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The Journal of Neuroscience, November 1, 2001, 21(21):8348-8353
Lifespan Extension and Rescue of Spongiform Encephalopathy in
Superoxide Dismutase 2 Nullizygous Mice Treated with Superoxide
Dismutase-Catalase Mimetics
Simon
Melov1,
Susan R.
Doctrow2,
Julie A.
Schneider3,
Joanna
Haberson1,
Manisha
Patel4,
Pinar E.
Coskun5,
Karl
Huffman2,
Douglas C.
Wallace5, and
Bernard
Malfroy2
1 Buck Institute for Age Research, Novato, California
94945, 2 Eukarion Inc., Bedford, Massachusetts 01730, 3 Rush Alzheimer's Disease Center, Rush Institute for
Healthy Aging, Rush-Presbyterian St. Luke's Hospital, Chicago,
Illinois 60612, 4 National Jewish Medical Research
Institute, Denver, Colorado 80206, and 5 Center for
Molecular Medicine, Emory University, Atlanta, Georgia 30322
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ABSTRACT |
Superoxide is produced as a result of normal energy metabolism
within the mitochondria and is scavenged by the mitochondrial form of
superoxide dismutase (sod2). Mice with inactivated SOD2 (sod2 nullizygous mice) die prematurely, exhibiting
several metabolic and mitochondrial defects and severe tissue
pathologies, including a lethal spongiform neurodegenerative disorder
(Li et al., 1995 ; Melov et al., 1998, 1999). We show that treatment of
sod2 nullizygous mice with synthetic superoxide
dismutase (SOD)-catalase mimetics extends their lifespan by threefold,
rescues the spongiform encephalopathy, and attenuates mitochondrial
defects. This class of antioxidant compounds has been shown previously
to extend lifespan in the nematode Caenorhabditis
elegans (Melov et al., 2000). These new findings in mice
suggest novel therapeutic approaches to neurodegenerative diseases
associated with oxidative stress such as Friedreich ataxia, spongiform
encephalopathies, and Alzheimer's and Parkinson's diseases, in which
chronic oxidative damage to the brain has been implicated.
Key words:
mitochondria; oxidative stress; superoxide dismutase; antioxidants; neurodegeneration; spongiform
encephalopathy
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INTRODUCTION |
Approximately 0.4-4% of all oxygen
consumed during normal respiration is converted into superoxide within
the mitochondrion (Chance et al., 1979; Turrens and Boveris, 1980;
Boveris, 1984; Turrens et al., 1985; Hansford et al., 1997), the chief
source of reactive oxygen species (ROS) within the cell. ROS have been implicated in a wide range of disorders including Alzheimer's disease,
Parkinson's disease, amyotrophic lateral sclerosis (ALS), prion
disease, and Friedreich ataxia (FA), as well as in
ischemia-reperfusion injury and aging (Beal, 1996; Rotig et al., 1997;
Beckman and Ames, 1998; Choi et al., 1998; Pandolfo, 1998; Schapira,
1998; Smith et al., 1998; Behl, 1999; Brown et al., 1999; Fridovich, 1999; White et al., 1999; Bradley et al., 2000; Cuajungco et al., 2000;
White et al., 2001). Consequently, studies have attempted to ameliorate
or attenuate the progression of neurodegenerative disease by chronic or
acute antioxidant treatment (Haller et al., 1996). Such studies have
yielded at best equivocal or mildly beneficial results with regard to
slowing disease progression or improving specific indicators (Jama et
al., 1996; Perrig et al., 1997; Morris et al., 1998). In theory,
efficacy should be improved by using catalytic antioxidants that can
destroy multiple toxic mitochondrial ROS without themselves becoming
inactivated. The compounds used in this study, synthetic mimetics of
superoxide dismutase and catalase, are examples of such agents (Baudry
et al., 1993).
