Gallic acid induces G0/G1 phase arrest and apoptosis in human leukemia HL-60 cells through inhibiting cyclin D and E, and activating mitochondria-dependent pathway.

Abstract.

Gallic acid (GA) induces apoptosis in different

types of cancer cell lines. In this study, we investigate the

apoptotic effects induced by GA in human promyelocytic

leukemia HL-60 cells, and clarify the underlying mechanism.

Our results showed that GA reduced the viability of HL-60

cells in a dose- and time-dependent manner. GA led to G

/G

phase arrest in HL-60 cells through promoting p21 and p27

and inhibiting the levels of cyclin D and cyclin E. GA caused

DNA damage and fragmentation in HL-60 cells as assayed

using DAPI staining and Comet assay. Flow cytometric

analysis revealed that GA increased Ca

levels and reduced

the mitochondrial membrane potential (ΔΨ

) in HL-60 cells.

Apoptotic protein expressions were determined by Western

blotting. The results indicated that GA-mediated apoptosis of

HL-60 cells mainly depended on mitochondrial pathway, by

promoting the release of cytochrome c, apoptosis-inducing

factor (AIF) and endonuclease G (Endo G) and by

up-regulating the protein expression of Bcl-2-associated X protein

(BAX), caspase-4, caspase-9 and caspase-3. In addition, GA

also activated the death receptor-dependent pathway by

enhancing the protein expressions of fatty acid synthase (FAS),

FAS ligand (FASL), caspase-8 and BCL-2 interacting domain

(BID). We determined the mRNA expression of the gene levels

of these proteins by real-time PCR. The results showed that

GA-mediated apoptosis of HL-60 cells mainly depended on

up-regulation of the mRNA of caspase-8, caspase-9, caspase-3,

AIF and Endo G. In conclusion, GA-induced apoptosis occurs

through the death receptor and mitochondria-mediated

pathways. The evaluation of GA as a potential therapeutic

agent for treatment of leukemia seems warranted.

Gallic acid (3,4,5-trihydroxybenzoic acid, GA), an

intermediate component of plant (1), has demonstrated

antioxidant (2), antibacterial (3), antifungal and antimalarial

(4), and antiherpetic action (1). GA was found to induce

apoptosis in human leukemia cells (5), lung cancer cell lines

(6), stomach cancer cells, colon adenocarcinoma cells (7)

and PC12 rat pheochromocytoma cells (8). GA can play an

important role in the prevention of malignant transformation

(9) and prevents amyloid beta (Aβ)-induced apoptotic

neuronal death (10). GA also had antitumor effects on LL-2

(11) and NCI-H460 lung cancer cells both in vitro and in

vivo (6). There is no report to show whether GA affects

human leukemia HL-60 cells in vitro. In the present study,

the effects of GA on the growth and apoptotic cells death of

human leukemia HL-60 cells in vitro were investigated.

Materials and Methods

Chemicals and reagents. GA, propidium iodide (PI), dimethyl sulfoxide (DMSO), ribonuclease A (RNase A), trypan blue and Triton X-100 were obtained from Sigma-Aldrich Corp. (St. Louis, MO, USA). RPMI-1640 medium, trypsin-EDTA, penicillin-streptomycin, Correspondence to: Jing-Gung Chung, Department of Biological

Science and Technology, China Medical University, No. 91, Hsueh-Shih Road, Taichung 404, Taiwan, R.O.C. Tel: +886 422053366 ext. 2161, Fax: +886 422053764, e-mail: [email protected] Key Words: Gallic acid (GA), human leukemia HL-60 cells, apoptosis, death receptor-mediated pathways, mitochondria-mediated pathways.

