondrial toxins produce selective damage in the
striatum of animals that closely resembles the pathology of HD (Beal et
al., 1993a ; Brouillet et al., 1995 ); and (4) there are reductions in
mitochondrial electron transport enzymes in HD postmortem (Gu et al.,
1996 ; Browne et al., 1997 ). Recent studies showed that mitochondria in
HD lymphoblasts and fibroblasts show an increased susceptibility to
depolarization that correlates directly with CAG repeat length (Sawa et
al., 1999 ). The maximal rate of mitochondrial ATP generation in muscle is significantly reduced in both symptomatic HD patients and
presymptomatic HD gene carriers, which correlates with CAG repeat
length (Lodi et al., 2000 ).
In addition, there is also substantial evidence linking excitotoxicity
to HD pathogenesis. Initial studies showed that kainic acid lesions
replicated many pathologic features of HD (McGeer and McGeer, 1976 ;
Schwarcz and Coyle, 1976 ). Subsequent studies with the NMDA agonist
quinolinic acid showed that it could more accurately model HD because
it produces relative sparing of NADPH-diaphorase neurons, which are
spared in HD (Beal et al., 1986 ; Ferrante et al., 1993 ). The
mitochondrial toxins malonate and 3-nitropropionic acid also produce
striatal lesions that mimic HD and are mediated by excitotoxic
mechanisms (Beal et al., 1993b ; Greene et al., 1993 ; Brouillet et al.,
1995 ). Both NMDA antagonists, as well as coenzyme
Q10, block striatal lesions produced by malonate
(Beal et al., 1993b , 1994 ; Greene et al., 1993 ). Furthermore, there are
additive neuroprotective effects of NMDA antagonists with coenzyme
Q10 (Schulz et al., 1996 ).
A major advance for studying disease pathogenesis and developing
therapeutics has been the introduction of transgenic mouse models of
HD. Transgenic mice expressing exon-1 of the human HD gene with an
expanded CAG repeat and transgenic mice (N171-82Q) expressing a cDNA
encoding a 171 amino acid N-terminal fragment of huntingtin containing
82 CAG repeats develop a progressive neurological disorder (Mangiarini
et al., 1996 ; Schilling et al., 1999 ). At ~6 weeks of age, the R6/2
mice develop loss of brain and body weight, and at 9-11 weeks they
develop an irregular gait, abrupt shuttering stereotypic movements,
resting tremors, and epileptic seizures. The brains of the R6/2 mice
show striatal atrophy and neuronal intranuclear inclusions that are
immunopositive for huntingtin and ubiquitin (Davies et al., 1997 ). The
N171-82Q mice show similar findings, but these mice have a more
delayed disease onset and longer survival (Schilling et al., 1999 ). In the present experiments, we examined whether oral administration of
coenzyme Q10 and remacemide either alone or in
combination could exert beneficial effects in the R6/2 and N171-82Q
mouse models of HD.
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MATERIALS AND METHODS |
Animals. Male transgenic HD mice of the R6/2 strain
were obtained from Jackson Laboratories (Bar Harbor, ME). The male R6/2 mice were bred with females from their background strain (B6CBAFI/J) for two generations. Male transgenic mice of the N171-82Q strain were
originally obtained from Drs. Ross and Borchelt (The Johns Hopkins University) and backcrossed to the B6CBA background through 15 generations. The offspring were genotyped using a PCR assay on tail
DNA. The mice were housed four to five in each cage under standard
conditions with ad libitum access to water and food. All
animal experiments were performed in accordance with the NIH Guide for the Care and Use of Laboratory Animals and were
approved by both the Veterans Administration and Boston University
Animal Care Committees.
