type Senile Dementia

Osaka City Medical Journal
Vol. 43, No.1 1- 5,
1997
Localization of Manganese Superoxide Dismutase in
the Cerebral Cortex and Hippocampus of Alzheimertype Senile Dementia
MITSUYO MAEDA!, HIROSHI TAKAGI l , HIDEYUKI HATTORI 2
and TAKASHI MATSUZAKI 3
I First Department of Anatomy, Osaka City University Medical School,
Osaka (Japan), 2 Psychiatric Devision, Mihara Hospital, Osalw (Japan)
and 3 Devision of Internal Medicine, Matsuzaki Hospital, Osaka (Japan)
Key words:
Mn-superoxide dismutase, Alzheimer's disease, Senile
plaque, Astrocyte, Glial fibrillar acidic protein
Summary
Manganese-superoxide dismutase (Mn-SOD) was localized in the cerebral cortex
and hippocampus of patients with Alzheimer-type senile dementia (ATD) by immunocytochemistry and the relationship of Mn-SOD with two major pathological
features of ATD, i.e" senile plaques and neurofibrillar tangles (NFTs), was
examined. Many astrocytes in senile plaques exhibited strong immunoreactivity
for both Mn-SOD and glial fibrillar acidic protein (GFAP) on serial section
analysis.
This suggests that Mn-SOD scavenger system is associated with the
formation of senile plaques.
On the other hand, Mn-SOD immunoreactivity was
not significant in NFT-Ioaded neurons.
Introduction
It has been suggested that free radicals are involved in the pathogenesis of
Alzheimer's type disease (ATD) 0, 2).
Copper/zinc (Cu/Zn) -superoxide dismutase
(SOD), an isozyme of scavenging enzymes of superoxide radical, may participate
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Correspondence and proof are to: Dr. Mitsuyo Maeda, Fist Department of Anatomy,
Osaka City University Medical School, 1-4-54
Asahimachi, Abeno-ku, Osaka 545, Japan
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MITSUYO MAEDA et al.
In
this process, since abundant Cu/Zn-SOD transcripts are present In neurofibrillar
tangle (NFT)-loaded neurons in the hippocampus (3) and this enzyme increases in
activity in platelets from patients with ATD (4). Manganese (Mn)-SOD, the second
major isozyme, has not yet been well studied in ATD brain.
We, therefore,
attempted to immunocytochemically localize Mn-SOD structures in the cerebral
cortex and hippocampus from ATD patients and to determine their morphological
rela tionship to senile plaques and NTFs.
Materials and methods
Brains from 7 ATD patients (69-76 years old) and 1 control subject (68 years
old) were examined. Two to six h after death, the brain was dissected and fixed
in 10 % formalin for several days and blocks were embedded in paraffin. Frontal
sections containing the cerebral cortex (temporal, parietal and frontal lobes) and
hippocampus were serially cut at a thickness of 4 fJm and mounted on glass
slides. The sections were incubated in Mn-SOD antiserum (dilution: 1:500) (given
by Dr. N. Taniguchi) overnight at 4 °C and stained by the avidin-biotin-complex
(ABC) method (5). Polyclonal antibody against Mn-SOD purified from the human
brain was produced in a rabbit. After reaction with 3,3 ' -diaminobenzidine tetra
HCl (DAB), the sections were lightly counterstained with hematoxyline and
dehydrated. The consecutive sections were subjected to ABC method to detect
glial fibrillary acidic protein (GFAP) (Dako) or stained by Bielschowsky method
to detect senile plaques and NFTs.
Results
Mn-SOD was visualized in both normal and ATD subjects as granular or rodshape immuno-precipitates (Fig. 1A), possibly corresponding to mitochondria as
shown in the rat brain (6). Cells with very strong Mn-SOD immunoreactivity were
frequently found in the peripheral portion of senile plaques in the cerebral cortex
(all lobes examined) (Fig. 1A) and hippocampus in ATD, whereas such strongly
labeled cells were not seen in both brain areas of the normal subject. Serial
section analysis demonstrated that many astrocytes had strong immunoreactivity
for both Mn-SOD and GFAP (Fig. lA, B). This coexistence was found in many
astrocytes not only in classical plaques (Fig. 1C) but also in primitive plaques
by Bielschowsky staining of the adjacent sections. Mn-SOD-immunoreactivity
was not significant in NFT-loaded neurons (Fig. 2).
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Mn-SOD m cerebral cortex and hippocampus in Alzheimer's disease
Fig.
Light micrographs of consecutive sections stained with Mn-SOD
antibody (A), with GFAP antibody (B) or by the Bielschowsky
method (C) in the ATD temporal cortex. Arrows indicate
neurons exhibiting strong immunoreactivity for both Mn-SOD
and GFAP. Scale: A-C, 20 11m.
Fig. 2 Light micrographs of consecutive sections stained with Mn-SOD
anti body (A) or by the Bielschowsky method (B) in the A TD
temporal cortex. A large cell containing NFT (arrow) shows
no significant immunoreactivity for Mn-SOD compared to the
other cells. Scale: A, B, 20 11m.
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MITSUYO MAEDA et aJ.
Discussion
Little information
IS
so far availale on immunocytochemical localization of
Mn- and Cu/Zn-SOD in glial cells (7).
Very strong immunoreactivity for Mn-SOD
in GFAP positive astrocytes in senile plaques suggests that the generation of
superoxide radical is facilitated in these astrocytes during plaque formation.
Although it remains unclear whether astrocytes are primarily or secondarily involved in the formation of senile plaques (8,9), astrocytic plaque-related reaction
with strong GFAP-immunoreactivity is suggested to develop very early during
plaque formation; this may precede dystrophic neuritic change and relate to subminimal amyloid deposits (0). Therefore, Mn-SOD synthesis may be induced in the
astrocytes from a relatively early stage of plaque formation.
of significant increase in Mn-SOD
immunoreactivity
in
However, the lack
NFT-Ioaded
neurons
suggests that Mn-SOD is not closely associated with NFT formation, compared
with Cu/Zn-SOD which showed an increased immunoreactivity and thus is speculated to playa role in NFT formatiom (3).
Differential regulation of synthesis
between Mn-SOD and Cu/Zn-SOD was also seen in the axotomized motoneuronal
reaction (11).
Acknowledgments
The authors are very grateful to Dr. N. Taniguchi for genenously supplying us
with Mn-SOD antiserum.
We also wish to thank Mr. K. Inoue for his technical
assistance.
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Received November 15, 1996
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