Jane A. McCrohon, Wendy Jessup, David J. Handelsman and David S. Celermajer
Endothelial Cell Expression of Vascular Cell Adhesion Molecule-1
Androgen Exposure Increases Human Monocyte Adhesion to Vascular Endothelium and
Print ISSN: 0009-7322. Online ISSN: 1524-4539
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Androgen Exposure Increases Human Monocyte Adhesion
to Vascular Endothelium and Endothelial Cell Expression of
Vascular Cell Adhesion Molecule-1
Jane A. McCrohon, MBBS, FRACP; Wendy Jessup, PhD;
David J. Handelsman, MBBS, PhD, FRACP; David S. Celermajer, MBBS, PhD, FRACP
Background—Male sex is an independent risk factor for coronary artery disease. Owing to the importance of monocyte
adhesion to endothelial cells in the development of atherosclerosis, we hypothesized that androgens might promote this
process. We therefore studied the effects of the nonaromatizable androgen dihydrotestosterone (DHT) on human
monocyte adhesion to human endothelial cells and on endothelial cell–surface expression of adhesion molecules.
Methods and Results—Human umbilical vein endothelial cells (HUVECs) were grown to confluence in media
supplemented with postmenopausal female serum, then exposed for 48 hours to either DHT (40 and 400 nmol/L), with
or without the androgen receptor blocker hydroxyflutamide (HF) (4 ?mol/L); HF alone; or vehicle control (ethanol
0.1%). Human monocytes obtained by elutriation were incubated for 1 hour with the HUVECs at 37°C, and adhesion
was measured by light microscopy. Compared with vehicle control, monocyte adhesion was increased in the
androgen-treated HUVECs in a dose-dependent manner (116?6% and 128?3% for DHT 40 and 400 nmol/L
respectively; P?0.001). HF blocked this increase (P?0.3 compared with control). Surface expression of endothelial cell
adhesion molecules was measured by ELISA and revealed an increased expression of vascular cell adhesion molecule-1
(VCAM-1) in the DHT-treated HUVECs (125?5% versus 100?4% in controls; P?0.002), an effect also antagonized
by HF (P?0.3 compared with controls). Furthermore, the DHT-related increase in adhesion was completely blocked by
coincubation with anti–VCAM-1 antibody. Comparable results were obtained in arterial endothelial cells and in
endothelium stimulated with the cytokine tumor necrosis factor-?.
Conclusions—Androgen exposure is associated with increased human monocyte adhesion to endothelial cells, a
proatherogenic effect mediated at least in part by an increased endothelial cell–surface expression of VCAM-1.
Key Words: hormones?atherosclerosis?cell adhesion molecules
excess mortality in men throughout adult life.1,2Although
there is a growing abundance of clinical and basic science
data supporting a favorable effect of estrogen and perhaps
progesterone on female cardiovascular risk and atherogenic
processes,3–6there are comparatively few data on the possible
proatherogenic effects of androgens. Recent animal studies in
chicks7and cynomolgus monkeys8support this possibility,
documenting increased plaque formation associated with
testosterone treatment. Few mechanistic studies, however,
have examined the vascular effects of androgens in humans,
although we have recently demonstrated an association be-
tween androgen deprivation and enhanced endothelial func-
tion in older men consistent with a deleterious effect of
androgens on vascular reactivity.9
here is an important sex difference in coronary heart
disease risk, with an earlier onset of disease in males and
Monocyte adhesion to endothelial cells is an important
early event in atherogenesis, controlled in part by expression
of adhesion molecules on the endothelial cell surface.10,11We
therefore aimed to explore the effects of the potent nonaro-
matizable androgen dihydrotestosterone (DHT) on monocy-
te–endothelial cell adhesion and on the expression of endo-
thelial cell adhesion molecules using primary human cells.
