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Red ginseng abrogates oxidative stress via mitochondria protection mediated by LKB1-AMPK pathway

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Background Korean ginseng (Panax ginseng C.A. Meyer) has been used as a botanical medicine throughout the history of Asian traditional Oriental medicine. Formulated red ginseng (one form of Korean ginseng) has been shown to have antioxidant and chemopreventive effects. Methods This study investigated the cytoprotective effects and mechanism of action of Korean red ginseng extract (RGE) against severe ROS production and mitochondrial impairment in a cytotoxic cell model induced by AA + iron. Results RGE protected HepG2 cells from AA + iron-induced cytotoxicity by preventing the induction of mitochondrial dysfunction and apoptosis. Moreover, AA + iron-induced production of ROS and reduction of cellular GSH content (an important cellular defense mechanism) were remarkably attenuated by treatment with RGE. At the molecular level, treatment with RGE activated LKB1-dependent AMP-activated protein kinase (AMPK), which in turn led to increased cell survival. The AMPK pathway was confirmed to play an essential role as the effects of RGE on mitochondrial membrane potential were reversed upon treatment with compound C, an AMPK inhibitor. Conclusions Our results demonstrate that RGE has the ability to protect cells from AA + iron-induced ROS production and mitochondrial impairment through AMPK activation.
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RES E A R C H A R T I C L E Open Access
Red ginseng abrogates oxidative stress via
mitochondria protection mediated by LKB1-AMPK
pathway
Guang-Zhi Dong
1
, Eun Jeong Jang
1
, Seung Ho Kang
2
, Il Je Cho
1
, Sun-Dong Park
1
, Sang Chan Kim
1
and Young Woo Kim
1*
Abstract
Background: Korean ginseng (Panax ginseng C.A. Meyer) has been used as a botanical medicine throughout the
history of Asian traditional Oriental medicine. Formulated red ginseng (one form of Korean ginseng) has been
shown to have antioxidant and chemopreventive effects.
Methods: This study investigated the cytoprotective effects and mechanism of action of Korean red ginseng
extract (RGE) against severe ROS production and mitochondrial impairment in a cytotoxic cell model induced by
AA + iron.
Results: RGE protected HepG2 cells from AA + iron-induced cytotoxicity by preventing the induction of
mitochondrial dysfunction and apoptosis. Moreover, AA + iron-induced production of ROS and reduction of cellular
GSH content (an important cellular defense mechanism) were remarkably attenuated by treatment with RGE. At the
molecular level, treatment with RGE activated LKB1-dependent AMP-activated protein kinase (AMPK), which in turn
led to increased cell survival. The AMPK pathway was confirmed to play an essential role as the effects of RGE on
mitochondrial membrane potential were reversed upon treatment with compound C, an AMPK inhibitor.
Conclusions: Our results demonstrate that RGE has the ability to protect cells from AA + iron-induced ROS
production and mitoch ondrial impairment through AMPK activation.
Keywords: Arachidonic acid, Red ginseng, AMPK, Oxidative stress, Mitochondria
Background
During oxidation of fatty acids and phospholipids,
phospholipase A
2
triggers the release of arachidonic acid
(AA), a ω-6 polyunsaturated fatty acid [1,2]. As a biologic-
ally active pro-inflammatory mediator, AA can induce
apoptosis through its effects on mitochondria (e.g. calcium
uptake into mitochondria, or production of ceramide)
[1,2]. Furthermore, in the presence of iron, which is a cata-
lyst of auto-oxidation, AA stimulates cells to produce
excess ROS, resulting in induction of mitochondrial dys-
function [3-7]. AMP-activated protein kinase (AMPK, an
important molecule sensing cellular energy status) is
activated to reserve cellular energy content, and it plays a
function in determining cell survival or death in patho-
logical progression [7,8]. This crucial role is supported by
increases in cell survival upon treatment with the AMPK
activators metformin and 5-aminoimidazole-4-carboxamide-
1-β-D-ribofuranoside (AICAR) [9,10]. Moreover, a line of
agents protecting cells has been shown to inhibit radical-
induced stress through A MPK activation as well as induc-
tion of antioxidant enzymes [11,12].
Korean ginseng (Panax ginseng C.A. Meyer) is one of
the oldest and most frequently used botanicals in the
history of traditional Oriental medicine. Korean ginseng
extract is recommended for its life-enhancing properties
as well as promotion of energy and longevity. Studies
have shown that ginseng attenuates free radical-induced
oxidative damage [13,14], prevents carcinogenesis induced
by toxicants [15], and possesses immunostimulating, anti-
* Correspondence: ywkim@dhu.ac.kr
1
Medical research center for Globalization of Herbal Formulation, College of
Oriental Medicine, Daegu Haany University, Daegu 706-828, Korea
Full list of author information is available at the end of the article
© 2013 Dong et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons. org/licenses/by/2.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.
Dong et al. BMC Complementary and Alternative Medicine 2013, 13:64
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tumorigenic, and chemopreventive effects [16-18]. These
numerous cytoprotective and chemoprotective properties
attributed to ginseng might be explained in part by its
ability to ameliorate oxidative or nitrosative stress [19].