Treatment. At 21 d of age, R6/2 and littermate
wild-type control mice were placed on either an unsupplemented diet or
a diet supplemented with 0.2% coenzyme Q10
(Vitaline, Ashland, OR) or 0.007% remacemide (Astra) or a combination
of the two within the same pellet. Forty mice from the same
generation were placed within each of the treatment groups. Groups were
randomly pooled from multiple liters (six to eight) to ensure
heterogeneity. N171-82Q mice were placed on the combination diet
alone. In all, behavioral and survival data were obtained from ~320
R6/2 mice and 160 N171-82Q mice. The diets were made into pelleted
mouse chow (Purina Test Diets, Richmond, IN). The amount of food intake
per mouse was found to be 4-5 gm/d, with no significant difference
between treated and untreated mice. The calculated dose for coenzyme
Q10 was 400 mg · kg 1 · d 1
and 14 mg · kg 1 · d 1
for remacemide. During the temporal progress of the disease, the food
consumed per gram of mouse weight was stable until end stage (12-14
weeks) in both the R6/2 and N171-82Q mice.
Behavior and weight assessment. Motor performance was
assessed weekly from 21-63 d of age and twice weekly from 63-90 d of age in the R6/2 mice. The mice were given two training sessions to
acclimate them to the rotarod apparatus (Columbus Instruments, Columbus, OH). During testing, the mice were placed on a rod rotated at
16 rpm. Each mouse had three separate trials at 60 sec each. The
maximum score was 180 sec. The combined total length of time remaining
on the rod was based as the measure of competency.
Survival. Mice were observed twice daily. The criterion for
euthanization was the point in time at which the mice were unable to
initiate movement after being gently prodded for 2 min. Mice had lost
~40-50% of their body weight at this time point. Two independent
observers confirmed the criterion for euthanization. This time point
was identified as the time of death. Mice from both genders were
equally included in the experimental paradigm. We have not experienced
gender differences in survival in either transgenic HD mouse model.
Mice dying prematurely (<70 d) were excluded from the study.
Nuclear magnetic resonance. Untreated
and coenzyme Q10/ remacemide-treated R6/2
and littermate wild-type mice were anesthetized using
halothane/N2O/O2 anesthesia
(0.75-1% halothane; 2:1
O2/N2O). Body temperature
was maintained using two water blankets surrounding the body at 38°C.
Nuclear magnetic resonance (NMR)-T2-weighted magnetic resonance
images were acquired with a repetition time/echo time of 3000/60 msec
and a field of view of 32 mm (256 × 128 matrix size) and 1 mm
slice thickness. A total of 5 untreated and 11 coenzyme
Q10/remacemide-treated animals were evaluated.
Mean age of the animals was 83.6 ± 4.2 versus 83.4 ± 6.1 d for the treated and untreated groups, respectively.
NMR data analysis. NMR-derived ventricular volumes were
measured using home-written software. Mean signal intensity in the striatum and cortex surrounding the ventricles was measured in the
T2-weighted images. Then the outline of the ventricles was segmented
from the tissue using a threshold of 3 SDs above the mean signal
intensity in the brain tissue. The ventricle size was measured in the
lateral ventricle and dorsal third ventricles only.
Histology evaluation. At 21 d, R6/2 transgenic mice and
negative littermate controls were fed diets containing 0.2% coenzyme Q10 or 0.007% remacemide, or the combination.
Groups of 20 animals from each treatment paradigm were deeply
anesthetized and then transcardially perfused with 4% buffered
paraformaldehyde at 63 and 90 d. Approximately 250 mice were used
for data collection in the neuropathological analysis. The brains were
removed, post-fixed with the perfusant for 2 hr, weighed, cryoprotected
in a graded series of 10 and 20% glycerol/2% DMSO solution, serially
frozen sectioned at 50 µm, stored in six-well tissue collection
clusters, and stained for Nissl substance (cresyl violet). Serially cut tissue sections were immunostained for huntingtin using an antibody (EM48; dilution, 1:1000) that recognizes the first 256 amino acids of
human huntingtin lacking the polyglutamine and polypeptide stretches
(Kuemmerle et al., 1999 ). The antibody reacts with N-terminal fragments
of huntingtin expressed by transfection. An antibody to ubiquitin
(dilution, 1:200; Dako, Carpinteria, CA) was also used in selected
tissue sections to confirm the presence of aggregates.
