Beer and Less Chromosome Aberration-Monobe and Ando (2002)

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J. RADIAT. RES., 43, 237245 (2002)

Drinking Beer Reduces Radiation-induced Chromosome

Aberrations in Human Lymphocytes

MANAMI MONOBE1,2 and KOICHI ANDO2*

Beer / Radioprotection / Chromosome aberration / X rays / Heavy ions

We here investigated and reported the effects of beer drinking on radiation-induced chro-

mosome aberrations in blood lymphocytes. Human blood that was collected either before or

after drinking a 700 ml beer was in vitro irradiated with 200 kVp X rays or 50 keV/m carbon

ions. The relation between the radiation dose and the aberration frequencies (fragments and

dicentrics) was significantly (p < 0.05) lower for lymphocytes collected 3 h after beer drinking

than those before drinking. Fitting the dose response to a linear quadratic model showed that thealpha term of carbon ions was significantly (p < 0.05) decreased by beer drinking. A decrease

of dicentric formation was detected as early as 0.5 h after beer drinking, and lasted not shorter

than 4.5 h. The mitotic index of lymphocytes was higher after beer drinking than before, indi-

cating that a division delay would not be responsible for the low aberrations induced by beer

drinking. An in vitro treatment of normal lymphocytes with 0.1 M ethanol, which corresponded

to a concentration of 6-times higher than the maximum ethanol concentration in the blood after

beer drinking, reduced the dicentric formation caused by X-ray irradiation, but not by carbon-

ion irradiation. The beer-induced reduction of dicentric formation was not affected by serum. It

is concluded that beer could contain non-ethanol elements that reduce the chromosome damage

of lymphocytes induced by high-LET radiation.

INTRODUCTION

The search for effective radioprotectors is a major

concern in the medical, military, environmental, and

space sciences. Densely ionizing radiation, such as

radon - particles and cosmic rays, has a characteris-

tic of high LET (linear energy transfer), and produces

lesions through direct action. Sparsely ionizing radia-

tion (X rays and rays) induces DNA lesions mostly

by indirect action, in which free radicals play an impo-

rtant role. Free radicals can be reduced by radical

scavengers, including alcohols, dimetylsulfoxide

(DMSO) and superoxide dismutase (SOD)14)

. Radio-

protectors that act by scavenging free radicals for the

most part find it difficult to prevent the occurrence of

direct damage. Phosphorothioates, including WR-

2721 and WR-151327, were the most effective class of

radioprotectors against high-LET radiation5)

. Conven-

tional radioprotectors generally display their radiopro-

tective properties only at high, toxic concentrations.

Radioprotectors with low toxicity have been searched

for many years. Some food elements, including vita-

mins, squalene and garlic extract, have recently been

reported to possess radioprotective activities against

damage caused by low-LET radiation68)

. There is,

however, no report on food elements that protect mam-

malian cells from damage caused by high-LET radia-

*Corresponding author: Phone: +81432063231,

Fax: +81432064149,

E-mail: [email protected] Graduate School of Science and Technology, Chiba University, 133,

Yayoi-cho, Inage-ku, Chiba 2638522, Japan2 Division of Heavy-ion Radiobiology Research Group, National Institute

of Radiological Sciences, 91, Anagawa-4-chome, Inage-ku, Chiba 263

8555, Japan


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M. MONOBE and K. ANDO238

tion.

In the present study, we found that beer drinking

reduced high- and low-LET radiation-induced chro-

mosome aberrations in lymphocytes irradiated in vitro.

MATERIALS AND METHODS

Irradiation

Whole blood samples were irradiated in air at

Fig. 1. Dose-response of chromosome aberrations in lymphocytes exposed to either 200 kVp X-radiation or LET 50 KeV/m carbon ion

either before or 3 h after beer drinking. (a) and (b), X rays; (c) and (d), carbon ions. The values represent means SEM (n=100).

