Article

Effect of Antihypertensive Therapy with Alpha Methyldopa on Levels of Angiogenic Factors in Pregnancies with Hypertensive Disorders

Khon Kaen University, Thailand
PLoS ONE (Impact Factor: 3.23). 07/2008; 3(7):e2766. DOI: 10.1371/journal.pone.0002766
Source: PubMed

ABSTRACT

Antihypertensive drugs are believed to lower blood pressure in pre-eclampsia by direct or central vasodilatory mechanisms. However, they could also act by decreasing production of anti-angiogenic proteins involved in the pathophysiology of hypertension and proteinuria in pre-eclampsia (PE). The aim of our study was to evaluate the impact of antihypertensive therapy with alpha methyldopa on maternal circulating levels and placental production of soluble fms-like tyrosine kinase 1 (sFlt-1), soluble endoglin (sEng), vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) in hypertensive disorders of pregnancy.
In a study conducted at University College Hospital and the Homerton University Hospital in London, we recruited 51 women with PE, 29 with gestational hypertension (GH), and 80 matched normotensive controls. Eight (16%) of the women with PE had severe disease. Placental samples were obtained from a further 48 women (14 PE, 10 GH and 24 matched controls). Serum levels of angiogenic factors were measured before and 24-48 hours after commencing antihypertensive therapy with alpha methyldopa for clinical indications. The same parameters were measured in placental extracts. In both PE (P<0.0001) and GH (P<0.05), serum sFlt-1 was increased and PlGF reduced at all gestations (P<0.001) compared to controls. Serum sEng levels were also increased in PE. Placental concentration of sFlt-1 and sEng was significantly higher in women with PE compared to controls and women with GH (P<0.0001). The concentration of PlGF was significantly lower in the placental tissue of women with PE compared to GH (P = 0.008). Antihypertensive treatment was associated with a significant fall in serum and placental content of sFlt1 and sEng in PE only.
Our data suggest that alpha methyldopa may have a specific effect on placental and/or endothelial cell function in pre-eclampsia patients, altering angiogenic proteins.

Full-text

Available from: Kevin Harrington, Dec 19, 2013
Effect of Antihypertensive Therapy with Alpha
Methyldopa on Levels of Angiogenic Factors in
Pregnancies with Hypertensive Disorders
Asma Khalil
1
*, Shanthi Muttukrishna
2
, Kevin Harrington
1
, Eric Jauniaux
2
1 The Homerton University Hospital NHS Trust, Queen Mary and Westfield College, University of London, London, United Kingdom, 2 Academic Department of Obstetrics
and Gynaecology, UCL Institute for Women’s Health, University College London, London, United Kingdom
Abstract
Background:
Antihypertensive drugs are believed to lower blood pressure in pre-eclampsia by direct or central vasodilatory
mechanisms. However, they could also act by decreasing production of anti-angiogenic proteins involved in the
pathophysiology of hypertension and proteinuria in pre-eclampsia (PE). The aim of our study was to evaluate the impact of
antihypertensive therapy with alpha methyldopa on maternal circulating levels and placental production of soluble fms-like
tyrosine kinase 1 (sFlt-1), soluble endoglin (sEng), vascular endothelial growth factor (VEGF) and placental growth factor
(PlGF) in hypertensive disorders of pregnancy.
Methodology/Principal Findings:
In a study conducted at University College Hospital and the Homerton University Hospital
in London, we recruited 51 women with PE, 29 with gestational hypertension (GH), and 80 matched normotensive controls.
Eight (16%) of the women with PE had severe disease. Placental samples were obtained from a further 48 women (14 PE, 10
GH and 24 matched controls). Serum levels of angiogenic factors were measured before and 24–48 hours after commencing
antihypertensive therapy with alpha methyldopa for clinical indications. The same parameters were measured in placental
extracts. In both PE (P,0.0001) and GH (P,0.05), serum sFlt-1 was increased and PlGF reduced at all gestations (P, 0.001)
compared to controls. Serum sEng levels were also increased in PE. Placental concentration of sFlt-1 and sEng was
significantly higher in women with PE compared to controls and women with GH (P,0.0001). The concentration of PlGF
was significantly lower in the placental tissue of women with PE compared to GH (P = 0.008). Antihypertensive treatment
was associated with a significant fall in serum and placental content of sFlt1 and sEng in PE only.
Conclusions:
Our data suggest that alpha methyldopa may have a specific effect on placental and/or endothelial cell
function in pre-eclampsia patients, altering angiogenic proteins.
Citation: Khalil A, Muttukrishna S, Harrington K, Jauniaux E (2008) Effect of Antihypertensive Therapy with Alpha Methyldopa on Levels of Angiogenic Factors in
Pregnancies with Hypertensive Disorders. PLoS ONE 3(7): e2766. doi:10.1371/journal.pone.0002766
Editor: Pisake Lumbiganon, Khon Kaen University, Thailand
Received March 7, 2008; Accepted June 24, 2008; Published July 23, 2008
Copyright: ß 2008 Khalil et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: The authors have no support or funding to report.