Stereology and quantitation. Serial-cut coronal tissue
sections from the rostral segment of the neostriatum at the level of the anterior commissure (interaural 5.34 mm/bregma 1.54 mm to interaural 3.7 mm/bregma 0.10 mm) (Franklin and Paxinos, 1997 ) were used for huntingtin aggregate analysis. Unbiased stereologic counts of huntingtin-positive aggregates ( 1.0 µm) were obtained from the neostriatum and layer 6 of the neocortex in 10 mice fed unsupplemented and supplemented diets containing the combination treatment of coenzyme Q10 and remacemide at 63 and 91 d, using Neurolucida Stereo Investigator software
(Microbrightfield, Colchester, VT). The total areas of the neostriatum
and motor cortex were defined from serial sections in which counting
frames were sampled randomly. The dissector counting method was used in
which huntingtin-positive aggregates were counted from an unbiased
selection of serial sections in a defined volume of the neostriatum.
Striatal neuron areas were analyzed by microscopic video capture using
a Windows-based image analysis system for area measurement (Optimas,
Bioscan Incorporated, Edmonds, WA). The software automatically
identifies and measures profiles. All computer-identified cell profiles
were manually verified as neurons and exported to Microsoft Excel.
Cross-sectional areas were analyzed using Statview.
Statistics. The data are expressed as the mean ± SEM.
Statistical comparisons of rotarod, weight data, and histological data were compared by ANOVA or repeated measures ANOVA. Survival data were
analyzed using the Mantel-Cox log-rank test and Kaplan-Meier survival curves.
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RESULTS |
The effects of oral administration of coenzyme
Q10, remacemide, and combined dietary supplement
of coenzyme Q10 and remacemide in the diet on
survival in the R6/2 and N171-82Q transgenic mice are shown in Figure
1. All three treatment paradigms
significantly improved survival. The mean survival in coenzyme
Q10-treated R6/2 mice increased by 14.5%
(coenzyme Q10: 112.9 ± 2.0 d;
unsupplemented: 96.5 ± 1.8 d; p < 0.001).
The percentage increase in survival using remacemide in the diet was
15.5% (remacemide: 114.2 ± 2.4 d; unsupplemented: 96.5 ± 1.8 d; p < 0.001). The combined treatment using both coenzyme Q10 and remacemide was
significantly more efficacious than either compound alone
(p < 0.001) and extended survival in the R6/2
mice by 31.8% (coenzyme Q10/remacemide:
127.2 ± 3.1 d; unsupplemented: 96.5 ± 1.8 d;
p < 0.0001). This increase was more than twice that
observed using either compound separately and is several times greater
than other treatment strategies tested in R6/2 mice to date. Combined
treatment in the N171-82Q mice also resulted in a significant
extension of survival (coenzyme Q10/remacemide:
153.3 ± 13.7 d; unsupplemented: 127.4 ± 11.7 d; p < 0.05). These findings suggest that multiple
compounds directed at different mechanistic targets may have additive
effects on outcome measures.

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Figure 1.
Kaplan-Meier survival curves showing the effects
of coenzyme Q10, remacemide, and the combination of
coenzyme Q10 and remacemide on cumulative survival in R6/2
transgenic mice (A) and the combined therapy in
N171-82Q transgenic mice. Although both coenzyme Q10 and
remacemide equally improved survival in the R6/2 mice
(p < 0.001), the combination treatment was
more than twice that of either compound alone
(p < 0.0001). Although the combined therapy
significantly extended survival in the N171-82Q mice
(p < 0.05), the significance value was much
lower because of marked variability in this murine model of
Huntington's disease. CoQ, Coenzyme
Q10.
