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The Journal of Neuroscience, March 15, 1999, 19(6):1959-1964
RNA Oxidation Is a Prominent Feature of Vulnerable Neurons in
Alzheimer's Disease
Akihiko
Nunomura1, 2,
George
Perry1,
Miguel A.
Pappolla3,
Ramon
Wade1,
Keisuke
Hirai1, 4,
Shigeru
Chiba2, and
Mark A.
Smith1
1 Institute of Pathology, Case Western Reserve
University, Cleveland, Ohio 44106, 2 Department of
Psychiatry and Neurology, Asahikawa Medical College, Asahikawa
078-8510, Japan, 3 Department of Pathology, University of
South Alabama, Mobile, Alabama 36617, and 4 Pharmaceutical
Research Laboratories I, Pharmaceutical Research Division, Takeda
Chemical Industries Limited, Osaka 532-8686, Japan
 |
ABSTRACT |
In this study we used an in situ approach to
identify the oxidized nucleosides
8-hydroxydeoxyguanosine (8OHdG) and 8-hydroxyguanosine (8OHG), markers
of oxidative damage to DNA and RNA, respectively, in cases of
Alzheimer's disease (AD). The goal was to determine whether nuclear
and mitochondrial DNA as well as RNA is damaged in AD. Immunoreactivity
with monoclonal antibodies 1F7 or 15A3 recognizing both 8OHdG and 8OHG
was prominent in the cytoplasm and to a lesser extent in the nucleolus
and nuclear envelope in neurons within the hippocampus, subiculum, and
entorhinal cortex as well as frontal, temporal, and occipital neocortex
in cases of AD, whereas similar structures were immunolabeled only
faintly in controls. Relative density measurement showed that
there was a significant increase (p < 0.0001) in 8OHdG and 8OHG immunoreactivity with 1F7 in cases of AD
(n = 22) as compared with senile
(n = 13), presenile (n = 10),
or young controls (n = 4). Surprisingly, the
oxidized nucleoside was associated predominantly with RNA because
immunoreaction was diminished greatly by preincubation in RNase but
only slightly by DNase. This is the first evidence of increased RNA
oxidation restricted to vulnerable neurons in AD. The subcellular
localization of damaged RNA showing cytoplasmic predominance is
consistent with the hypothesis that mitochondria may be a major source
of reactive oxygen species that cause oxidative damage in AD.
Key words:
Alzheimer's disease; oxidative stress; RNA oxidation; DNA oxidation; 8-hydroxyguanosine; 8-hydroxydeoxyguanosine; mitochondrial damage
 |
INTRODUCTION |
Neuron-specific oxidative stress in
Alzheimer's disease (AD) is well documented (for review, see Smith et
al., 1996a ; Markesbery, 1997 ; Smith and Perry, 1998 ), including
oxidative damage to proteins and lipids (Smith et al., 1996b ; Sayre et
al., 1997 ) as well as the induction of specific antioxidant systems
(Pappolla et al., 1992 ; Smith et al., 1994 ; Premkumar et al., 1995 ).
One of the major findings of these studies is that oxidative damage is
not limited to the pathology of AD but rather uniformly involves
members of entire populations of neurons at risk of death in AD,
whereas other neurons and glia remain indistinguishable from controls. This localization, together with the low diffusion of most reactive oxygen, suggests that neuronal cell bodies may be the site of reactive
oxygen production that leads to oxidative stress in AD. Because
mitochondria are responsible for the majority of cytoplasmic reactive
oxygen production, we undertook this study to determine whether
mitochondrial damage, as assessed by the oxidation of cytoplasmic DNA,
shows the same restriction to vulnerable neurons.
Previous studies found higher levels of an oxidative modification of
DNA, 8-hydroxy-2'-deoxyguanosine (8OHdG), in mitochondrial DNA isolated
from AD brain tissue (Mecocci et al., 1993 , 1994 , 1997 ). However, these
studies did not define the cell types contributing the modified DNA nor
whether artifactual modifications might have been introduced during
isolation (Floyd et al., 1990 ; Claycamp, 1992 ; Collins et al., 1996 ;
Helbock et al., 1998 ). Addressing the relationship of mitochondrial
damage to oxidative stress requires an understanding of the specific
neuronal populations displaying the damage. Moreover, in AD and other
neurodegenerative diseases very little is known about the extent and
distribution of oxidative damage to RNA, which may be susceptible to
reactive oxygen attack because of its widespread cytosolic
distribution. We examined AD and control cases immunocytochemically
with antibodies recognizing both oxidized nucleosides, 8-OHdG and
8-hydroxyguanosine (8OHG), which are markers of oxidative damage to DNA
and RNA, respectively (Fiala et al., 1989 ; Rhee et al., 1995 ; Wamer and
Wei, 1997 ; Wamer et al., 1997 ), to determine which cell types displayed
the greatest differences. We found not only that the oxidized
nucleosides are increased in AD but that the increase is limited to the
neuronal populations showing oxidative damage to proteins and lipids.