Competing Interests: The authors have declared that no competing interests exist.
* E-mail: asmakhalil79@googlemail.com
Introduction
Anti-angiogenic and pro-angiogenic factors are known to play an
important role in the pathophysiology of pre-eclampsia (PE) [1–5].
Studies of maternal serum levels of these factors have shown that
soluble endoglin (sEng) and soluble fms-like tyrosine kinase 1 (sFlt-1)
are elevated in women presenting with PE whereas vascular
endothelial growth factor (VEGF) and placental growth factor
(PlGF) are decreased. Some of these changes can be detected several
weeks before the appearance of clinical symptoms of PE [6–8].
Soluble Flt-1 is a splice variant of VEGF receptor 1 (Flt-1) which
is produced by a variety of tissues. Investigation of uterine vein
levels of sFlt-1 at cesarean section in pre-eclampsia has suggested a
uterine source [9]. The fact that there is a rapid fall in circulating
levels of sFlt-1 within 48 hours of delivery is consistent with this
concept [4]. Extra-placental sources have also been identified,
including endothelial cells, monocytes and peripheral blood
mononuclear cells [10–12]. Endoglin is a trans-membrane
glycoprotein found on cell surfaces highly expressed in endothelial
cells and syncytiotrophoblasts [13,14]. sEng is the soluble form of
endoglin found in serum. Its level is increased in the circulation of
patients with angiogenic tumours, neovascularisation and myeloid
malignancies, and of pregnant women [3]. VEGF and P1GF are
vascular endothelial growth factors which are key molecules in
angiogenesis and vasculogenesis, in particular during embryogen-
esis [15]. The main source of VEGF and PlGF during pregnancy
is the placental trophoblast. VEGF and PlGF are also expressed in
many other tissues, including the villous trophoblast [16–25].
The most commonly used drug for the treatment of hyperten-
sive disorders in pregnancy in the UK is alpha methyldopa (aMD).
Alpha methyldopa acts on alpha-2 adrenoreceptors and is believed
to exert its antihypertensive effect primarily in the central nervous
system [26,27]. Trophoblast cells also possess alpha-2 adrenore-
ceptors. The activation of these receptors is thought to modulate
intracellular messengers such as cyclic AMP (cAMP) [28,29], so it
is possible that aMD also has an effect at this level.
Belgore et al [30] have suggested that, in non-pregnant women
with essential hypertension, plasma levels of VEGF and sFlt-1 are
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elevated compared to normotensive controls, and treatment of
hypertension significantly reduces the circulating levels of these
molecules. The effect of antihypertensive therapy on trophoblast
production and/or release of angiogenic factors and thus on their
plasma levels in pregnancy is unknown. The aim of this study was
to investigate the effect of antihypertensive therapy with alpha
methyldopa on maternal serum concentrations and placental
production of sFlt-1, sEng, VEGF and PlGF in pregnant women
presenting with hypertensive disorders including pre-eclampsia
and gestational hypertension.
Methods
Subjects and samples
Serum and placental tissue samples were obtained over an 18
month period from women with singleton pregnancies prospec-
tively recruited in the second and third trimesters of pregnancy at
the Homerton University Hospital, London. During this period,
approximately 6,000 deliveries took place. Demographic and
clinical data including age, body mass index (BMI), parity, blood
pressure (BP) and gestational age (GA) were recorded. Gestational
age was established on the basis of menstrual date and/or
ultrasonographic examination prior to 20 weeks of gestation.
All women were followed up until after delivery, and fetal and
maternal outcomes were obtained from the women’s medical
records and labour ward records. Written consent was obtained from
each woman after receiving full written information about the
research project. This study was approved by the Camden &
Islington Community Local Research Ethics Committee and The
University College London Hospitals Committee on the Ethics of
Human Research. Exclusion criteria included multiple pregnancy,
history of hypertension, diabetes, renal disease or immune disorders
or women taking medication which could affect blood pressure.
The study group in whom serum levels were measured included
51 women presenting with PE, 29 with gestational hypertension
and 80 controls (Figure 1a).
Another group of 48 women were recruited for measurement of
placental levels: 24 with hypertensive disorders in pregnancy (14
PE, 10 gestational hypertension), and 24 controls matched for
maternal age, gestational age and parity (Figure 1b).
BP was measured in duplicate using a standard mercury
sphygmomanometer and the average of two readings taken. All
readings were taken by the same investigator (AK) with the subject in
the sitting position. Korotkoff sounds 1 and 5 were used to define
systolic and diastolic BP respectively. Mean BP was calculated as
diastolic BP+
1
/
3
pulse pressure. PE was defined according to the
guidelines of the International Society for the Study of Hypertension
in Pregnancy [31]. Diagnosis required two recordings of diastolic
blood pressure $90 mm Hg, at least four hours apart; or one
recording of diastolic BP$120 mm Hg, in a previously normoten-
sive woman; and urine protein excretion $300 mg in 24 hours, or
two readings of ++ or more on dipstick analysis of a midstream or
catheter specimen of urine, if no 24 hour collection was available.
