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Purple Sweet Potato Anthocyanin Inhibits the Proliferation of Human Retinal Pigment Epithelial Cell by Blocking Cell Cycle and Inducing Apoptosis

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  • Tasly institute

Abstract and Figures

Purple Sweet Potato Anthocyanin (PSPA), a class of naturally occurring anthocyanins derived from purple sweet potato storage roots, possesses unique color and multiple bioactivities. This study investigated the anti-proliferative effect of PSPA in human Retinal Pigment Epithelial (RPE) cells, the proliferation of which accounts for Proliferative Vitreoretinopathy (PVR). Blueberry Anthocyanin (BBA) was used as a contrast. PSPA and BBA inhibited RPE proliferation time-and dose-dependently through blocking the cell cycle in G0/G1 phase and inducing apoptosis via ROS accumulation, DNA damage and caspase 3/7 activation. Meanwhile, PSPA showed stronger potential than BBA in inhibiting RPE growth. Hence, we highlighted the importance of dietary supplementation of anthocyanins in PVR prevention and the application of PSPA in health industry.
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Advance Journal of Food Science and Technology 11(8): 561-569, 2016
DOI:10.19026/ajfst.11.2702
ISSN: 2042-4868; e-ISSN: 2042-4876
© 2016 Maxwell Scientific Publication Corp.
Submitted: August 5, 2015 Accepted: September 3, 2015 Published: July 15, 2016
Corresponding Author:
Xiaoling Lu, Key Laboratory of Food Nutrition and Safety of the Ministry of Education, College of
Food Engineering and Biotechnology, Tianjin University of Science and Technology, No. 29, 13th
Avenue, Tianjin Economic and Technological Development Area (TEDA), Tianjin 300457, P.R.
China, Tel.: 86-22-60912343; Fax: 86-22-60912343
This work is licensed under a Creative Commons Attribution 4.0 International License (URL: http://creativecommons.org/licenses/by/4.0/).
561
Research Article
Purple Sweet Potato Anthocyanin Inhibits the Proliferation of Human Retinal Pigment
Epithelial Cell by Blocking Cell Cycle and Inducing Apoptosis
Xiaoling Lu, MinSun, Lei Hao, Tao Wu, Huanjiao Zhao and Chao Wang
Key Laboratory of Food Nutrition and Safety of the Ministry of Education, College of Food Engineering
and Biotechnology, Tianjin University of Science and Technology, Tianjin, China
Abstract: Purple Sweet Potato Anthocyanin (PSPA), a class of naturally occurring anthocyanins derived from
purple sweet potato storage roots, possesses unique color and multiple bioactivities. This study investigated the anti-
proliferative effect of PSPA in human Retinal Pigment Epithelial (RPE) cells, the proliferation of which accounts for
Proliferative Vitreoretinopathy (PVR). Blueberry Anthocyanin (BBA) was used as a contrast. PSPA and BBA
inhibited RPE proliferation time-and dose-dependently through blocking the cell cycle in G0/G1 phase and inducing
apoptosis via ROS accumulation, DNA damage and caspase 3/7 activation. Meanwhile, PSPA showed stronger
potential than BBA in inhibiting RPE growth. Hence, we highlighted the importance of dietary supplementation of
anthocyanins in PVR prevention and the application of PSPA in health industry.
Keywords: Apoptosis, cell cycle, proliferation, purple sweet potato anthocyanin, retinal pigment epithelial
INTRODUCTION
The Retinal Pigment Epithelium (RPE), interposed
between the neural retina and the choroidal blood, is a
monolayer responsible for maintaining the health of the
retina by providing structural and nutritional support
(Adijanto and Philp, 2014; Sparrrow et al., 2010;
Strauss, 2009). In vivo, highly differentiated RPE cells
have a limited proliferation capacity (Hecquet et al.,
2002). However, several pathological insults may
induce RPE cells to dedifferentiate and proliferate,
which accounts for Proliferative Vitreoretinopathy
(PVR), a major cause of failure in retinal detachment
surgery (Garweg et al., 2013). The inhibition of the
proliferation of RPE cells may be helpful in preventing
the recurrence of retinal detachment (Hou et al., 2013).