Gallic Acid Induces G

₀

/G

₁

Phase Arrest and Apoptosis in

Human Leukemia HL-60 Cells through Inhibiting Cyclin D and

E, and Activating Mitochondria-dependent Pathway

RU-DUAN YEH

, JUNG-CHOU CHEN

, TUNG-YUAN LAI

, JAI-SING YANG

,

CHUN-SHU YU

, JO-HUA CHIANG

, CHI-CHENG LU

, SU-TSO YANG

, CHIEN-CHIH YU

,

SHU-JEN CHANG

, HUI-YI LIN

and JING-GUNG CHUNG

1

_{The School of Chinese Medicine for Post-baccalaureate, I-Shou University, Kaohsiung 824, Taiwan, R.O.C.;}

_{Department of Chinese Medicine, E-DA Hospital, Kaohsiung 824, Taiwan, R.O.C.;}

Schools of

Chinese Medicine, and

Pharmacy, Departments of

Pharmacology, and

_{Biological Science and Technology, China Medical University, Taichung 404, Taiwan, R.O.C.;}

_{Department of Life Sciences, National Chung Hsing University, Taichung 402, Taiwan, R.O.C.;}

7

_{Department of Radiology, China Medical University Hospital,}

China Medical University, Taichung 404, Taiwan, R.O.C.;

fetal bovine serum (FBS) and L-glutamine were obtained from Invitrogen by Life Technologies (Carlsbad, CA, USA). The fluorescence probes 2,7-dichlorodihydrofluorescein diacetate (H₂DCFDA), 3,3’-dihexyloxacarbocyanine iodide (DiOC₆), Fluo-3/AM and 4,6-diamidino-2-phenylindole dihydrochloride (DAPI) were obtained from Invitrogen.

Cell culture. Human promyelocytic leukemia cell line (HL-60) was obtained from the Food Industry Research and Development Institute (Hsinchu, Taiwan, R.O.C.). Cells were placed into 75-cm2_tissue culture flasks and maintained at 37˚C under a humidified 5% CO₂ atmosphere in RPMI 1640 medium supplemented with 10% FBS, 100 U/ml penicillin, 100 μg/ml streptomycin and 2 mM L-glutamine. Assessments of morphological changes and viability in HL-60 cells. Cells were seeded in 24 well plates at a density of 1×105_cells/well and grown for 24 h until 80% confluency. Different concentrations (0, 10, 25, 50, 75 and 100 μM) of GA were added to each well and cells were incubated for 24 and 48 h at 37˚C, 5% CO₂ and 95% air. To determine morphological changes and cell viability, the phase-contrast microscopy and a PI exclusion method by using a FACSCalibur utilizing BD CellQuest Pro software (Becton-Dickinson, San Jose, CA, USA) were used as previously described (12-13).

Flow cytometric analysis for DNA content of HL-60 cells. To estimate cell cycle distribution in HL-60 cells, cellular DNA contents were measured by flow cytometry as described elsewhere (14-15). Approximately 2×105 _{cells/well in 24-well plates were} treated with different concentrations of GA (0, 10, 25, 50, 75 and 100 μM) for 24 h. After cells were harvested by centrifugation, cells from each treatment were fixed by 70% ethanol in 4˚C overnight and re-suspended in PBS containing 40 μg/ml PI and 100 μg/ml RNase A and 0.1% Triton X-100 in the dark for 30 min at room temperature. The cell cycle distribution was determined and analyzed by flow cytometry as described previously (14, 16). DAPI staining for determining the apoptotic cells. Cells at a density of 1×105_{cells/well were plated onto 24-well plates and incubated} with different concentrations of GA (0, 10, 25, 50, 100 and 200 μM) for 24 h treatment before being isolated for DAPI staining as described previously (17-18). After staining, the cells were examined and photographed using a fluorescence microscope. Comet assay for examining DNA damage. Approximately 2×105 cells/well in 12-well plates were incubated with GA at final concentrations of 0, 50, 75 and 100 μM, vehicle (1 μl DMSO) and 5 μM of hydrogen peroxide (H₂O₂, positive control) grown for 24 h at 37˚C in 5% CO₂and 95% air. At the end of incubation, cells were harvested and examined for DNA damage using the Comet assay as previously described (19-20). Comets for PI-stained DNA tails of the individual nucleus in GA-treated HL-60 cells were visualized, measured and photographed by using a fluorescence microscope and were quantified by TriTek Comet Score V 1.5 software (TriTek Crop., Sumerduck, VA, USA) (17, 21).

