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original papers
Adv Clin Exp Med 2012, 21, 3, 331–335
ISSN 1899–5276
© Copyright by Wroclaw Medical University
Beata Nowak1, 2, Magdalena Szmyrka-Kaczmarek2, Anna Durazińska2,
Rafał Płaksej3, Krzysztof Borysewicz2, Lucyna Korman2, Piotr Wiland2
Anti-Ox-LDL Antibodies
and Anti-Ox-LDL-Β2GPI Antibodies in Patients
with Systemic Lupus Erythematosus
Przeciwciała przeciwko oksydowanym LDL
oraz przeciwko kompleksom oxLDL-β2GPI
u chorych na tocznia rumieniowatego układowego
Department of Pharmacology, Wroclaw Medical University, Poland
Department of Rheumatology and Internal Medicine, Wroclaw Medical University, Poland
3
Department of Cardiology, Wroclaw Medical University, Poland
1
2
Abstract
Objectives. The aim of the study was to assess the concentration of anti-oxidized low-density lipoprotein (antioxLDL) antibodies and antibodies against oxLDL-β2GPI (oxLDL-beta 2 glycoprotein I) complexes in the serum
of patients with systemic lupus erythematosus (SLE). Correlations between clinical and laboratory factors and the
intima media thickness (IMT) were also investigated.
Material and Methods. The study included 16 patients (14 females, 2 males) with an established diagnosis of SLE.
The mean disease duration was 6.3 years (range: 2–23 years). Thirteen age-matched healthy volunteers comprised
the control group. IMT, the concentration of anti-oxLDL and anti-oxLDL-β2GPI antibodies and lipid profile were
assesed. Data concerning other cardiovascular risk factors were also collected.
Results. In the SLE group the intima media was significantly thicker than in control group. In the SLE group
a statistically significant positive correlation was noted between age and mean IMT. Immunological assays revealed
elevated serum concentration of anti-oxLDL antibodies in the SLE group; serum concentration of IgG anti-oxLDLβ2GPI antibodies and IgM anti-oxLDL-β2GPI antibodies were also elevated in the SLE group compared to the controls. There was a statistically significant positive correlation between LDL concentration and anti-oxLDL antibody
concentration in the SLE group.
Conclusions. The study findings support the thesis that cardiovasular risk is significantly higher in SLE patients.
Elevated concentrations of anti-oxLDL antibodies, IgG anti-oxLDL-β2GPI antibodies and IgM anti-oxLDL-β2GPI
antibodies were detected in the SLE group, which may contribute to the elevated cardiovascular risk in SLE patients
(Adv Clin Exp Med 2012, 21, 3, 331–335).
Key words: anti-oxidizes-low density lipoprotein antibodies, anti-oxidized-low density lipoprotein – beta2-glicoprotein I antibodies, systemic lupus erythematosus.
Streszczenie
Cel pracy. Ocena stężenia przeciwciał skierowanych przeciwko cząsteczkom oxLDL (utlenowanych lipoprotein
o niskiej gęstości) oraz przeciwko kompleksom zawierających oxLDL i beta2-glikokoproteinę I (oxLDL-β2GPI)
w surowicy chorych na toczeń rumieniowaty układowy (SLE). Ponadto szukano związku między czynnikami klinicznymi i laboratoryjnymi a grubością błony wewnętrznej (IMT).
Materiał i metody. Do badania włączono 16 chorych (14 kobiet i 2 mężczyzn) z ustalonym rozpoznaniem SLE oraz
13 zdrowych ochotników jako grupę kontrolną. U wszystkich uczestników badania oceniono IMT, stężenia przeciwciał anty-oxLDL oraz anty-oxLDL-β2GPI i gospodarkę lipidową, a także zebrano dane dotyczące klasycznych
czynników ryzyka chorób sercowo-naczyniowych.
Wyniki. W grupie chorych na SLE stwierdzono istotne pogrubienie IMT w porównaniu z grupą kontrolną. W grupie chorych na SLE stwierdzono dodatnią korelację między wiekiem a IMT. Badania immunologiczne wykazały
zwiększone stężenie przeciwciała anty-oxLDL w grupie chorych na SLE. Wykazano także istotnie zwiększone stęże-
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B. Nowak et al.
nie przeciwciał anty-oxLDL-β2GPI w klasie IgG oraz w klasie IgM w grupie chorych na SLE. W grupie chorych na
SLE stwierdzono także istotną statystycznie dodatnią korelację między stężeniami LDL i przeciwciał anty-oxLDL.
