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Carcinogenesis vol.19 no.10 pp.1873–1875, 1998
SHORT COMMUNICATION
Age and gender dependent levels of glutathione and glutathione
S-transferases in human lymphocytes
Esther M.M.van Lieshout and Wilbert H.M.Peters
1
Department of Gastroenterology, University Hospital St. Radboud, PO Box
9101, 6500 HB Nijmegen, The Netherlands
1
To whom correspondence should be addressed
Glutathione S-transferases (GSTs) are a family of enzymes
involved in the detoxification of a wide range of chemicals
including chemical carcinogens. Human cytosolic GSTs are
divided into four major classes; α, µ, π and θ. This study
was performed to evaluate the influence of age and gender
on the GST isoenzyme expression and glutathione (GSH)
content in lymphocytes. Blood was collected from 124
healthy controls, which were divided into age groups of
20–40 years (21 females, 20 males), 40–60 years (20 females,
21 males) and 60–80 years (20 females, 22 males). Lympho-
cyteswere isolatedbydensitycentrifugationonHistopaque-
1077. After homogenization, cytosolic fractions were isol-
ated. Herein, GST isoenzyme levels were determined by
densitometrical analysis of western blots after immuno-
detection with monoclonal antibodies. Total GSH content
was determined by high performance liquid chromato-
graphy after conjugation with monobromobimane. Spear-
man rank correlation and Wilcoxon rank sum tests were
used for statistical evaluation. Lymphocytic GSTµ and π
levels were not correlated with age or gender. GSTα was
not detectable in lymphocytes. GSH contents were not
different in males and females, but decreased with age in
both males and females. In age group 60–80, GSH content
was significantly lower as compared with age groups 20–
40 and 40–60 in both sexes. Since high GSH is an essential
factor in the detoxification of many compounds, these data
indicate that the detoxification potential of the GSH/GST
system in lymphocytes may decrease with age in man.
Human cytosolic glutathione S-transferases (GSTs) are a family
of dimeric enzymes, divided into the main classes α, µ, π and
φ (1–3). GSTs catalyse the binding of a large variety of
electrophiles to the sulphydryl group of glutathione (GSH),
generally resulting in less harmful and more water soluble
molecules (1). The GSH/GST system may be a critical factor
in protecting cells and organs against toxicity and disease.
GSH, an important factor in the normal functioning of the GSH/
GST system, is involved in the detoxification of xenobiotics,
carcinogens, free radicals and peroxides (1). Low GSH contents
have been found in several pathological conditions, including
alcoholic liver disease (4), acquired immunodeficiency syn-
drome (5), xenobiotic-induced oxidative stress and toxicity (6)
and (pre)cancerous lesions (7). From these studies it may be
concluded that the availability of GSH might be a key factor
in the maintenance of health, and that GSH concentration may
serve as a useful indicator of disease risk in humans.
Abbreviations: GSH, glutathione; GST, glutathione S-transferase.
© Oxford University Press
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Little is known about the differences in GST and GSH
expression between men and women. Also data on GST and
GSH levels with respect to aging in humans are scarce.
Loguercio et al. (8) showed that GSH content in body and
antrum of the stomach decreased with age. They did not find
a sex dependency in GSH content. To obtain information of
the lymphocytic GSH/GST system during aging, we investi-
gated GST isoenzyme levels and GSH contents in human
lymphocytes from 124 healthy subjects, aged 20–80 years.
Blood was collected by venapuncture into sterile siliconized
EDTA K3 10 ml vacutainer tubes (Beckton Dickinson, San
Jose, CA). Controls were divided into three age groups; 20–
40 years (21 females, 20 males), 40–60 years (20 females,
21 males) and 60–80 years (20 females, 22 males). Lympho-
cytes were isolated by density centrifugation on Histopaque-
1077, according to the manufacturers instructions (Sigma
diagnostic, St Louis, MO). Lymphocytes were pelleted and
stored at –20°C until use. For preparation of cytosolic fractions,
lymphocytes were thawed slowly, homogenized in 100 µlof
20 mM Tris–HCl buffer pH 7.4, containing 1 mM dithiothreitol
using a glass/glass potter. Homogenates were centrifuged at
12 000 g (4°C) for 20 min. Aliquots of the supernatant were
stored at –20°C until use. The investigations were approved
by the local ethical committee on human experimentation.
