Download Beta 1-adrenergic receptor-directed autoimmunity as a cause of

International Journal of Cardiology 112 (2006) 7 – 14
www.elsevier.com/locate/ijcard
Beta 1-adrenergic receptor-directed autoimmunity as a cause of dilated
cardiomyopathy in rats
Roland Jahns a,b,⁎, Valérie Boivin b , Martin J. Lohse b
a
Department of Internal Medicine, Medizinische Klinik und Poliklinik I, University of Wuerzburg, Josef-Schneider-Strasse 2, D-97080 Wuerzburg, Germany
b
Institute of Pharmacology and Toxicology, University of Wuerzburg, Versbacher Strasse 9, D-97078 Wuerzburg, Germany
Received 14 April 2006; accepted 10 May 2006
Available online 26 July 2006
Abstract
Progressive cardiac dilatation and pump failure of unknown etiology has been termed idiopathic dilated cardiomyopathy (DCM). During
recent years a large body of data has accumulated indicating that functionally active antibodies or autoantibodies being able to recognize and
to stimulate the cardiac β1-adrenergic receptor (anti-β1-AR) may play an important role in the initiation and/or clinical course of DCM.
Recent experiments in rats even point towards a cause-and-effect relation between stimulatory anti-β1-AR antibodies and DCM.
Immunization of rats against the second extracellular loop of the human β1-adrenergic receptor (100% sequence-identity between human and
rat) resulted in both development of stimulatory anti-β1-AR antibodies and development of progressive cardiac dilatation and dysfunction.
Isogenic transfer of stimulatory anti-β1-AR from cardiomyopathic into healthy inbread animals reproduced the disease, hence providing
conclusive proof for a β1-receptor-directed autoimmune attack as a possible cause of cardiomyopathy. This kind of cardiomyopathy is now
referred to as anti-β1-AR-induced dilated immune-cardiomyopathy (DiCM).
The following article reviews recent evidence obtained from experimental animal-models implying a significant role of the cardiac β1adrenergic receptor as a pathophysiologically and clinically relevant autoantigen also in human DCM.
© 2006 Elsevier Ireland Ltd. All rights reserved.
Keywords: β1-adrenergic receptor; Receptor-antibodies; Autoimmunity; Dilated cardiomyopathy; Rat
1. Introduction
Cardiac disease characterized by progressive dilatation
and loss of contractile function in the absence of coronary
artery disease has been termed idiopathic dilated cardiomyopathy (DCM) [1]. In younger adults, DCM still represents
one of the main causes for severe heart failure and
subsequent heart transplantation [2]. Genetic disorders [3]
and a limited number of cardiotoxic substances (i.e., alcohol,
anthracyclines) account for about one third of the cases. The
etiology of the remaining 60–70% is, however, poorly
understood.
⁎ Corresponding author. Medizinische Klinik und Poliklinik I, University
of Wuerzburg, Josef-Schneider-Strasse 2, D-97080 Wuerzburg, Germany.
Tel.: +49 931 201 71190; fax: +49 931 201 70730.
E-mail address: [email protected] (R. Jahns).
0167-5273/$ - see front matter © 2006 Elsevier Ireland Ltd. All rights reserved.
doi:10.1016/j.ijcard.2006.05.008
Because alterations in both humoral and cellular immunity are frequently present in patients with DCM [4–7],
induction of the disease has been claimed to be associated
with abnormal or misled immune responses to noninflammatory (i.e., toxic) or inflammatory cardiac tissue
injury (i.e., caused by cardiotropic viruses, bacteria, or
parasites) [8–10]. As a surrogate of this immunologic
response a substantial number of cardiomyopathic patients
develop cross-reacting antibodies and/or autoantibodies to a
wide panel of cardiac antigens, including membrane proteins
(i.e., G protein-coupled receptors) [4,11,12], mitochondrial
proteins (i.e., adenine nucleotide translocator) [13], and/or
myocyte structural proteins (i.e., actin, tubulin, myosin, and
troponin) [9,14,15]. The clinical relevance of each of these
cardiac (auto-)antibodies is, however, far from clear. Low
titers of autoantibodies to several housekeeping antigens can
also be detected in the healthy population as a part of the
8
R. Jahns et al. / International Journal of Cardiology 112 (2006) 7–14
natural immunologic repertoire [10]. In addition, under
physiologic conditions, at least the intracellularly localized
cardiac antigens are not easily accessible for circulating
antibodies.