Wnioski. Uzyskane wyniki potwierdzają tezę o istotnie zwiększonym ryzyku sercowo-naczyniowym u chorych na
toczeń rumieniowaty układowy. Stwierdzone zwiększone stężenie przeciwciał anty-oxLDL oraz anty-oxLDL-β2GPI
w klasie IgG i w klasie IgM w grupie chorych na SLE może być jednym z czynników zwiększającym to ryzyko (Adv
Clin Exp Med 2012, 21, 3, 331–335).
Słowa kluczowe: przeciwciała przeciwko utlenowanym lipoproteinom o niskiej gęstości, przeciwciała przeciwko
kompleksom utlenowanych lipoprotein o niskiej gęstości i beta2-glikoproteiny I, toczeń rumieniowaty układowy.
Premature atherosclerosis in patients with systemic lupus erythematosus (SLE) was described for
the first time more than thirty years ago by Bulkley and Roberts [1]. Since then many authors have
reported symptomatic or asymptomatic premature
atherosclerosis in SLE patients. As the traditional
Framingham risk factors cannot fully explain the
reasons for accelerated atherosclerosis in systemic
lupus erythematosus [2], other risk factors need to
be identified and interactions between traditional
and immunological risk factors are under investigation.
The aim of the current study was to assess the
concentration of anti-oxLDL-antibodies and antibodies against oxLDL-β2GPI complexes in the serum of SLE patients. A correlation was also sought
between clinical and laboratory factors and the intima media thickness (IMT), which is one of the
markers of the presence and extent of atherosclerosis [3–5].
Material and Methods
The study involved 16 patients (14 females,
2 males) aged 27–60 (mean age 44.4) with an established diagnosis of SLE. The inclusion criteria
were an established diagnosis of SLE and age above
18 years; exclusion criteria for the SLE group included overlap syndromes, chronic and acute
infections, and a history of malignant neoplasm.
The mean disease duration was 6.3 years (range:
2–23 years). The characteristics of the SLE patients
are shown in Table 1.
Thirteen age-matched healthy volunteers made
up the control group. The exclusion criteria for the
control group included SLE or any other connective tissue disease, chronic and acute infections,
and history of malignant neoplasm. Volunteers
were also excluded if their medical history revealed
any cardio-vascular disease. People with elevated
blood pressure, any abnormalities in ECGs or significant abnormalities in physical examinations
were excluded from the study.
The patients and the healthy volunteers gave
their informed consent prior to their inclusion in
the study.
Table 1. Characteristics of the SLE group
Tabela 1. Charakterystyka grupy chorych na SLE
SLEDAI#
0–34 (10)
SLICC/ACR#
0–7 (2.87)
Concomitant diseases (Choroby współistniejące)
antiphospholipid syndrome*
5 (31.25%)
diabetes type II*
1 (6.25%)
hyperlipidemia*
10 (62.5%)
hypertension *
7 (43.75%)
Manifestations of atherosclerosis (Objawy miażdżycy)
coronary heart disease*
1 (6.25%)
peripheral vascular disease*
0 (0%)
stroke*
1 (6.25%)
Treatment for SLE (Leczenie SLE)
number of patients receiving
GCs
14 (87.5%)
dose of GCs (counted as
dose of prednisone#
5–30 (15.5%)
number of patients receiving
immunosuppressive drugs*
9 (7 – AZA,
1 – Cy, 1 – other)
(56%)
SLE – systemic lupus erythematosus.
SLEDAI – SLE Disease Activity Index.
SLICC/ACR – SLE Collaborating Clinics/American
College of Rheumatology Damage Index.
GCs – glicocorticosteroids.
AZA – azathioprine.
Cy – cyclophosphamide.
# – results presented as range (mean).
* – results presented as number (%).
SLE – toczeń rumieniowaty układowy.
SLEDAI – wskaźnik aktywności SLE.
SLICC/ACR – wskaźnik uszkodzenia narządów
w przebiegu SLE.
GCs – glikokortykosteroidy.
AZA – azatiopryna.
Cy – cyklofosfamid.
# – wyniki przedstawione w postaci: zakres (średnia).
* – wyniki przedstawione w postaci: liczba (%).