In vitro, cultured RPE cells can be used to investigate
PVR related pathogenesis and the inhibition of RPE cell
proliferation has been achieved by using statins
(Wu et al., 2011), daunorubicin (Wang et al., 2002) and
hypericin (Zhou et al., 2007), indicating their potential
to prevent PVR. However, the most economic and
convenient way to gain the potential to prevent PVR is
from food rather than medicine. Therefore, it’s more
practical and meaningful to identify protective
components with no side effects in daily diet.
Polyphenolic compounds are the most abundant
antioxidants people can get from dietary and they are
known to be protective to retina (Hanneken et al.,
2006). Meanwhile, anthocyanins are the most available
flavonoid constituents of fruits and vegetables. The
daily intake of anthocyanins is estimated to be 9-fold
higher than that of other dietary flavonoids (Wang and
Stoner, 2008). Anthocyanins have been reported to
inhibit the proliferation of human umbilical vein
endothelial cells and human retinal microvascular
endothelial cells (Matsunaga et al., 2010a, 2010b;
Tanaka et al., 2012), but their effect on RPE cells
hasn’t been proven. Besides, the anthocyanins in these
researches are limited to nonacylated anthocyanins.
Although nonacylated anthocyanins contributed more
than acylated anthocyanins in food intake (Wu et al.,
2006), acylated anthocyanins are more promising in
food processing industry for their better stability
(Netzel et al., 2007). Purple sweet potato is a good
source of acylated anthocyanins. Mainly constituted by
cyanidinacylglucosides and peonidinacylglucosides,
Purple Sweet Potato anthocyanin (PSPA) possesses
multiple bioactivities including attenuating the
proliferation of hepatic stellate cells (Choi et al., 2011)
and inhibiting Sarcoma S180 cell growth in ICR mice
(Zhao et al., 2013). Furthermore, PSPA can be
absorbed directly into rat and human in intact acylated
forms (Harada et al., 2004; Oki et al., 2006; Suda et al.,
2002) and anthocyanins can pass the blood-brain barrier
and blood-retinal barrier and accumulate in eyes, as
observed in vivo (Kalt et al., 2008; Matsumoto et al.,
2006).
Adv. J. Food Sci. Technol., 11(8): 561-569, 2016
562
In view of all these considerations, the purpose of
the present study was to evaluate the anti-proliferative
effects of PSPA in RPE cells. Blueberry Anthocyanin
(BBA), well-known to promote vision health (Wang
et al., 2015) and mainly constituted by nonacylated
anthocyanins, was used as a contrast in this study. This
investigation was aimed at providing a new source for
preventing PVR from dietary and increasing the
application of acylated anthocyanins from purple sweet
potato in health industry.
MATERIALS AND METHODS
Materials: The human retinal pigment epithelial (RPE)
cell line (no. D407) was purchased from the Animal
Experiment Center of Sun Yat-sen University
(Guangzhou, China). D407 is a spontaneous
immortalized cell line retaining many of the metabolic
and morphologic characteristics of RPE cells in vivo
(Davis et al., 1995) and the same cell line was also used
in other research conducted by Xu et al. (2010). PSPA
used in the study were supplied by Huludao Maohua
Biology Co., Ltd. (Liaoning, China), the major
components of PSPA by HPLC-MS analysis are
cyanidinacylglucosides and peonidinacylglucosides
(Sun et al., 2015). BBA were supplied by Tianjin
Jianfeng Natural Product R and D Co., Ltd (Tianjin,
China), the major components of BBA are cyanidin and
petunidin glucosides (Peng et al., 2012). Dulbecco’s
modified Eagle’s Medium (DMEM), penicillin,
streptomycin, 0.5 % (vol/vol) trypsin/EDTA and Fetal
Bovine Serum (FBS) were purchased from Gibco Life
Technologies (Grand Island, NY, USA).3-(4, 5-
dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium
bromide (MTT), 2’,7’-dichlorofluorescin diacetate
(DCFDA), Hoechst 33342 (HOE) and Propidiumiodide
(PI) were bought from Sigma-Aldrich, Inc. (St. Louis,
MO, USA). Muse
TM
count and viability assay kit, cell
cycle kit, Ki67 proliferation kit, Annexin and dead
cell kit, oxidative stress kit, multicolor DNA damage kit
and Caspase-3/7 kit were purchased from Merck
Millipore (Billerica, MA, USA).