Data was fitted to a linear-quadratic dose response function. The open circles ( ), before beer drinking; solid square ( ), 3 h after

beer drinking. The statistic significance was obtained between control and beer drinking (p < 0.05 by analysis of Two-way factorial

ANOVA test; Statview, Macintosh).


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BEER AND CHROMOSOME ABERRATION

239

room temperature with either X rays (200 kVp; 20

mA; 0.5 mm Cu + 0.5 mm Al filters; focus center dis-

tance, 55 cm) at a dose rate of 1 Gy/min or carbon-12

ion beams. Carbon ions were accelerated up to 290

MeV/u by HIMAC synchrotron at the National Insti-

tute of Radiological Science (NIRS, Chiba, Japan).

Lucite absorbers with 141 mm thickness were used to

select a LET of 50 keV/

m, which is a dose-averaged

value including the contribution of fragments. X-ray

irradiations were performed within 30 min after blood

collection, while carbon-ion irradiations were made 4

h after blood collection with a variable dose rate of

between 1 and 5 Gy/min.

Blood sampling

A healthy, non-smoking 28-year-old female vol-

unteer drank a 700 ml beer (ethanol content; 40 mg/

ml) within 15 min. Blood was collected in heparinized

tubes (Becton Dickinson Co., NJ, USA) either before

beer drinking or 0.5, 1, 2, 3, 4 and 4.5 h afterwards.

The ethanol concentration in plasma was measured by

gas chromatography at the KOTO microorganism lab-

oratory (Tokyo, Japan).

Isolation of lymphocytes and plasma

Lymphocytes were isolated using LeucoPREP

tubes (Becton Dickinson Co., NJ, USA). Each tube

was centrifuged for 30 min at 3000 rpm, and a white

layer containing mononuclear cells was collected by a

pipette and transferred to a conical centrifuge tube

(Becton Dickinson Co., NJ, USA). Phosphate-buff-

ered saline (PBS) was added up to 14 ml, and the tube

was centrifuged for 5 min at 1500 rpm. The resulting

pellet was washed 5 once again in PBS and resuspend-

ed in either the RPMI 1640 medium (Gibco-BRL,

N.Y., USA) or the plasma 3 h after beer drinking. In

order to avoid dilution by the separation liquid con-

tained in LeucoPREP, the blood plasma was isolated

Table 1.

Parameters of dose-response for the induction of dicentrics and acentric fragments.

X rays

Dicentric Acentric fragment

(

10

2

)

SD(Gy

1

)

(

10

2) SD(Gy2) (102) SD(Gy1) (102) SD(Gy2)

Non-treatment 14.21.8 7.10.4 15.9 4.1 14.90.8

beer drinking 8.11.0* 5.70.2 11.74.8 14.91.1

0.1 M ethanol 14.04.5 2.60.9 11.68.4 9.01.7

0.01 M ethanol 24.13.0 2.40.6 23.67.1 10.41.4

carbon ions

Dicentric Acentric fragment

(102) SD(Gy1) (102) SD(Gy2) (102) SD(Gy1) (102) SD(Gy2)

Non-treatment 46.60.9 104.43.6

beer drinking 28.70.7* 67.41.7

0.1 M ethanol 39.40.9 104.62.1

0.01 M ethanol 38.60.7 102.53.6

Parameters and were derived from maximum-likelihood fits of data to linear quadratic dose response functions;

Y = D + D2

For carbon ions is not significantly different from zero. Thus, the coefficient for carbon ions was set to zero.

*: p < 0.05


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using heparinized tubes. Each tube was centrifuged for

5 min at 3000 rpm, and the contents were transferred

to a conical tube (Becton Dickinson Co., NJ, USA).

In vitro ethanol experiments

Ninety-nine (99%) ethanol was added to whole

blood samples in vitro, providing a final concentration

of 10 mM, which roughly corresponded to the blood

ethanol concentration 3 h after beer drinking. Blood

samples with a high concentration of 100 mM ethanol

were also prepared. The samples were kept at room

temperature for 1 h before irradiation.