From a theoretical point of view, the possible pathophysiologic (and thus clinical) relevance of a specific autoantibody is mainly determined by two factors, (a) the
accessibility, and (b) the functional relevance of the target
[16]. Thus, it seems conceivable that autoantibodies directed
against myocyte surface β1-adrenergic receptors (β1-AR),
which moreover have the potential to affect cardiac function
by interaction with these “key regulators” of myocardial
contractility and relaxation, may play an important role in the
initiation and/or progression of cardiac dilatation and
dysfunction [17,18].
This article will summarize previous and most recent
experimental findings focusing on the cardiac β1-adrenergic
receptor as an autoantigen in the pathogenesis of a newly
defined DCM entity, now referred to as anti-β1-AR-induced
dilated immune-cardiomyopathy (DiCM).
2. Structure and antigenicity of the cardiac
β1-adrenergic receptor
The β1-adrenergic receptor (β1-AR), which constitutes
about 70–80% of the cardiac β-AR complement, belongs to
the superfamily of G protein-coupled membrane receptors
(GPCR) [19]. GPCR's transduce extracellular signals to an
intracellular effector mechanism by means of interaction
with a GTP-regulated heterotrimeric protein (G protein) [20].
The β1-AR consists of seven transmembrane (TM) αhelices, which are linked together by three extracellular (β1ECI–III) and three intracellular loops (β1-ICI–III) and form a
kind of hydrophobic “pocket” [21]. The aminoterminal head
of the receptor molecule is located in the extracellular, the
carboxyterminal tail in the intracellular space (Fig. 1).
Activation of the β1-AR by its physiologic agonists adrenaline or noradrenaline triggers a signaling cascade leading to
sequential activation of the stimulatory G protein Gs,
adenylate cyclase (which katalyzes formation of cAMP),
and the cAMP-dependent protein kinase (PKA) [16,22].
Activated PKA phosphorylates molecules involved in the
regulation of sarcoplasmic Ca2+ concentration, thereby
increasing myocyte inotropy and lusitropy [17,18,23].
In the case of the β2-adrenergic receptor (β2-AR), amino
acids in TM-helices III, V, and VI have been assigned an
anchoring function for agonists, suggesting that the extracellular loops do not directly participate in ligand binding
[24,25]. On the other hand, the primary amino-acid
composition of the second extracellular loop (ECII) allows
for the formation of a β-hairpin in almost all GPCRs which
dips down partly into the ligand binding site. Consequently,
the instantaneous conformation of this loop may influence
receptor–ligand interactions to some extent [21]. The ECIIhairpin contains conformation-stabilizing cysteines which
form an intra-loop disulfide bridge (assumed to be localized
at the top of the hairpin), and a second disulfide bridge with a
conserved cysteine at the top of TM III, linking ECI with
ECII [21] (see also Fig. 1). For the β2-AR it has been
demonstrated that reduction or mutation of one or several of
Fig. 1. Scheme depicting the predicted secondary structure of the β1-adrenergic receptor. The receptor consists of seven transmembrane α-helices (I–VII)
forming a hydrophobic pocket which spans the membrane lipid bilayer (dark grey). The transmembrane domains are linked together by three extracellular
(ECI–III) and three intracellular loops. The N-terminus is located in the extracellular, the C-terminus in the intracellular space. In addition, the presumed disulfidebonds (S–S) between conserved and non-conserved cysteines of the first and second extracellular receptor loop are depicted (according to Noda et al. [27]).