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Oral administration of coenzyme Q10, remacemide,
and the combined coenzyme Q10/remacemide
supplement significantly improved motor performance in the R6/2 mice
(Fig. 2A). In contrast
to unsupplemented R6/2 mice, dietary coenzyme Q10
supplementation significantly improved rotarod performance throughout
the measured life span of the R6/2 mice (coenzyme
Q10: 134.1 ± 19.5 sec; unsupplemented: 92.8 ± 19.0 sec; p < 0.01; data represent
combined means and SDs from 4-13 wks). Dietary supplementation with
remacemide also resulted in significant motor improvement throughout
the 4-13 week period, showing greater improved motor behavior than
with coenzyme Q10 (remacemide: 143.6 ± 17 sec; unsupplemented: 92.8 ± 19.0 sec; p < 0.001;
data represent combined means and SDs from 4-13 wks). In comparison
with coenzyme Q10 or remacemide alone, the
combined coenzyme Q10/remacemide treatment showed
the greatest improvement in motor behavior (coenzyme
Q10/remacemide: 150.5 ± 15.0 sec; unsupplemented: 92.8 ± 19.0 sec; p < 0.001; data
represent combined means and SDs from 4-13 wks). Motor performance of
the wild-type littermate control mice was ~180 sec throughout the
duration of the testing. The percentage increase in rotarod performance
for coenzyme Q10, remacemide, and combined diet
supplementation with both coenzyme Q10 and
remacemide was 44.5, 54.7, and 62.2%, respectively, which is greater
than the effect of 2% creatine supplementation (33%) that we reported
previously (Ferrante et al., 2000 ).

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Figure 2.
Effects of coenzyme
Q10, remacemide, and the combination of coenzyme
Q10 and remacemide on rotarod performance in R6/2
transgenic mice (A). All three treatments
significantly improved motor performance throughout the extent of the
lifespan of the mice. The combined treatment was more efficacious than
either treatment alone. Effects of coenzyme Q10,
remacemide, and the combination of coenzyme Q10 and
remacemide resulted in significant attenuation of body weight loss in
comparison with the unsupplemented R6/2 mice (B).
The combined oral supplement resulted in less weight loss than either
compound separately in the R6/2 transgenic mice. There was a
significant reduction in weight loss from 9 and 7 weeks in the
separate compound trials and combined treatment, respectively
(p < 0.05; p < 0.01).
The combined oral supplement resulted in a significant attenuation of
weight loss in the N171-82Q mice at ~15 weeks and continued
throughout the remaining lifespan (C).
CoQ, Coenzyme Q10.
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The effects of oral administration of coenzyme
Q10, remacemide, and the combined dietary
supplement of coenzyme Q10 and remacemide on body
weight in R6/2 and N171-82Q transgenic mice are shown in Figure 2,
B and C. Although all three dietary regimens
resulted in significant attenuation of body weight loss in comparison
with the unsupplemented R6/2 mice, the combined coenzyme
Q10 and remacemide treatment resulted in less
body weight loss than either coenzyme Q10 or
remacemide treatment alone, again suggesting an additive effect.
Significant body weight improvement began at 9 weeks for both coenzyme
Q10 and remacemide and at 7 weeks for the
combined coenzyme Q10 and remacemide treatment
and continued throughout the course of the study until death. The total
percentage increase in body weight from 4 to 14 weeks for coenzyme
Q10, remacemide, and combined diet in R6/2
animals in comparison with unsupplemented R6/2 mice was 12.7, 10.1, and
20.3%, respectively. Although no significant differences were observed
between coenzyme Q10 and remacemide, significance
was found between combined coenzyme Q10 and
remacemide treatment and either coenzyme Q10 or
remacemide alone (p < 0.01). The combined
treatment also resulted in a significant attenuation of body weight
loss in N171-82Q mice (Fig. 2C) beginning at 110 d and
continuing throughout the course of treatment until death. The total
increase in body weight of treated mice from 3 to 21 weeks was 7.9%
greater than that of unsupplemented N171-82Q mice.