Korean red ginseng is one form of Korean ginseng that is
marinated in an herbal brew (i.e. heating Panax ginseng
either by sun-drying or steaming), resulting in the root
becoming extremely fragile. It has been shown that red
ginseng inhibits oxidative cell death through Nrf2 activation
and protects smokers from oxidative DNA damage
[20,21]. Although the biological effects of red ginseng have
been well studied, it is not yet clear whether or not its
cytoprotective effects against mitochondrial impairment
are induced by AA + iron.
In view of the numerous beneficial effects of red ginseng
as well as the importance of AMPK in the protection of
mitochondr ia, this study investigated whether or not
Korean red ginseng extract (RGE) is capable of protecting
B)
AA+iron
Procaspase-3
β-Actin
Control - RGE RGE
A)
PARP
C)
AA+iron
Control - RGE RGE
TUNEL-positive cell population (%)
##
∗∗
0
20
40
60
80
100
0
20
40
60
80
100
120
AA+iron
Control - 0.03 0.1 0.3 1 RGE (mg/ml)
Relative cell viability (%)
∗∗
##
##
##
Figure 1 The effect of Korean red ginseng extract (RGE) on hepatocyte viability. A) The effect of RGE on hepatocyte viability. HepG2 cells
were incubated with 10 μM arachidonic acid (AA) for 12 h and then were treated with 5 μM iron for 6 h. Cell viability was assessed by the MTT
assay. Data represent the mean ± S.E.M. of five replicates (treatment mean significantly different from vehicle-treated control,
**
p < 0.01; treatment
mean significantly different from AA + iron,
##
p < 0.01). B) TUNEL assay. HepG2 cells were treated with 1 mg/ml RGE for 1 h and were
continuously incubated with 10 μM AA for 12 h, followed by exposure to 5 μM iron for 6 h. The percentage of TUNEL-positive cells was quantified.
Data represent the mean ± S.E.M. of three separate experiments (treatment mean significantly different from vehicle-treated control,
**
p < 0.01;
treatment mean significantly different from AA + iron,
##
p<0.01).C) Immunoblottings for the proteins associated with apoptosis. Immunoblot analyses
were performed on the lysates of HepG2 cells that had been incubated with 1 mg/ml RGE for 1 h, continuously treated with 10 μM AA for 12 h, and
then exposed to 5 μM iron for 3 h. Equal protein loading was verified by β-actin immunoblotting. Results were confirmed by repeated experiments.
Dong et al. BMC Complementary and Alternative Medicine 2013, 13:64 Page 2 of 9
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mitochondria against the severe oxidative stress induced by
AA + iron and, if so, whether or not this extract has the
ability to prevent apoptosis. Our work demonstrates that
RGE protects cells against severe oxidative burst by
inhibiting mitochondrial impairment and ROS production
through AMPK activation.
Methods
Reagent
RGE was provided by Korea Tobacco & Ginseng Corporation
(Daejeon, Korea) [22]. AA and compound C were purchased
from Calbiochem (San Diego, CA). Anti-procaspase-3, anti-
phospho-acetyl-CoA carboxylase (ACC), anti-PARP, anti-
phospho-LKB1 and anti-phospho-AMPK antibodies were
obtained from Cell Signaling Technology (Beverly, MA).
Anti-AMPK, anti-ACC and anti-LKB1 antibodies were
purchased from Santa Cruz Biotechnology (Santa Cruz,
CA). Horseradish peroxidase-conjugated goat anti-rabbit,
rabbit anti-goat, and goat anti-mouse IgGs were obtained
from Zymed Laboratories (San Francisco, CA). Ferric ni-
trate, nitrilotriacetic acid [9], 3-(4,5-dimethylthiazol-2-yl)-
2,5-diphenyl-tetrazolium bromide (MTT), rhodamine 123,
2
0
,7
0
-Dichlorofluorescein diacetate (DCFH-DA), anti-β-actin
antibody, and other reagents were purchased from Sigma
(St. Louis, MO). The solution of iron-N TA complex was
prepared as described previously [7].
Cell culture
HepG2 (human), H4IIE (rat), and AML12 (mouse)
hepatocyte-derived cell lines were purchased from ATCC
(Rockville, MD). Cells were incubated in Eagles minimum
essential medium without 10% FBS for 12 h. Then, cells
were incubated with 10 μM AA for 12 h, followed by ex-
posure to 5 μM iron after washing with PBS. To assess the
effects of RGE, the cells were treated with RGE for 1 h prior
to the incubation with AA at the indicated doses [12].
MTT assay
The MTT assay was performed as previously described
[12]. Briefly, HepG2 cells were plated at a density of 1 × 10
5
cells per well in a 48-well plate. After treatment, viable cells
were stained with 0.25 mg/ml MTT for 2 h. The media
was then removed, and formazan crystals produced in the
wells were dissolved with the addition of 200 μldime-
thylsulfoxide. Absorbance at 540 nm was measured using
an ELISA microplate reader (Tecan, Research Triangle
Park, NC). Cell viability was defined relative to untreated
control [i.e. viability (% control) = 100 × (absorbance of
treated sample)/ (absorbance of control)].