Blood cultures and chromosome analysis

Either 1.0 ml of irradiated whole blood or lym-

phocytes was suspended in 9 ml of a RPMI 1640

medium (Gibco-BRL, N.Y., USA) supplemented with

20% (v/v) fetal bovine serum, 0.06 mg/ml kanamycin

(antibiotics) (Meiji Seika, Tokyo, Japan), 1.25 mg/ml

sodium bicarbonate, 90 g/ml PHA-M (Murex Bio-

tech Ltd., UK), and 0.05 g/ml colcemid (Wako pure

Chemical Industries, Ltd., Osaka, Japan). Cells were

plated in T-25 flasks and incubated at 37C in a

humidified atmosphere containing 95% air plus 5%

CO2. Colcemid was added to the medium at the begin-

ning of the culture in order to obtain a sufficient num-

ber of cells at the metaphase in the first cell division9)

.

After 53 h of incubation, cultured cells were treated

with a hypotonic solution (75 mM KCl) for 20 min at

37C and fixed with methanol-acetic acid (3:1). Chro-

mosome slides were made by the conventional method

of air-drying under a warm and humid condition.

Chromosome slides were stained by Giemsa in phos-

phate buffered saline (pH 6.8), embedded in Eukitt (O.

Kindler, Germany), and finally observed under a light

microscope. with the highest magnification ( 1000).

Fig. 2. Time course of the chromosome aberration frequency in lymphocytes and plasma ethanol concentrations after beer drinking. Lym-

phocytes were exposed in vitro to 4 Gy of X rays (a) or carbon ions (b). The values of the chromosome aberration frequency repre-

sent means SEM (n=100). The statistic significance (*; p < 0.05, t-test) was obtained between control and beer drinking.

Fig. 3. Mitotic index of lymphocytes after 53 h culture. Lympho-

cytes were collected either before beer drinking ( ) or 3

h after beer drinking ( ), and were irradiated with 4 Gy

of either X rays (left) or carbon ions (right). The mitotic

index was determined as the percentage of dividing cells

among 10000 cells. The statistic significance (*; p < 0.01,

t-test) was obtained between before drinking and beer

drinking.


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241

One hundred metaphase figures were examined to

detect unstable types of chromosome aberrations, such

as dicentrics and acentric fragments, while 1000 cells

were examined for non-radiation control. The experi-

ments were repeated twice, and all of the data were

combined for analysis.

Fig. 4.

Effects of ethanol on radiation-induced chromosome aberrations of lymphocytes. Ethanol of either 0.01 M ( ) or 0.1 M ( ) was

added to the collected blood in vitro 1 h before irradiation with X rays (a; dicentric, b; fragment) or carbon ions (c; dicentric, d;

fragment). Closed circles ( ), before beer drinking. Data (n =100, mean SEM) were fit to a linear-quadratic dose response func-

tion.


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Curve fit and statistical analysis

Dose-response data were fit to the following lin-

ear-quadratic regression: Y =

D +

D

2

, where Y is

the yield of induced chromosome aberrations per cell,

D is the dose in Gy, and and are fit coefficients.

No fragments or dicentrics were detectable for the

non-radiation control. The data were analyzed by

using a two-way factorial ANOVA test (Statview, SAS

Institute Inc.).

RESULTS

Figure 1 shows the dose-response curve of either

X rays or carbon ions before and 3 h after beer drink-

ing. The chromosome aberrations induced by radiation

were significantly lower (p < 0.05 by analysis of the

two-way factorial ANOVA test; Statview, Macintosh)

for lymphocytes collected from a donor 3 h after beer

drinking than those without beer drinking. The alpha

() components of both X rays and carbon ions were

decreased (p < 0.05) after beer drinking (Table 1).

The number of dicentrics per cell induced by 4

Gy X rays was significantly (p < 0.05) decreased from

1.75, a pre-beer drinking value, to 1.24 when lympho-

cytes were collected as early as 30 min after beer

drinking, and continued to be low up to 4.5 h after beer

drinking (Fig. 2a). The number of dicentrics per cell

induced by 4 Gy of carbon ions was also significantly

(p < 0.05) decreased from 1.85 to 1.38 when lympho-

cytes were collected 30 min after beer drinking (Fig.