Severe pre-eclampsia was defined as severe hypertension
(diastolic blood pressure $110 mmHg) and mild proteinuria, or
mild hypertension and severe proteinuria (a 24-hour urine sample
that contained $3.5 g protein or a urine specimen $3+ protein by
dipstick measurement). Patients with an abnormal liver function
test (aspartate aminotransferase .70 IU/L) and thrombocytope-
nia (platelet count ,100,000/cm
3
) were also classified as having
severe pre-eclampsia. Gestational hypertension (GH) was defined
as a diastolic blood pressure $90 mm Hg on at least two
consecutive occasions in the second half of pregnancy, without
proteinuria, in a previously normotensive woman [32]. Fetal
growth restriction (FGR) was defined as birth weight less than the
5
th
centile for gestational age. The controls consisted of 80
Figure 1. Women recruited to the study. Flow diagrams of women recruited to the serum (a) and placental (b) arms of the study respectively.
doi:10.1371/journal.pone.0002766.g001
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normotensive women matched for maternal age (63 years) and
parity (none or one to two deliveries).
We collected blood samples at similar gestational periods (64
days) from the hypertensive and matched control participants. All
women in the control group had uncomplicated pregnancies.
They had no history of cardiovascular disease, hypertension,
proteinuria or fetal growth restriction, and were not taking
medication that could affect blood pressure. The diastolic blood
pressure of all women with PE or gestational hypertension was
higher than 95 mm Hg. They received oral antihypertensive
therapy in the form of alpha methyldopa 750–1500 mg/day for
clinical indications according to local clinical protocols. In
accordance with local protocols, co-existing fetal growth restriction
did not influence the decision to institute antihypertensive therapy.
Venous blood was collected before and after (24–48 hours)
antihypertensive therapy was commenced. A single venous blood
sample was collected from controls. The samples were centrifuged
at 3,000 rpm for ten minutes. The serum was separated and
frozen at 280uC for subsequent analysis.
Placental samples were collected from another group of women
(n = 48) undergoing cesarean section (CS) before the onset of labour,
including 14 presenting with PE, 10 with gestational hypertension
(GH) and 24 normotensive controls matched for gestational age,
maternal age (63 years) and parity (none or one to two deliveries),
and who were delivered by CS for obstetric reasons other than
hypertension (e.g. preterm labour with an abnormal presentation or
breech presentation at term). The hypertensive group included 12
women who received antenatal antihypertensive therapy (alpha
methyldopa 750–1500 mg/day). They were matched for gestational
age with 12 women who were not taking antihypertensive treatment.
Four to five placental biopsies were obtained at random from the
maternal surface of the placenta, free of placental membranes.
Serum Assays
Using commercially available kits for the measurement of
human sFlt-1, PlGF, free VEGF and sEng (R & D Systems,
Minneapolis, Minnesota, USA), two-site enzyme linked immuno-
sorbent assays (ELISAs) were conducted in duplicate according to
the manufacturer’s protocol. The minimum detectable levels for
serum sFlt-1, PlGF, VEGF and sEng were 5 pg/ml, 7 pg/ml,
9 pg/ml and 7 pg/ml respectively. The VEGF level in the serum
samples was below the detectable levels. Intra- and inter-assay co-
efficients of variation respectively in our laboratory were as
follows: serum sFlt-1 7%, 9%; PlGF 5%, 6%; and sEng 6%, 8%.
Placental protein extraction and assays
The samples (placental villi, 164–559 mg wet weight) were
rinsed in sterile phosphate buffered saline and snap frozen. A
known weight of placental biopsy was homogenized manually in
four volumes (w/v) of Tris buffered saline containing EDTA-free
serine-/cysteine-protease inhibitor cocktail, diluted according to
the manufacturer’s instructions (Roche Biochemicals, Indiana,
USA) using a homogenizer. The protein extract was collected after
centrifugation (3,000 rpm for 10 minutes) and stored at 280uC
until quantitative analyses were performed in batches.
The total protein concentration was determined with the Bradford
assay (Pierce, Lausanne, Switzerland) using human serum albumin
as a standard. Commercial ELISAs from R&D systems (Minnea-
polis, Minnesota, USA) were used to measure sFlt-1, PlGF, sEng and
‘free’ VEGF in placental extracts according to the manufacturer’s
protocol. All samples were assayed in duplicate and the intra- and
inter-assay variations were ,12% for all assays. The minimum
detectable limits for the assays were: sFlt-1: 31.3pg/ml; PlGF:
3.9 pg/ml; sEng: 62.5 pg/ml; and free VEGF 7.8 pg/ml. These
assays were validated for placental samples. Placental samples from
cases with PE were diluted parallel to the standard curve in the sFlt-
1, PlGF, sEng and VEGF ELISAs.