Phenol red–free variable amino acid RPMI cell culture medium was
obtained from Life Technology. The sex-steroid hormone used was
DHT (Sigma Chemical Co) because it cannot be aromatized to
estrogenic metabolites. Hydroxyflutamide (HF), a nonsteroidal
androgen-receptor antagonist, was a gift from Dr David Handelsman,
Department of Andrology, Royal Prince Alfred Hospital, Sydney,
Australia. Interleukin-1? (IL-1?) was obtained from Genzyme Corp.
Received August 27, 1998; revision received December 8, 1998; accepted December 29, 1998.
From the Heart Research Institute (J.A.M., W.J., D.S.C.); the Departments of Cardiology (J.A.M., D.S.C.) and Andrology (D.J.H.), Royal Prince Alfred
Hospital; and the Department of Medicine, Sydney University (D.J.H., D.S.C.), Sydney, Australia.
Correspondence to Dr Jane A. McCrohon, Department of Cardiology, Royal Prince Alfred Hospital, Missenden Rd, Camperdown 2050, Sydney,
Australia. E-mail firstname.lastname@example.org
© 1999 American Heart Association, Inc.
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Tumor necrosis factor-? (TNF-?) was obtained from Boehringer
Mannheim. Mouse anti-human monoclonal antibodies against vas-
cular cell adhesion molecule-1 (VCAM-1), intercellular adhesion
molecule-1 (ICAM-1), and E-selectin were obtained from Becton-
Dickinson, and isotype mouse IgG1 and IgG2 not directed against
endothelial cell antigens were obtained from ICN Immunobiologi-
cals. Sheep anti-mouse antibody–horseradish peroxidase conjugate
was obtained from Amersham International.
Endothelial Cell Culture
Human umbilical vein endothelial cells (HUVECs) were harvested
enzymatically from male infant umbilical cords under sterile condi-
tions as described by Minter et al12and established as primary cell
cultures in phenol red–free M199 (Gibco Life Sciences) containing
L-glutamine 2 mmol/L (ICN Biomedicals), 0.5% endothelial cell
growth promoter (Starrate Products), penicillin 100 U/mL, strepto-
mycin 0.1 mg/mL, and 20% filtered human serum from healthy
postmenopausal female volunteers not taking hormone replacement
therapy. Human umbilical arterial endothelial cells (HUAECs) were
harvested and cultured by the same methods. Commercially bottled
media had been filtered at 0.1 ?mol/L, and powdered medium was
reconstituted with endotoxin-free water and filtered at 0.2 ?mol/L.
Endothelial cell monolayers (passages 2 to 4) were propagated on
gelatin-coated flasks in phenol red–free medium, then trypsinized
and replated onto gelatin-coated 24-mm-diameter tissue-culture
wells or 96-well plates for monocyte adhesion and cell adhesion
molecule expression studies, respectively. Wells were gelatin coated
with 1 mL/5 cm2Hemaccel (Behringwerke AG) diluted 1:250 in
PBS and incubated for 1 hour at 37°C, and excess solution was
removed before use. Endothelial cells were grown to confluence
before sex-steroid hormone treatment and were used within 72 hours.
The purity of the endothelial cell monolayers was confirmed mac-
roscopically by their cobblestone pattern and periodically by cell
staining with a monoclonal antibody specific for von Willebrand
factor. At the end of the 48-hour treatments, cell viability was ?95%
(by Trypan blue exclusion) for each condition.
Isolation of Human Monocytes
White cell concentrates (Red Cross Blood Bank) were obtained from
the peripheral blood of healthy human volunteers, and monocytes
were removed within 24 hours of collection by density gradient
separation of the white cells on Lymphoprep (Nycomed Pharma)
followed by counterflow centrifugation elutriation at 20°C, as
previously described by our group,13,14by use of a Beckman J2–21
M/E centrifuge equipped with a JE-6B elutriation rotor and a 4.2-mL
elutriation chamber (Beckman Instruments, Inc). The elutriation
buffer was HBSS without calcium or magnesium (Sigma) supple-
mented with EDTA (0.1 g/L) and 1% heat-inactivated human serum.