To investigate the protective activity of synthetic catalytic
antioxidants in oxidative neurodegenerative disease, we used mice
lacking SOD2, the mitochondrial form of superoxide dismutase, on a CD1
background (sod2tm1Cje  sod2 nullizygous mice). Sod2 nullizygous mice die
within the first week of life and show a dilated cardiomyopathy,
hepatic lipid accumulation, metabolic defects, mitochondrial enzymatic defects, DNA oxidative damage, and organic aciduria (Li et al., 1995;
Melov et al., 1999). In a previous study we treated sod2 nullizygous mice with the catalytic antioxidant manganese
5,10,15,20-tetrakis (4-benzoic acid) porphyrin (MnTBAP) (Melov et al.,
1998). We found that the MnTBAP treatment significantly increased the
mean lifespan of the mice and ameliorated dilated cardiomyopathy and
hepatic lipid accumulation. However, MnTBAP does not cross the
blood-brain barrier (Melov et al., 1998). In extending the life of
sod2 nullizygous mice beyond 2 weeks of age through
protection of peripheral tissues, MnTBAP treatment uncovered a severe
neurological disorder from the endogenous production of free radicals
within mitochondria of the brain, attributable to the inability
of MnTBAP to protect against ROS produced within the brain. The
neurological phenotype seen in the MnTBAP-treated sod2
nullizygous mice is characterized by a severe disturbance in motor
control, and the underlying neuropathology is that of spongiform change
predominantly within the frontal cortex and focally in brainstem nuclei
(Melov et al., 1998).
The present study is focused on the ability of neurologically active
synthetic catalytic ROS scavengers to rescue the oxidative neurodegenerative phenotype and further extend the lifespan of sod2 nullizygous mice. The salen manganese complexes,
exemplified by the prototype EUK-8, are mimetics of both SOD and
catalase (Baudry et al., 1993; Gonzalez et al., 1995; Baker et al.,
1998). The compounds have shown efficacy in a variety of oxidative
stress paradigms, including in vivo models for stroke,
Parkinson's disease, autoimmune disease, excitotoxic neuronal death,
and familial ALS (Doctrow et al., 1997; Malfroy et al., 1997; Rong et
al., 1999; Jung et al., 2001). Recently these compounds have proven
effective in extending the wild-type lifespan of the invertebrate
Caenorhabditis elegans, demonstrating the importance of ROS
as a major factor in limiting lifespan (Melov et al., 2000). It was
therefore of considerable interest to determine whether the compounds
would be effective in a mammalian model involving mitochondrial
dysfunction and accelerated oxidative tissue damage, and in particular
whether they would rescue an oxidative neurodegenerative process.
Therefore, in the present study, sod2 nullizygous mice
received salen manganese complexes via daily injection from 3 d of
age to assess effects on lifespan as well as oxidative pathologies.
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MATERIALS AND METHODS |
EUK-8, EUK-134, or EUK-189 was synthesized and assayed for SOD
and catalase activity as described previously (Baker et al., 1998).
They were assayed for lipophilicity by solvent partitioning that was
conducted as follows. A total of 20 nmol of the compound was dissolved
in 100 µl of water; next, 500 µl of N-octanol was added. The sample was vortexed and the organic and aqueous phases were
allowed to separate. The amount of compound partitioned into each phase
was determined by HPLC on an octadecyl-silica column eluted
isocratically with a mobile phase of 100 mM NaCl
in water/methanol (60:40) with quantitation by UV absorbance.
For animal studies, EUK-8, EUK-134, and EUK-189 were dissolved in
sterile water at 5 mg/ml. MnTBAP was prepared and injected as described
previously (Melov et al., 1998). Mice were genotyped as described
previously (Melov et al., 1998) and then injected intraperitoneally on
a daily basis at 1 or 30 mg/kg body weight for EUK compounds or at 5 mg/kg body weight for MnTBAP from 3 d of age until death or until
they were killed.
Tissue harvesting, histology, histochemistry, electron microscopy, and
immunohistochemistry against glial fibrillary acidic protein (GFAP)
were performed as described previously (Melov et al., 1998). Survival
analysis was performed using the Kaplan-Meier (product-limit) method
with the JMP Statistics program (SAS Institute, Inc., Cary, NC)
or PRISM (Graphpad software, San Diego, CA). Differences in survival
between treatment groups were assessed by nonparametric analysis
(log-rank and Wilcoxon analysis). Animals that became moribund were
killed and therefore were counted as dead in the survival analysis,
whereas animals killed early for various analyses were counted as
censored. Mitochondria were isolated and assayed for aconitase and
fumarase from each brain region as described previously (Patel et al.,
1996; Melov et al., 1999). Fumarase activity did not vary significantly
between control and experimental groups in any comparison, and
therefore is not shown.