We reported previously that the brain weight of R6/2 mice decreases
significantly over time until death (Ferrante et al., 2000 ). Coenzyme
Q10, remacemide, and the combined dietary
supplement of coenzyme Q10 and remacemide delayed
brain weight loss in the R6/2 mice in comparison with their littermate
control mice (Table 1). A significant
decrease in brain weight was delayed using each of the treatment
paradigms until late in the disease process in the R6/2 mice. Although
less brain weight loss was observed in the combined dietary supplement
than in either coenzyme Q10 or remacemide alone,
no significant differences were found between any of the three
therapeutic strategies. At 13 weeks, there was a 16.1, 16.9, and 17.5%
delayed brain weight loss in remacemide, coenzyme
Q10, and the combined dietary supplement of
coenzyme Q10 and remacemide, respectively, in the
R6/2 mice as compared with unsupplemented R6/2 mice. The marked gross
brain atrophy and ventricular enlargement in the unsupplemented R6/2
mice was attenuated using each treatment, especially with the coenzyme Q10 and remacemide combination (Fig.
3). NMR in vivo imaging
confirmed these findings in the unsupplemented and coenzyme
Q10/remacemide-treated R6/2 mice (Fig.
4). The average ventricle size in the
coenzyme Q10/remacemide mice at 12 weeks of age
was 13.6 ± 6.6 and 20.9 ± 3.5 mm3 in the untreated mice
(p < 0.03) and 3.4 ± 0.2 mm3 in control mice.

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Figure 3.
Effects of the combined treatment of coenzyme
Q10 and remacemide on gross atrophy and ventricular
enlargement in R6/2 mice at 13 weeks. In comparison with a littermate
nonmutant transgene mouse (A), marked gross
atrophy and enlarged lateral ventricles are evident in the
unsupplemented R6/2 mouse (B) in coronal sections
at the rostral level of the anterior commissure. Less atrophy and
ventricular enlargement are seen in the supplemented mouse
(C). Scale bar (shown in A): 2 mm.
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Figure 4.
A, Selected T2-weighted
images from four consecutive 1 mm slices in both a coenzyme
Q10/remacemide-treated and an untreated animal. Note
the much larger ventricles in the untreated animals. B,
Bar graph of the effect of coenzyme
Q10/remacemide treatment on ventricular size in the
HD mice. CoQ, Coenzyme Q10;
Rem, remacemide; Untreat,
untreated.
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Consistent with the brain weight loss and gross atrophy, striatal
neuron atrophy is present in the R6/2 mice with a ~38% overall decrease in area measurements (Ferrante et al., 2000 ). The
neuroprotective effect of coenzyme Q10 and
remacemide together significantly delayed striatal neuron atrophy at
91 d of age (wild-type littermate control: 120.9 ± 9.6 µm2; unsupplemented R6/2: 58.3 ± 14.7 µm2; coenzyme
Q10: 89.1 ± 14.3 µm2; remacemide: 89.7 ± 12.3 µm2; coenzyme
Q10/remacemide supplemented R6/2: 108.9 ± 12.4 µm2; p < 0.001)
(Fig. 5). Neuronal atrophy was present in
all the treated mice at end stage disease.

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Figure 5.
Photomicrographs of Nissl-stained tissue sections
from the dorsomedial aspect of the neostriatum in a littermate
nonmutant transgene mouse (A), unsupplemented
R6/2 mouse (B), and a combined coenzyme
Q10 and remacemide-treated R6/2 mouse
(C) at 91 d of age. There is marked neuronal
atrophy with small angulated neurons in the unsupplemented mouse
(B), with relative preservation of neuronal size
and number in the treated mouse (C). Scale bar
(shown in A): 100 µm.
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Huntingtin-positive aggregate formation is an early and progressive
process throughout the brains of R6/2 mice. These aggregates increase in both size and number with age. Dietary supplementation with
combined treatment of coenzyme Q10 and remacemide
resulted in significant reductions of striatal aggregate number.
Aggregate counts within the striatum at 9 and 13 week time points were
significantly reduced in comparison with untreated R6/2 mice
(p < 0.01) (Figs. 6, 7).