Surprisingly, instead of being restricted to mitochondrial DNA, most of
the oxidized nucleoside is associated with RNA. Our findings
demonstrate that oxidative damage to RNA is a prominent feature of
vulnerable neurons in AD.
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MATERIALS AND METHODS |
Tissue. Brain tissue was obtained at autopsy from
clinically and pathologically confirmed cases of AD (ages 57-93 years,
average 78; n = 22), using National Institute on Aging
and the Consortium to Establish a Registry for Alzheimer's Disease
(CERAD) criteria (Khachaturian, 1985 ; Mirra et al., 1991 ), and was
compared with tissue from nondemented control cases, i.e., senile
controls (ages 67-86 years, average 77; n = 13),
presenile controls (ages 42-64 years, average 54; n = 10), and young controls (ages 3-31 years, average 17;
n = 4) with similar postmortem intervals before
fixation (2-22 hr in AD cases and 4-27 hr in control cases).
Hippocampal slices (~1 cm thick and including the surrounding
subiculum, entorhinal cortex, and adjacent temporal neocortex) were
fixed in methacarn (methanol/chloroform/acetic acid, 6:3:1) for
16 hr at 4°C, dehydrated through graded ethanol followed by xylene,
and embedded in paraffin. Sections were cut 6 µm thick and mounted on
Silane-coated (Sigma, St. Louis, MO) glass slides. From the same cases,
cerebellum from nine control and four AD, occipital cortex from one
control and three AD, and frontal cortex from three control and three
AD were examined.
Immunocytochemistry and antibodies. After deparaffinization
with xylene, the sections were hydrated through graded ethanol. Endogenous peroxidase activity in the tissue was eliminated by a 30 min
incubation with 3% H2O2 in methanol, and
nonspecific binding sites were blocked in a 30 min incubation with 10%
normal goat serum in Tris-buffered saline (150 mM Tris-HCl
and 150 mM NaCl, pH 7.6). In some cases the
H2O2 step was omitted as a control to assess
whether H2O2-mediated oxidation during
processing contributed to 8OHdG and 8OHG. Additionally, sections of
three control cases were incubated with 3%
H2O2 and iron [0.1 mM iron(III)
citrate and 0.1 mM iron(II) chloride] in methanol for 30 min to test whether hydroxyl radicals generated by the Fenton reaction
are capable of oxidizing nucleic acids as well as protein in sections.
Protein oxidation was detected by increased reactive carbonyls via
2,4-dinitrophenylhydrazine labeling (Smith et al., 1998 ).
To detect oxidized nucleosides, we used two monoclonal antibodies
developed by immunizing mice with 8OHG: 1F7 (1:30; Yin et al., 1995 )
(gift of Regina M. Santella, Division of Environmental Sciences, School
of Public Health, Columbia University, New York, NY) and 15A3 (1:250;
Park et al., 1992 ) (QED Bioscience, San Diego, CA). Both antibodies
recognize RNA-derived 8OHG as well as DNA-derived 8OHdG (Park et al.,
1992 ; Yin et al., 1995 ; Al-Abdulla and Martin, 1998 ). Antibody 1F7 is
reported to exhibit similar binding affinities for 8OHdG and 8OHG,
although affinities for deoxyguanosine and guanosine are 20,000- and
10,000-fold lower than those for 8OHdG and 8OHG, respectively (Yin et
al., 1995 ). For 1F7 the sections were pretreated with proteinase-K (10 µg/ml in PBS, pH 7.4, for 40 min at 37°C; Boehringer Mannheim,
Indianapolis, IN).
Immunostaining was developed by the peroxidase-antiperoxidase
procedure (Sternberger, 1986 ), using 0.75 mg/ml 3,3'-diaminobenzidine cosubstrate in 0.015% H2O2 and 50 mM Tris-HCl, pH 7.6, for exactly 10 min.