Detection of the level of mitochondrial membrane potential (ΔΨ_m), Ca2+_{production and reactive oxygen species (ROS). Approximately}

5×105_{cells/well were treated with or without 50 μM GA for 0, 3, 6,} 12 and 24 h to detect the alterations of ΔΨm and Ca2+_{. Cells were} harvested, re-suspended in 500 μl of DiOC₆(1 μmol/l) and

Fluo-3/AM (2.5 μg/ml), respectively (13, 18) and then analyzed by flow cytometry. Untreated cells and cells treated with GA at a concentration of 50 μM for 0.5, 1, 3, 6 and 12 h were stained with H₂DCFDA (10 μM) in 500 μl PBS for analysis of changes in ROS (22). All of the cells were incubated with the fluorescent probes for 30 min at 37˚C in a water-bath and analyzed immediately by flow cytometry as described elsewhere (13, 18, 22).

Western blotting analysis. Approximately 5×106 _{cells/well were} treated with 50 μM GA for 0, 6, 12 and 24 h. Cells from each treatment were lysed in PRO-PREPTM protein extraction solution (iNtRON Biotechnology, Seongnam, Gyeonggi-Do, Korea). The total proteins from lysed cells were determined by using the Bio-Rad protocol as described previously (18, 22). The levels of proteins associated with G₀/G₁ phase regulation (p27, p21, cyclin E and cyclin D1/2/3) and apoptosis (fatty acid synthase (FAS), FASL, caspase-8, -9, -3, cytochrome c, apoptosis-inducing factor (AIF), endonuclease G (Endo G), BID, BAX, BCL-2 and caspase-4) were determined by sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE). Each sample was stained with primary antibodies (Santa Cruz Biotechnology Inc., Santa Cruz, CA, USA) and then washed twice, followed by staining by secondary antibody which was then detected by chemiluminescence (ECL kit; Millipore, Billerica, MA, USA) and autoradiography using X-ray film (17, 22). Real-time PCR for caspase-3, -8 and -9, AIF and Endo G. The total RNA was extracted from HL-60 cells after treatment with 50 μM GA for 0, 12, 24 h by using Qiagen RNeasy Mini Kit (Qiagen, inc, Valencia, CA, USA) as described previously (13, 23). RNA samples were reverse-transcribed for 30 min at 42˚C with High Capacity cDNA Reverse Transcription Kit according to the standard protocol of the supplier (Applied Biosystems, Foster City, CA, USA). Quantitative PCR was performed using the following conditions: 2 min at 50˚C, 10 min at 95˚C, and 40 cycles of 15 s at 95˚C and 1 min at 60˚C, using 1 μl of the cDNA reverse-transcribed as described above, 2× SYBR Green PCR Master Mix (Applied Biosystems) and 200 nM of forward and reverse primers (Table I) (17-18). Each assay was run on an Applied Biosystems 7300 Real-Table I. Primer sequences for real-time PCR.

Primer name Primer sequence (5’-3’)

Caspase-3 F-CAGTGGAGGCCGACTTCTTG R-TGGCACAAAGCGACTGGAT Caspase-8 F-GGATGGCCACTGTGAATAACTG R-TCGAGGACATCGCTCTCTCA Caspase-9 F-TGTCCTACTCTACTTTCCCAGGTTTT R-GTGAGCCCACTGCTCAAAGAT AIF F-GGGAGGACTACGGCAAAGGT R-CTTCCTTGCTATTGGCATTCG Endo G F-GTACCAGGTCATCGGCAAGAA R-CGTAGGTGCGGAGCTCAATT GAPDH F-ACACCCACTCCTCCACCTTT R-TAGCCAAATTCGTTGTCATACC Caspase: Cysteine aspartate-specific protease; AIF: apoptosis-inducing factor; Endo G: endonuclease G ; GAPDH: glyceraldehyde-3-phosphate dehydrogenase. Each assay was conducted in at least triplicate to ensure reproducibility.

Figure 1. GA affected cell morphological changes and the percentage of viable HL-60 cells. Cells were plated in RPMI 1640 medium + 10% FBS with 0, 10, 25, 50, 75 and 100 μM GA for 24 or 48 h. The morphological changes were examined under a phase-contrast microscope (A), and the cell viability was measured and determined by flow cytometry (B) as described in the Materials and Methods. Each point is the mean±S.D. of three experiments.