2b). During the period of 30 min through 4.5 h after

beer drinking, the ethanol concentration in plasma

changed ~ 8 times, and ranged from 2 to 16 mM (Fig.

2 a, b).

Figure 3 shows a mitotic index of lymphocytes

that received 4 Gy of either X rays or carbon ions 3 h

after beer drinking. The mitotic index was significant-

ly (p < 0.01) higher for the post-beer drinking condi-

tion than the pre-beer drinking condition. The ratio of

post- to pre-beer drinking groups was 1.65 (3.07 /

1.86) for X rays, and 2.05 (2.48 / 1.21) for carbon

ions.

The addition of ethanol to the blood samples

before X rays significantly reduced the chromosome

aberrations (p < 0.05 by analysis of the two-way fac-

torial ANOVA test; Statview, Macintosh) (Fig. 4 a, b).

The addition of 10 mM ethanol to the blood samples

before 4 Gy of X-radiation reduced chromosome aber-

rations; the number of dicentrics per cell decreased

from 1.75 to 1.30, and the number of acentric frag-

ments per cell decreased from 2.91 to 2.34, respective-

ly. These numbers were similar to the values obtained

for lymphocytes collected 3 h after beer drinking (Fig.

Fig. 5. Effects of plasma on dicentric formation. Lymphocytes in peripheral blood that were collected either before ( ) or 3 h after ( )

beer drinking were separated from plasma, and were then suspend either in serum that was collected 3 h after beer drinking or in a

RPMI medium. Lymphocytes were exposed in vitro to 4 Gy of X rays (a) or carbon ions (b). The values represent means

SEM

(n=100).


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243

1a, b). Ethanol also showed reduced carbon-induced

dicentrics (p < 0.05 by analysis of Two-way factorial

ANOVA test; Statview, Macintosh). However, an

increase of the ethanol concentration from 10 to 100

mM did not increase the reduction of dicentrics (Fig.

4c). Ethanol failed to reduce any acentric fragments

induced by carbon-ion radiation (Fig. 4d).

A possibility that plasma could contain aberra-

tion-reducing substances was examined by separating

the lymphocytes from the plasma. As shown in Fig. 5,

replacing the plasma with RPMI 1640 medium did not

affect the yields of chromosome aberrations. Less

dicentrics were detected for the post-beer drinking

lymphocytes than for the pre-beer drinking lympho-

cytes

DISCUSSION

In the present study, we showed that beer drink-

ing reduced the chromosome aberration in lympho-

cytes that were in vitro irradiated with X rays or 50

keV/

m carbon ions.

Beer drinking decreased the alpha component

rather than the beta component of X rays as well as of

carbon ions (Table 1). The alpha component is a coef-

ficient that suggests the single track-2 hits event in

DNA

10)

. Slow electrons of 700 eV would produce

densely ionizing events over a dimension of ~ 10 nm,

which could be responsible for mammalian cell killing

by the single-hit mechanisms of X rays and charged

particles as well. A scavenger of the hydroxyl (OH)

radical, DMSO, protects mammalian cell kill by

reducing the alpha component of not only X rays, but

also of high-LET charged particles

11)

. The mechanismby which high-concentration DMSO suppresses high-

LET radiation-induced cell killing is not yet under-

stood.

Some food elements, including vitamins, squ-

alene and garlic extract, have recently been reported to

possess radioprotective activities against damage

caused by low-LET radiation68)

. The protective effect

observed in vitamins has been explained by the scav-

enging of oxidizing free-radicals. The mechanism of

radioprotection is, however, not clear. Ghiselli et al.12)

report that beer increases the plasma antioxidant

capacity in humans, and that ethanol alone dose not

affect the plasma antioxidant capacity. Beer is effec-

tive to inhibit salmonella mutations caused by hetero-

cyclic amines (HAs), 2- chloro-4-methylthiobutanoic

acid (CMBA) and N-methyl-N-nitro-N-nitrosoguani-

dine (MNNG)1315)

; this inhibition is not due to alco-

hol. However, there is no report that beer decreases

chromosome aberration.