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Anti-Ox-LDL Antibodies and Anti-Ox-LDL-Β2GPI in SLE
The data for analysis were obtained from medical histories, physical examinations, laboratory
tests and ultrasound examinations of the carotid
arteries. In the SLE group the disease activity was
measured with the Systemic Lupus Erythematosous Disease Activity Index (SLEDAI) and organ
damage was assessed using the SLE Collaborating
Clinics/ American College of Rheumatology Damage Index (SLICC/ACR).
The ultrasound examinations of the carotid arteries in both groups were carried out using a high frequency linear transducer (10 MHz,
Vingmed System 5). Two measurements of the
IMT of the common carotid artery (CCA), internal carotid artery (ICA) and the bulb of common
carotid artery (BCCA) were performed bilaterally.
The mean IMT was calculated as mean value of all
these measurements.
Serum concentrations of anti-oxLDL antibodies and anti-oxLDL-β2GPI IgG and IgM antibodies were assessed with ELISA tests (Oxidized LDL,
Mercodia and Anti-AtherOx Test Kit IgG, and
Anti-AtherOx Test Kit IgM, both from Corgenix
Medical Corporation, USA).
The statistical analysis was performed using Statistica Software. The differences in mean
IMT, anti-oxLDL antibodies, anti-oxLDL-β2GPI
IgG and IgM antibodies were compared using
a U-Mann Whitney test. Correlations between the
assessed parameters were tested using non-parametrical tests.
The study protocol was reviewed in November 2005 (KB923/2005) by the Ethics Committee
of Wroclaw Medical University, and the study was
been performed in accordance with the ethical
standards of the1964 Declaration of Helsinki.
Results
The results of IMT measurements and immunological assays are shown in Table 2. In the SLE
group the intima media was significantly thicker
than in the control group (the mean IMT in the
SLE group was 0.71 ± 0.21 mm, as opposed to
the mean IMT in the control group, which was
0.50 ± 0.04 mm; p = 0.00015). This proved that
arteriosclerosis was more advanced in the SLE patients.
In the SLE group a statistically significant positive correlation was found between age and mean
IMT (RS = 0.68; p = 0.004). In the SLE group there
was also a statistically significant negative correlation between mean IMT and dose of glicocorticosteroids (RS = –0.64; p = 0.013). There was no
significant correlation between SLICC/ACR and
IMT.
In the control group a statistically significant
positive correlation was detected between mean
IMT and serum concentration of IgG anti-oxLDLβ2GPI antibodies (RS = 0.64; p = 0.019)
The immunological assays revealed elevated
serum concentration of anti-oxLDL antibodies in
the SLE group (97.8 ± 22.6 U/L vs. 70.2 ± 19.0 U/L;
p = 0.0023). The serum concentrations of IgG antioxLDL-β2GPI antibodies and IgM anti-oxLDL-
Table 2. IMT and immunological assays in the SLE group and the control group
Tabela 2. IMT I wyniki badań immunologicznych w grupie chorych na SLE I w grupie kontrolnej
SLE group
(Grupa SLE) n = 16
Control group
(Grupa kontrolna) n = 13
p*
IMT – mm
0.71 ± 0.21
0.50 ± 0.04
0.00015
Anti-oxLDL antibodies
(Przeciwciała anty-oxLDL) U/l
97.8 ± 22.6
70.2 ± 19.0
0.0023
Anti-oxLDL-β2GPI IgG antibodies – G Units – number
of positive sera
(Przeciwciała anty-oxLDL-β2GPI klasy IgG – jednostki
G] – liczba surowic z wynikiem dodatnim)
38.7 ± 41.0 (10)
11.9 ± 5.6 (1)
0.0015
Anti-oxLDL-β2GPI IgM antibodies – M Units – number
of positive sera
(Przeciwciała anty-oxLDL-β2GPI klasy IgM – jednostki
M – liczba surowic z wynikiem dodatnim)
42.1 ± 63.7 (7)
11.7 ± 6.7 (2)
0.008
Results presented as mean ± SD.
SD – standard deviation.
IMT – intima media thickness.
SLE: systemic lupus erythematosus.
oxLDL: oxidized LDL cholesterol.
oxLDL-β2GPI – complex of oxLDL and β2-glycoprotein I.
* p values concern the comparison of levels in the two groups.
Wyniki przedstawiono w postaci: średnia ± SD.
SD – odchylenie standardowe.
IMT – grubość błony wewnętrznej.