Terminal deoxynucleotidyl transferase dUT P nick end
labeling (TUNEL) assay
The TUNEL assay was performed using the DeadEnd
Col-
orimetric TUNEL System, according to the manufacturers
Vehicle
AA+iron+RGE
Vehicle
Vehicle
AA+iron
RGE
A)
B)
AA+iron
Control - RGE RGE
GSH contents (nmol/mg protein)
##
∗∗
DCFH-DA>>
0
20
40
60
80
100
Figure 2 The cellular antioxidant effect of RGE. A) Cellular H
2
O
2
production. H
2
O
2
production was monitored by measuring
dichlorofluorescein (DCF) fluorescence. HepG2 cells were incubated
with 1 mg/ml RGE for 1 h, followed by incubation with AA (12 h)
and iron (1 h). RGE treatment attenuated AA + iron-induced ROS
production. B) Cellular GSH content. The GSH content was assessed
in cells that had been treated as described in the legend to
Figure 1C. Data represent the mean ± S.E.M. of three separate
experiments. The statistical significance of differences between
treatments and either the vehicle-treated control (
*
p <0.05,
**
p <0.01)
or cells treated with AA + iron (
##
p < 0.01) was determined.
Dong et al. BMC Complementary and Alternative Medicine 2013, 13:64 Page 3 of 9
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instruction [23]. HepG2 cells were fixed with 10% buffered
formalin in PBS at room temperature for 30 min and were
permeabilized with 0.2% Triton X-100 for 5 min. After wash-
ing with PBS, each sample was incubated with biotinylated
nucleotide and terminal deoxynucleotidyltransferase in
100 μl equilibration buffer at 37°C for 1 h. The reaction
was stopped by immersing the samples in saline so-
dium citrate buffer for 15 min. Endogenous peroxidases
were blocked by immersing the samples in 0.3% H
2
O
2
for
5 min. The samples were treated with 100 μlofhorserad-
ish peroxidase-labeled streptavidin solution (1:500) and
were incubated for 30 min. Finally, the samples were devel-
oped using the chromogen, H
2
O
2
and diaminobenzidine
for 10 min. The samples were washed and examined under
light microscope (200×). The counting of TUNEL-positive
cells was repeated three times, and the percentage from
each counting was calculated.
Immunoblot analysis
Cell lysates and Immunoblot analysis were performed
according to previously published methods [23]. Protein
bands of interest were develope d using an ECL chemilu-
minescence system (Amersham, Buckinghamshire, UK).
Equal protein loading was verified by immunoblotting
for β-actin.
Rhodamine 123
A)
B)
M1fraction (%)
##
Control - RGE RGE
∗∗
0
20
40
60
80
M1 M1
M1 M1
AA+iron
Control AA+iron
RGE AA+iron+RGE
Figure 3 Abrogation of mitochondrial dysfunction by RGE. A) Mitochondrial membrane permeability (MMP). HepG2 cells were treated with
1 mg/ml RGE for 1 h, followed by incubation with AA (12 h) and iron (1 h). The cells were harvested after rhodamine 123 staining. Treatment of
cells with AA + iron increased the subpopulation of M1 fraction (low rhodamine 123 fluorescence), as indicated by the left shift of the
population. B) Relative MMP. Data represent the mean ± S.E.M. of three separate experiments. The statistical significance of differences between
treatments and either the vehicle-treated control (
**
p < 0.01) or cells treated with AA + iron (
#
p < 0.05,
##
p < 0.01) was determined.
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Measurement of H
2
O
2
production
DCFH oxidation was determined using a FACS flow
cytometer (Partec, Münster, Germany). DCFH-DA is a
cell-permeable non-fluorescent probe that is cleaved by
intracellular esterases and is turned into the fluorescent
DCF upon reaction with H
2
O
2
[23]. The level of H
2
O
2
generation wa s determined by the concomitant increase
in DCF fluorescence. After treatment, cells were stained
with 10 μM DCFH-DA for 1 h at 37°C. Fluorescence in-
tensity in the cells was measured using FACS. In each
analysis, 10,000 events were recorded.
Determination of reduced GSH content
Reduced GSH in the cells was quantified using a commer-
cial GSH determination kit (Oxis International, Portland,
OR) [12]. Briefly, the GSH-400 method was a two-step
chemical reaction. The first step led to the formation of
substitution products (thioethers) between 4-chloro-1-me-
thyl-7-trifluromethyl-quinolinum methylsulfate and all mer-
captans present in the sample. The second step included β-
elimination reaction under alkaline conditions. This reaction
was mediated by 30% NaOH which specifically transformed
the substituted product (thioether) obtained with GSH into
a chromophoric thione.
Flow cytometric analysis of mitochondrial membrane
potential (MMP)
MMP was measured with rhodamine 123, a membrane-
permeable cationic fluorescent dye [12]. The cells were
treated as specified, stained with 0.05 μg/ml rhodamine 123
for 1 h, and harvested by trysinization. The change in
MMP was monitored using a F A CS flow cytometer (Partec,
Münster, Germany). In each analysis, 10,000 events were
recorded.
Data analysis
One way analysis of variance procedures were used to
assess significant differences amon g treatment groups.
For each significant treatment effect, the Newman-Keuls
test was utilized to compare multiple group means.
Results
Inhibition of AA + iron-induced hepatocyte death
AA + iron-induced cytotoxicity model is an effective ex-
perimental model for screening drugs for liver disease [7].