Cell culture and treatment: The RPE cells were
grown in whole culture medium, namely, DMEM with
10 FBS and a 1% antibiotic mixture of penicillin (100
U/mL) and streptomycin (100 mg/mL). Cells were
incubated at 37°C under a humidified 5% CO
2
atmosphere. Before treating with anthocyanins, the cells
were incubated in FBS-free DMEM medium for 1 day.
PSPA and BBA were dissolved in DMEM at a
concentration of 125 µg/mL
(Cyanidin 3-O-glucoside
equivalent) as a stock solution and stored at -20°C.
Before all experiments, the stock solution was sterilized
by processing through a 0.1 µm filter and then it was
diluted with DMEM to certain concentrations.
Evaluation of proliferation: RPE cells were seeded in
96-well plates at a concentration of 2×10
5
cells/mL
and
allowed to attach for 1 day. The cells were then
incubated in FBS-free DMEM medium for another day
followed by anthocyanins treatments for 1, 2 and 3 days
at concentrations ranging from 6.25 to 18.75 µg/mL.
The control groups were processed exactly the same,
just with 0 µg/mL anthocyanins. Then MTT assay (Wu
et al., 2009) was used to detect the Optical Density
(OD) values of each group and the proliferation was
calculated as % of the control group in each day.
Assay of cell viability: RPE cells were seeded in 6-
well plates at a concentration of 5×10
5
cells/mL
and
allowed to attach for 1 day. The cells were then
incubated in FBS-free DMEM medium for another day
followed by 12.5 µg/mL anthocyanins treatments for 1,
2 and 3 days. (The same process was used in the
following measurements, except where noted.) Then the
cells were digested and collected. The viabilities were
performed according to the count and viability assay kit
user’s manual, using Muse
TM
Cell Analyser (Merck-
Millipore, Germany), 2, 000 cells were acquired for
each sample. The viable cells and total cells were each
counted and viability was expressed as a percentage of
the viable cells.
Assessment of apoptosis and necrosis: Morphological
changes in cells treated with PSPA and BBA were
assessed by double staining with HOE and PI. Having
been incubated on cover slips with anthocyanins for 2
d, the cells were washed twice with PBS and then 0.5
mL HOE (10 µg/mL) was added to each slip and
incubated for 10 min at 37°C, followed by another 10-
min incubation with PI (10 µg/mL) in total darkness.
Then the cells were washed twice with PBS and
observed by fluorescence microscopy (Olympus
CKX41, Japan).
Muse
TM
Annexin and dead cell kit was also used
to measure the percentages of apoptosis and necrosis
after 12.5 µg/mL
anthocyanins treatment for 1, 2 and 3
days according to the user’s manual.
Analysis of cell cycle: After being treated with 12.5
µg/mL anthocyaninsfor 1 and 2 days, RPE cells were
collected to analyze cell cycle distribution using
Muse™ cell cycle kit. 20, 000 cells were recorded for
each sample. The results were analyzed using Modfit
3.2 (Verity Software House, USA).
Detection of Ki67 expression: RPE cells treated with
12.5 µg/mL anthocyaninsfor 1, 2 and 3 days were
conducted the assay of Ki67 according to the
Muse
TM
Ki67 proliferation kit user’s guide with the
Muse
TM
Cell Analyser.
