HEALTH, 2009, 1, 8-16
Published Online June 2009 in SciRes.
Studies on biological effect of lycopene on Hippocampus
of hyperlipemia rats
Yao-Chi Zeng1,4, Min-Yu Hu1*, Shu-Lin Qu2, Liang Zeng3
1Department of Nutrition and Food Hygiene, School of Public Health, Central South, University, Changsha, 410078, China. (Yao-chi
ZENG,, 2The Medical College of Hunan Normal University, Changsha, 410006, China, 3Tumor Hospital
of Hunan Province, Changsha, 410006, China, 4Shenzhen Nanshan Health Bureau, Shenzhen, 518059, China; *Corresponding author:
Prof. Min-Yu Hu, Ph.D, Department of Nutrition and Food Hygiene, Tel & Fax: +86-731-4805452, School of Public Health, Central
South, University, Changsha , Hunan 410078, P. R. China. (E-mail:
Received 13 April 2009; revised 1 May 2009; accepted 7 May 2009.
Objective: This study investigated into the ef-
fect of lycopene on expression of APP, bax and
bcl-2 in hippocampal CA1 region of rats with
hyperlipidemia. Methods: By total cholesterol
(TC) and body weight, 48 adult male SD rats
were randomized into six groups, a normal
control group, fed with basic feed; a high-fat
model group, fed with high-fat feed; a positive
drug control group, fed with high-fat feed and
administrated with fluvastatin sodium at a dose
of 10 mg·kg·bw-1·d-1 by gastric perfusion; and
lycopene groups at three dose levels, fed with
high-fat feed and administrated with lycopene at
doses of 11, 22 and 44 mg·kg·bw-1·d-1 respec-
tively also by gastric perfusion. Caudal venous
blood samples of rats in all groups were taken at
week 0, week 1 and week 3 after the experiment
started so as to assay TC, TG, LDL-C and HDL-C;
at the end of the experiment, rat brains were
taken and sections of the hippocampal CA1 re-
gion were prepared. Expression of APP, bax and
bcl-2 in the CA1 region was determined by im-
munohistochemical methods and morphologi-
cal examination was carried out. Results: One
week after fed with high-fat feed, models of hy-
perlipidemia rats were established; at the end of
experiment, hippocampal APP and bax expres-
sion was enhanced while bcl-2 expression was
significantly weakened (p<0.05); to rats with
hyperlipidemia, both lycopene and fluvastatin
sodium could reduce TC, TG and LDL-C, inhibit
expression of hippocampal APP and bax and
promote expression of bcl-2 (p<0.05). Conclu-
sion: Lycopene down-regulates the expression
of bax and up-regulates that of bcl-2 mainly by
reducing serum TC and LDL-C and weakening
expression of APP in the hippocampal CA1 re-
gion of rats with hyperlipidemia, thereby main-
taining normal morphology of hippocampal
neurons and facilitating the protection of the
Keywor ds: lycopene; hyperlipidemia; hippocampus;
APP; bax; bcl-2
Lycopene is a potent singlet oxygen scavenger and has
the effect of preventing free radical injuries. Studies
have shown that it has many important bioactivities, e.g.,
quenching singlet oxygen, eliminating reactive oxygen
species, blocking lipid peroxidation, suppressing cell
reproduction, reinforcing immunity, and inducing gap
junction intercellular communication [1,2,3,4]. Both
epidemiological and laboratorial studies suggest that
lycopene, a powerful antioxidant agent, can reduce the
risk of cardiovascular diseases [5,6]. Early studies indi-
cate that lycopene can effectively lower levels of serum
TC, TG and LDL-C of rabbits with artherosclerosis in-
duced with high fat and inhibit atherogenesis with an
effect equivalent to that of fluvastatin [7,8]. As is sug-
gested by studies, hyperlipidemia can cause injuries to
the brain. Rise of blood cholesterol may harm endothe-
lial cells of cerebral arteries and capillaries, accelerate
progress of atherosclerosis and slow cerebral blood flow,
thereby injuring cerebral metabolism and increasing
risks of cognitive function impairment and dementia. In
addition, blood cholesterol increase may also directly
lead to neuronal degeneration related to cognitive func-
tion. The biological mechanism [9] may be that blood
cholesterol increase affects APP metabolism of neurons
Y. C. Zeng et al. / HEALTH 1 (2009) 8-16 9
SciRes Copyright © 2009 HEALTH
and accelerates production and sediment of Aβ, thereby
leading to cognitive function impairment. Every 10%
increase of blood cholesterol can double the quantity of
Aβ plaques in the brain [10]. Morphological changes of
cranial neurons and decrease of cognitive ability both