There was an 8.2 and 15.7% decrease in striatal volume loss at 9 and
13 weeks, respectively, in the combined treatment as compared with the
untreated R6/2 mice in the estimated area of rostral striatum measured
(striatal volumes, untreated 9 and 13 weeks: 12.8 and 10.9 mm3). The percentage decrease in aggregate
number in treated mice was 32 and 36% at those same time points
[estimated striatal huntingtin (htt) aggregates, untreated 9 and 13 weeks: 363 × 103 and 530 × 103; combined coenzyme
Q10 and remacemide, 9 and 13 weeks: 275 × 103 and 390 × 103].

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Figure 6.
Graph of the number of huntingtin-positive
aggregates in the neostriatum at 9 and 13 weeks in unsupplemented
(unsup) and combined coenzyme Q10 and
remacemide-treated (CoQ/Rem) R6/2 mice. There was a
significant (p < 0.01) delay in the
formation of aggregates within the neostriatum in the combined
treatment mice at both time points, in comparison with the
unsupplemented mice.
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Figure 7.
Photomicrographs of immunostained
huntingtin tissue sections from the dorsomedial aspect of the
neostriatum at the rostral level of the anterior commissure in combined
coenzyme Q10 and remacemide-treated and unsupplemented R6/2
mice at 9 weeks (A and B, respectively)
and at 13 weeks (C and D, respectively).
There are significantly fewer huntingtin-positive aggregates in treated
mice at 9 and 13 weeks (A, C) in
comparison with the unsupplemented mice at the same time points
(B, D). Scale bar (shown in
D): 100 µm.
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DISCUSSION |
Previous work has shown that both coenzyme
Q10 and remacemide exert neuroprotective effects.
Coenzyme Q10 is an essential cofactor of electron
transport chain where it accepts electrons from complexes I and II
(Beyer, 1992 ). Coenzyme Q10 also serves as an
important antioxidant in both mitochondria and lipid membranes (Beyer,
1992 ; Noack et al., 1994 ). Coenzyme Q10
administration significantly increases brain mitochondrial
concentrations of coenzyme Q10 in mature and
older animals (Matthews et al., 1998 ). Administration of coenzyme
Q10 also increases -tocopherol concentrations in mitochondria, consistent with a sparing effect (Lass et al., 1999 ).
Coenzyme Q10 is neuroprotective against
experimental ischemia in rats (Ostrowski, 2000 ), and it protects
against striatal lesions produced by administration of the
mitochondrial toxins malonate and 3-nitropropionic acid (Beal et al.,
1994 ; Matthews et al., 1998 ). Coenzyme Q10
improves survival in a transgenic animal model of amyotrophic lateral
sclerosis (Matthews et al., 1998 ). Some patients with mitochondrial
disorders treated with coenzyme Q10 show clinical
and biochemical improvement (Ihara et al., 1989 ; Nishikawa et al.,
1989 ; Abe et al., 1991 ; Chariot et al., 1999 ).
Remacemide is an NMDA receptor channel blocker that has a lower
affinity for the receptor than several other NMDA channel blockers
(Porter and Greenamyre, 1995 ). This may be related to better
tolerability and fewer behavioral side effects than those seen with
agents such as MK-801, which dissociates from the channel slowly, and
may therefore block normal synaptic activity. Remacemide attenuates
excitotoxicity in vitro and focal ischemic lesions in
vivo (Bannan et al., 1994 ; Black et al., 1995 ) and is effective in
blocking malonate lesions (Greene et al., 1996 ). Remacemide has been
tolerated well in clinical trials for cerebral ischemia and in HD
patients (Kieburtz et al., 1996 ; Dyker and Lees, 1999 ).