Observation of ROS generation: The generation of
Reactive Oxygen Species (ROS) in the cells with
anthocyanins treatment for 2 days was observed by
fluorescence microscopy using DCFDA assay (Lu
et al., 2011). The production of ROS was also evaluated
Adv. J. Food Sci. Technol., 11(8): 561-569, 2016
563
by Muse
TM
oxidative stress kit after incubating with
anthocyanins for 1, 2 and 3 days as described in user’s
guidance.
Determination of DNA damage: Treated with 12.5
µg/mL PSPA and BBA for 1, 2 and 3 days, DNA
damage of RPE cells in each group was determined by
multicolor DNA damage kit at the end of each day.
Examination of caspase-3/7 expression: The
activation of Caspase-3/7 in RPE cells treated with
anthocyanins was examined by Muse™ Caspase-3/7
kit, utilizing a novel Muse™ Caspase-3/7 reagent
NucView™ for the detection.
Statistical analysis: All experiments were performed in
triplicate; results were given in means ± standard
deviation. One-way ANOVA with Duncan’s multiple
comparison tests were performed with SPSS software,
version 18.0 (SPSS Inc., Chicago, IL, USA). Results
were considered statistically significant at p<0.05.
RESULTS
Inhibitory effects of anthocyanins on RPE cell
proliferation and viability: The inhibition in RPE cell
proliferation induced by anthocyanins was assayed
following treatment with different doses of PSPA and
BBA for 1~3 days (Fig. 1A). Both anthocyanins
exhibited inhibitory effects in the dose-and time-
dependent manner, as observed at each time point
analyzed. PSPA showed an obviously stronger activity
than BBA at the same concentrations (cyanidin 3-O-
glucosideequivalent). Anthocyanins at the concentration
of 12.5 µg mL had significantly better inhibitory effect
than that of 6.25 µg/mL, but there were no very
dramatic differences between the groups of 12.5 and
18.25 µg/mL. Thus, 12.5 µg/mL anthocyanins were
selected for the following study.
When given the individual cell rather than cell
population, viabilities of RPE cells treated with 12.5
µg/mL PSPA and BBA were detected by counting the
numbers of living and dead cells (Fig. 1B). The control
group maintained 84.73% living cells after 3-day
incubation, while the viabilities of PSPA and BBA
groups decreased marvelously during the treatment.
Notably, the preserved percentages of viability (Fig.
1B) were higher than that of proliferation (Fig. 1A) at
the end of each day’s treatment with anthocyanins,
which suggested that the loss of cell viability partially
accounted for the decrease in proliferation treated by
anthocyanins.
Effects of anthocyanins on RPE cell apoptosis and
necrosis: Double staining with Hoechst 33342 and PI
was used to observe the morphological changes in cells
treated with anthocyanins for 2-day (Fig. 2A).
Anthocyanins treated cells showed more early apoptotic
cells (intensive bright-blue fluorescence) and late
apoptotic cells (blue-violet fluorescence). BBA
treatment resulted in more apoptotic cells than PSPA
treatment, showing the typical apoptosis-like
morphological changes like chromatin condensation
and fragmentation (Fig. 2A). The percentages of
apoptosis and necrosis after 12.5 µg/mL
anthocyanins
treatment for 1, 2 and 3 days were also measured by
Annexinand dead cell kit (Fig. 2B). Numbers of late
apoptotic and dead cells increased sharply after PSPA
and BBA treatment for 2 days. BBA had better
apoptosis-inducing effect than PSPA, while PSPA led
to more cell death in all at the end of third day (47.76%
vs 38.98%).