Uterine artery Doppler measurements
Uterine artery Doppler pulsatility index (PI) was measured in
the hypertensive and control groups at the time of recruitment. In
women who received antihypertensive therapy, Doppler measure-
ments were taken before and after (24–48 hours) therapy was
initiated. The uterine artery was identified by a combination of
real-time and colour Doppler techniques (iU22 Ultrasound
System, Philips Medical Systems, Bothell, WA, USA). Blood
velocity waveforms were recorded by the pulsed Doppler method
(3.5 MHz curved probe; 120 Hz high-pass filter). Five consecutive
flow velocity waveforms of good quality were recorded, and the
mean pulsatility index (PI) derived.
Statistical analysis
D’Agostino and Pearson Omnibus test was used to assess
normality of continuous data. Analysis of variance (ANOVA) with
Bonferroni post hoc tests were carried out to study the differences
among the three groups. Data were analyzed in two gestational age
intervals: ,34 weeks representing early-onset disease and $34 weeks
representing late-onset disease. Paired t tests were used to compare
marker levels before and after antihypertensive therapy. The data
were normally distributed after logarithmic transformation. Pearson
correlation analysis was carried out to investigate the relationship
between the parameters measured. Data were analyzed using SPSSH
(SPSS version 15, 2007, SPSS Inc., Chicago, Illinois, USA).
GraphPad PrismH 5.0 for Windows (InStata, GraphPad Software
Inc., San Diego, California, USA) was used to test the normality of
data. Results were considered statistically significant at P,0.05.
Results
Figures 1 (a) and (b) are flow diagrams of the women recruited
to the serum and placental arms of the study respectively. The
baseline characteristics, mean blood pressure and uterine artery
mean pulsatility index of the serum study groups are shown in
Table 1. The time interval between serum sampling in the
hypertensive women is also shown in Table 1. Among the 51
women with pre-eclampsia in this arm of the study, 16 (31%) had
associated fetal growth restriction (FGR) and 8 (16%) had severe
PE. All the severe PE cases were in the early-onset group.
Serum levels prior to treatment
Figure 2 shows serum levels of angiogenic markers before and
after antihypertensive therapy. Prior to treatment in women with
PE, serum levels of sFlt-1 (Figure 2a) were significantly higher than
normotensive controls ( P ,0.0001 both before 34 weeks and $34
weeks), and higher than women with GH (before 34 weeks,
P,0.05; $34 weeks, P,0.0001). Serum sFlt-1 levels were also
higher in GH compared with controls (before 34 weeks,
P,0.0001; $34 weeks, P,0.05). Figure 2b shows that, prior to
treatment in women with PE, serum PlGF levels were significantly
lower than in controls (before 34 weeks, P,0.0001; $34 weeks,
P,0.01) but not significantly different from women with GH.
Levels in GH were also significantly lower than in controls (before
34 weeks, P,0.0001; $34 weeks, P,0.05). Figure 2c shows that,
prior to treatment in women with PE, serum sEng was significantly
higher than in normotensive controls (before 34 weeks, P,0.0001;
$34 weeks, P,0.01), and higher than women with GH (before 34
weeks, P,0.0001; $34 weeks, P,0.05). Serum levels of sEng were
not significantly different between GH and normotensive controls.
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Figure 3 shows serum levels of these markers in early compared
with late onset, and mild compared with severe pre-eclampsia.
Serum levels of sFlt-1 were higher in early-onset compared with
late-onset (P = 0.002), and in severe compared with mild pre-
eclampsia (P = 0.004). Similarly, serum levels of sEng were higher
in early-onset compared with late-onset (P = 0.001), and in severe
compared with mild pre-eclampsia (P,0.0001). Serum PlGF was
lower in early-onset compared with late-onset (P = 0.001), and in
severe compared with mild pre-eclampsia (P,0.0001).
Effect of treatment on serum levels
Figure 2 shows the effect of treatment with methyldopa on
serum levels of sFlt-1, PlGF and sEng. In women presenting with
PE, antihypertensive treatment was associated with a significant
fall in the serum concentrations of both sFlt-1 (before 34 weeks,
P,0.01; $34 weeks, P,0.001) and sEng (before 34 weeks,
P,0.001; $34 weeks, P,0.05) (Figures 2 a and c respectively).
Antihypertensive therapy had no significant effect on serum levels
of PlGF in women with PE (Figure 2b), or on the level of any of
these proteins in women with GH.