In the present experiments, we examined whether oral administration of
coenzyme Q10 or remacemide or a combination of
both could exert beneficial effects in transgenic mouse models
of HD. We found that oral administration of both coenzyme
Q10 and remacemide produces a significant
improvement of survival in a transgenic mouse model of HD. The increase
in survival in the R6/2 model was 14.5% using coenzyme
Q10, 15.5% using remacemide, and 32% using the
combined coenzyme Q10/remacemide treatment. We
also found that administration of coenzyme Q10
and remacemide produces significant improvement in motor performance, a
delay in loss of body weight, a delay in gross brain and
striatal neuron atrophy, and attenuation of the development of neuronal
intranuclear inclusions in the striatum. Both coenzyme
Q10 and remacemide therefore produce significant
benefit, and the combination was more efficacious than oral
administration of creatine (Ferrante et al., 2000 ), minocycline (Chen
et al., 2000 ), or intracerebroventricular administration of caspase
inhibitors (Ona et al., 1999 ). These findings strongly suggest that
combined therapies, targeting different mechanisms of cell death, may
have cumulative beneficial effects.
Both a delay of onset and an altered course in the progression of
disease can be identified in the behavioral and neuropathological analyses by comparison of the slopes of the curves throughout the
course of treatment. Although there is a significant extension of
survival in the treated R6/2 mice, there does not appear to be an
effect on disease progression. The slopes of the Kaplan-Meier curves
are similar. However, these mice have a particularly severe phenotype,
which makes this difficult to assess. In the N171-82Q mice, the slope
of the survival curve is more gradual with treatment, suggesting a
treatment effect on disease progression. The body weight curve of the
combined therapy reflects a delay in onset. This is also observed in
the motor performance profiles, such that remacemide and the combined
therapies delay motor dysfunction, whereas coenzyme
Q10 presents with a more gradual course of
dysfunction from the onset until end stage disease. In addition, htt
aggregate counts in the combined treatment paradigm have a more gradual slope, suggesting again a less rapid disease progression.
The present results extend those found previously with mitochondrial
toxin models of HD to transgenic mouse models, showing significant
improvements on survival, motor performance, weight loss, and
neuropathological features. The present findings are of great interest
in the context of a recent clinical trial of coenzyme
Q10 and remacemide in HD patients (Huntington
Study Group, 2002 ). The CARE-HD trial of the Huntington Study
Group randomized 340 patients to coenzyme Q10 or
remacemide or the combination using a 2 × 2 factorial design
(Kieburtz, 1999 ). The patients were treated for 30 months, and the
primary outcome measure was the total functional capacity (TFC) scale
of the unified Huntington's disease rating scale. The results of this
trial showed no significant effects of either agent on the primary
outcome measure (Huntington Study Group, 2001 ). Treatment with coenzyme
Q10 showed a trend toward slowing in TFC decline
(13%) over 30 months (p = 0.15); however, the
study was not powered to be able to detect an effect of this magnitude.
There was a nominally significant effect in slowing functional decline
(22% slowing; p = 0.02) and a trend toward slowing
functional decline (18% slowing; p < 0.06) on the independence scale. Coenzyme Q10 also showed
trends toward a beneficial effect on two cognitive tests and on behavior.
There is discordance between the outcome we observed in the transgenic
mice and the outcome of the human clinical trial. The results with
coenzyme Q10 alone in the R6/2 mice were an
improved survival of 14.5%, which is similar to the magnitude of
improvement seen in HD patients (Huntington Study Group, 2002 );
however, there was no effect of remacemide in HD patients, whereas it
was efficacious in the mice. This raises an important issue of whether
therapeutic testing in the HD mice will be useful in predicting
efficacy in humans. There are a number of potential explanations for
the observed discrepancy. One is that HD patients are much more
heterogeneous than genetically modified mice. Most importantly, the
dose of remacemide used in the HD patients was 5.7 mg · kg 1 · d 1,
which was at the limit of tolerability, whereas a dose of 14 mg · kg 1 · d 1
was used in the mice (a 2.5-fold difference). The lack of efficacy of
remacemide in HD patients therefore may be the result of too low a dose
to adequately block the NMDA receptor. Alternative NMDA-antagonists may
prove more efficacious. Another important issue is that the HD
transgenic mice used in the experiments have a high expression of an
N-terminal fragment of huntingtin, rather than full-length huntingtin.