(a) (b)
Fig. 1: PSPA and BBA inhibited RPE cell proliferation and viability; (a): Time-dependent and dose-dependent effect of PSPA
and BBA on cell proliferation assayed by MTT; (b): time course of 12.5 µg/mL PSPA and BBA inhibition in cell viability
determined by count and viability assay kit. The means of the values marked with different lowercase letters are
significantly different (p<0.05) relative to others in each day of incubation
Adv. J. Food Sci. Technol., 11(8): 561-569, 2016
564
Fig. 2: PSPA and BBA induced apoptosis and necrosis in RPE cells; (A): Fluorescence micrographs stained with Hoechst 33342
and PI of RPE cells treated with 12.5 µg/mL PSPA and BBA for 2-day. Scale bar: 25 µm. * intensive bright-blue
fluorescence, early apoptotic cells;blue-violet fluorescence, late apoptotic cells;→chromatin condensation; and ▲
fragmentation; (B): apoptosis of RPE cell assessed by Annex in and dead cell kit. The means of the values marked
with different lowercase letters are significantly different (p<0.05) relative to others in each day of incubation
Fig. 3: PSPA and BBA induced cell cycle arrest in RPE cells. (A, B) Cell cycle distribution of RPE cells treated with PSPA and
BBA analyzed by cell cycle kit; (C): percentages of Ki67-positive cells treated with PSPA and BBA for 1~3 days, The
means of the values marked with different lowercase letters are significantly different (p<0.05) relative to others in each
day of incubation
Adv. J. Food Sci. Technol., 11(8): 561-569, 2016
565
Effects of anthocyanins on RPE cell cycle and Ki67
expression: Cell cycle analysis revealed the RPE cell
cycle distribution after anthocyanins treatment (Fig. 3A
and B). PSPA and BBA incubation both resulted in
striking increases of G1/G0 stage cells whereas the
percentages of G2/M phase decreased significantly at
the end of the first day. Similar changes accompanied
by declines in the relative amount of S-phase cells were
recognized on the second day. Altogether, anthocyains
blocked PRE cells in G0/G1 phase and led to the cell
cycle arrest. And it was remarkable that an obvious sub-
G1 phase was detected after 2-day treatment by BBA,
which indicating the noteworthy apoptosis in BBA
group. This finding was in line with the results in HOE-
PI staining (Fig. 2A) and Annexin and dead analysis
(Fig. 2B).
Ki67 is a prototypic cell cycle-related nuclear
protein, expressed by proliferating cells in all phases of
the active cell cycle (G1, S, G2, M phases), but it is
absent in the resting G0 phase (Scholzen and Gerdes,
2000). In Fig. 3C, anthocyanins treatment diminished
the percentages of Ki67+ cells observably in each day,
which meant fewer cells were undergoing mitosis after
incubating with anthocyanins. And PSPA exhibited a
more intense effect than BBA in giving rise to G0 phase
cells. With the extension of incubation time, an evident
decline of Ki67+ percentages in the control group was
also found. Ki67 assay together with cell cycle analysis
revealed that anthocyanins induced a decrease of
continuously cycling cells and a blockage in G0/G1
phase, contributing to cell proliferation inhibition.
Effects of anthocyanins on ROS generation in RPE
cells: Anthocyanins induced ROS generation in RPE
cells could be seen in fluorescence microscopical
photos (Fig. 4A). More green fluorescence stained cells
were observed in anthocyanins treated groups. The data
measured by Muse oxidative stress kit (Fig. 4B) also
proved that the production of ROS was significantly
(p<0.05) increased by anthocyanins treatment,
especially from the second day of incubation. In
addition, PSPA led to a larger augmentation of the ROS
generation than BBA did on the third day (44.31% vs
34.38%, p<0.05). Notably, the control group also
showed a sharp rise in ROS generation on the third day.
Effects of anthocyanins on DNA damage in RPE
cells: Ataxia-Telangiectasia Mutated kinase (ATM) is a
DNA damage-inducible protein kinase (Tichy et al.,
2010) and once activated, ATM phosphorylates a
number of downstream factors, including histone
H2A.X (Burma et al., 2001). The activation of ATM
was easily detected in anthocyanins treatment in time
course of incubation, while phospho-H2A.X didn’t
change a lot (Fig. 5). And there were significant
differences between PSPA and BBA treatment,
resulting in 17.6% p-ATM in PSPA group and 9.57% in
BBA group on the third day.