correlate with Aβ increase. Aβ can also mediate disor-
ders of signal transduction pathways and lead to apop-
tosis in the end [11]. Lycopene can penetrate the
blood-brain barrier and be present in the central nervous
system [12]. Charu K. et al found that after eight weeks’
feeding with lycopene at a dose of 10μ, this
substance became detectable at various concentrations
from blood and tissue of mice and the lycopene concen-
tration in the brain tissue was 9.24±3.19 ng.g-1 wet tis-
sues, indicating that lycopene taken from food can pass
through the blood-brain barrier and reach the brain tissue
[13]. Studies carried out by Foy CJ et al. [14] showed
that deficiency of a series of anti-oxidation nutrients
including lycopene is related to such neurodegenerative
diseases as Parkinson’s disease, vascular dementia, Alz-
heimer disease, etc. To sum up, hyperlipemia can impair
the brain tissue, while lycopene has blood lipid lowering
action and can pass through the blood-brain barrier, so
we think lycopene has protective effect on brains of hy-
perlipemia rats.
In this study, hyperlipidemia animal models were es-
tablished by feeding rats with high-fat feed and then,
lycopene was administrated to see its effect on serum
lipid and expression of APP, bax and bcl-2 in the hippo-
campal CA1 region of the subject animals so as to inves-
tigate into the possible protective effect of lycopene on
the hippocampus.
2.1. Formulation and Supply of High-Fat Feed
Basic feed comprising wheat (20%), rice (20%), corn
(10%), bean cake (24%), fish flour (10%), wheat bran
(10%), salt (1%), bone meal (2%), milk powder (2) and
multivitamins (1%) was prepared by Experimental Zo-
ology Division, Xiangya Medical College of Central
South University. The content of protein in the feed was
19% assayed by Kjeldah method.
High-fat feed: Animal models were established with
reference to the method adopted by Deepa et al [15] us-
ing high-fat feed containing basic feed (94.5%), choles-
terol (4%), cholic acid (1%) and propylthiouracil (0.5%).
2.2. Apparatus and Reagents
Amyloid precursor protein (APP) rabbit anti-mouse
polyclonal antibodies (Lot: 20080601) were purchased
from Wuhan Boster Bioengineering Co., Ltd; bax and
bcl-2 rabbit anti-mouse polyclonal antibodies and DAB
color development kits were all produced by Beijing
Zhong Shan-Golden Bridge Biological Technology Co.,
Ltd and were expected to expire in July of 2009. Lyco-
pene powder with a purity of 90% (Lot: 041202) was
obtained from North China Pharmaceutical Co., Ltd.
Fluvastatin sodium capsules (Lot: X0006) were supplied
by Novartis AG. Kits of serum lipid indexes were pro-
duced by BioSino Bio-technology and Science Inc.
Other instruments used in the study included a TP1020
auto dehydrating machine for organic tissue (Germany
Leica), a ZT-14s staining machine (Yaguang, Xiaogan of
Hubei), a Finesse325 common paraffin section machine
(Thermo Shandon) and a BX40 light microscope
Fluvastatin is used together with lifestyle changes
(diet, weight-loss, exercise) to reduce the amount of
cholesterol (a fat-like substance) and certain other fatty
substances in the blood. Fluvastatin is in a class of
medications called HMG-CoA reductase inhibitors
(statins). It works by slowing the production of choles-
terol in the body. Fluvastatin sodium is an approved lipid
lowering drug having passed numerous animal experi-
ments and widely applied to the clinic. In animal ex-
periments, the optimal dose for rats and rabbits is 10mg.
kg-1 [16,17].
2.3. Animals and Grouping
48 adult male SD rats, weighing 195±10 g, were sup-
plied by Experimental Zoology Division, Xiangya
Medical College of Central University. After adaption
feeding for one week with the basic feed, the animals
were weighed on an empty stomach and caudal blood
was taken to assay serum TC. Then, according to the
body weight and TC level, the rats were divided ran-
domly into six groups, each containing eight, and caged
by two. Arranged were a normal control group (C), fed
with basic feed; a high-fat model group (F), fed with
high-fat feed; a positive drug control group (FF), fed
with high-fat feed and administrated with fluvastatin
sodium at a dose of 10 mg·kg·bw-1·d-1; and lycopene
groups at three dose levels (FL1, FL2 and FL3), fed re-
spectively with high-fat feed and administrated with
lycopene at doses of 11, 22 and 44 mg·kg·bw-1·d-1.