The system and tubing were rinsed with 250 mL each of 70%
ethanol, endotoxin-free water, 6% hydrogen peroxide, endotoxin-
free water, and elutriation buffer in that order before the
Lymphoprep-derived mononuclear cell fraction was loaded at 9
mL/min into the elutriation rotor chamber (2020 rpm at 20°C). Flow
rate was increased by 1-mL/min increments every 10 minutes, and
monocytes were typically eluted at between 16 and 17 mL/min.
Collected fractions were examined by a Cytospin system (Shandon)
and Wright’s stain (Diff-Quik, Laboratory-Aids). Monocyte purity of
?90% and viability of ?95% by Trypan blue exclusion were
confirmed on light microscopy, and the monocytes were resuspended
in RPMI containing 2% human serum and used immediately for
Monocyte–Endothelial Cell Adhesion Assay
Endothelial cells were propagated for ?1 passage in phenol red–free
RPMI supplemented with 20% human postmenopausal female serum
from healthy donors. This serum was used because of the low
baseline levels of sex-steroid hormones (estradiol ?75 pmol/L,
progesterone ?0.8 nmol/L, and testosterone ?2 nmol/L). Confluent
endothelial monolayers were established in 24-mm-diameter wells
before incubation for 48 hours with the following treatments:
(1) control wells treated with 0.1% ethanol (used to dissolve the
sex-steroid hormones); (2) DHT 40 nmol/L; (3) DHT 400 nmol/L
(the normal range of testosterone in human male serum is 4 to 40
nmol/L); (4) DHT 40 nmol/L and HF 400 nmol/L; (5) DHT 400
nmol/L and HF 4 ?mol/L; and (6) HF 4 ?mol/L. Each treatment
group was divided after 24 hours of hormone treatment into basal
and stimulated states, the latter receiving IL-1? (50 U/mL) or TNF-?
(500 U/mL) for the final 24-hour period. Separate adhesion experi-
ments were performed 5 times for control and DHT-treatment groups
and 3 times for HF exposure. Each experiment used at least triplicate
wells for each condition. An additional series of experiments
investigated the interaction of DHT and IL-1? in terms of stimulat-
ing cell adhesion and involved sequential and/or coincubation
conditions, as described in the Results section.
The adhesion assay involved the addition of 1.5?106monocytes
per milliliter of RPMI/2% human serum to the endothelial monolayer
and incubation for 1 hour at 37°C under 5% CO2in air. After 1 hour,
nonadherent cells were removed by gentle washing with a 1000-?L
automatic pipette (Gilson), and the 1-mL suspension was stored on
ice until the cell concentration was determined with a Neubauer
hemocytometer (Weber Scientific). The initial suspensions and the
suspension from each well were counted 4 times by an observer
blinded to the treatment conditions. The percentage of adherent
monocytes was calculated by comparison with the initial concentra-
tion. This method has been shown to have a low intraobserver error,
with a coefficient of variation of ?5% and maximal basal adhesion
after 1 hour of incubation.13Basal monocyte–endothelial cell adhe-
sion in these experiments was 25?5%, increasing with IL-1?
stimulation to 55?6% (P?0.01).
Endothelial Cell Adhesion Molecule Expression
The cell-surface expression of adhesion molecules on the endothelial
cell monolayers exposed to different treatments was assessed with an
ELISA technique. Confluent cell monolayers were established in
96-well plates and, as was done for the adhesion studies, exposed for
48 hours to the control or hormone treatments as outlined above,
with or without IL-1? stimulation (50 U/mL) for the last 24 hours of
treatment. Wells were then washed twice with HBSS; monoclonal
antibodies to ICAM-1, VCAM-1, E-selectin, and isotype mouse IgG
(0.1 ?g in 100 ?L of HBSS with 10% heat-inactivated human
serum) were added and left for 30 minutes. The layers were washed
3 times with HBSS and 0.05% Tween 20 before a 30-minute
incubation with sheep anti-mouse antibody/horseradish peroxidase
conjugate (1:500 in 100 ?L of HBSS with 10% heat-inactivated
human serum and 0.05% Tween 20). After an additional 4 washes,
150 ?L of ABTS substrate (Kirkegaard and Perry Laboratories) was
added to each well and allowed to develop for 15 minutes. Results
were expressed as units of optical density measured at 414 nm with
an ELISA plate reader (Titretek Multiscan, Flow Laboratories).