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RESULTS |
Three salen manganese complexes, EUK-8, EUK-134, and EUK-189, were
used in this study (Fig. 1). They belong
to a class of stable organometallic complexes that contain tightly
bound manganese, enabling them to mimic the active site of
metalloenzymes such as SOD2 (Baudry et al., 1993; Doctrow et al.,
1997). These three compounds share similarities but also have some
distinctive properties. EUK-134 has an SOD activity equivalent to that
of EUK-8 but is a more active catalase and is more effective in a rat
stroke model (Baker et al., 1998). EUK-189, a novel analog whose
in vivo efficacy has not yet been reported, has SOD and
catalase activities equivalent to those of EUK-134 but is more
lipophilic, based on solvent partitioning. The catalytic activities and
lipophilicities of the three compounds are compared in Table
1.
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Figure 1.
Structures of salen manganese complexes. The ring
substituents (R) of the three compounds differ as
shown. The axial ligand (X) is chloride
for EUK-8 and EUK-134 and acetate for EUK-189.
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As shown in Figure 2, EUK-8, EUK-134, or
EUK-189 (30 mg/kg), significantly extended the lifespan of
sod2 nullizygous mice beyond that of untreated mice and mice
treated with MnTBAP (5 mg/kg). A prominent feature of the survival
curves is that all salen manganese complexes dramatically increased the
percentage of sod2 nullizygous mice living beyond 3 weeks of
age. This is the approximate age at which MnTBAP-treated
sod2 nullizygous mice succumb to the previously described
neurodegenerative phenotype (Melov et al., 1998). Key parameters of the
survival data obtained with all treatment groups are summarized in
Table 2. The effect of EUK-8 and EUK-134
was dose dependent, with 30 mg/kg enhancing survival significantly more
than 1 mg/kg. EUK-189 at 30 mg/kg significantly enhanced survival
beyond that observed with EUK-134 at the same dose. EUK-8 at 30 mg/kg
appeared to have an intermediate effect compared with the other two
analogs, with survival differences not achieving statistical
significance with either EUK-189 or EUK-134. The percentage of mice
surviving beyond 3 weeks of age was greater with EUK-189 treatment
(80%), compared with 54% and 49% for EUK-8 and EUK-134, respectively
(Table 2).
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Figure 2.
Survival analysis of sod2
nullizygous mice treated with synthetic catalytic antioxidants.
Kaplan-Meier survival analysis demonstrates enhanced survival of
sod2 nullizygous mice treated with EUK-8, EUK-134, or
EUK-189 (30 mg/kg) versus untreated sod2 nullizygous
mice. MnTBAP was administered at the limiting dose of 5 mg/kg as
described previously (Melov et al., 1998).
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At 3 weeks of age, mice treated with EUK-8, EUK-134, or EUK-189 (30 mg/kg) showed no clinical evidence of the severe brain disorder
uncovered in the MnTBAP study. This is consistent with the salen
manganese complexes crossing the blood-brain barrier and rescuing the
neurological phenotype that is the likely cause of death in
MnTBAP-treated animals. The neuropathological observations discussed
below are consistent with this interpretation. Histopathological analysis revealed no spongiform change in the brains of sod2
nullizygous mice treated with 30 mg/kg EUK-8, 30 mg/kg EUK-134, or 30 mg/kg EUK-189 at any age (19-44 d of age, n = 12).
Electron microscopic analysis of the frontal cortex from the brains of
two mice treated with EUK-8 at 30 mg/kg at 42 and 44 d of age
revealed no significant differences compared with EUK-8-treated
wild-type controls. In combination with the neuropathological findings
at the light level, this is consistent with a rescue of the spongiform
encephalopathy observed previously in MnTBAP-treated sod2
nullizygous mice by EUK-8, EUK-134, and EUK-189 at 30 mg/kg.
As with survival, rescue of the spongiform encephalopathy by EUK-8 and
EUK-134 was dose dependent, with pathological observations indicating
complete prevention of the spongiform changes at 30 mg/kg and lesser
protection at 1 mg/kg (Fig. 3).