During the experiment, except group C, which was fed
with basic feed, all groups were fed with high-fat feed.
In the second week of the experiment, 1% CMC-Na
solvent was administrated to group C and group F by
gastric perfusion, and fluvastatin sodium and lycopene
powder with 1% CMC-Na as the solvent were adminis-
trated, also by gastric perfusion, to animals in other
groups at the designed doses (the gastric administration
volume was 1 ml·d-1 for rats in all groups). The animals
were allowed to drink freely and their daily food intakes
were recorded. The temperature and relative humidity
were respectively controlled at 25±2 and 60%~70%.
The rats were weighed twice a week and the gastric ad-
ministration volumes of fluvastatin sodium and lycopene
10 Y. C. Zeng et al. / HEALTH 1 (2009) 8-16
SciRes Copyright © 2009 HEALTH
were adjusted according to the body weights. However,
since the dose relative to body weight remained constant,
gastric administration was performed according strictly
to the designed doses. All experimental procedures were
conducted in accordance with the guidelines of the ani-
mal ethical committee for animal experimentation in
3.1. Specimen Collection
At the ends of week 0, week 1 and week 3 of the ex-
periment, the animals were fasted for 12h and then, their
tails were cut; blood samples were taken to assay the
levels of serum TC, TG, LDL-C and HDL-C. At the end
of the experiment, pentobarbital sodium at a dose of bw-1 was administrated by peritoneal injection
to anesthetize the animals, and then, the animals were
deeply anesthetized and perfused via left ventricular
with 0.9% saline followed by 4% paraformaldehyde
(20ml/min for 5 min). Following decapitation, the brains
were removed. After the cerebral meninges was stripped,
the brains was fixed in 10% formaldehyde solution .And
24h later, the specimen was cut with a coronal-shaped
opening about 5mm in front of the posterior extremity of
the biparietal suture; from the plane of the hippocampus
and the dentate band under macroscopic observation, a
tissue piece about 1cm thick was cut in the direction of
the procerebrum and imbedded with paraffin. The cor-
onal plane was cut continuously to produce eight sec-
tions with a thickness of 4μm for each rat. According to
the preparation order, sections of each group were di-
vided into eight sets. Immunohistochemical staining was
applied to sections of the 1st, 2nd, 4th, 5th, 6th and 8th
sets, while HE routine staining was applied to the 3rd
and 7th sets.
3.2. Assay Methods
Serum TG and TC were analyzed by enzymatic methods
of glycerol phosphate oxidase-peroxidase- 4- aminoan-
tipyrine (GPOPAP) and cholesterol oxidase-peroxidase-
4-aminoantipyrine (CHOD-PAP) respectively) [18].
Concentrations of HDL-C were determined in the su-
pernatant after precipitation of lipoprotein-B using
phosphototungstic acid/Mg2+ (PTA/Mg2+), and the con-
centrations of LDL-C were calculated as described by
Friedewald et al. [19]. All the operation procedures were
carried out according to instructions of the kits. Immu-
nohistochemical SABC [20] or HE staining of the histo-
logical sections was performed to detect APP, bax and
bcl-2 positive particles and pathological changes of the
hippocampal CA1 region. The principal procedures in-
cluded paraffin section deparaffinage and dehydration;
3% H2O2 incubation for 20min; phosphate buffer (PBS)
washing; microwave treatment in 0.01mol/L citrate
buffer for antigen retrieval; blocking serum application
and incubation for 20min; primary antibody application
and incubation at 37 for 1-2h; horse radish peroxidase
labeled secondary application and incubation for 15min;
color development with diaminobenzidine (DAB) solu-
tion; hematine counterstaining; dehydration; mounting;
and light microscopic observation. For the negative con-
trol, the operation was basically the same as that for the
test groups except that the primary antibody was substi-
tuted by phosphate buffer. Presence of brown-yellow
particles in the nucleus or the endochylema was consid-
ered as indication of positive results. Under a 400× high
power lens, 10 fields of view without edge overlap were
selected randomly for each section (five fields of view
for the hippocampal CA1 region of each side, each field
being about 0.075 squm) to count positive particles in
each high power field. The number of positive particles
was calculated by the following formula: number of
positive particles = (the total number of positive cells/the
total number of cells)/10 (the number of fields of view).