To determine whether or not RGE protects liver cells from
AA + iron-induced injury, HepG2 cell viability was mea-
sured by MTT assay after treatment with different doses of
RGE. Treatment with AA + iron significantly reduced cell
viability compared with the control group as shown in
Figure 1A. However, RGE treatment inhibited AA + iron
treatment-induced cell death in a dose-dependent manner,
and cell viability was completely recovered by treatment
with 1 mg/ml of RGE (Figure 1A). To further investigate
the cytoprotective effects of RGE on AA + iron-induced
liver cell injury, TUNEL assay was performed at a dose of
1mg/ml.Treatmentwith1mg/mlofRGEalonedidnot
induce hepato-cytotoxicity, whereas the same dose (1 mg/
ml) of RGE significantly reduced AA + iron-induced cell
death (Figure 1B). To confirm the cytoprotective effects of
RGE on AA + iron-induced cell death, the levels of P ARP
and procaspase-3 were measured by immunoblot analysis.
Treatment with AA + iron induced cleavage of P ARP and
p-AMPKα
p-ACC
A)
β-Actin
AMPKα
Relative level of protein (fold)
∗∗
∗∗
∗∗
RGE
10’ 30’ 1 3 6 (h)
Control
p-AMPKα
RGE
10’ 30’ 1 3 6 (h)
Control
B)
0
1
2
3
4
HepG2
HepG2
H4IIE
p-AMPKα
RGE
10’ 30’ 1 3 6 (h)
Control
β-Actin
p-AMPKα
β-Actin
AML12
C)
Figure 4 The activation of AMPK by RGE. A) AMPK activation.
Immunoblot analyses were performed on lysates of HepG2 cells that
had been treated with RGE for the indicated time period. B) Relative
protein level of AMPKα phosphorylation (p-AMPKα). Results were
confirmed by three experiments. Data represent the mean ± S.E.M.
(treatment mean significantly different from vehicle-treated control,
*
p < 0.05,
**
p < 0.01). C) AMPK activation by RGE in H4IIE and AML12
cell lines.
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procaspase-3, resulting in cell death. In contrast, decreases
in the levels of PARP and procaspase-3 induced by AA +
iron were inhibited by treatment with RGE (Figure 1C).
These results indicate that RGE has cytoprotective effects
against apoptosis in hepatocytes induced by AA + iron.
Inhibition of AA + iron-induced ROS generation
To investigate the mechanism underlying the protective
effects of RGE on AA + iron-induced liver cell death,
ROS generation was measured by FACS with or without
RGE treatment. There was no ROS generation in RGE
alone-treated cells comparable to control cells. AA + iron
treatment significantly induced ROS generation, whereas
RGE treatment completely inhibited ROS production
(Figure 2A). To further investigate the anti-oxidative effects
of RGE on AA + iron-treated cells, GSH was measured by
the colorimetric method. The intracellular concentration
of GSH in HepG2 cells was reduced by treatment with
AA + iron (Figure 2B). Treatment with RGE increased the
intracellular concentration of GSH and inhibited the AA +
iron-induced reduction of GSH. Taken together, these data
indicate that RGE inhibits AA + iron-induced ROS gener-
ation and GSH reduction.
Inhibition of MMP dysfunction
Next, we determined whether or not AA + iron-induced
liver cell death is mediated by mitochondrial dysfunction.
We measured fluorescence intensity in HepG2 cells stained
with rhodamine 123 by FA CS. MMP was not altered by
treatment with RGE alone compared with the control
group (Figure 3A). The number of rhodamine 123-negative
cells increased AA + iron treatment, whereas it was signifi-
cantly reduced by RGE co-treatment (Figure 3B). These re-
sults indicate that RGE prohibits AA + iron-induced ROS
generation and dysfunction of MMP to protect liver cells.
Activation of AMPK-ACC pathway via phosphorylation of
LKB1
To further investigate the mechanism of RGE during hep-
atocyte protection, the AMPK pathway was analyzed by
immunoblot analysis. The phosphorylation levels of AMPK
and ACC increased upon RGE treatment, and protein
levels reached their maximums at 0.5-1 h and 1-3 h, re-
spectively (Figure 4A and B). AMPK and ACC were also
phosphorylated upon RGE treatment in both H4IIE and
AML12 immortalized hepatocyte cell lines (Figure 4C).
Figure 5 The activation of AMPK by LKB1. A) LKB1 activation. Immunoblot analyses were performed on lysates of HepG2, H4IIE and AML12
cells that had been treated with RGE for the indicated time period. B) Phosphorylation of AMPKα by LKB1. Immunoblot analyses were performed
on lysates of LKB1 null HeLa cell and LKB1 wild-type HepG2 cells following treatment of RGE for 30 mins. Results were confirmed by repeated
experiments. C) Reduction of AMPKα phosphorylation by knock-down LKB1. D) The effect of CaMKK-β inhibitor on the activation of AMPK by
RGE. After treatment with 1 μg/ml STO-609, HepG2 cells were continuously incubated with RGE.