These mice show little cell loss and are resistant to excitotoxins,
whereas mice expressing full-length huntingtin show enhanced
vulnerability to excitotoxicity (Hansson et al., 1999 ; Zeron et al.,
2001 ). It is possible that the pathophysiology of neurodegeneration in
the HD transgenic mice that we studied may not be entirely reminiscent
of that occurring in the human illness. Finally, the disease stage in
which the therapeutic trials were initiated was markedly different. The
mice were started on treatment at day 21, well before the onset of
clinical symptoms, whereas the human trials were initiated in patients
with symptomatic HD. Therefore, it will be of interest to determine
whether remacemide shows efficacy in the mice if administered after the
onset of symptoms, as in human clinical trials.
Transgenic mouse models of HD hold great promise for the screening of
novel therapeutics that may then be successfully translated to the
treatment of HD patients. The present results, however, suggest that
issues of dosing and timing of drug administration will need to be
carefully considered to predict efficacy in humans. The findings that
remacemide and coenzyme Q10 improve the clinical and neuropathological phenotype in transgenic mice provides further evidence that mitochondrial dysfunction and excitotoxicity may contribute to HD pathogenesis. The present results also suggest that
multicombination therapies with agents targeting differing pathogenic
mechanisms may exert additive therapeutic effects.
 |
FOOTNOTES |
Received Sept. 20, 2001; revised Dec. 7, 2001; accepted Dec. 12, 2001.
This work was supported by The Department of Defense and National
Institutes of Health Grants NS38180 (M.F.B.), NS35255 (S.M.H., R.J.F.),
NS37102 and AG13846 (R.J.F.), AG12992 (M.F.B., R.J.F.), and AT00613
(S.M.H., R.J.F., M.F.B.), the Veterans Administration (R.J.F.), the
Hereditary Disease Foundation (R.J.F., S.M.H., M.F.B.), the
Huntington's Disease Society of America (R.J.F., S.M.H., M.F.B.), and
the Norwegian Research Council (O.A.A.). The secretarial assistance of
Sharon Melanson is gratefully acknowledged. Photographic assistance and
histology preparation were provided by James Kubilus, Kerry Cormier,
and Karen Smith.
Correspondence should be addressed to Dr. M. Flint Beal,
Neurology Department, New York Hospital-Cornell Medical Center, 525 East 68th Street, New York, NY 10021, E-mail:
fbeal{at}mail.med.cornell.edu, or Dr. Robert J. Ferrante, GRECC Unit,
182B, Bedford VA Medical Center, 200 Springs Road, Bedford, MA 01730, E-mail: rjferr{at}bu.edu.
 |
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H. Ryu, J. Lee, K. Zaman, J. Kubilis, R. J. Ferrante, B. D. Ross, R. Neve, and R. R. Ratan
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Z.-X. Yu, S.-H. Li, J. Evans, A. Pillarisetti, H. Li, and X.-J. Li
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E. Hockly, V. M. Richon, B. Woodman, D. L. Smith, X. Zhou, E. Rosa, K. Sathasivam, S. Ghazi-Noori, A. Mahal, P. A. S. Lowden, et al.
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V. C. Wheeler, L.-A. Lebel, V. Vrbanac, A. Teed, H. te Riele, and M. E. MacDonald
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L. Djousse, B. Knowlton, L. A. Cupples, K. Marder, I. Shoulson, and R. H. Myers
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A. Dedeoglu, J. K. Kubilus, T. M. Jeitner, S. A. Matson, M. Bogdanov, N. W. Kowall, W. R. Matson, A. J. L. Cooper, R. R. Ratan, M. F. Beal, et al.
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C. D. Keene, C. M. P. Rodrigues, T. Eich, M. S. Chhabra, C. J. Steer, and W. C. Low
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