R. Jahns et al. / International Journal of Cardiology 112 (2006) 7–14
these cysteines – most notably those in β2-ECII(Cys184,
Cys190/191), or Cys106 situated at the top of TM III – results
in a significant reduction of agonist as well as antagonist
affinities [26–28]. Subsequent in vitro experiments have
confirmed that the extracellular disulfide bridges between
conserved and non-conserved cysteines do in fact stabilize
the “high affinity” state of the β2-AR [27], and that a
reduction of the conformation-stabilizing intra- and interloop disulfide bridges also inactivates the β1-AR subtype
[29]. Taken together, these data indicate that correct folding
of one or both extracellular loops (ECI/II) is essential for the
formation of the ligand binding pocket in both β1- and β2AR subtypes. This might explain why antibodies or
autoantibodies directed against these loops can (a) interfere
with ligand binding, (b) alter receptor conformation, and
thereby also (c) affect receptor activity [16,30].
The sequence of pathophysiological events, however,
which leads to the generation of functionally active anti-β1AR in the human has not yet been clarified. Homologies
between myocyte surface molecules such as membrane
receptors and microbial determinants represent one possible
mechanism for the elaboration of endogenous receptor
autoantibodies by antigen mimicry [31]. Alternatively,
potentially antigenic components of the cell surface or
from the cytosol of the myocytes themselves, which are
protected against the immune system under physiological
conditions, may be accessible following myocyte damage. It
may be hypothesized that such damage most likely occurs
during ischemic or inflammatory myocyte injury leading to
apoptosis and necrosis of myocardial cells. Subsequent
liberation and presentation of myocardial autoantigens to the
immune system may then engender an autoimmune response
[7,9,10,16]. To serve as an autoantigen, (endogenous)
myocyte membrane receptors must be degraded by proteolysis to small fragments (oligopeptides), and one or several
of the generated fragments must be able to form a complex
with one of the major histocompatibility complexes (MHCs)
or human leucocyte antigen (HLA) class II molecules [31].
Via their membrane MHC class II molecules endosomes may
then present receptor-derived antigenic peptide stretches (at
least 10–12 amino-acids long) to T-cells [32]. In the worst
case, the subsequent receptor-directed immune response
results in perpetuation of myocyte injury involving either
cellular (i.e., T-cell) or humoral (i.e., B-cell) immune
reactions, or leads to co-activation of both, the innate and
the adaptive immune system [14,33].
To further elucidate the antigenicity of the human β1-AR,
the receptor protein has previously been analyzed for
potential immunogenic amino-acid stretches based on the
structural analysis of a human HLA class II molecule [34].
This analysis was performed using a homology scanning
algorithm which compares short receptor-fragments with
peptides known to be immunogenic under a mouse (!) MHC
haplotype [31,35]. Not surprisingly, the analysis confirmed
previous experimental data [36,37] inferring that the only
β1-AR fragment which contains B- and T-cell epitopes, and
9
is easily accessible to antibodies, is in fact the predicted
second extracellular receptor loop (β1-ECII) [31]. In
addition, the analysis revealed some possibly immunogenic
amino-acid sequences within the first and third extracellular
β1-AR loops. In the following, only one peptide corresponding to the first extracellular receptor loop (β1-ECI) was used
successfully to immunize rabbits [32]. Significant anti-β1ECI antibody titers, however, were obtained only after
coupling of the ECI-peptide to bovine serum albumin,
suggesting the absence of a T-cell epitope in the β1-ECI
sequence. This is in clear contrast to β1-ECII peptides, which
in the last decade have been widely used to generate large
amounts of specific anti-β1-ECII antibodies in a variety of
animals/animal-models — with or without utilizing carrier
proteins, suggesting the presence of a T-cell epitope in the
β1-ECII sequence (i.e., rabbit, mouse, rat) [30,38–43].
3. Stimulatory anti-β1-AR (auto-)antibodies are
conformational
As already mentioned, the harmful potential of a specific
(auto-)antibody depends on the accessibility and the
functional relevance of its target. Therefore, (auto-)antibodies directed against cell surface adrenoceptors which
have the potential to influence cardiomyocyte function by
modulating receptor activity, represent proper candidates for
a pathophysiologically significant role in the development
and course of cardiac dysfunction and failure [17,18,44]. In
particular, autoantibodies targeting epitopes within the
functionally relevant first and – probably even more
important – second extracellular loops of the β1-adrenergic
receptor (β1-ECI/II) are thought to play a pathogenic role in
human DCM [12,30,44].