Placental levels in hypertensive disorders
The results of the placental analysis are presented in Figure 4 and
Table 2. Figure 4 shows the placental extract concentrations of sFlt-
1, PlGF, sEng, and VEGF in 24 controls, 14 PE cases and 10 GH
cases. Placental levels of sFlt-1 were significantly higher (5-fold) in PE
compared to GH (P,0.001) or controls (P,0.001). There was no
significant difference in sFlt-1 levels between women with GH and
controls (Figure 4a). Placental levels of PlGF were significantly lower
(P = 0.01) in PE compared to controls (Figure 4b). Placental levels of
PlGF were lower in GH compared with controls but this difference
did not achieve statistical significance (P = 0.5). Placental concentra-
tions of sEng were significantly higher (P,0.0001) in women with PE
compared to GH or normotensive controls (Figure 4c). There was no
significant difference in placental sEng between controls and women
with GH (P = 0.07). Placental VEGF was significantly higher in
women with either PE or GH (P,0.0001) compared with
normotensive controls (Figure 4d). There was no significant
difference in placental VEGF between women with PE and women
with GH (P = 0.6).
Antihypertensive treatment and placental levels
Table 2 shows the placental concentrations of the same four
markers in women with PE and gestational hypertension, grouped
according to whether they received antihypertensive therapy (all
with methyldopa) or not. In women with PE, treatment with
methyldopa was associated with a significantly (almost 50%) lower
placental concentration of sFlt-1 (P = 0.01). In women with GH,
treatment was also associated with a lower placental sFlt-1
concentration but this did not achieve statistical significance
(P = 0.06). Antihypertensive treatment was also associated with
significantly (P = 0.02) lower placental sEng in women with PE,
but not in gestational hypertension. Treatment with methyldopa
did not affect placental levels of PlGF or VEGF.
There was no significant difference in mean uterine artery
Doppler pulsatility index before and after methyldopa treatment,
in either the PE (,34 weeks, P = 0.07; $34 weeks, P = 0.6) or GH
group (,34 weeks, P = 0.18; $34 weeks, P = 0.6).
Discussion
Pre-eclampsia remains one of the most complex disorders of
human pregnancy. The lack of suitable animal models with
placental features of the disease means that we have to rely, for the
most part, on human studies. The maternal response to the
presence of a pregnancy and placental activity remain the focus of
research into the disease. The data from this study confirm that, in
both early and late onset PE, maternal serum levels of sFlt-1 and
sEng are higher, and PlGF lower, in women presenting with PE
[1–3]. In addition, we found that placental sFlt-1 and sEng were
Table 1. Baseline characteristics of the study groups in whom serum levels of angiogenic factors were measured, according to
gestational age at recruitment.
,34+0 weeks $34+0 weeks
Controls PE GH
P
value
Controls PE GH
P
value
n 412813 3923 16
Age (years) { 3164306532640.6316430643265 0.2
BMI (kg/m
2
) { 276430642764 0.07 286327652965 0.2
Nulliparity [n (%)] 25 (61) 20 (71) 7 (54) 0.6 21 (53) 16 (70) 9 (56) 0.3
Current smoker [n (%)] 1 (2) 0 (0) 0 (0) 1 2 (5) 1 (4) 0 (0) 1
Caucasian [n (%)] 20 (48) 13 (46) 7 (54) 0.7 23 (59) 13 (57) 9 (56) 0.4
GA at recruitment (days) { 3061.3 3060.4 30.460.8 0.5 36.662.4 3662.3 36.462 0.4
GA at delivery (days) { 39.762.3 3361.7 36.762.9 ,0.001 39.861.6 37.362 38.662.3 ,0.001
Birth weight (grammes) { 33986529 16856204 27256198 ,0.001 34056526 28966689 31746591 ,0.001
Mean BP (mmHg) 85612 126.6612 125.1612 ,0.0001 85611 121.1611.1 114.566.1 ,0.0001
Mean Pulsatility Index (PI) 0.7660.1 1.5160.5 0.8460.1 ,0.0001 0.5960.1 0.8560.2 0.616
0.1 ,0.0001
Interval between samples (hours) 3264346338663967
BMI = body mass index.
GA = gestational age.
Mean BP = mean blood pressure.
PE = pre-eclampsia.
GH = gestational hypertension.
{
Data presented as mean6SD and analyzed by one-way ANOVA with Bonferroni post hoc analysis.
doi:10.1371/journal.pone.0002766.t001
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significantly increased, and PlGF decreased, in women with PE
compared to controls.
Our data suggest that, in pre-eclampsia, placental concentra-
tions of sFlt-1, sEng and PlGF mirror the maternal serum changes.
These findings are consistent with the view that the placenta is the
main source of sFlt-1, sEng and PlGF during pregnancy [9].
Circulating sFlt-1 can bind to PlGF and VEGF, effectively
inhibiting their actions [11,33]. Soluble Flt-1 is therefore
considered to be a circulating anti-angiogenic factor. In our study,
as previously described, levels of sFlt-1 were elevated and PlGF
reduced in the serum of women with PE prior to treatment [1,4].