Neurofibrillary tangles and senile plaques were identified by
counterstaining the sections with Congo red and viewing them under
plane polarized light or, alternatively, by immunostaining the adjacent
section with an antiserum to tau (1:1000; Perry et al., 1991 ) or a
mouse monoclonal antibody to phosphorylated tau, AT8 (1:500; Biosource
International, Camarillo, CA). Additionally, sections of three AD cases
were double-immunostained with 1F7 and the antiserum to tau.
The specificity of 1F7 and 15A3 to 8OHdG and 8OHG was confirmed by (1)
comparison with adjacent sections in which the primary antibody was
omitted, or (2) absorption with purified 8OHdG (Sigma), 8OHG (Cayman
Chemical, Ann Arbor, MI), or guanosine (Sigma). Antibodies were
incubated for 5 hr at room temperature in serial dilutions of the
proteins in PBS from 0.23 mg/ml through 0.23 ng/ml and applied to the sections.
After the proteinase-K treatment, additional sections were pretreated
with DNase I (10 U/µl in PBS for 1 hr at 37°C; Boehringer Mannheim), S1 DNase (10 U/µl in PBS for 1 hr at 37°C; Boehringer Mannheim), RNase (5 µg/µl in PBS for 1 hr at 37°C; Boehringer Mannheim), or a combination of all of these nucleases before incubation with 1F7 or 15A3. After enzyme treatment the DNA or RNA that was remaining was evaluated by immunostaining with a mouse monoclonal antibody to DNA, clone 16-13 (1:1000; Chemicon, Temecula, CA), or by
histochemical staining with methyl green-pyronin (Bancroft and Stevens,
1996 ), a method that differentially stains DNA and RNA.
Relative scale of 8OHdG and 8OHG. The intensity of
immunoreaction of 8OHdG and 8OHG with the 1F7 antibody was evaluated by measuring the optical density (OD). The OD in an area comprising the
cytoplasm and nucleus was determined with a Quantimet 570C Image
Processing and Analysis System (Leica) linked to a COHU solid state
camera mounted on a Leitz Laborlux 12 ME ST microscope, according to
the methods of Masliah et al. (1990) . Neurons from all 27 control cases
and 22 AD cases were measured in the following manner. Three adjacent
fields (each field = 460 × 428 µm) of stratum pyramidale
of prosubiculum adjacent to the CA1 field of hippocampus were selected.
In each field of the video camera, five neurons sectioned near their
equator, based on a section plane that included the nucleolus, were
selected and outlined manually. The OD measurement was obtained for
each of the three fields and averaged. Finally, the OD value was
corrected for background by subtracting the OD of the white matter on
the same section. The cross-sectional size of the selected neuron was
measured also. All measurements were done under the same optical and
light conditions, and an electronic shading correction was used to
compensate for any unevenness that might be present in the
illumination. Statistical analysis for the differences in the corrected
OD value among the AD and control subgroups was performed with
ANOVA, using the StatView 4.11 program (Abacus Concepts,
Berkeley, CA). Fisher's Protected Least Significant Difference was
applied in the post hoc analysis.
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RESULTS |
When sections of hippocampus, subiculum, and entorhinal cortex as
well as frontal, temporal, and occipital neocortex from cases of AD
were examined, the most striking feature was the prominent immunolabeling of the oxidized nucleosides (8OHdG and 8OHG) in the
neuronal cytoplasm (Fig.
1A,C,E), with a similar
pattern found for both antibodies, 1F7 and 15A3. Cytoplasmic
immunoreaction was on granular structures with a Nissl substance-like
distribution extending from the cell bodies to dendrites, but with no
axonal elements displaying the immunoreaction (Fig. 1C,E).
Intranuclear immunoreaction with 1F7 or 15A3 in AD cases was less
intense than that found for the cytoplasmic immunoreaction.
Interestingly, nuclear chromatin, demonstrated with the antibody to DNA
(data not shown), was poorly detected with 1F7 or 15A3. The relative paucity of DNA-based staining can be noted clearly in the
intranucleolar vacuolar region that contains chromatin (Peters et al.,
1991 ) and is not immunolabeled with either 1F7 or 15A3 (Fig.
1E). In comparison to AD the control cases, both aged
and young, showed the same pattern of staining but with much reduced
intensity in vulnerable neurons (Fig. 1B,D). In fact,
the difference in immunoreactivity with 1F7 or 15A3 between AD and
controls was most striking for cerebral pyramidal neurons, whereas the
Purkinje neurons of the cerebellum showed no difference between AD and
controls.