Figure 2. GA induced G 0 /G 1 phase arr

est and a sub-G

1

gr

oup of HL-60 cells. Cells wer

e plated in RPMI-1640 medium +10% FBS with 10, 25, 50, 75 and 100 μM GA for 24 h and the cells

wer e analyzed for DN A content. A: Repr esentati ve pr of

iles for Modf

it softw

ar

e; B: DN

A content of cells in eac

h phase (%); C: pr

of

ile of sub-G1 population fr

om BD CellQuest Pr

o softw

ar

e;

D: quantif

ication of apoptosis (%) by flo

w c

ytometry

. Eac

h point is the mean±S.D. of thr

ee e xperiments. *p<0.05, Signif icantly dif fer ent fr om the contr ol (0 μM GA).

Time PCR system in triplicate and expression fold-changes were derived using the comparative C_Tmethod.

Immunofluorescence staining by confocal laser scanning microscopy. Approximately 2×105 _{cells/well plated on 4-well} chamber slides were treated without or with 50 μM GA for 24 h. Cells were then fixed in 4% formaldehyde (Sigma-Aldrich Corp.) in PBS for 15 min, permeabilized with 0.3% Triton X-100 in PBS for 1 h with blocking of non-specific binding sites using 2% BSA. Fixed cells were incubated with primary anti-AIF, anti-Endo G and anti-growth arrest DNA damage 153 (GADD153) (1:100 dilution) overnight and then exposed to the secondary antibody (fluorescein isothiocyanate-conjugated goat anti-mouse IgG at 1:100 dilution), followed by DNA staining with PI. Photomicrographs were obtained using a Leica TCS SP2 Confocal Spectral Microscope (13, 19). Statistical analysis. All data were expressed as mean±S.D. from at least three separate experiments. Statistical calculations of the data were performed by one-way ANOVA followed by Dunnett’s test. A p-value of less than 0.05 was taken as being statistically significant.

Results

Effects of GA on morphology and viability of HL-60 cells.

After cells were treated with GA, morphological changes were

examined after 24 h or 48 h exposure under a phase-contrast

microscope and cell viability was determined by flow

cytometry. Figure 1A shows that GA-induced morphological

changes, cell membrane shrinkage and apoptotic bodies were

observed. Figure 1B shows that viable cells decreased as time

and concentration increased. This finding suggests that GA had

a dose- and time-dependent cytotoxic effect on HL-60 cells.

GA-induced G

/G

phase arrest and apoptosis in HL-60 cells.

Cells were treated with different concentrations of GA for 24 h,

and DNA content and the sub-G

population were examined by

flow cytometry. The results showed that increased concentrations

of GA led to an increase in the percentage of cells in G

/G

, and

a decrease in G

/M and S phases (Figure 2A and B). The data

indicated GA induced G

/G

phase arrest of HL-60 cells.

Moreover, a sub-G

group (apoptotic cells) also appeared in the

cell cycle distribution, suggesting that GA induced apoptosis in

HL-60 cells (Figure 2A and C). After exposure to 50 μM GA,

the percentage of apoptotic cells reached 39.43% in HL-60 cells.

GA induced from 11.55% to 78.73% apoptosis of treated cells

and these effects were dose-dependent (Figure 2D).

Effects of GA on the expressions of G

/G

phase regulated

proteins from HL-60 cells. Cells were treated with 50 μM

GA for 6, 12 and 24 h, and we then examined the associated

protein levels (p27, p21, cyclin E and cyclin D1/2/3) by

Western blotting. As shown in Figure 3, the levels of p21 and

p27 increased, while the levels of cyclin D1/2/3 and cyclin E

decreased on treatment with GA. Based on these results,

these effects might lead to G

/G

phase arrest in GA-treated

HL-60 cells.