Effects of anthocyanins on the expression of caspase
3/7: The effect of anthocyanins on the expression of
caspase 3/7 was demonstrated in Fig. 6. Increases of
caspase 3/7 activation in early apoptotic RPE cells were
only observed when cells were treated with
anthocyanins for 3 days, with percentages less than 3%
in each group. While the expression of caspase 3/7 in
late apoptotic or dead cell elevated prominently by
Fig. 4: PSPA and BBA induced ROS generation; (A): Fluorescence micrographs stained with DCFDA of RPE cells treated with
12.5 µg/mL PSPA and BBA for 1 and 2-day. Scale bar: 25 µm; (B): ROS generation after 12.5 µg/mL PSPA and BBA
treatment detected by oxidative stress kit. The means of the values marked with different lowercase letters are
significantly different (p<0.05) relative to others in each day of incubation
Adv. J. Food Sci. Technol., 11(8): 561-569, 2016
566
Fig. 5: PSPA and BBA induced DNA damage. The distribution of phosphor-ATM, H2A.X and double-strand breaks measured
by multicolor DNA damage kit after 12.5 µg/mL PSPA and BBA treatment. The means of the values marked with
different lower case letters for each indicator are significantly different (p<0.05) relative to others in each day of
incubation
Fig. 6: PSPA and BBA induced caspase 3/7 activation. The caspase 3/7 activation in RPE cells treated by 12.5 µg/mL PSPA and
BBA was examined by Caspase-3/7 kit. The means of the values marked with different lowercase letters for each
indicator are significantly different (p<0.05) relative to others in each day of incubation
anthocyanins treatment, reaching the percentage of 30%
at the end of the second day. PSPA showed a distinct
stronger enhancement in caspase 3/7 activation than
BBA.
DISCUSSION
Pure anthocyanins and anthocyanin-rich extracts
from fruits and vegetables have exhibited anti-
Adv. J. Food Sci. Technol., 11(8): 561-569, 2016
567
proliferative activity towards multiple cell types in vitro
(Choi et al., 2011; Matsunaga et al., 2010a; Shih et al.,
2005; Tanaka et al., 2012; Wang and Stoner, 2008;
Zhang et al., 2005). The non-toxic anthocyanins from
purple sweet potato and blueberry used in this study
demonstrated potent growth inhibitory properties in
RPE cells, the proliferation of which might cause PVR.
Both PSPA and BBA showed the time- and dose-
dependently anti-proliferation effect through cell cycle
arrest and induced cell apoptosis.
Notably, enhanced reductions in proliferation rate
(Fig. 1A) and Ki67 positive percentage (Fig. 3C), more
pronounced cell cycle arrest (Fig. 3A and B); ROS
generation (Fig. 4); DNA damage (Fig. 5) and Caspase
3/7 activation (Fig. 6) were found in PSPA group when
compared to BBA group at the same concentration.
And BBA treatment resulted in more remarkable early
apoptosis than PSPA (Fig. 2 and 3A). Since the
anthocyanins used in this study are compounds, it’s
difficult to put the discrepant effect between PSPA and
BBA treatment down to the structure differences of
their aglycone anthocyanidins. But the acylation of
aglycon in PSPA might responsible for the discrepancy
partly. Compared to BBA, cyanidindiacyl glucosides
and peonidindiacyl glucosides in PSPA have higher
molecular weights, which makes the PSPA group
received more anthocyanins than BBA group did when
the concentration was calculated as cyanid in 3-O-
glucoside equivalent. Furthermore, coffeoyl and
feruloyl in PSPA molecules might contribute to the
anti-proliferative effect as well, which could be
supported by the inhibitory effect of caffeic and ferulic
acid in cancer cells (Eitsuka et al., 2014; Rajendra
Prasad et al., 2011; Serafim et al., 2011).