Adhesion Assay With Neutralizing Antibodies to
Cell Adhesion Molecules
Endothelial cells grown to confluence and exposed to different
hormone conditions (as described above) were incubated with human
monoclonal antibodies (2 ?g/mL) to either ICAM-1, VCAM-1,
E-selectin, or all 3 for 60 minutes at 37°C, as described by Meng et
al.15The cells were then washed 3 times with RPMI immediately
before the addition of the monocyte suspension. Adhesion was then
measured as before, and each treatment group was compared with a
baseline state in which no antibodies had been added to assess the
relative importance of each cell adhesion molecule under the
different treatment conditions.
All descriptive data are expressed as mean?SEM, and the data were
analyzed on SPSS for Windows 6.0. Because each experiment
involved both endothelial cells and monocytes from different donors,
results for the adhesion assays and ELISAs for cell adhesion
molecule expression were expressed as a percentage of the control
condition within each experiment. Groups were compared by 1-way
Androgen and Increased Cell Adhesion
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ANOVA followed by the Student-Newman-Keuls test for multiple
comparisons and independent-samples t tests for comparisons be-
tween groups. Statistical significance was inferred at a 2-sided value
Monocyte-Endothelial Cell Adhesion and
Expression of Endothelial Cell Adhesion Molecules
Androgen exposure was associated with an increase in
monocyte adhesion to IL-1?–stimulated endothelial cell
monolayers (Figure 1). This was dose related (116?6% and
128?3% for DHT 40 nmol/L and 400 nmol/L, respectively,
compared with control; P?0.001 by ANOVA and P?0.01
for each DHT concentration compared with control) (Figure
2) and was not observed in basal state (non–IL-1?–stimu-
lated) endothelium (data not shown). This androgen-mediated
increase in adhesion was abolished by cotreatment with the
androgen-receptor antagonist HF (95?8% and 105?4% for
DHT 40 nmol/L-HF 400 nmol/L and DHT 400 nmol/L-HF
4 ?mol/L, respectively; P?0.3 compared with control). HF
alone did not affect adhesion (94?6% compared with con-
trols; P?0.4). These results suggest an androgen-mediated
amplification of monocyte–endothelial cell adhesion that is at
least partially receptor dependent.
The effect of androgen treatment on endothelial cell–
surface adhesion molecule expression was then studied with
an ELISA technique. Treatment of endothelial cell monolay-
ers for 24 hours with IL-1? increased cell-surface expression
of all 3 cell adhesion molecules: ICAM-1 (optical density,
0.55?0.02 versus 0.98?0.02; P?0.001), VCAM-1 (optical
density, 0.22?0.01 versus 0.48?0.03; P?0.001), and
E-selectin (optical density, 0.12?0.01 versus 0.30?0.02;
P?0.02). In the stimulated state, there was an increase in
endothelial surface expression of VCAM-1 with DHT com-
pared with control wells (DHT 40 nmol/L 125?5% and DHT
400 nmol/L 123?7% versus control 100?4%; P?0.01 for
each comparison) (Figure 3). Furthermore, this increase in
Figure 1. Photomicrographs of a representative area of mono-
cyte adhesion to IL-1?–stimulated endothelial cells (top) under
control conditions and (bottom) after treatment with DHT, show-
ing increased monocyte adhesion with androgen pretreatment
(magnification ?20). Adherent monocytes are represented by
brighter dots against background of endothelial cell monolayer.