The lower levels of free PlGF found in the serum of women with
PE may be the result of impaired placental production or
secretion, or due to increased binding by sFlt-1 in maternal serum.
Our findings indicate that antihypertensive treatment with alpha
methyldopa is associated with a significant fall in serum concentra-
tions of both sFlt-1 and sEng in women presenting with either early
onset or late onset PE. Methyldopa therapy had no significant effect
on the serum levels of these markers in women presenting with
gestational hypertension. Consistent with the trend in maternal
serum, antihypertensive treatment with methyldopa was also
associated with significantly lower placental concentrations of both
sFlt-1 and sEng in PE, but not in gestational hypertension. These
findings suggest that, in pre-eclampsia, alpha methyldopa may have
a direct effect on placental synthesis and/or secretory functions and
that this effect may not be simply the result of a reduction in
maternal blood pressure and/or a change in utero-placental blood
flow. However, sFlt-1 and sEng are also produced by vascular
Figure 2. Serum concentrations of angiogenic factors in normotensive women, women with pre-eclampsia and women with
gestational hypertension who received methyldopa. Mean serum sFlt-1 (a), PlGF (b) and sEng (c) concentrations in normotensives (controls),
women with pre-eclampsia and women with gestational hypertension according to gestational age (GA) interval [early onset ,34 weeks (41 controls,
28 PE, 13 GH) and late onset $34 weeks (39 controls, 23 PE, 16 GH)]. Error bars represent standard errors. Comparison of controls and cases (with PE
or GH) was performed after logarithmic transformation. Levels before and after alpha methyldopa therapy are shown for women with pre-eclampsia
and women with gestational hypertension. The levels in the three groups were compared using ANOVA with Bonferroni Dunn’s posthoc tests. The
levels before and after antihypertensive therapy are compared using the paired t test. ****P,0.0001, ***P,0.001, **P,0.01, *P,0.05. P values are
shown only for differences which are statistically significant.
doi:10.1371/journal.pone.0002766.g002
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endothelial cells and we cannot exclude an endothelial cell effect of
the medication in women with PE. The specific effect in PE with no
effect in GH indicates that methyldopa has a different effect on
placental and/or endothelial production and/or secretion of
angiogenic factors depending on the pathophysiology of the
hypertensive disorder. These findings support the concept of a
fundamental difference in pathophysiology between gestational
hypertension and the pathological endothelial toxic effect of pre-
eclampsia.
Alpha methyldopa acts on a
2
-adrenergic receptors, primarily in
the central nervous system (CNS) although an effect on peripheral
a
2
-adrenoreceptors may also play a part [34–35]. Its main active
metabolite is alpha-methyl norepinephrine, which resembles
norepinephrine in its effects. Stimulation of pre-synaptic a
2
-
adrenoreceptors in the CNS leads to a reduction of central
sympathetic outflow. This causes a reduction in blood pressure
[36]. a
2
-adrenoreceptors have also been identified in a variety of
other human tissues outside the CNS, including myometrium and
placenta [37–38]. An almost universal effect of a
2
-adrenoreceptor
stimulation is the inhibition of adenylyl cyclase which leads to
decreased production of cAMP [39–40]. cAMP has been shown to
be a strong inducer of Flt-1 expression in mice [41–42].
In 2007, Muthig et al demonstrated that down-regulation of
a
2b
-adrenoceptors in mice placenta resulted in increased levels of
Flt-1 and sFlt-1, [43] suggesting that stimulation of a
2b
-
adrenoceptors can suppress production of sFlt-1. Deletion of the
gene encoding a
2b
-adrenoceptors resulted in upregulation of Flt-1
in spongiotrophoblast cells. These data support a direct link
Figure 3. Maternal serum concentrations of angiogenic factors in early and late onset PE, and in mild and severe PE. Mean maternal
serum concentrations of sFlt-1 (a), PlGF (b) and soluble endoglin (c) in women with early onset and late onset PE, and in women with mild and severe
PE. Error bars represent standard errors. Early onset were compared with late onset, and mild with severe PE after logarithmic transformation using
unpaired t test.
doi:10.1371/journal.pone.0002766.g003
Table 2. Antihypertensive therapy and placental concentrations of angiogenic factors.
PE GH
Controls
Anti-hypertensive
(n = 7)
No anti-hypertensive
(n = 7)
P
value
Anti-hypertensive
(n = 5)
No anti-hypertensive
(n = 5)
P
value
sFlt-1 (ng/ml) 17.7 (3)* 33.9 (5)* 0.01 3.1 (0.4) 5.3 (0.8) 0.06 5.2 (1.2)
PlGF (pg/ml) 8.4 (1.8)* 7.7 (2)* 0.56 20.7 (3) 15.9 (4) 0.18 23.9 (5)
sEng (ng/ml) 13.1 (1.6)* 19.6 (1.7)* 0.02 3.8 (0.4) 4.3 (0.3) 0.35 3.5 (0.2)
VEGF (pg/ml) 107.5 (30)* 247 (82)* 0.09 108 (39)* 166 (32)* 0.1 10.4 (1.2)
Placental concentrations of sFlt-1, PlGF, sEng and VEGF (expressed per mg protein) in normotensive controls, pre-eclampsia (PE) and gestational hypertension (GH),
grouped according to whether they received antihypertensive therapy or not. The mean gestational ages for the three groups were (mean6SD): controls 242616; pre-
eclampsia 238613; gestational hypertension 243620. The P values represent the statistical difference between the groups with hypertension who received
antihypertensive therapy or not.