Histopathological analysis of the brains of sod2 nullizygous
mice treated with 1 mg/kg of either compound at 3 weeks of age
demonstrated a regional specific spongiform encephalopathy in six of
six mice that was similar to that seen in MnTBAP-treated mice
(Melov et al., 1998) (Fig. 3). Vacuoles ranged from 4 to >40 µm
(Fig. 3A), impinged on neighboring structures such as
neurons and blood vessels, and were occasionally seen within neuronal
perikaryon. Vacuoles showed occasional septa, and changes were noted
focally within the cerebral cortex in all cases, predominately
involving frontal regions, although the parietal and occipital regions
were also involved. All but two cases showed moderate to severe
involvement of the motor nucleus of the trigeminal nerve. Four of the
six cases showed a mild to moderate degree of involvement in the
retrosplenial granular and agranular cortex, the somatosensory cortex,
and the motor cortex. Occasional vacuoles were also observed in the
secondary sensory and motor cortex, cingulate, entorhinal cortex,
subiculum, perirhinal cortex, auditory and visual cortices, lateral
orbital cortex, periolivary nucleus, and lateral superior olive. There was preferential involvement of the midlayers of the cortex except in
the cingulate and in the retrosplenial cortex and M1 and M2, where the
molecular layers were predominately affected. There was general sparing
of the white matter and subcortical nuclei. Immunohistochemistry using
antibodies specific for GFAP, showed some positivity in areas of
vacuolization and in areas not affected by vacuoles. However, this was
not considered different from the GFAP positivity in the brains of
control animals, suggesting a histologic absence of reactive gliosis in
affected animals (data not shown). The prominent GFAP positivity
(reactive gliosis) in association with vacuolization observed
previously in MnTBAP-treated mice (Melov et al., 1998) was not observed
in sod2 nullizygous mice treated with either dose of EUK-8
or EUK-134. These observations, in conjunction with the lesser severity
of the vacuolar changes, are consistent with a partially
neuroprotective effect of the lower dose of EUK-8 and EUK-134. Figure
3B shows the equivalent region of a 3-week-old
sod2 nullizygous mouse treated with EUK-8 at 30 mg/kg,
demonstrating an absence of spongiform pathology.
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Figure 3.
Dose-dependent rescue of spongiform encephalopathy
in sod2 nullizygous mice. A shows the
trigeminal motor nuclei (hematoxylin and eosin) (400×
magnification) of a 3-week-old sod2 nullizygous
mouse treated with EUK-8 at 1 mg/kg; prominent spongiform changes are
seen that are consistent with those reported previously in
MnTBAP-treated sod2 nullizygous mice (Melov et al.,
1998). B shows the equivalent regions from a 3-week-old
sod2 nullizygous mouse treated with EUK-8 at 30 mg/kg,
demonstrating the rescue of spongiform changes.
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Mice in the 30 mg/kg treatment groups that survived to >25 d of age
developed a progressive movement disorder (n = 67)
concurrent with a loss of weight, at which point they were killed.
However, this was not associated with gross spongiform changes because, as noted above, brains from sod2 nullizygous mice at any age
in the 30 mg/kg dose treatment groups did not exhibit this pathology. Sod2 nullizygous mice treated with EUK-8 or EUK-134 at 1 mg/kg became ataxic at an earlier age (between 15 and 21 d of age)
(n = 69). Wild-type mice treated chronically with the
compounds at either dose showed no ill effects with up to 41 d of
continuous treatment, and there were no mortalities in any wild-type groups.
Previous studies indicate that untreated sod2 nullizygous
mice suffer mitochondrial damage, as indicated by a loss of activity of
certain oxidation-sensitive mitochondrial enzymes in the brain and
peripheral tissues. For example, mitochondrial aconitase is decreased
by 70-80% in striatum, frontal cortex, cerebellum, and brain stem of
sod2 nullizygous mice, whereas another tricarboxylic acid
cycle enzyme, fumarase, is unaffected (Melov et al., 1999). Because
EUK-8 rescues the neuropathology in these animals, consistent with
penetrating the blood-brain barrier, we investigated whether it
concomitantly prevented the loss of mitochondrial aconitase activity in
the brains of sod2 nullizygous mice. For this experiment, sod2 nullizygous mice treated with EUK-8 (30 mg/kg) were
compared with those treated with MnTBAP (5 mg/kg) at 3 weeks of age.
Untreated sod2 nullizygous mice could not serve as controls
in this study because they do not live long enough in sufficient
numbers to exhibit the neuropathology. The mitochondrial aconitase
activity in the brains of EUK-8-treated sod2 nullizygous
mice, although not achieving the levels observed in mitochondria from
wild-type and other control mice, was 2.5-fold to threefold higher than that of MnTBAP-treated mice (Fig. 4).
This is consistent with EUK-8 protecting mitochondrial aconitase from
inactivation by endogenously generated mitochondrial superoxide.
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Figure 4.
Increase in mitochondrial aconitase activity in
the brains of sod2 nullizygous mice at 3 weeks of age.