Ethanol protects DNA from X rays inducing

strand breaks by OH radical scavenging1)

. In the

present study, the in vitro addition of 10 mM ethanol

that corresponded to a plasma concentration of ethanol

23 h after beer drinking, reduced the X-ray-induced

chromosome aberrations (Fig. 1a, b; Fig. 4a, b). The

OH radical scavenging by ethanol could be responsi-

ble for the X-ray induced-aberration reduction by beer

drinking. However, the plasma ethanol concentration

at 4.5 h after beer drinking is around 2 mM, which is

8-times lower than the highest concentration at 0.5 h,

and much lower than the ethanol in vitro used (Fig. 2).

Also, ethanol showed little efficacy to protect carbon-

induced chromosome aberrations. An increase in the

ethanol concentration from 10 to 100 mM was not

effective to further reduce dicentrics (Fig. 4c). It is,

therefore, unlikely that the beer-induced aberration

reduction is solely due to ethanol. Figure 5 shows the

possibility of an intracellular change. Schlorff et al.

(1999)16)

report that manganese-superoxide dismutase

(Mn-SOD) activity significantly increases in a dose-

dependent manner. SODs play a key role in preventing

the DNA damage caused by reactive free radicals. Jok-

sic et al (2000)17) report that Mn-SOD plays an impor-

tant role in decreasing chromosome aberrationinduced by radiaton in lymphocytes. The intracellular

changes induced by beer drinking may, in part, be due

to increased SODs activity in lymphocytes.

The densely-ionizing radiation induces severe

cell-cycle delay1820)

, which can modify the shape of

the dose-response curve at M-phase analysis21)

. The

cell-cycle delay may not, however, contribute to the

aberration reduction by beer drinking, because the

mitotic indices rather increased upon beer drinking


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(Fig. 3). Because our cell-culture method allows only

few (1.6%) lymphocytes to progress to the second

mitosis9)

, it is not likely that the escape of cells from

the colcemid block could largely contribute to the

aberration reduction by beer drinking.

The radiation-induced chromosome aberrations

could be influenced by a hormonal condition in wom-

en. The female estradiol concentration in serum varies

depending on the sexual cycle. Kanda et al.22) have

reported that estradiol in blood decreases mitosis and

increases chromosome aberration in lymphocytes.

Because the present studies were performed at a ran-

dom period in the sexual cycle of a volunteer, the sex-

ual cycle may not, if any, significantly contribute to

the present results.

Dicentrics and translocations of lymphocytes

are most often used to estimate the radiation doses

received by astronauts, people involved in radiation

accidents and during radiation therapy2327)

. Dicen-

trics are well associated with long-term effects caused

by radiation. Similar yields of dicentrics and translo-

cations are induced by ionizing radiation2830)

. Beer

drinking may affect the biological dose estimation

using human lymphocytes.

Further studies are required to elucidate the

mechanisms of chromosome aberration reduction

induced by beer drinking.

ACKNOWLEDGEMENTS

This work was supported in part by a Grant-in-

Aid from the Ministry of Education, Science, Sports

and Culture of Japan and by the Special Coordination

Funds for Research Project with Heavy Ions at theNational Institute of Radiological Sciences Heavy

ion Medical Accelerator in Chiba (NIRS-HIMAC). We

would like to thank Drs. K. Fujitaka, H. Yamaguchi,

S. Kakinuma, Y. Shimada, K. Nojima and S. Koike for

their helpful comments.

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Solicited at the 44 th. JRRS Annual Meeting (OSAKA)

Received on October 6, 2001

1st. Revision on April 22, 2002

2nd. Revision on May 10, 2002

Accepted on May 27, 2002

Beer and Less Chromosome Aberration-Monobe and Ando (2002)

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