PE = pre-eclampsia.
GH = gestational hypertension.
Data presented as mean (standard error of the mean), and analyzed by independent t test.
*
P,0.05 compared with normotensive control group.
doi:10.1371/journal.pone.0002766.t002
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between adrenergic receptor signalling and angiogenic regulation
by the VEGF system. This may be the mechanism by which alpha
methyldopa leads to the reduction in sFlt-1 which our data
support. Although this study [43] was done in mice, several
functionally relevant polymorphisms that may potentially affect
sFlt-1 expression and blood vessel formation have been identified
in human adrenoceptor genes. This adds weight to the argument
that methyldopa has an effect on maternal production of
vasoactive substances: the fact that we see a different response in
women with pre-eclampsia may reflect the finding that women
with this disease are producing abnormal amounts of these
substances in the first place.
Due to the rapid evolution of hypertensive diseases in our study
groups, we could investigate only the biological effects of the
antihypertensive treatment over a short time interval (maximum
48 hours). Compared to long-term studies in non-pregnant
women [30], studies during pregnancy are limited by the fact
that it is not possible to analyze the placenta before and after
initiating treatment. Thus we decided to compare women with
hypertensive disorders receiving methyldopa with women with
hypertensive disorders not receiving treatment. Clinically, the
need for antihypertensive treatment is a marker of disease severity;
thus, prior to treatment, higher levels of sFlt-1 and sEng would be
expected in the treatment group compared with the non-treatment
group. Nevertheless, we found that antihypertensive treatment was
associated with significantly lower levels of these two markers in
the placenta of women treated with methyldopa compared to the
placenta of untreated women.
A potential limitation of our study is the short time interval (24
to 48 hours) from initiation of antihypertensive treatment to
venous blood sampling. It would be interesting to investigate the
effect on angiogenic markers levels at longer intervals, e.g. a week
after starting treatment. However, most women with hypertensive
disorders in pregnancy, and particularly PE, will need delivery
soon after starting antihypertensives, such that long-term follow-up
is often precluded.
Our findings suggest that any future research into the use of serum
markers to screen or monitor hypertensive disorders of pregnancy
should take account of possible effects of antihypertensive therapy on
marker levels. Further research is needed to evaluate whether
different antihypertensive drugs have different effects on anti-
angiogenic factors. Such research will improve our understanding of
the pathophysiology of pre-eclampsia but may also lead to better
therapeutic clinical protocols. Raised maternal serum levels of sFlt-1
can be detected several weeks prior to the onset of clinical pre-
eclampsia. It is worth investigating whether administration of a-
methyldopa at this point might have an effect on levels of anti-
angiogenic factors and modify the disease process. Our findings also
have potential implications outside the specialty of obstetrics.
Women who develop pre-eclampsia are at significantly increased
risk, later in life, of cardiovascular disease such as ischemic heart
disease and stroke. Within this context, it is not known whether the
use of specific antihypertensive drugs can also have a long-term
beneficial effect. Furthermore, it remains to be determined whether
the use of these antihypertensive drugs outside pregnancy could have
a similar beneficial effect on anti-angiogenic factors and subsequently
translate into clinical benefit. We hope that our data will stimulate
further research in these areas.
It is not yet clear whether sFlt-1 and sEng are directly involved
in the pathophysiology of PE or are simply markers of the disease
process. Our data showing that antihypertensive treatment with
alpha methyldopa is associated with a significant fall in their
concentrations in both maternal serum and placenta is consistent
with a positive effect on the control of disease progress. This
Figure 4. Placental concentrations of angiogenic factors in normotensive women, women with pre-eclampsia and gestational
hypertension. Concentrations of sFlt-1(a), PlGF (b), soluble endoglin (c) and VEGF (d) (expressed per mg protein) in placental tissue from
normotensive (controls, n = 24, pre-eclampsia (PE, n = 14) and gestational hypertension (HT, n = 10 pregnancies. Error bars represent standard errors.
Comparison of controls and cases (with PE or GH) was performed after logarithmic transformation. The mean gestational ages (days) for the three
groups were (mean6SD): controls 242616; pre-eclampsia 238613; gestational hypertension 243620.
doi:10.1371/journal.pone.0002766.g004
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PLoS ONE | www.plosone.org 7 July 2008 | Volume 3 | Issue 7 | e2766
Page 7
finding supports the concept that pre-eclampsia combines an
excessive maternal response to the presence of a pregnancy and
placenta and progressive utero-placental insufficiency during the
second half of pregnancy at the time of maximal fetal growth.