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LKB1, the upstream kinase of AMPK, was also phos-
phorylated by RGE treatment in HepG2, H4IIE, and
AML12 cell lines (Figure 5A). Phosphorylation of AMPK
and ACC was not detectable in LKB1-null HeLa cells
(Figure 5B). Furthermore, phosphorylation of AMPK and
ACC was decreased by knock-down of LKB1 in RGE-
treated HepG2 cells (Figure 5C). Additionally, STO609
(1 μg/ml), an inhibitor of calcium/calmodulin-dependent
kinase kinase (CaMKK) β, another upstream kinase of
AMPKα, had no effect in reversing RGE-induced AMPKα
phosphorylation (Figure 5D). These data indicate that
RGE treatment activates the AMPK-ACC pathway in he-
patocytes via activation of LKB1.
Inhibition of AA + iron-induced stress via AMPK pathway
To determine the involvement of AMPK in RGE-induced
protection of hepatocytes, MMP was measured after treat-
ment with Compound C, an AMPK inhibitor (Figure 6A).
There was no protective effect of RGE against AA + iron-
induced mitochondrial dysfunction in AMPK inhibitor-
treated cells (Figure 6B), verifying that AMPK is the key
protein protecting liver cells upon RGE treatment. All of
these data indicate that RGE activates the AMPK pathway
to protect hepatocytes against AA + iron (Figure 6C).
Discussion
Korean red ginseng is frequently used as a crude sub-
stance in traditional Oriental medicine and is also a well-
known, highly used raw medicinal material. RGE have
been reported to exhibit various biological activities, in-
cluding anti-inflammatory and antitumor effects [16-18].
In this study, we report that RGE has cytoprotective ef-
fects against AA + iron-induced oxidative burst, as con-
firmed by inhibition of apoptosis, ROS production, and
mitochondrial dysfunction, which were comparable to the
efficacies of other known antioxidants (e.g., resveratrol
and some flavonoids) [7,12,23,24]. Our results provide evi-
dence that RGE may be beneficial for treatment of liver
diseases by protecting cells from radical stress-induced
damage.
Figure 6 The role of AMPK activation in protecting mitochondrial function. A) Inhibition of RGE-induced AMPKα phosphorylation by
compound C treatment. Cells were incubated with RGE for 30 min following treatment of 5 μM compound C for 30 min. Results were confirmed
by repeated experiments. B) Reversal of the effect of RGE on MMP by compound C. After treatment with 5 μM compound C for 30 min, cells
were incubated with RGE and/or iron + AA. The subpopulation of M1 fraction was analyzed as described in the legend to Figure 3A. Data
represent the mean ± S.E.M. of three replicates (treatment mean significantly different from iron + AA,
**
p < 0.01). NS, not significant. C)A
schematic diagram illustrating the proposed mechanism by which RGE protects hepatocytes against AA + iron-induced oxidative stress.
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AA, a representative pro-inflammatory fatty acid de-
rived from cell membranes, stimulates ROS generation,
thereby inducing lipid peroxidation. AA is an important
mediator of the pathophysiological processes of various
diseases, although the role of AA in responding to toxic
stress remains controversial. In most cases, AA pro-
motes cellular ROS production and induces decreases in
mitochondrial respiratory activity, and ROS generated by
metabolism of AA contributes to the process of tissue
damage [25,26]. In addition, AA releases Ca
2+
from intra-
cellular stores and increases mitochondrial uptake of Ca
2+
,
which may cause apoptosis [27]. In other cases, prosta-
glandins, the main byproducts of AA, may be responsible
for the protection of some tissues [28,29]. Nevertheless,
AA-stimulated oxidative stress has been shown to have a
direct effect on mitochondria [1,2].
Iron accumulation in specific tissues (e.g. liver) is com-
monly associated with oxidative and inflammatory dam-
age, including metabolic disease and cancer [3,30], which
enhances oxidant production, lipid peroxidation, protein
oxidation, and DNA damage. Since iron is a catalyst of
auto-oxidation, the combination of AA and iron increases
radical stress and cell death in a synergistic manner
[7,12,31]. Moreover, HepG2 cells were used to apply the
well-established culture conditions of synergism to this
model. In fact, a series of cytoprotective and important
agents have been evaluated using this model [7,12,24,32].
This cell line was employed to comparatively evaluate the
protective effects of RGE in cells and mitochondria. To
determine the effects of RGE on oxidative stress, we
employed an in vitro approach using a combination treat-
ment with AA and iron to HepG2 cells.
AMPK (an intracellular sensor of energy status) serves
as a crucial regulator of cell survival or death in response
to pathological stress (e.g., oxidative stress, endoplasmic
reticulum stress, and osmotic stress) [8,33]. This import-
ant function of AMPK is supported by the finding that cell
viability is increased by treatment with AMPK activators,
including AICAR or resveratrol [12,24]. Moreover, a series
of beneficial compounds have shown the ability to pro-
tect mitochondria, thereby inhibiting ROS production
through activation of AMPK (e.g., oltipraz, resveratrol,
isoliquiritigenin, and sauchinone) [7,12,23,24].