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Figure 1.
Stratum pyramidale of the hippocampal CA1 field
immunostained with 1F7 antibody. Oxidized nucleosides, 8OHdG and 8OHG,
are abundant in the neuronal cytoplasm for a case of Alzheimer's
disease (age, 76 years; postmortem interval, 4 hr) (A,
C, E) although it is virtually
undetectable in a control (age, 80 years; postmortem interval, 4 hr)
(B, D). Immunolabeling of the nucleoli and nuclear
envelopes is moderate and chromatin is faint as compared with the
intense reaction in the cytoplasm (C, E).
The relative lack of DNA staining as compared with RNA staining can be
noted for the nucleolus, whereas the small vacuolar region
(arrow), which is rich in DNA, remains unstained, the
outer region, which contains rRNA, is stained more strongly
(E). Counterstaining with Congo red and viewing
under plane polarized light shows birefringent neurofibrillary tangles
(outlined with small arrowheads in two
neurons) and shows that the immunoreaction is not only absent from
neurofibrillary tangles but also reduced in the cytoplasm excluded from
the neurofibrillary tangle (F). Images are shown
with differential interference contrast optics, except for
F. Scale bars: A, B, 100 µm; C, D, 50 µm; E,
F, 10 µm.
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The presence of oxidized nucleosides in neurons was not related to the
presence of neurofibrillary tangles or apposition to senile plaques,
seen with tau or Congo red staining. In fact, neurons containing
neurofibrillary tangles showed reduced immunoreactivity. Although in
part this might be a result of the exclusion of normal cytoplasm from
the region containing the neurofibrillary tangles (Fig.
1F), even the remaining cytoplasm showed lower
immunoreactivity with 1F7 or 15A3 than neurons lacking neurofibrillary
tangles. Double immunostaining with 1F7 and antibodies to tau revealed no overlap between oxidized nucleoside and tau immunoreactivity as well
as low levels of immunoreactivity with 1F7 in the cytoplasm surrounding
the neurofibrillary tangles (data not shown).
Assessment of oxidized nucleoside, using a relative scale of the
intensity of immunoreactivity with 1F7, demonstrated that the increase
was significant (p < 0.0001) in AD when
compared with each control subgroup, i.e., senile control, presenile
control, or young control group (Fig. 2).
These results cannot be explained by neuronal shrinkage, because the
average cell profile area remained unchanged between AD cases (257-534
µm2; average of all cases, 395 µm2) and control cases (268-534
µm2; average of all cases, 380 µm2). Furthermore, we found no significant effect
of postmortem intervals on the immunoreactivity with 1F7 in either
control cases (r2 = 0.096;
p = 0.131) or AD cases
(r2 = 0.057; p = 0.285)
by linear regression analysis. An agonal state before death also failed
to alter the relative immunoreactivity. Indeed, similar average values
for relative immunoreactivity with 1F7 was seen in controls who died
from hanging (n = 1), traffic accident
(n = 2), internal malignancy (n = 2),
chronic cardiac failure (n = 3), or myocardial
infarction (n = 3).

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Figure 2.
Relative scale of 8OHdG and 8OHG immunoreactivity
with 1F7 antibody in prosubiculum neurons of 4 young controls, 10 presenile controls, and 13 senile controls, as defined in Materials and
Methods, and in 22 cases of AD. Values shown are the means with SE. The
difference among all controls and AD is significant by ANOVA
(p < 0.0001), with post hoc
analysis showing significant differences between young controls and AD
(p = 0.0015), between presenile controls and
AD (p = 0.0001), and between senile controls
and AD (p = 0.0001).
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Localization of 8OHdG and 8OHG was specific because similar results
were seen with both antibodies 1F7 and 15A3, and the recognition of
neurons was blocked completely by previous incubation with either 8OHdG
or 8OHG at 23 ng/ml (Fig. 3), but not by
over a thousand-fold greater concentration of guanosine. When
antibodies were preincubated with graded 8OHdG or graded 8OHG
competitively, similar blocking of immunoreaction was obtained.