The result was expressed as the mean [21]. Pictures were
3.3. Quality Control
All glassware used for the experiment were soaked in a
sulfuric acid solution of potassium bichromate for 24h,
washed clean with deionized water, rinsed with redis-
tilled water for three times and then dried for use. A cer-
tain quantity of paraffin sections was drawn for prelimi-
nary experiment of immunohistochemical staining so as
to elicit the optimal experimental conditions. Lycopene
was dissolved in 1% CMC-Na and the gastric admini-
stration solution was freshly prepared before use.
3.4. Statistical Methods
The data were analyzed with SPSS13.0 software and all
measurement data were expressed as mean ± standard
deviation (x±S). Analysis of variance was used for
group comparisons. Statistical analyses were performed
using analysis of variance for mean comparison of mul-
tiple samples, S-N-K and LSD tests for paired compari-
son, and analysis of variance of data of replicate meas-
urements for comparison of different experiment inter-
vals. Kruskal-Wallis H test and Spearman correlation
analysis were applied to data in non-normal distribution,
which were also tested by Nemenyi method of paired
comparison. The level of statistical significance for all
analyses was set at α=0.05.
4.1. General Conditions and Body Weight
Changes of Rats
During the experiment, rats of all groups exhibited nor-
mal activities and had smooth and glossy fur as always.
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SciRes Copyright © 2009
No significant difference was found in body weight in
all groups with the exception of group C at all time
points during the experiment (P>0.05). Analysis of vari-
ance of replicate measurements showed that, in different
stages, body weights of the animals in all groups have
significant difference (P<0.05).
4.2. Serum Lipid Index Changes of Rats in
Different Stages
Analysis results of serum lipid indexes of rats in differ-
ent stages are shown in Figure 1.
As is indicated by the analysis results in Figure 1, at
the end of the first week of the experiment, serum TC,
TG and LDL-C of rats in the group fed with high-fat
feed increased significantly (P<0.05) compared with
those of rats in group C, suggesting the success of estab-
lishment of hyperlipidemia rat models with no statistical
significance of lipid index differences among the groups
(P>0.05). At the end experiment, no significant differ-
ence was present between TC levels of group FL3 and
group FF (P>0.05), neither between TG levels of group
FL2 and FL3 and group FF (P>0.05). Compared with
the result of group F, the LDL-C levels of all other
groups were significantly decreased (P<0.05); the LDL-
C level of group FL3 was lower than that of group FF
(P<0.05). HDL-C differences of rats in these groups
during the experiment had no statistical significance
4.3. Expression of APP in the Hippocampal
CA1 Region
Positive APP reaction products are brown-yellow parti-
cles distributed in cell membranes and cytoplasma. The
analysis results in Table 1 show that: the number of
positive APP particles in group F increased significantly
compared with that in group C (P<0.05); the number of
APP positive particles in groups FF, FL2 and FL3 was
significantly lower than that in group F (P<0.05); the
difference between group C and group FL1 had no sta-
tistical significance (P=0.492); the difference of the
Figure 1. The serum lipids of rats at different experimental stage (x±S). Different alphabet superscripts of the same column indi-
cate the significant differences between groups (p<0.05); Different symbol (*, #, &) represent significant differences at 0, 1, 3w in
the same group (p<0.05).
12 Y. C. Zeng et al. / HEALTH 1 (2009) 8-16
SciRes Copyright © 2009
number of APP positive particles in group FL2 and
group FL3 had no statistical significance (P=0.535). A
few APP positive reaction particles could be seen in the
hippocampal CA1 region of rats in group C. The quan-
tity of positive particles significantly increased and the
color was rat deep in group F. Tabove findings
indicated that lycopene can inhibit expression of APP in
hippocampal CA1 region of rats with hyperlipidemia. The
effect in lycopene groups of 22mg·kg·bw-1·d-1 and
44mg·kg·bw-1·d-1 was more satisfactory than that in the
10mg·kg·bw-1·d-1 fluvastatin sodium group (see Figure 2).