In the present study, RGE activated AMPK in hepato-
cytes. Moreover, AMPK inhibition induced by compound
C also prevented the ability of RGE to increase dysfunc-
tion of MMP, suggesting that AMPK indeed inhibits AA +
iron-induced oxidative stress. In mammalian cells, LKB1
and CaMKKβ are the major upstream kinases of AMPK
[34,35]. RGE phosphorylation of AMPK was inhibited by
LKB1 knock-down but not by treatment with CaMMK in-
hibitor. Overall, it appears that AMPK activation induced
by RGE may protect hepatocytes against AA + iron-
induced oxidative stress. However, LKB1-AMPK might
not be a direct target of RGE. Protein kinase C-ζ or pro-
tein kinase A are the kinases that phosphorylate LKB1, an
upstream kinase of A MPK [36]. The pharmacological up-
stream target of RGE remains to be confirmed.
Conclusions
Our results demonstrate that RGE exerts cytoprotective
effects by inc reasing antioxidant capacity and recovery
of mitochondrial function, which may be associated with
AMPK activation. The present results may be inform-
ative in elucidating the action mechan ism and efficacy of
RGE in hepatocyte protection as well as in determining
its potential in treating various diseases related with oxi-
dative stress.
Abbreviations
AA: Arachidonic acid; ACC: Acetyl-CoA carboxylase; AMPK: AMP-activated
protein kinase; DCFH-DA: 2
0
,7
0
-dichlorofluorescein diacetate;
DMEM: Dulbeccos modified Eagles medium; FACS: Fluorescence activated
cell sorter; GSH: Glutathione; MMP: Mitochondrial membrane potential;
MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide;
NTA: Nitrilotriacetic acid; RGE: Korean red ginseng extract; ROS: Reactive
oxygen species; TUNEL: Terminal deoxynucleotidyl transferase dUTP nick end
labeling.
Competing interests
The authors declare that they have no competing interests.
Authors contributions
GZD: acquisition of data; analysis and interpretation of data; statistical
analysis; drafting of the manuscript. EJJ: acquisition of data; analysis and
interpretation of data. SHK: acquisition of data; analysis and interpretation of
data. IJC: obtained funding; administrative support. SDP: analysis and
interpretation of data; review of the manuscript. SCK: analysis and
interpretation of data; obtained funding; administrative support; study
supervision. YWK: acquisition of data; analysis and interpretation of data;
drafting of the manuscript; statistical analysis; obtained funding; study
supervision. All authors read and approved the final manuscript.
Acknowledgements
This work was supported by the National Research Foundation of Korea
(NRF) grant funded by the Korea government [MEST](No. 2012-0009400).
And, this was also partly by a grant from Daegu Haany University Ky. lin
Foundation in 2012.
Author details
1
Medical research center for Globalization of Herbal Formulation, College of
Oriental Medicine, Daegu Haany University, Daegu 706-828, Korea.
2
Sunlin
University, Pohang, Kyungsangbuk-do 791-712, Korea.
Received: 13 September 2012 Accepted: 26 February 2013
Published: 18 March 2013
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doi:10.1186/1472-6882-13-64
Cite this article as: Dong et al.: Red ginseng abrogates oxidative stress
via mitochondria protection mediated by LKB1-AMPK pathway. BMC
Complementary and Alternative Medicine 2013 13:64.
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... 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyl-tetrazolium bromide (MTT), dimethyl sulfoxide (DMSO) and other reagents were purchased from Sigma-Aldrich (St. Louis, MO, USA). RG was kindly provide as previously described [48]. ...
... HepG2, Hep3B and Huh7 hepatocyte-derived cells, and HeLa cells were purchased from the ATCC (Rockville, MD, USA). HepG2 cells and Hep3B (ATCC (Rockville, MD, USA) were cultured in Dulbecco's Modified Eagle Medium (DMEM) with 10% FBS and 50 units/ml penicillin and 50 mg/ml streptomycin, and Huh7 were grown in RPMI 1640 [48]. ...
... HepG2 and Hep3B cells were plated and cultured to confluency of 80-90 % and incubated in FBS free media for 12 h. Huh7 cells were plated in 5 % FBS added media and cultured to equal confluency [48]. Microplate reader (Tecan, Research Triangle Park, NC, USA) was used to assess. ...
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Background: Hepatocellular carcinoma (HCC) has a high incidence and is one of the highest mortality cancers when advanced stage is proceeded. However, Anti-cancer drugs available for treatment are limited and new anti-cancer drugs and new ways to treat them are minimal. We examined that the effects and possibility of Red Ginseng (RG, Panax ginseng Meyer) as new anti-cancer drug on HCC by combining network pharmacology and molecular biology. Materials and methods: Network pharmacological analysis was employed to investigate the systems-level mechanism of RG focusing on HCC. Cytotoxicity of RG was determined by MTT analysis, which were also stained by annexin V/PI staining for apoptosis and acridine orange for autophagy. For the analyze mechanism of RG, we extracted protein and subjected to immunoblotting for apoptosis or autophagy related proteins. Results: We constructed compound-target network of RG and identified potential pathways related to HCC. RG inhibited growth of HCC through acceleration of cytotoxicity and reduction of wound healing ability of HCC. RG also increased apoptosis and autophagy through AMPK induction. In addition, its ingredients, 20S-PPD (protopanaxadiol) and 20S-PPT (protopanaxatriol), also induced AMPK mediated apoptosis and autophagy. Conclusion: RG effectively inhibited growth of HCC cells inducing apoptosis and autophagy via ATG/AMPK in HCC cells. Overall, our study suggests possibility as new anti-cancer drug on HCC by proof for the mechanism of the anti-cancer action of RG.