Author Contributions
Conceived and designed the experiments: AAK SM EJ. Performed the
experiments: AAK. Analyzed the data: AAK. Contributed reagents/
materials/analysis tools: SM EJ. Wrote the paper: AAK SM KH EJ.
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  • Source
    • "The dense networks of blood vessels within the placenta are responsible for exchanging respiratory gases, nutrients, and wastes between the mother and fetus throughout pregnancy, which is essential for proper fetal growth [1]. Throughout gestation the vasculature of the placenta is continually evolving to accommodate the mounting demands of the fetus and can be directly influenced by a number of exogenous factors such as maternal diet, smoking, and medication use2345. Furthermore, conditions which subject the placenta to stress, such as increased dietary fats and exposure to the chemicals in cigarette smoke, can also result in altered levels of immune and growth factors which may impact the proper development of placental vasculature678. "
    [Show abstract] [Hide abstract] ABSTRACT: Proper placental development and function are central to the health of both the mother and the fetus during pregnancy. A critical component of healthy placental function is the proper development of its vascular network. Poor vascularization of the placenta can lead to fetal growth restriction, preeclampsia, and in some cases fetal death. Therefore, understanding the mechanisms by which uterine stressors influence the development of the placental vasculature and contribute to placental dysfunction is of central importance to ensuring a healthy pregnancy. In this review we discuss how oxidative stress observed in maternal smoking, maternal obesity, and preeclampsia has been associated with aberrant angiogenesis and placental dysfunction resulting in adverse pregnancy outcomes. We also highlight that oxidative stress can influence the expression of a number of transcription factors important in mediating angiogenesis. Therefore, understanding how oxidative stress affects redox-sensitive transcription factors within the placenta may elucidate potential therapeutic targets for correcting abnormal placental angiogenesis and function.
    Full-text · Article · Jan 2015 · BioMed Research International
  • Source
    • "However, PE is a disorder of deep invasive placentation, limiting the study of pharmacologic interventions to humans and a few other higher primates. We have previously shown the anti-hypertensive drug α-methyldopa (Mdopa) has an effect on maternal serum levels of angiogenic proteins and placental hormones in pregnancies complicated by PE [16], [17]. This effect may be independent of Mdopa known antihypertensive central action and we have suggested that Mdopa may directly influence trophoblastic protein synthesis and/or release and thus some of the main placental biological functions. "
    [Show abstract] [Hide abstract] ABSTRACT: IntroductionAntihypertensive drugs lower the maternal blood pressure in pre-eclampsia (PE) by direct or central vasodilatory mechanisms but little is known about the direct effects of these drugs on placental functions.ObjectiveThe aim of our study is to evaluate the effect of labetolol, hydralazine, α-methyldopa and pravastatin on the synthesis of placental hormonal and angiogenic proteins know to be altered in PE.DesignPlacental villous explants from late onset PE (n = 3) and normotensive controls (n = 6) were cultured for 3 days at 10 and 20% oxygen (O2) with variable doses anti-hypertensive drugs. The levels of activin A, inhibin A, human Chorionic Gonadotrophin (hCG), soluble fms-like tyrosine kinase-1 (sFlt-1) and soluble endoglin (sEng) were measured in explant culture media on day 1, 2 and 3 using standard immunoassays. Data at day 1 and day 3 were compared.ResultsSpontaneous secretion of sEndoglin and sFlt-1 were higher (p<0.05) in villous explants from PE pregnancies compared to controls. There was a significant time dependant decrease in the secretion of sFlt-1 and sEndoglin in PE cases, which was seen only for sFlt-1 in controls. In both PE cases and controls the placental protein secretions were not affected by varying doses of anti-hypertensive drugs or the different O2 concentration cultures, except for Activin, A which was significantly (p<0.05) higher in controls at 10% O2.InterpretationOur findings suggest that the changes previously observed in maternal serum hormones and angiogenic proteins level after anti-hypertensive treatment in PE could be due to a systemic effect of the drugs on maternal blood pressure and circulation rather than a direct effect of these drugs on placental biosynthesis and/or secretion.
    Full-text · Article · Sep 2014 · PLoS ONE
  • Source
    • "All recommended drugs in PE, a-Methyldopa and clonidine, hydralazine and calcium antagonists or nitrates, share the main action mechanism of vasodilating the distal arteriolar bed in order to achieve reduced SVR. Reduced antiangiogenic tone [155] with a-Methyldopa, and improved angiogenesis with calcium antagonists are reported [156]. NO donors such as sildenafil, have also shown to improve hypertension and proteinuria in experimental models [157]. "
    Full-text · Dataset · Jan 2014
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