4.4. Expression of bax and bcl-2 in the
Hippocampal CA1 Region
After immunohistochemical staining of neurons, the
main phenomenon was the presence of brown-yellow
substance depositing in cytoplasm. Part cell membrane
and caryotheca were also stained with the manifestation
of neuron profiles. According to result analysis in Table
2, bax and bcloth expressed hippocampal
CA1 region of roup C; in rats of group F, the
-2 were b
ats in gr
Table 1. The expression APP in the hippocampus CA1 region
[Median(QR)]. Different alphabet superscripts of the iso-column
indicate the significant differences between groups (a: p<0.05,vs.
group C; b: p<0.05, vs. group F; c: p<0.05, vs. group FF).
Group N
C 8 26.5 (4.5) b c
58.5 (10.3) a c
2.0 (3.3) a b
25.0 (3.5) b c
0.0 (0.0) a b
0.0 (0.8) a b
Figure 2. The hippocampus APP change of rat with immuno-
histochemistry by using the high power light microscope
(×400). Panel C: control; Panel F: hyperlipidemia model; Panel
FF: positive control, fluvastatin sodium; Panel FL1:
11mg·kg·bw-1·d-1 of lycopene; Panel FL2: 22mg·kg·bw-1·d-1 of
lycopene; Panel FL3: 44mg·kg·bw-1·d-1 of lycopene.
number of bax positive particles significantly increased
while that of bcl-1 positive particles significantly de-
creased (P<0.05); the number of bax positive particles in
groups F, FL1 and FL2 was higher than in group FF and
the differences were statistically significant (P<0.05). the
number of bax positive particles in groups FF, FL3 with
differences of no statistical significance (P=0.957); the
number of bclpositive particles inroups FF, FL1,
FL2 and FL3 were higher than in group FF with differ-
ences of statistical significance (P<0.05). As is shown in
Figure 3, bax-expression neurons degenerated with cell
shape irregularity and the cell edges were not so smooth.
Figure 4 indicates that bcl-2-expression neurons had
nearly normal shapes; the cells didn’t swell and were
mostly oval-shaped, and the edges were smooth.
4.5. Pathological Changes of Hippocampal
CA1 Region
By HE staining, in observations under high power lenses,
Table 2. The expression bax and bcl-2 in the hippocampus
CA1 region [Median(QR)]. Different alphabet superscripts of
the iso-column indicate the significant differences between
groups (a:p<0.05, vs. group C; b:p<0.05, vs. group F; c: p<
0.05, vs. group FF
-2 g
GroupNbax bcl-2 bcl-2/bax
6.5(1.8) b c
60.5(11.0) a c
11.0(3.0) a b
26.0(4.5) a b c
22.5(3.3) a b c
15.5(2.8) b c
0.0(0.8) a c
16.0(2.5) b
23.5(4.8) a b c
49.0(8.8) a b c
2.31 b c
0.00 a c
1.53 a b
0.90a b c
2.18 b c
811.0(2.0) a b 67.5(4.8) a b c 6.06 a b c
Figure 3. The hippocampus bax change of rat with immuno-
histochemistry by using the high power light (×400). Panel
C:control; Panel F; hyperlipidemia model; Panel FF; positive
control, fluvastatin sodium; Panel FL1: 11mg·kg·bw-1·d-1 of
lycopene; Panel FL2: 22mg·kg·bw-1·d-1 of lycopene; Panel FL3:
44mg·kg·bw-1·d-1 of lycopene.
Y. C. Zeng et al. / HEALTH 1 (2009) 8-16 13
SciRes Copyright © 2009
Figure 4. The hippocampus bcl-2 change of rat with immuno-
histochemistry by using the high power light (×400). Panel C:
control; Panel F: hyperlipidemia model; Panel FF: positive
control, fluvastatin sodium; Panel FL1: 11mg·kg·bw-1·d-1 of
lycopene; Panel FL2: 22mg·kg·bw-1·d-1 of lycopene; Panel FL3:
44mg·kg·bw-1·d-1 of lycopene.
the rats in group F of the number of hippocampal pyra-
mid cells decreased; the neurons were disorderedly ar-
ranged and were mostly stained deeply and triangular
with degeneration and karyopyknosis. In contrast, the
rats in other groups, large amounts of hippocampal
pyramid cells arranged tightly and regularly , clear
profiles and distinct demarcation between surrounding
tissue; the nuclei were blue and the cytoplasm was light
red; in shape, size and arrangement, neurons of all
groups were approximately normal (see Figure 5).