Protein was assayed in triplicate by the method of Lowry
et al. (9), using bovine serum albumin as a standard. Specific
GST isoenzyme levels were determined as described previously
(10). In short, cytosolic fractions were subjected to SDS–
PAGE [11% acrylamide (w/v)], and subsequently to western
blotting, using a semi-dry blotting system (Novablot II, Pharm-
acia, Uppsala, Sweden). Western blots were incubated with
monoclonal antibodies against human GST classes α, µ and
π. Class α antibodies react with human GST A1-1, GST
A1-2 and GST A2-2 (10). Class µ antibodies recognize human
GST M1a-1a, GST M1a-1b and GST M1b-1b (11,12). Class
π antibodies react with human GST P1-1 (13). The specific
binding of the monoclonal antibodies to the isoenzymes was
demonstrated by incubation with peroxidase-conjugated rabbit
anti-mouse immunoglobulins (Dakopatts, Glostrup, Denmark)
andsubsequent stainingwith 4-chloro-1-naphtholand hydrogen
peroxide. Staining intensity on the immunoblots was quantified
using a laser densitometer (Ultroscan XL, LKB, Bromma,
Sweden). Known amounts of purified GSTs were run in parallel
with the experimental samples and served as standards for the
calculation of the isoenzyme levels in the cytosolic fractions.
The detection limit of this assay is ~50 ng/mg protein. Total
GSH was quantified by high performance liquid chromato-
graphy after reaction with monobromobimane, as described
previously (14). In this assay, oxidized GSH present is reduced
by adding sodium borohydride to the reaction mixture. A
Spearman rank correlation test was used to correlate
lymphocytic GSH content and GST isoenzyme expression
with age and gender. A Wilcoxon rank sum test was used to
assess statistical significance of differences between age
E.M.M.van Lieshout and W.H.M.Peters
Table I. GSH content and GSTα, µ and π isoenzyme levels in human lymphocytes
Age group GSH (nmol/mg protein) GSTα (ng/mg protein) GSTµ (ng/mg protein) GSTπ (ng/mg protein)
20–40 Total (n 5 41) 21.5 6 4.1 (4.7–43.7)
**
ND 368 6 76 (0–1766) 883 6 97 (0–2743)
Males (n 5 20) 19.4 6 1.8 (4.7–43.7)
***
ND 278 6 99 (0–1199) 892 6 199 (0–2743)
Females (n 5 21) 23.8 6 3.2 (5.1–25.4)
**
ND 454 6 97 (0–1766) 874 6 95 (0–2377)
40–60 Total (n 5 41) 17.9 6 1.1 (5.5–41.7)
**
ND 383 6 90 (0–2864) 871 6 102 (0–3025)
Males (n 5 21) 16.8 6 1.2 (5.5–26.7)
*
ND 376 6 146 (0–2864) 969 6 182 (0–3025)
Females (n 5 20) 19.0 6 1.8 (8.9–41.7)
**
ND 389 6 96 (0–1230) 769 6 97 (0–1701)
60–80 Total (n 5 42) 12.3 6 0.6 (2.4–26.3) ND 363 6 55 (0–917) 791 6 57 (207–1816)
Males (n 5 22) 13.3 6 0.9 (8.2–26.3) ND 357 6 70 (0–872) 879 6 70 (409–1618)
Females (n 5 20) 11.2 6 0.9 (2.4–18.7) ND 370 6 88 (0–917) 695 6 90 (217–1816)
GSH content and GST isoenzyme levels in lymphocytes were determined as described in the text.