In previous work, we and others have independently
demonstrated that (auto-)antibodies directed against β1-ECII
preferentially recognize a native β1-AR conformation in
different immunologic assays (i.e., enzyme-linked immunoassay and/or immunofluorescence using intact whole
cells, immunoprecipitation experiments). Further, the same
antibodies also affected receptor function, such as intracellular cAMP-production and/or cAMP-dependent protein
kinase (PKA) activity [30,45]. In contrast, antibodies
directed against the β1-aminoterminus or the intracellularly
localized β1-carboxyterminus were not sensitive to denaturation of the receptor and did not affect receptor function
[30,32,38]. In addition, we have shown that the functional
effects of distinct anti-β1-ECII antibodies may differ
considerably, although all of them were generated against
the same small stretch of amino acids (i.e., those forming the
β1-ECII loop) [30]. This suggests that anti-β1-ECII are
“conformational” and act indeed as allosteric regulators of
receptor activity; they may promote, reduce or stabilize
conformational changes of the receptor similar to those
induced by agonist or partial agonist ligands [16,22,
24,30,46]. Because most anti-β1-ECII generated and/or
described so far are polyclonal, one possible explanation
10
R. Jahns et al. / International Journal of Cardiology 112 (2006) 7–14
for the observed functional diversity is that some receptorantibodies may recognize the active, and others the inactive
receptor conformation. In addition, the subtype and the
source of the immunoglobulin (i.e., the species in which it
was generated) may also influence its functional properties.
We have previously proposed to describe the different
functional effects of anti-β1-ECII according to a model [47]
which assumes two receptor states, inactive (R) and active
(R⁎) [30]. Agonists (A) can bind to both states, but induce
and/or stabilize the active state, forming preferentially AR⁎.
Antibodies (=immunoglobulins, I) can bind to the active
(IR⁎) or inactive (IR) states, and can also do so in the
presence of agonist. In our experiments, inhibitory anti-β1ECII (generated in rabbits or mice) [30] reduced the amount
of active β1-receptors expressed in CHW cells probably by
stabilizing an inactive state IR. In the presence of agonist,
they had a similar inhibitory effect, either because they
reduced agonist binding (forming again IR), or because they
returned the receptors to an inactive state even with agonist
bound (AIR). These anti-β1-ECII behaved as inverse
agonistic allosteric regulators because they inhibited basal
as well as stimulated receptor activities. In contrast,
functionally active human or rat anti-β1-ECII increased
basal receptor activity, presumably by forming an active state
(IR⁎) [30,41]. Again, they might have done so by
preferentially binding to an active state R⁎ (as suggested
for antibodies against the β2-AR [46]), or by inducing an
active receptor conformation (IR⁎). In the presence of
agonist, all our rat anti-β1-ECII and the large majority of antiβ1-ECII from human patients caused a further increase in
receptor activity. However, some human anti-β1-ECII were
also able to decrease agonist-induced β1-AR activity in vitro,
comparable to the effect of a partial agonist [30]. According
to our proposed model, purely activating anti-β1-ECII may
either induce a state AIR⁎, which is more active than the
agonist-activated state AR⁎, or alternatively, induce more
receptors to switch into the active state than even high
agonist concentrations do [30].
4. Stimulatory anti-β1-ECII (auto-)antibodies are
pathogenic
According to Witebsky's postulates indirect evidence for
the autoimmune etiology of a disease requires (a) identification of the responsible “self-antigen”, and (b) induction of a
corresponding self-directed immune response in an experimental animal, which subsequently should develop a similar
disease [48,49]. Direct evidence, however, requires reproduction of the disease by transfer of homologous pathogenic
antibodies or pathogenic autoreactive T-cells from one to
another individual of the same species [49].