SLE – toczeń rumieniowaty układowy.
oxLDL – utlenowany cholesterol frakcji LDL.
oxLDL-β2GPI kompleks oxLDL i β2-glikoproteiny I.
* wartości „p” dotyczą porównywanych stężeń.
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B. Nowak et al.
β2GPI antibodies were also elevated in the SLE
group as compared to the controls (38.7 ± 41.0 G
Units vs. 11.9 ± 5.6 G Units; p = 0.0015 and
42.1 ± 63.7 M Units vs. 11.7 ± 6.7 M Units; p =
0.0080, respectively). No correlations between the
levels of IgG and IgM anti-oxLDL-β2GPI antibodies were found.
In the SLE group there were statistically significant correlations between the concentration
of anti-oxLDL antibodies and the concentrations
of LDL, triglycerides and total cholesterol (RS =
0.74, p = 0.0027; RS = 0.57, p = 0.032; and RS =
0.53, p = 0.047, respectively). No correlations between the SLEDAI values and the concentrations
of anti-oxLDL and anti-oxLDL-β2GPI antibodies were detected. However, there was a statistically significant negative correlation between
erythrocyte sedimentation rate (ESR) and high
density lipoprotein (HDL) concentration (RS =
–0.60; p < 0.05). No correlation between SLICC/
ACR scores and concentrations of anti-oxLDL and
anti-oxLDL-β₂GPI antibodies were detected.
Discussion
Thicker intima media were found in the SLE
patients than in the healthy volunteers. As prospective studies have revealed a strong correlation between carotid atherosclerosis and the risk
of myocardial infarction [6] and the Carotid Atherosclerosis Progression Study (CAPS) proved
that carotid IMT independently predicted future
vascular events and that its predictive value was
high in younger and older subjects [7], the current
findings support the thesis that cardiovasular risk
is significantly higher in SLE patients.
Elevated concentrations of anti-oxLDL antibodies were found in the SLE group. Acting as autoantigens, oxLDL particles stimulate the synthesis of anti-oxLDL-antibodies, which are elevated
in patients with unstable angina and myocardial
infarction [8, 9]. The findings of the current study
indicate that anti-oxLDL antibodies may also contribute to the elevated cardiovascular risk in SLE
patients. Although in most studies, a positive correlation between anti-oxLDL antibodies and IMT
was found, suggesting that these antibodies might
be markers of progression of atherosclerosis, some
experimental data indicate that anti-oxLDL antibodies may play a protective role [10, 11].
β2glycoprotein I (β2GPI), which is one of the
main antigens for antiphospholipids antibodies,
binds to oxLDL, forming stable complexes. These
complexes increase the uptake of oxLDL by macrophage scavenger receptors and accelerate foam
cell formation. The presence of antibodies against
oxLDL-β2GPI-complexes accelerates their internalization and strongly correlates with the risk of
arterial thrombosis [12]. The in vitro macrophage
uptake of oxLDL-β2-GPI-complexes increases in
the presence of autoantibodies against those complexes [13]. Like Lopez et al. [14], the current authors detected significantly elevated level of IgG
anti-oxLDL-β2GPI antibodies in the serum of SLE
patients. In contrast to Lopez’s study, the current
study revealed a correlation between mean IMT
and serum concentration of IgG anti-oxLDL-β2GPI
antibodies. This supports the hypothesis that those
antibodies contribute not only to thrombosis formation, but also to the growth of atherosclerotic
plaque. It has been suggested by other authors
that IgG antibodies are proatherogenic, while IgM
antibodies may be protective, but the role of antioxLDL-β2GPI antibodies in atherogenesis remains
controversial [14, 15]. Some authors suggest that
anti-oxLDL-β2GPI antibodies may be involved in
organ damage in SLE patients [16], but the current
study revealed no correlation between IgG or IgM
antibodies and SLICC/ACR scores.
The authors concluded that in SLE patients,
anti-oxLDL, IgG and IgM anti-oxLDL-β2GPI antibodies may contribute to premature atherogenesis.
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Address for correspondence:
Beata Nowak
Department of Pharmacology
Wroclaw Medical University
Mikulicza-Radeckiego 2
50-345 Wrocław
Poland
Tel.: +48 71 784 1442
Mobile: +48 607 924 471
E-mail: [email protected]
Conflict of interest: none declared
Received: 2.06.2011
Revised: 28.12.2011
Accepted: 6.06.2012