Values are given as mean 6 SEM. Ranges are indicated in parentheses. ND, not detectable.
Wilcoxon rank sum test was used for statistical evaluation: *P , 0.02, **P , 0.005 and ***P , 0.002 as compared with age group 60–80 years.
groups. Table I shows the GSH contents and GST isoenzyme
levels of all age groups studied.
GSTα was not detectable in lymphocytes. In 54 (44%) of
the samples, no GSTµ protein was found, in 51% (60% males,
43% females) of the age group 20–40 years, in 34% (38%
males, 30% females) of the age group 40–60 years and in
45% (41% males, 50% females) of age group 60–80 years.
GSTµ null phenotype was not related to gender or age. GSTπ
expression was equally distributed among the different age
groups, as well as in males and females. GSH content in
lymphocytes was similar in male and female controls, but
expression declined with age: females R
s
5 –0.36 (95%
CI –0.56–0.12; P 5 0.004); males R
s
5 –0.42 (95%
CI –0.61–0.20; P 5 0.0005). This significant decline in GSH
content with age persisted when males and females were
combined: R
s
5 –0.39 (95% CI –0.53–0.23; P , 0.0001).
GSH content in age group 60–80 years was significantly
reduced as compared with the age groups 20–40 and 40–60
years in both sexes, whereas no difference was observed when
comparing GSH contents in age groups 20–40 and 40–60 years.
GSTs are involved in the protection against potentially
harmful chemical compounds (1). Little data are available
concerning age-related changes in the levels of GSH and GST
isoenzymes in humans. This may be relevant with respect to
the possible role of the GSH/GST system in the enhanced
cancer rates at increased age. We now showed that the
expression of the GSTα, µ and π isoenzymes in human
lymphocytes did not change with age, although in females
there was a tendency for lower levels of GSTπ at older age
(P 5 0.06; 20–40 versus 60–80 year age group). No gender-
related effects were found. Unfortunately, due to lack of
sufficient material we were unable to measure GST enzyme
activity and levels of the most recently discovered GSTφ
forms. Cebalos-Picot et al. (15) demonstrated a negative
correlation between age and GST activity (R 5 0.58, P ,
0.001) in human erythrocytes (120 females, 65 males), but
they found no gender-related differences.
Several studies have suggested that GSH might be a critical
factor in protecting cells and organs against toxicity and
disease, since GSH as an important factor in the GST/
GSH peroxidase systems is involved in the detoxification of
xenobiotics, carcinogens, free radicals and peroxides (1).
However, no information is available on the variation of GSH
in lymphocytes in relation to gender and age in healthy
subjects. We noticed no differences in GSH levels of human
lymphocytes between males and females. Similar results were
found previously in human blood by Richie et al. (16) (484
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males, 231 females) and Michelet et al. (17) (107 males, 94
females), in plasma by Yang et al. (18) (125 males, 157
females), and in body and antrum of the stomach by Loguercio
et al. (8) (12 males, 10 females). We showed that GSH levels
in human lymphocytes decreased with age in both males and
females. Similar results were found by Lang et al. (19), who
found a significant increase (P , 0.001) in the proportion of
elderly individuals with low blood GSH values compared with
younger adults. Also plasma GSH levels in Chinese male and
female volunteers were found to decrease with increasing age
(18). Loguercio et al. (8) showed that GSH content in body
and antrum of the stomach decreased with age.
In summary, we demonstrated that GST expression in human
lymphocytes was not related to sex or age. GSH content was
similar in males and females and decreased with age in both
sexes. Since GSH is correlated with protection against cellular
or cytogenetic damage, reduction of GSH content during aging
may be a factor of relevance for the increased risk of developing
diseases such as cancer at an older age.
Acknowledgement
This work was supported by grant 94-715 (EMMvL) from the Dutch
Cancer Society.
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Received on April 29, 1998; revised on June 5, 1998; accepted on June 5, 1998
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