Open bars, MnTBAP-treated sod2/ mice
(n = 11); gray
bars, EUK-8-treated sod2/ mice
(n = 6); closed bars, EUK-8- or
MnTBAP-treated sod2+/+ mice or untreated
sod2+/+ mice. BS, Brain stem;
Str, striatum; Ctx, cortex;
Cb, cerebellum. Mitochondrial aconitase activity in the
brains of sod2 nullizygous mice treated with EUK-8
compared with mitochondria isolated from MnTBAP-treated mice at 3 weeks
of age via nonparametric t tests reveals that EUK-8
treatment results in statistically significant increases in the level
of mitochondrial aconitase activity (*p < 0.05;
**p < 0.01). No statistically significant
difference was observed in the activity of brain mitochondrial
aconitase from sod2+/+ mice treated with either EUK-8 or
MnTBAP compared with untreated controls; therefore, these mice were
grouped together. Error bars represent the SEM.
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DISCUSSION |
Mice lacking SOD2, the mitochondrial form of the enzyme, generally
die within a few days of birth, exhibiting mitochondrial enzyme
deficiencies and numerous severe pathologies resulting from
mitochondrial oxidative stress (Li et al., 1995; Melov et al., 1998,
1999). This is in dramatic contrast to mice lacking the far more
abundant cellular enzyme SOD1, which show a very mild phenotype and
normal lifespan (Reaume et al., 1996). This difference alone
illustrates the profound impact that mitochondrial oxidative stress can
have on tissue function and, therefore, on disease. Thus, it is of
considerable interest to examine the pathologies manifested by
sod2 nullizygous mice as well as the potential effects of
specific pharmacological interventions on these pathologies. For
example, we have reported previously that when sod2
nullizygous mice, which normally die of a dilated cardiomyopathy, are
treated with a synthetic antioxidant that does not cross the
blood-brain barrier, they live longer and develop a lethal develop a
spongiform encephalopathy (Melov et al., 1998). This disorder,
resulting from mitochondrial oxidative damage to the brain, was
unmasked when earlier-onset peripheral pathologies were alleviated. As will be discussed further below, this phenotype is remarkably similar
to that observed in a recently reported mouse model for FA, a severe
neurodegenerative mitochondrial disease (Puccio et al., 2001). More
broadly, mitochondrial dysfunction and oxidative stress have been
implicated in such prevalent neurodegenerative disorders as
Alzheimer's and Parkinson's diseases (Cherny et al., 2001; Conn et
al., 2001). Thus, insofar as the spongiform encephalopathy represents a
model for pathological consequences of brain mitochondrial dysfunction,
our studies with the sod2 nullizygous mouse may provide some
insight into potential therapeutic approaches to human
neurodegenerative disease.
Consequently, the current study was focused on investigating whether
the spongiform encephalopathy in sod2 nullizygous mice could
be rescued by treatment with a class of synthetic catalytic antioxidants that have been shown previously to be neuroprotective (Baker et al., 1998; Rong et al., 1999; Jung et al., 2001). Our data
show that the compounds, administered daily at 30 mg/kg, extended the
lifespan of sod2 nullizygous mice approximately threefold, beyond the age (~2-3 weeks) at which, with MnTBAP treatment, they succumb to the spongiform encephalopathy. In addition, at 2-3 weeks of
age, the treated mice showed no clinical signs of the associated
neurobehavioral phenotype described previously, which consists of
severe motor disturbances (Melov et al., 1998). Finally, analysis of
the brains of the treated mice showed an absence of spongiform
pathology at all ages examined (up to 44 d). Together, these data
indicate that the compounds, unlike MnTBAP, can cross the blood-brain
barrier and rescue the spongiform encephalopathy. This protection was
dose dependent, as evidenced by the partial protection, with respect to
survival as well as brain pathology, observed with the lower dose (1 mg/kg EUK-8 or EUK-134) treated groups.
The eventual cause of death in sod2 nullizygous mice treated
with the compounds is not yet known. Mice surviving for >25 d exhibited a progressive movement disorder, but this was not associated with gross spongiform changes as is the phenotype seen in the MnTBAP-treated mice. Hence, the mechanistic basis for the later-onset neurological disorder is likely to be different from that unmasked by
MnTBAP treatment (Melov et al., 1998) and remains to be further characterized.