4.6. Correlation between the Parameters
Correlation analyses of TC, LDL-C and TG data in
Figure 1 and APP data in Table 1 found that Spear-
man’s rho was 0.821, 0.785 and 0.695 respectively and
P values were all 0.000, so it can be considered that
TC and LDL-C changes are closely related to exces-
sive expression of APP. Findings in this study showed
that hyperlipidemia could lead to excessive expression
of APP and bax in hippocampal CA1 region of rats and
their expressions were positively correlated, where
Spearman’s rho was 0.774 and P was 0.000; bcl-2 ex-
pression was reduced and was in negative correlation
with APP expression, where Spearman’s rho was
-0.737 and P values was 0.000; bcl-2/bax ratio de-
creased and was significantly lower than that of the
normal control group (P<0.05).
Figure 5. The hippocampus change of rat dyed with HE by
using the high power light (×400). Panel C: control; Panel F:
hyperlipidemia model; Panel FF; positive control, fluvastatin
sodium; Panel FL1: 11mg·kg·bw-1·d-1 of lycopene; Panel FL2:
22mg·kg·bw-1·d-1 of lycopene; Panel FL3: 44mg·kg·bw-1·d-1 of
Hyperlipidemia is closely related to the occurrence of
coronary heart diseases, myocardial infarction, hyper
tension, diabetes mellitus, apoplexy, etc. and also poses a
risk of AD. Results of this study also suggest that high-
fat feed intake can cause hyperlipidemia in rats while
lycopene intervention can lower the serum lipid level of
rats fed continually with high-fat feed and decelerate the
rise of serum lipid.
Clinical studies have also confirmed the positive cor-
relation between excessive increase of serum cholesterol
and AD occurrence [22]. In recent years, some studies
showed that hyperlipemia is an important factor for de-
velopment and progress of AD [23,24]. Yanagisawa [25]
et al found that the level of low density lipoprotein cho-
lesterol in the serum of AD patients significantly in-
creased, while that of high density lipoprotein choles-
terol significantly decreased. Epidemiological studies
proved that old people with blood cholesterol are more
subject to AD [26,27] and that people with hypercholes-
teremia in middle age are more prone to suffer from AD
when old [28]. Cholesterol lowering measures, espe-
cially taking statins, can reduce the risk of AD [29,30]
14 Y. C. Zeng et al. / HEALTH 1 (2009) 8-16
SciRes Copyright © 2009
ospective study on a population taking
onnected to cholesterol level [35,36]. Basic
at high cholesterol is relate
g atherosclerosis can aggravate depletion
sgenic mice [37]. In vitro
gested that whether by in-
nervous system. The normal physiological fun
tion (s) of APP in learning and memory remains unclear.
y processed by site-specific proteoly-
e Aβ will be
so mediate disor-
d that the contents o
se of serum TC, LDL-C and TG
of fluvastatin
has been no study
ng-term low APP
t the number of
-2 vector
and relieve cognitive function impairment of AD pa
tients [31]. A retr
statins showed that the AD incidence rate was 70%
lower in people taking the drugs than in the control
group [32]. It is a characteristic pathological change of
AD that β-amyloid (Aβ) deposits abnormally in special
encephalic regions[33,34] and the development of Aβ is
intimately c
studies have proved thd to
nervous system development, when more than half of
ring neurons will be cleared away; apopto
cognitive function impairment and that intake of foods
learning abilities of APP tran
cell culture experiments sug
hibiting cholesterol synthesis with HMG-CoAR inhibit-
ers or by lowering intracellular cholesterol with physical
methods, cellular Aβ content could be reduced [38].