As reported, anti-proliferation activity in RPE cells
is mainly regulated by inhibition in growth and
induction of apoptosis and many signaling pathways are
involved (Sawada et al., 2014; Sun and You, 2014; Wu
et al., 2011). Our present study tried to shed light on the
role of ROS mediated pathway in PSPA induced
growth inhibition and apoptosis. ROS have crucial roles
in normal physiological processes; either too low or too
high level of ROS could cause health problems (Brieger
et al., 2012). Anthocyanins are known to act as ROS
scavengers in many bioactivities, whereas they also
could lead to accumulations of ROS and subsequent
apoptosis in certain cells (Cvorovic et al., 2010; Feng
et al., 2007). The paradoxical effect of anthocyanins
might due to different cell redox state and the double-
edged sword property of ROS in determining cell fate
(Wang and Yi, 2008). Increased ROS generations were
observed in anthocyanins treated RPE cells, especially
from the second day of incubation (Fig. 4). Many
studies have demonstrated that ROS is responsible for
DNA damage (Dhillon et al., 2014; Lv et al., 2013),
while the data in our present work seemed that DNA
damage was partially independent on ROS production,
since more aggravated increases in DNA damage than
ROS generation were observed on the first day of
treatment (Fig. 5). Cleavage of the DNA backbone
during DNA base excision repair might account for
DNA strand break in this stage (Watt et al., 2007). And
anthocyanin might induce oxidative DNA cleavage, as
reported by Webb et al. (2008). Within DNA damage,
the activation of ATM was easily detected in
anthocyanins treated RPE cells while histone H2AX
phosphorylation and DNA double-strand breaks were
limited (Fig. 5). Besides, PSPA treatment led to
distinguished phospho-ATM than BBA, accompanied
by the severer cell cycle arrest in G0/G1 phase and
decrease in Ki67 positive cells. DNA damage and
repairmen in addition to ROS generation might
responsible for the cell cycle arrest and inhibition of
quiescent RPE cells transiting into cell cycle (Surova
and Zhivotovsky, 2013).
Although it’s been reported that necrosis, but not
apoptosis, is a major type of cell death in RPE cells in
response to oxidative stress (Hanus et al., 2013), we
drew a conclusion here that anthocyanins induced RPE
cell death mainly through caspase 3/7 mediated
apoptosis, when taken the results from cell
apoptosis/necrosis analysis (Fig. 2) and the outcome of
caspase 3/7 detection (Fig. 6) together. Caspase 3
activation has been demonstrated to be involved in RPE
cell apoptosis (Yang et al., 2007) and anthocyanins
induced cell death (Forbes-Hernandez et al., 2014),
which aid the reliability of our conclusion. Both ROS
and DNA damage could act as intracellular death
signals to trigger the intrinsic cell death pathway,and
then activate executioner caspases (caspase 3, 6, 7),
which finally induce cell apoptosis (Radogna et al.,
2015).
To conclude, anthocyanins from purple sweet
potato and blueberry inhibited RPE cell proliferation
through cell cycle arrest and the induction of apoptosis,
which involved in ROS generation, DNA damage and
caspase 3/7 activation. The findings from our study
have highlighted the important role PSPA can play in
inhibiting RPE cell proliferation, which is responsible
for the progression of PVR. Dietary supplementation
with fruits and vegetables rich in anthocyanins can be
an effective strategy for prevention of eye diseases like
PVR. And we believe that acylated anthocyanins from
purple sweet potato are worth to be popularized and
applied in food and health industry.
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... Interestingly, purple sweet potato showed an inhibitory effect on breast cancer, gastric cancer, bladder cancer cell, and colon adenocarcinoma proliferation1. [17][18][19] This suggests that purple sweet potato might both stimulate or inhibit cell proliferation depending on the type of cells. ...
... We observed that the PSPA inhibited the BC cell viability in a dose-dependent manner. This effect was largely attributed to the acylated anthocyanins in PSPA, which was supported by a previous study (27). Caffeic and ferulic acid also demonstrated anti-proliferative abilities in cancer cells (28,29), therefore, coffeoyl and feruloyl in PSPA provided the beneficial antitumor effect. ...
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