Therefore, 1F7 and 15A3 are equally capable of detecting oxidized DNA
(8OHdG) and oxidized RNA (8OHG) by immunocytochemistry. Omission of the
primary antibody yielded no immunostaining. Further, little difference
in staining intensity was noted if the H2O2
treatment was omitted. However, the incubation of control sections with
H2O2 and iron caused a modest increase in the
immunoreaction with 1F7. The increased immunoreaction of oxidized
nucleosides after H2O2 and iron treatment
differed from that of oxidized nucleosides created in
vivo because the nucleus and cytoplasm of glial as well as
neuronal cells were stained. This treatment also caused damage to
protein, as noted by increased reactive carbonyls, and, as with nucleic
acid, oxidative damage to protein was noted in all cell types. This
contrasts with the relative limitation of the oxidized nucleoside to
neuronal cytoplasm in sections from cases of AD that have not been
treated with H2O2 and iron.

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Figure 3.
Neuronal immunolabeling with 1F7 antibody in AD
(A) is abolished completely by adsorption with
purified 8OHG (B). Images are shown with
differential interference contrast optics. *indicates landmark blood
vessel in adjacent section. Scale bar, 50 µm.
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Enzymatic treatment with a mixture of both DNases and RNase essentially
abolished 8OHdG and 8OHG immunoreactivity, attesting to the specificity
of immunoreaction for modified nucleic acids. In separate treatments we
noted a consistently greater reduction in the immunoreaction after
RNase, with faint residual labeling in both nucleus and cytoplasm (Fig.
4B). In contrast, DNase
I treatment did not change either the intensity or the distribution of
the immunoreaction significantly (Fig. 4C). The effect of
DNase or RNase was confirmed by a complete absence of DNA
immunostaining or RNA staining with methyl green-pyronin, respectively.
Further, even after proteinase-K treatment, which does expose
additional 8OHdG and 8OHG immunoreactivity, oxidized nucleosides in RNA
still dominate those in DNA. Therefore, RNA is a major site of nucleic acid oxidative damage in AD.

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Figure 4.
Immunoreaction with 1F7 antibody in AD
(A) was diminished greatly by the RNase treatment
(B) but only slightly by DNase I treatment
(C). Arrows indicate the same
neurons in adjacent serial sections. Images are shown with differential
interference contrast optics. Scale bar, 50 µm.
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DISCUSSION |
Not only do our findings confirm previous studies demonstrating
that nucleic acid oxidation is increased in AD (Mecocci et al., 1993 ,
1994 , 1997 ), but our cytological approach allows us to determine that
the increase is restricted to vulnerable neurons. This distinction is
significant because it shows that oxidative damage to nucleic acid,
like proteins, is limited to a defined group of neurons, the same
neurons that degenerate in AD. Further, by analyzing the full spectrum
of oxidized nucleic acids, we noted that oxidative damage in vulnerable
neurons of AD mainly involves cytoplasmic RNA. This view is supported
by the marked reduction of the immunolabeling of the oxidized
nucleosides with RNase pretreatment as well as the subcellular
localization of the oxidized nucleosides, with a distribution
equivalent to Nissl substance. Further, the findings support
cytoplasmic specificity of the damage because the nucleolus, a
structure rich in RNA with an RNA/DNA ratio of 1.2 in brain (Takahashi,
1984 ), was immunolabeled only modestly with the antibodies to 8OHdG and
8OHG. Additionally, chromatin, a structure rich in DNA with an RNA/DNA
ratio of 0.045 in brain (Takahashi, 1984 ), was poorly immunolabeled.
This is the first evidence of increased oxidative damage to neuronal
RNA in AD. In light of the previous studies showing that cytoplasmic
RNA is reduced in vulnerable neurons in AD (Mann et al., 1981 ; Colurso
et al., 1995 ), we suspect that the amount of oxidized RNA as well as
the extent of oxidative modification is increased in AD. It is not
surprising that RNA bears substantial oxidative damage, because it is
single-stranded and is not covered with protective histones like
nuclear DNA. The relative paucity of DNA oxidative damage may be
explained by the DNA repair mechanism, whereas the only compensation of
increased RNA oxidation is higher turnover rate (Dani, 1997 ). Indeed,
previous studies in vitro showed significant levels of RNA
oxidation, without DNA oxidation, in human skin fibroblasts after
exposure to ultraviolet radiation (Wamer and Wei, 1997 ; Wamer et al.,
1997 ). Similarly, in vivo, RNA is more susceptible to
oxidative damage than DNA in rat liver treated with a hepatocarcinogen,
2-nitropropane (Fiala et al., 1989 ). In consideration of the short
diffusion distance of hydroxyl radicals through tissue, which is
estimated in the order of several nanometers (Joenje, 1989 ), and the
low permeability of superoxide through cell membrane (Takahashi and
Asada, 1983 ), the predominance of oxidized nucleoside in the cytoplasm
is consistent with the idea that mitochondria are a major source of
damaging reactive oxygen species. Although inflammatory cells present
in most senile plaques may participate in the neuronal oxidative damage
by producing nitric oxide (Smith et al., 1997b ), 8OHdG is not a major
product of peroxynitrite-mediated oxidation of deoxyguanosine (Uppu et al., 1996 ). Therefore, the most likely source of oxidized nucleosides is from hydroxyl radicals formed from the reaction of highly diffusible H2O2 with redox-active metals (Schubert and
Wilmer, 1991 ). Of note, redox-active heme and nonheme iron and copper
exist within the mitochondrial and the cytosolic compartments
(Prohaska, 1987 ), whereas iron within the nucleus is oxidized fully
[i.e., iron(III)] (Smith et al., 1997a ) and thus could not support
hydroxyl radical formation in the nucleus.