APP is a transmembrane glycoprotein, mainly in the
centralc- TU
APP physiologicall
sis firstly by α- secretases or β-secretases, releasing a
large fragment called APP (S) that contains most of the
extracellular sequences of APP, a small extracellular
, the transmstubembrane region and the cytoplasmic tail
of APP. These are subsequently cleaved by γ-secretase
at multiple sites in the transmembrane region, releasing
small peptides, Aβ (1-40) and Aβ (1-42), the major
components of AD-associated amyloid fibrils [39]. Aβ,
principal constituent of senis aile plaques (degenerated
axons surrounding amyloid substance in essence, one of
the main pathological changes of AD) [40]. Then the
cholesterol level in the blood rises, mor
produced in the brain [41]. Morphological changes of
cranial neurons and decrease of cognitive ability both
correlate with Aβ increase. Aβ can al
ders of signal transduction pathways and lead to apop-
tosis in the end [42]. It has been found in studies that
excessive expression of APP genes is the cause for
deposition of β-amyloid [43] anf β- normal. The study indicates that lycopene can maintain
morphological normality of hippocampal neurons of
hyperlipidemia rats and, possibly by inhibiting excessive
expression of hippocampal APP, up-regulate expression
APP mRNA and APP protein in hippocampal region of
senescence accelerated mice (SAM) increase with the
growth of age and excessive expression of hippocampal
APP is related to memory loss of SAMs [44]. This study
suggests content increa
and also excessive APP expression in hippocampal CA1
region of hyperlipidemia rat models established after
feeding high-fat feed for three weeks. Lycopene can
inhibit excessive APP expression by lowering serum TC
and LDL-C levels of rats, reducing injuries to the nerv-
ous system caused by hyperlipidemia. Analysis results in
Table 1 indicate that APP expression so-
dium group and lycopene group of 22 and 44
mg·kg·bw-1·d-1 was significantly lower than that of the
normal control group. So far, there
report on low expression of APP. In this study, no
marked abnormality was found in hippocampus mor-
phology observation of rats in the above three groups.
Whether lycopene plays its hippocampus protection role
through other routes and whether lo
expression will bring adverse effect on the organic body
should be addressed in further studies.
Neuron apoptosis is necessary to dynamic equilibrium
maintenance of growth and development of the nervous
m and takes place mainly in early stages of the
atusis can
also remove injured or diseased neurons [45]. However,
apoptosis is also an important way of neuron dying; ex-
cessive apoptosis may aggravate cerebral ischemic-
reperfusion injuries [46]. Apoptosis is the cause for cog-
nitive impairment before massive neuron death [47]. It
has been proved in studies that neuron loss in AD origi-
nates from apoptosis, evidenced by tha
NEL positive cells is found by TUNEL method to
increase in AD autopsied brain tissue [48] and that apop-
tosis-related bcl-2 is found be down-regulated in brains
of AD patients [49,50]. Genes related to cerebral neuron
tosis include apapopoptosis inhibiting genes and apop-
tosis inducing genes. Bcl-2 is an apoptosis inhibiting
gene while genes inducing apoptosis mainly include bax,
Fas, p53, etc. Bcl-2 and bax are in a balanced system in
healthy people. Excessive expression of bcl-2 will in-
hibit apoptosis while excessive expression of bax can
accelerate apoptosis. The bcl-2/bax ratio regulates the
occurrence of apoptosis. A study showed by maintaining
the local ratio of bcl-2/bax using the HSV bcl
one may protect CA1 pyramidal cell from the delayed
neuronal death of transient global ischemia [51].
As is suggested in in vivo and in vitro studies, APP
can down-regulate expression of bcl-2 while up-regulate
of bax [52]. Morphological observation showed thathat t
hippocampal pyramidal cells of the model group de-
creased and were arranged disorderedly while morphol-
ogy of hippocampal region of other groups was basically
of apoptosis inhibiting gene bcl-2, down-regulate ex-
pression of apoptosis promoting gene bax and maintain-
ing constancy of bcl-2/bax ratio so as to protect hippo-
campal neurons.
To conclude, lycopene can effectively reduce serum
lipid level of experimental hyperlipidemia rats with the
dose of 44mg·kg·bw-1 having the most marked effect.
pene down-regulates theLyco expression of bax and
up-regulates that bcl-2of mainly by reducing serum TC
and LDL-C and weakening expression of APP in the
hippocampal CA1 region of rats with hyperlipidemia,
thereby facilitating the protection of the brain. However,
the specific working mechanism, the optimal effectiv
doses in different tissues and the adverse effect still re-
Y. C. Zeng et al. / HEALTH 1 (2009) 8-16 15
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Competing Interests
The authors declare that they have no competing inter-
Authors’ Contributions
YZ carried out the experiment of this manuscript and
drafted the manuscript and approved the final manu-
script; MH and SQ participated in the design of the study
and revised the manuscript. LZ participated the experi-
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