Mean values for monocyte adhesion pooled from n?9 endothe-
lial donors are displayed in the Results section and Figure 2.
Figure 2. Monocyte adhesion to IL-1?–stimulated endothelium
for each treatment condition, expressed as percentage of con-
trol. Percentage values are pooled from n?9 separate experi-
ments. *P?0.001 by ANOVA for trend.
Figure 3. Endothelial cell–surface expression of VCAM-1,
ICAM-1, and E-selectin for each treatment group. Results are
expressed as percentage of control. *P?0.01 by ANOVA. CAM
indicates cell adhesion molecule.
McCrohon et alMay 4, 1999
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VCAM-1 expression was reduced to control levels in HU-
VECs treated with both DHT and HF (97?6% compared
with control; P?0.7). HF alone did not alter VCAM-1
expression (105?7% versus control; P?0.5). There was no
association between treatment condition and surface expres-
sion of either ICAM-1 or E-selectin (data not shown). In the
basal state (without IL-1?), surface expression of VCAM-1,
ICAM-1, and E-selectin did not change significantly between
treatment conditions, similar to the results of the adhesion
studies described above. In all experiments, there was no
significant binding of isotype IgG to endothelial cells in
either the basal or stimulated state.
These results were derived from endothelial cells coincu-
bated with IL-1? during the final 24 hours of treatment
exposure. To further explore the interaction between DHT
and IL-1?, similar experiments were performed with sequen-
tial exposures in which (1) DHT was washed off the endo-
thelial cells completely after 48 hours, followed by a subse-
quent 24-hour exposure to IL-1?, or (2) IL-1? was added to
the media for 24 hours (and then washed off) before a 48-hour
exposure to DHT (that is, the reverse of experiment 1 above).
In both cases, the IL-1?– and DHT-exposed HUVECs
demonstrated increased adhesion and increased VCAM-1
expression compared with DHT-vehicle (ethanol 0.1%)–
treated controls similarly exposed to IL-1?. In experiment 1,
DHT exposure before IL-1? increased adhesion (DHT 400
nmol/L 131?4% versus 100?2% for controls; P?0.03) and
VCAM-1 expression (DHT 400 nmol/L 110?3% versus
100?2% for controls; P?0.03). In experiment 2, IL-1?
exposure before DHT treatment also increased adhesion
(DHT 400 nmol/L 124?3% versus 100?1% for controls;
P?0.03) and VCAM-1 expression (DHT 400 nmol/L
131?6% versus 100?7% for controls; P?0.01). In each
case, HF antagonized the effect of DHT (data not shown).
To demonstrate whether these effects would also be ob-
served with arterial endothelial cells, additional experiments
were performed with HUAECs. DHT-treated HUAECs were
similarly associated with an increase in monocyte adhesion
after IL-1? stimulation (DHT 400 nmol/L 131?7% versus
100?7% for controls; P?0.03), and this effect could be
blocked by coincubation with HF (DHT 400 nmol/L-HF
4 ?mol/L 88?4%; P?0.1 compared with control). Further-
more, as was seen in the equivalent HUVEC experiments,
this androgen-mediated increase in monocyte–endothelial
cell adhesion was associated with an increase in VCAM-1
expression (DHT 400 nmol/L 116?5% versus 100?1% for
controls; P?0.04), which was reduced by coadministration of
HF (107?3%; P?0.1 compared with control).
To demonstrate that this effect was not confined to endo-
thelium costimulated with DHT and IL-1?, experiments were
performed with another cell-adhesion–promoting cytokine,
TNF-?. DHT-treated HUVECs stimulated with TNF-? also
showed increased monocyte adhesion (DHT 400 nmol/L
130?1% versus 100?2% for controls; P?0.002) and
VCAM-1 expression (DHT 400 nmol/L 114?2% versus
100?4% for controls; P?0.02). As seen with IL-1? stimu-
lation, the androgen-mediated increase in adhesion and
VCAM-1 expression observed in TNF-?–stimulated endothe-
lium could be antagonized by HF (100?5% and 103?8% for
adhesion and VCAM-1 expression, respectively; P?0.5 com-
pared with control). E-selectin and ICAM-1 expression were
not significantly different between conditions (102?6% and
101?4% for E-selectin and ICAM-1, respectively, after
androgen exposure; P?0.5 compared with control).