Effects of GA on chromatin condensation and DNA damage

in HL-60 cells. GA-induced chromatin condensation (an

apoptotic characteristic) and DNA damage were examined

by DAPI staining and Comet assay, respectively. Apoptosis

of treated cells was observed by DAPI staining (Figure 4A),

and the results indicated that GA induced apoptosis in a

dose-dependent manner (Figure 4B). The comet assay

showed that higher concentrations (75 and 100 μM) of GA

led to a longer DNA migration smear (comet tail) (Figure

4C) as compared to the control that did not show Comet

occurrence. The results further support GA-induced DNA

damage in HL-60 cells in a dose-dependent manner.

Effects of GA on ΔΨ

, Ca

and ROS. Cells were exposed

to 50 μM GA for various periods of time, and ΔΨ

was

analyzed and quantified by flow cytometry and BD

CellQuest Pro software. Results indicated that ΔΨ

was

significantly reduced after 24-h treatment with GA (Figure

5A). When cells were treated with 50 μM GA, Ca

level

significantly increased at 6, 12 and 24 h exposure (Figure

5B). Nevertheless, our results showed that GA at 50 μM did

not stimulate ROS production in HL-60 cells after

co-incubation for 0.5, 1, 3, 6 and 12 h (Figure 5C).

Effects of GA on the expressions of apoptosis-associated

proteins in HL-60 cells. In order to characterize the

molecular mechanism of GA-induced apoptosis in HL-60

cells, we examined the expressions of apoptosis-associated

proteins by Western blotting. The protein levels of FAS and

FASL were increased at early periods (6-12 h) (Figure 6A),

Figure 4. GA induced apoptosis and DNA damage in HL-60 cells. Cells were incubated with 0, 10, 25, 50, 75 or 100 μM GA for 24 h. Apoptotic cells were photographed by fluorescence microscopy with DAPI staining (A) and for quantification of apoptosis (B). DNA damage was assessed by fluorescence microscopy for comet assay (C) as described in the Materials and Methods. MFI: Mean fluorescence intensity.

Figure 5. Effects of GA on the levels of mitochondrial membrane potential (ΔΨ_m), intracellular Ca2+_{and reactive oxygen species (ROS) in HL-60} cells. Cells were incubated with 50 μM GA for various time periods before being stained by DiOC₆for the ΔΨ_mlevels (A), Fluo-3/AM for the intracellular Ca2+_{levels (B), 2,7-dichlorodihydrofluorescein diacetate for ROS levels determined (C), then by flow cytometric analysis as described} in the Materials and Methods. Each experiment was carried our with triple sets. *p<0.05, Significantly different from the control.

Figure 6. GA affected protein and mRNA expression of apoptosis-related proteins in HL-60 cells. A total of 5×105_{HL-60 cells/ml cells were treated} with 50 μM GA for 0, 6, 12 and 24 h. Cells were harvested from each sample and associated proteins were measured by Western blotting. The protein levels of FAS, FASL (A); and caspase-8, caspase-9, caspase-3, cytochrome c, AIF and Endo G (B); BID, BAX, BCL-2 (C); caspase-4 protein levels were examined by using SDS-PAGE gel electrophoresis and Western blotting as described in the Materials and Methods. The total RNA was extracted from HL-60 cells after exposure to 50 μM GA for 0, 12 and 24 h and RNA samples were reverse-transcribed cDNA for real-time PCR. The expressions of caspase -3, caspase-8, caspase-9, AIF and Endo G mRNA relative to that of GAPDH presented in panel (E). Data represent the mean±S.D. of three experiments. *p< 0.05, Significantly different from the 0 h GA treatment.

Figure 7. GA stimulated translocation of AIF, EngoG and GADD153 proteins. HL-60 cells (5×104_{cells/well) were plated on 4-well chamber slides} and then were treated with or without 50 μM GA for 24 h, before they were stained by antibodies as described in the Material and methods. The results from confocal laser microscopy are shown A: AIF; B: Endo G; C: GADD153.

and the levels of cytochrome c, caspase-3, -8 and -9, AIF,

Endo G (Figure 6B), BID, BAX, BCL-2 (Figure 6C), and

caspase-4 (Figure 6D) were up-regulated in GA-treated

HL-60 cells. Thus, these findings suggest that GA-triggered

apoptotic death in HL-60 cells is mediated through caspase

cascades and mitochondria-dependent pathways.