... Pharmacological studies have indicated that ginseng and its extract, ginsenosides, exhibit favorable regulatory effects on iron metabolism, reducing cellular damage caused by iron overload. Ginsenosides reportedly activate the AMPK pathway to protect cells from iron-induced ROS production and mitochondrial damage [92]. Ginseng may also be involved in the regulation of iron metabolism in vivo by inducing estrogen-like effects [93]. ...
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Cognitive impairment associated with diabetes and Alzheimer’s disease has become a major health issue affecting older individuals, with morbidity rates growing acutely each year. Ferroptosis is a novel form of cell death that is triggered by iron-dependent lipid peroxidation. A growing body of evidence suggests a strong correlation between the progression of cognitive impairment and diabetes, Alzheimer’s disease, and ferroptosis. The pharmacological modulation of ferroptosis could be a promising therapeutic intervention for cognitive impairment associated with diabetes and Alzheimer’s disease. In this review, we summarize evidence on ferroptosis in the context of cognitive impairment associated with diabetes and Alzheimer’s disease and provide detailed insights into the function and potential action pathways of ferroptosis. Furthermore, we discuss the therapeutic importance of natural ferroptosis products in improving the cognitive impairment associated with diabetes and Alzheimer’s disease and provide new insights for clinical treatment.
... RG used here was a commercially available extract-type product and kindly provided by Korea Tobacco & Ginseng Corporation (Daejeon, Korea), which is the GMP company approved by Korea FDA and standardized RG according to the Korean Pharmacopoeia. 31 RG was dissolved in the water to treat cells and animals as previously described. 32 PARP, pro-Caspase3, BCL-XL, β-actin, phospho-AMPK, phospho-ACC, phospho-liver kinase B1 (LKB1), phospho-YAP, Yap and phospho-large tumor suppressor (LATS1) Antibodies against this were purchased from Cruz Biotechnology ( ...
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... Multiple types of research have shown that hepatic cells are protected from diethyl nitrosamine-induced cancer by pre-treatment with Panax ginseng, which also lowers the hallmark of liver cancer, that is glutathione-S-transferase P (GST-P) [141]. It also regulates the p53 pathway by suppressing BCL-1, Cdc2a, cyclin G1 and Igf-1 expression [148,149]. Korean red ginseng and its oil are potent hepatoprotective agents, protecting from oxidative stress and mitochondrial dysfunction via the AMPK/MAPK pathway [150,151]. Red ginseng also encourages apoptosis induced by TRAIL via upregulating the C/EBP protein in HepG2, Huh-7 and Hep3B cell lines [152]. ...
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... [82][83][84][85][86][87] , 황기[88][89][90] , 녹용[91][92][93][94] 등의 보기보양약(補氣補陽藥)은 미토콘드리아 기능 부전과 저산소증을 개선시킨다고 알려 져 있다. 비만 어혈형(瘀血型)에 빈용되는 도홍사물탕(桃 紅四物湯)은 허혈성 뇌손상에서 신경 염증과 저산소증을 개선시킴으로써 신경 손상을 완화시킨다 95) . ...
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Iron-overload disorders cause hepatocyte injury and inflammation by oxidative stress, possibly leading to liver fibrosis and hepatocellular carcinoma. This study investigated the efficacy of sauchinone, a bioactive lignan, in preventing iron-induced liver injury and explored the mechanism of sauchinone's activity. To create iron overload, mice were injected with phenylhydrazine, and the effects on hepatic iron and histopathology were assessed. Phenylhydrazine treatment promoted liver iron accumulation and ferritin expression, causing hepatocyte death and increased plasma arachidonic acid (AA). Sauchinone attenuated liver injury (EC50 = 10 mg/kg) and activated AMPK in mice. Treatment of hepatocytes with iron and AA simulated iron overload conditions: iron + AA synergistically amplified cytotoxicity, increasing H2O2 and the mitochondrial permeability transition. Sauchinone protected hepatocytes from iron + AA-induced cytotoxicity, preventing the induction of mitochondrial dysfunction and apoptosis (EC50 = 1 μM), similar to the result using metformin. Sauchinone treatment activated LKB1, which led to AMPK activation: these events contributed to cell survival. Evidence of cytoprotection by LKB1 and AMPK activation was revealed in the reversal of sauchinone's restoration of the mitochondrial membrane potential by either dominant negative mutant AMPKα or chemical inhibitor. In conclusion, sauchinone protects the liver from toxicity induced by iron accumulation, and sauchinone's effects may be mediated by LKB1-dependent AMPK activation.