The comparative efficacies of the three analogs in the sod2
nullizygous mice are of interest. EUK-8 and EUK-134 were approximately equipotent, as indicated by their comparable effects at both doses (Table 2). Thus, in this model, the enhanced catalase activity of
EUK-134 did not confer a greater protectiveness than that seen with
EUK-8. EUK-8 appeared to be slightly more effective than EUK-134,
although this difference was not statistically significant. This
observation is consistent with SOD activity, rather than catalase
activity, being of primary importance for an agent to rescue the
sod2 nullizygous phenotype, because EUK-8 and EUK-134 have
equivalent SOD activities. This is in contrast to certain other models,
for example a rat stroke model, in which EUK-134 was significantly more
effective than EUK-8 (Baker et al., 1998). EUK-189 has SOD and catalase
activities equivalent to those of EUK-134 but is significantly more
lipophilic than EUK-8 or EUK-134 (Table 1). Thus, the increased
effectiveness of EUK-189 compared with EUK-134 in the sod2
nullizygous mice might be attributable to an enhanced ability to cross
the blood-brain barrier and/or gain access to the mitochondria. In
support of the latter concept, EUK-189 has been shown recently to be
substantially more potent than EUK-134 in protecting neuronal cultures
against staurosporine-induced apoptosis but equipotent in protecting
cells against an extracellular hydrogen peroxide insult (Pong et al.,
2001). Interestingly, the maximum lifespan of the treated
sod2 nullizygous mice remained approximately the same with
EUK-189 treatment as it did with the other compounds (Fig. 1). This
suggests a late-onset (>25 d) phenotype that is not amenable to
treatment with these compounds, at least under the protocol used in
this study.
As noted above, the pathologies observed in the sod2
nullizygous mice are consistent with damage from mitochondrial
oxidative stress, and indeed, the mice have been shown to have numerous defects in mitochondrial enzymes (Melov et al., 1999). Analysis of
isolated brain mitochondria from treated sod2 nullizygous
mice (Fig. 4) strongly supports our hypothesis that the compounds
investigated in this study exert their neuroprotective function
directly through protection of brain mitochondria from endogenously
generated ROS. Essentially, these data demonstrate that EUK-8-treated
sod2 nullizygous mice showed a significant preservation of
active cis-aconitase, a known target of mitochondrial
oxidative damage, compared with age-matched MnTBAP-treated mice
exhibiting the spongiform neuropathy.
Overall these observations in sod2 nullizygous mice suggest
that the class of synthetic catalytic antioxidants exemplified by EUK-8
and its analogs can permeate the brain, gain access to the
mitochondria, and attenuate the mitochondrial damage attributable to
oxidative stress, as well as its resulting pathologies. This may have
important clinical implications in the design and implementation of
therapeutic approaches to several diseases. Interestingly, a recent
report describing a mouse model of FA (Puccio et al., 2001) shows a
highly similar phenotype to the sod2 nullizygous mouse
treated with MnTBAP (Melov et al., 1998). Commonalities between these
two mouse models include a regional spongiform encephalopathy, cardiomyopathy, and mitochondrial enzymatic abnormalities (Melov et
al., 1998; Puccio et al., 2001). This implies that mitochondrial oxidative stress may be a central feature of the pathology of FA and
that, therefore, "mito-protective" antioxidants such as the ones
described in this report would be efficacious for the human disease. In
addition, a recent report demonstrated that oxidative stress precedes
amyloid formation in the brains of Tg2576 Alzheimer mice, indicating
that effective antioxidant therapy in this model might prevent the
development of the pathology (Pratico et al., 2001). More generally,
the observations of a prolonged lifespan in the sod2
nullizygous mice by threefold and the concomitant rescue of the
spongiform neurodegenerative disorder imply that such mito-protective
SOD-catalase mimetics might retard the pathogenesis of other
neurodegenerative disorders with reactive oxygen species implicated in
their etiology, such as Parkinson's and Alzheimer's diseases and,
perhaps, the degenerative processes of aging.
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FOOTNOTES |
Received June 27, 2001; revised Aug. 13, 2001; accepted Aug. 16, 2001.
This work was supported by National Institutes of Health Grants
DCW-AG13154, HL45572, NS21328, and AG18679 (S.M.). We thank B. A. Day and J. D. Crapo for their kind gift of MnTBAP, T.-T. Huang and
C. J. Epstein for the gift of sod2 nullizygous
mice, and Tamara Golden for helpful comments. All procedures with
animals were performed under approved Buck Institute or Emory
University Institutional Animal Use and Care Committee protocols.
Correspondence should be addressed to Simon Melov, Buck
Institute for Age Research, 8001 Redwood Boulevard, Novato, CA 94945 E-mail: smelov{at}buckinstitute.org.
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TOP
ABSTRACT
INTRODUCTION