Effects of GA on the mRNA expression in HL-60 cells. Total

RNA was isolated and expression of apoptosis-associated

genes was examined by real-time PCR after cells were

treated without or with GA for 12 and 24 h. Expression

levels of caspase-3, -8 and -9, AIF and Endo G mRNA were

significantly increased in GA-treated HL-60 cells, as can be

seen in Figure 6E.

GA translocated protein levels of AIF, Endo G and

GADD153 in HL-60 cells. As shown in Figure 7, increased

levels of AIF, Endo G and GADD153 were observed after

treatment with GA for 24 h. In the merged panels, it can be

seen that GA promoted AIF and Endo G (Figure 7A and B)

release from mitochondria and GADD153 was trafficked to

nuclei in HL-60 cells (Figure 7C).

Discussion

GA, one of the components in traditional Chinese medicine

‘Wen-Pi-Tang’, has been used for the treatment of various

diseases, including chronic renal failure (24). Much evidence

supports the anticancer activity of GA in human and mouse

cell lines (25-27). In the present study, we first demonstrated

that GA reduced the percentage of viable leukemia HL-60

cells in a time- and dose-dependent manner (Figure 1B). We

suggest that GA induced the extrinsic apoptotic pathway

through FAS and the intrinsic apoptotic pathway (Figure 8).

GA also induced caspase-3, -8 and -9 expression in HL-60

cells (Figure 6B). On the other hand, BCL-2 family proteins

were affected, resulting in a pro-apoptotic cell environment

(Figure 6C). HL-60 cells appeared to be more sensitive to

GA effects as compared with normal cells (28, 29). We

suggest that GA-triggered cell death was mediated through

the regulation of multiple signaling pathways, which then

resulted in cell apoptosis by the mechanism as shown in

Figure 8.

GA induced G

/G

phase arrest in HL-60 cells inhibiting

cell cycle progression at G

/G

phase (Figure 2B). Cell

cycle arrest in cancer cells is considered one of the most

effective strategies for the control of tumor growth (30).

GA also interfered with the G

/M phase in colon

adenocarcinoma cells (31), but it did not affect cell cycle

in other cancer lines (5, 32). We suggest that GA-induced

cell death or cell cycle arrest may differ depending on the

type of cancer cell line used (33). Our results showed that

GA-induced apoptosis was mainly associated with an

increase the number of apoptotic cells (sub-G

population)

which was dose-dependent (Figure 2D). Nuclear staining

with DAPI confirmed the appearance of apoptotic HL-60

cells after exposure to GA (Figure 4A and B). Moreover,

GA promoted intracellular Ca

release (Figure 5B) and

reduced the level of ΔΨ

(Figure 5A), which led to the

release of cytochrome c from mitochondria. This is

agreement with a previous study, which indicated that GA

induced apoptosis through generation, Ca

influx and

activation of calmodulin (5).

We also investigated the role of BCL-2 family proteins in

GA-induced apoptosis and found an increase in the expression

of BAX protein and a decrease in the expression of BCL-2 in

examined HL-60 cells (Figure 6C). An increase in the ratio of

BAX/BCL-2 stimulates the release of cytochrome c from the

mitochondria into the cytosol, promoting activation of

caspase-9 which then binds to apoptotic protease activating

factor-1 (APAF-1), leading to the activation of caspase-3 and

poly(ADP-ribose) polymerase (PARP) (34-35). Our results

showed that HL-60 cells treated with GA, had increased

protein and mRNA levels of caspase-3,-8 and -9, AIF, and

Endo G protein supporting the induction of the caspase

cascades in GA-induced apoptosis. It was reported that agents

can induce apoptosis through AIF-mediated

caspase-independent mitochondrial pathway (36-38).

The possible effects of GA on cell cycle and

apoptosis-related proteins and the possible mechanism of action are

summarized in Figure 8. Our findings of the present study

provide new perspectives for further research on toxicology

and pharmacology of GA as a possible candidate for

treatment of leukemia.

Acknowledgements

This work was supported by a grant from Taiwan Department of Health China Medical University Hospital Cancer Research Center of Excellence (DOH100-TD-C-111-005).

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Received April 3, 2011

Revised May 24, 2011

Accepted May 26, 2011