Neutralizing Antibodies to Cell
The ELISA results showing increased surface expression of
VCAM-1 on HUVECs treated with androgen were confirmed
by repeat adhesion studies involving a 60-minute incubation
of the endothelial monolayers with antibodies to VCAM-1,
ICAM-1, and E-selectin before the addition of human mono-
cytes. In these experiments, VCAM-1 antibody effectively
eliminated the androgen-related increase in monocyte–endo-
thelial cell adhesion (DHT 400 nmol/L 91?6% compared
with control 97?5%; P?0.4) (Figure 4). ICAM-1 antibody
reduced overall monocyte adhesion compared with baseline
but did not change the relative increase seen between control
and DHT treatment (DHT 400 nmol/L 113?8% compared
with control 75?4%; P?0.002); results were similar for
E-selectin (DHT 400 nmol/L 118?6% compared with control
93?8%; P?0.02). As expected, incubation with all 3 cell
adhesion molecule antibodies greatly reduced overall adhe-
sion and eliminated any difference between control and
androgen-treated wells (DHT 400 nmol/L 74?4% compared
with control 75?3%; P?0.9).
The effect of androgens on different aspects of atherogenesis
has received little attention despite the marked male predis-
position to occlusive vascular disease.1,2In the present study,
we have demonstrated that androgen exposure leads to a
dose-related and receptor-mediated increase in human mono-
cyte adhesion to endothelial cells, a key early event in
atherosclerosis. This effect is mediated at least in part by an
Figure 4. Effect of preincubation of cell-adhesion neutralizing
antibodies on androgen-mediated increase in adhesion, showing
loss of proadhesion effect of DHT with anti–VCAM-1 antibody
and with triple antibody blockade (see Methods). *P?0.02 and
**P?NS comparing control with DHT.
Androgen and Increased Cell Adhesion
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androgen receptor–dependent increase in endothelial cell
expression of the important adhesion molecule VCAM-1.
A proatherogenic effect of androgens is supported by
recent work in experimental animals. For example, Adams et
al8documented an approximate doubling of coronary artery
plaque size in female postmenopausal cynomolgus monkeys
treated with testosterone and a cholesterol-enriched diet, and
Hutchison et al16documented arterial endothelial dysfunction
in hypercholesterolemic rabbits that were administered an-
drogens. Similar data are not available in humans.
The incidence of coronary deaths in men aged 35 to 64
years exceeds that in age-matched females by up to 500%.17
Within each gender, however, there has been no consistent
association between androgen levels and cardiovascular event
rates. Although most cross-sectional data suggest either no
effect or an inverse correlation between serum testosterone
levels and cardiovascular event rates in men,18–21prospective
studies have not shown a significant correlation.22–27There-
fore, although small physiological variations in androgen
levels within genders may not correlate clearly with patterns
of atherosclerosis, it is likely that the large difference in
androgen levels and receptors between genders is a signifi-
cant contributor to the sex difference in cardiovascular risk.