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Polychlorinated biphenyls (PCBs) are ubiquitous environmental contaminants that display a broad spectrum of biological and toxicological properties. There has been compelling evidence supporting that PCB-induced cytotoxicity is mediated through generation of reactive oxygen species (ROS). Considerable attention has been focused on identifying naturally occurring phytochemicals that are able to scavenge excess ROS, thereby protecting against oxidative cell death. Red ginseng, which has a variety of biological and pharmacological activities including antioxidant, anti-inflammatory, antimutagenic and anticarcinogenic effects, has been used for thousands of years as a general tonic in traditional oriental medicine. In this study, we have investigated the effect of red ginseng extract (RGE) on PCB126-induced oxidative cell death in cultured rat pheochromocytoma (PC12) cells. PC12 cells treated with PCB126 exhibited increased accumulation of intracellular ROS and underwent apoptosis as determined by positive in situ terminal end-labeling (TUNEL staining) and the perturbation of the mitochondrial membrane potential (ΔΨ(m)). RGE treatment attenuated PCB126-induced cytotoxicity, apoptotic features and intracellular ROS accumulation. RGE treatment upregulated heme oxygenase-1 (HO-1) and glutamate cysteine ligase (GCLC) that are key antioxidant enzymes essential for cellular defense against oxidative stress. To elucidate the molecular mechanisms underlying RGE-mediated HO-1 and GCLC induction, we have examined the possible involvement of NF-E2-related factor 2 (Nrf2), a redox-sensitive transcription factor, that plays an important role in the transcriptional regulation of diverse antioxidative genes via interaction with the antioxidant response element (ARE). Treatment of PC12 cells with RGE increased the nuclear translocation, ARE-binding and transcriptional activity of Nrf2. Moreover, U0126 and LY294002, pharmacological inhibitors of MEK1/2 and phosphatidylinositol 3-kinase which are upstream of ERK1/2 and Akt/protein kinase B, respectively attenuated HO-1 and GCLC expression as well as the ARE-driven transcriptional activation of Nrf2. These findings, taken together, suggest that HO-1 and GCLC induction via Nrf2 activation may contribute to cytoprotection exerted by RGE against PCB126-induced oxidative stress.
Article
Isoliquiritigenin (ILQ), a flavonoid compound originated from Glycyrrhiza species, is known to activate SIRT1. Arachidonic acid (AA) in combination with iron (a catalyst of auto-oxidation) leads cells to produce excess reactive species with a change in mitochondrial permeability transition. In view of the importance of oxidative stress in cell death and inflammation, this study investigated the potential of ILQ to protect cells against the mitochondrial impairment induced by AA+iron and the underlying basis for this cytoprotection. Treatment with ILQ inhibited apoptosis induced by AA+iron, as evidenced by alterations in the levels of the proteins associated with cell viability: ILQ prevented a decrease in Bcl-x(L), and cleavage of poly(ADP-ribose)polymerase and procaspase-3. Moreover, ILQ inhibited the ability of AA+iron to elicit mitochondrial dysfunction. In addition, superoxide generation in mitochondria was attenuated by ILQ treatment. Consistently, ILQ prevented cellular H2O2 production increased by AA+iron, thereby enabling cells to restore GSH content. ILQ treatment enhanced inhibitory phosphorylation of glycogen synthase kinase-3beta (GSK3beta), and prevented a decrease in the GSK3beta phosphorylation elicited by AA+iron, which contributed to protecting cells and mitochondria. GSK3beta phosphorylation by ILQ was preceded by AMP-activated protein kinase (AMPK) activation, which was also responsible for mitochondrial protection, as shown by reversal of its effect in the experiments using a dominant negative mutant of AMPK and compound C. Moreover, the AMPK activation led to GSK3beta phosphorylation. These results demonstrate that ILQ has the ability to protect cells from AA+iron-induced H2O2 production and mitochondrial dysfunction, which is mediated with GSK3beta phosphorylation downstream of AMPK.
Article
Arachidonic acid (AA, a proinflammatory fatty acid) in combination with iron promotes excess reactive oxygen species (ROS) production and exerts a deleterious effect on mitochondria. We have shown previously that activation of AMP-activated protein kinase (AMPK) protects hepatocytes from AA + iron-induced apoptosis. Resveratrol, a polyphenol in grapes, has beneficial effects mediated through SIRT1, LKB1, and AMPK. This study investigated the potential of resveratrol to protect against the mitochondrial impairment induced by AA + iron and the underlying mechanism for this cytoprotection. Resveratrol treatment inhibited apoptosis, ROS production, and glutathione depletion elicited by AA + iron in HepG2 cells. In addition, resveratrol attenuated superoxide generation in mitochondria and inhibited mitochondrial dysfunction induced by AA + iron. Overall, AMPK activation by resveratrol contributed to cell survival, as supported by the reversal of its restoration of mitochondrial membrane potential by either overexpression of a dominant-negative mutant of AMPKalpha or compound C treatment. Resveratrol increased inhibitory phosphorylation of glycogen synthase kinase-3beta (GSK3beta) downstream of AMPK, which contributed to mitochondrial protection and cell survival. Likewise, small interfering RNA knockdown of LKB1, an upstream kinase of AMPK, reduced the ability of resveratrol to protect cells from mitochondrial dysfunction. Furthermore, this LKB1-dependent mitochondrial protection resulted from resveratrol's poly(ADP-ribose)polymerase activation, but not SIRT1 activation, as supported by the experiment using 3-aminobenzamide, a poly(ADP-ribose)polymerase inhibitor. Other polyphenols, such as apigenin, genistein, and daidzein, did not activate AMPK or protect mitochondria against AA + iron. Thus, resveratrol protects cells from AA + iron-induced ROS production and mitochondrial dysfunction through AMPK-mediated inhibitory phosphorylation of GSK3beta downstream of poly(ADP-ribose)polymerase-LKB1 pathway.