Nucleic acid damage is not dependent on proximity to senile plaques and
was reduced in neurons containing neurofibrillary tangles. Therefore,
surprisingly, redox-active iron accumulation in association with AD
pathology (Smith et al., 1997a ) seems to make little contribution to
the nucleic acid oxidation. Nucleic acid oxidation must precede lesion
formation. Indeed, it is notable that neurons containing
neurofibrillary tangles actually show reduced nucleic acid damage,
whereas protein-related damage is increased (Good et al., 1996 ; Montine
et al., 1996 ; Smith et al., 1996b , 1997b ; Sayre et al., 1997 ). Although
it could be that the reduction is attributable to the exclusion of
RNA-containing structures from the neurofibrillary tangles, recent
studies show that neurofibrillary tangles accumulate RNA (Ginsberg et
al., 1997 ), and Nissl substance is abundant in the cytoplasm excluded
from neurofibrillary tangles. Therefore, the lack of oxidized nucleic
acid in neurofibrillary tangles and in the excluded cytoplasm suggests
a real reduction in oxidative damage to RNA in those neurons. These
findings may differ from protein-related damage because, although
oxidatively modified proteins accumulate, RNA is turned over; thus RNA
may reflect steady-state balance rather than history. Certainly, more work is required to understand these distinctions.
The cytoplasmic nucleic acid damage reported here may lie not only in
RNA but also in mitochondrial DNA, which, because of the absence of
histones, proximity to reactive oxygen, and poor repair mechanisms, is
highly susceptible to oxidative damage (Beal, 1995 ). Not
surprisingly, previous studies of AD showed mitochondrial DNA has
greater 8OHdG levels than nuclear DNA (Mecocci et al., 1994 ).
Mitochondrial DNA damage can be associated with increased DNA deletions
or mitochondrial proliferation, both features that we have identified
specifically in vulnerable neurons (K. Hirai, G. Perry, A. Nunomura,
R. B. Petersen, and M. A. Smith, unpublished observations).
Because the amount of mitochondrial DNA, <0.1% of total cellular DNA,
is ~3000-fold less than the amount of RNA in neurons (Davison, 1981 ;
Giuffrida, 1983 ), oxidized mitochondrial DNA is inconspicuous when it
is compared with oxidized RNA.
RNA seldom is analyzed for oxidative damage because such modifications
are not inheritable and thus not mutagenic; further, and perhaps most
importantly, analytical approaches require the isolation of specific
nucleic acid fractions before analysis. Nevertheless, it has been
suggested that oxidatively damaged RNA may interfere with correct base
pairing and could compromise the accuracy of transcription and
translation (Rhee et al., 1995 ). These aspects may be particularly
important in the case of highly metabolic cells such as neurons. As
such, it may be that oxidative damage to RNA contributes to the
pathophysiology of AD.
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FOOTNOTES |
Received Oct. 20, 1998; revised Dec. 11, 1998; accepted Dec. 23, 1998.
This work was supported by National Institutes of Health Grants AG09287
and AG14249 and the American Health Assistance Foundation. R.W. is
supported by a Ruth Salta Student Fellowship. We thank Dr. Regina M. Santella for providing the 1F7 antibody as well as the reagents for the
absorption assay and Dr. Lawrence M. Sayre for critical discussions.
Correspondence should be addressed to Mark A. Smith, Ph.D., Institute
of Pathology, Case Western Reserve University, 2085 Adelbert Road,
Cleveland, OH 44106.
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