In the body, testosterone is partially metabolized by aromata-
ses to estrogen and by 5?-reductase to DHT. Testosterone
may therefore not be a clear marker of androgen action owing
to its estrogenic metabolites. In the present study, the andro-
gen DHT was used to assess the effect of androgens on
monocyte–endothelial cell adhesion for several reasons: it is
nonaromatizable, thus avoiding confounding estrogenic ef-
fects, and it is one of the most potent androgens in androgen-
sensitive tissues, binding to the cytoplasmic androgen recep-
tor 2 to 10 times more avidly than testosterone.28
In the present study, DHT-treated endothelial cells showed
an increased surface expression of VCAM-1, which suggests
increased production and/or recruitment of VCAM-1 to the
endothelial cell surface. In concordance with the functional
adhesion data, this androgen-mediated increase in surface
expression of VCAM-1 was abrogated by HF, which indi-
cates that these processes are mediated at least in part via
androgen receptors. Interestingly, 17?-estradiol, the potent
estrogen, decreases endothelial cell adhesion molecule ex-
pression and monocyte adhesion, also via its sex-steroid
receptor.29The intracellular events accounting for such
changes require further study; however, receptor-activated
stimulation of gene transcription is a likely mechanism. Of
note, the endothelial cells treated with androgen in the current
experiments were coincubated with whole human serum. This
suggests that androgen-mediated monocyte–endothelial cell
adhesion is a physiologically relevant event, even in the
presence of lipoproteins such as HDL, which have been
shown to be protective against cell adhesion molecule
Our experiments involved an in vitro model of HUVECs
and monocytes obtained from peripheral blood by elutriation,
which may differ from the in vivo situation. Endothelial cells
in vivo do not usually express high levels of ICAM-1,
VCAM-1, or E-selectin,31,32whereas the HUVECs used in
our experiments did express these adhesion molecules, pre-
sumably owing to the tissue-culture environment. This may
be similar to the situation seen in atherosclerosis in which
cytokines such as IL-1? and TNF-? are present and endothe-
lial expression of adhesion molecules is stimulated.31,33,34In
this context, the androgen-related increase in cell adhesion
observed after stimulation with IL-1? or TNF-?, as well as
the similarity of findings with both venous and arterial
endothelial cells in the present experiments, is consistent with
potentially important effects in vivo at arterial sites prone to
The interaction between androgen and cytokine required to
promote monocyte–endothelial cell adhesion did not require
coincubation with DHT and IL-1? and was observed regard-
less of the order of DHT or IL-1? stimulation. Although the
exact intracellular mechanism of this interaction is not
known, these data suggest that the sequential or simultaneous
presence of androgen and cytokine might promote monocyte
adhesion in the in vivo situation.
In the present study, we observed an androgen-related
increase in endothelial cell expression of the adhesion mole-
cule VCAM-1. Recent reports have confirmed an important
role for VCAM-1 in atherogenesis.31,35Studies have demon-
strated a significant upregulation of VCAM-1 in plaques
found in diet-induced atherosclerosis in animal models36and
in human atherosclerotic lesions.31,37In contrast to other
adhesion molecules, VCAM-1 in isolation is able to mediate
leukocyte adhesion via integrin interaction,38whereas
E-selectin and ICAM-1 can mediate only part of the complex
adhesion process.39In addition, VCAM-1 expression pre-
cedes and is correlated with the degree of macrophage
accumulation in human plaques. In our experiments, IL-1?–
induced adhesion of monocytes to endothelium was only
reduced by ?30% in the presence of anti–VCAM-1, anti–
ICAM-1, and anti–E-selectin antibodies, which suggests ei-
ther incomplete blockade of these adhesion molecules or the
coexistence of other important proadhesion factors not
blocked in our study. These might include surface-associated
chemokines such as monocyte chemoattractant protein,
growth-regulated protein, and monocyte colony stimulating
factor, as well as other, as-yet-unidentified adhesion
In summary, DHT increases human monocyte adhesion to
vascular endothelium, at least in part through an androgen
receptor–mediated effect on endothelial expression of
VCAM-1. This androgen-mediated increase in monocyte
adhesion may be an important mechanism in the greater
susceptibility of men to the development of premature
Dr McCrohon is supported by Sydney University and the Depart-
ment of Cardiology, Royal Prince Alfred Hospital; Dr Jessup by The
National Health and Medical Research Council; and Dr Celermajer
by The Medical Foundation, University of Sydney. We are thankful
to S. Nakhla, Dr M.R. Adams, and Dr K.K. Stanley for their
technical advice and assistance.
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