For almost two decades it has been well established that
β1-ECII represents a potent “self-antigen” [32,36,37]. However, it took about 10 more years of time until Matsui et al. in
1997 presented a first animal-model, in which they could
demonstrate that rabbits after 12 months of immunization
with a β1-ECII-homologous peptide developed biventricular
dilatation (as determined by histology), and an upregulation
of total cardiac β-AR (which was not expected in the
presence of stimulatory anti-β1-ECII antibodies) [39]. Using
a similar rabbit model, 4 years later the experiment was
repeated by Iwata et al. [40]. In contrast to the results obtained
by Matsui et al., total cardiac β-AR (predominantly β1-AR)
were significantly downregulated in anti-β1-ECII-positive
animals. Moreover, after 6 months of immunization the
rabbits were found to develop LV-hypertrophy rather than
LV-dilatation (as determined by echocardiography and
histology) which was, however, no longer present after
12 months of immunization, perhaps indicating the transition
into an early DCM-phenotype [40]. In the following time,
(indirect) evidence for a pathogenic role of anti-β1-ECII has
been supported further by the fact that intraperitoneal
injection of blood lymphocytes either from immunized antiβ1-ECII-positive rabbits [50], or from anti-β1-AR-positive
DCM patients [51] into immunodeficient mice – in order to
avoid the expected immune reaction against rabbit or human
non-self proteins – may lead to an early stage of cardiac
dilatation. Nonetheless, direct evidence for a cause-andeffect relation between anti-β1-AR antibodies and DCM still
remained to be established.
In order to clarify the pathogenic potential of stimulatory
anti-β1-AR, we chose an experimental in vivo-approach
which met the Witebsky criteria for autoimmune diseases.
We attempted to induce dilated cardiomyopathy by immunizing rats against β1-ECII (100% sequence homology
between human and rat; indirect evidence), and then to
reproduce the disease in healthy rats of the same strain by
isogenic transfer of the generated anti-β1-ECII (direct
evidence) [49]. In our study, we immunized inbred rats
against β1-ECII every month over a 15-month period. All
immunized animals developed high titers of stimulatory antiβ1-ECII-antibodies and then, after 9 months of immunization, progressive left ventricular dilatation and dysfunction
(as determined by echocardiography (Fig. 2a), left heart
catheterization, and histology) [41]. Subsequent isogenic
transfer of anti-β1-ECII antibodies from immunized into
healthy rats of the same strain (in order to mimic
autoantibodies) within 6–9 months also transferred the
disease, hence providing the first direct evidence for a causeand-effect relationship between activating anti-β1-AR antibodies and dilated cardiomyopathy (Fig. 2b). The cardiomyopathic phenotype in our rats was characterized by (a)
progressive LV dilatation and dysfunction, (b) a relative
decrease in LV wall-thickness, and (c) selective downregulation of β1-AR, a feature that is also seen in human
DCM [23,52]. Recently, Larsson et al. [42] were able to
reproduce the first part of our previous study, again by active
immunization of rats with a β1-ECII-peptide. In perfect
agreement with our results they found a significant reduction
in LV fractional shortening in anti-β1-ECII-positive rats (as
determined by echocardiography) and, at the molecular
level, a significant increase in cardiac tissue β1-adrenergic
R. Jahns et al. / International Journal of Cardiology 112 (2006) 7–14
11
Fig. 2. Echocardiography of rat hearts. (a) Immunization experiment, month 15: representative M-Mode tracings of an anti-β1-ECII antibody-positive animal (left
panel), and a corresponding control animal (right panel); LVED/LVES, left ventricular end-diastolic/ end-systolic diameters [numbers in mm]. (b) Time course of
echocardiographically determined LVED and LVES in the immunization (left panel) and serum transfer experiment (right panel). Error bars indicate mean ±
SEM; ⁎P < 0.05, ⁎⁎P < 0.01, ⁎⁎⁎P < 0.001 (ANOVA and Bonferroni post hoc test). (Figures adopted with permission from Jahns et al. [41]).
receptor kinase mRNA (as determined by RT-PCR), which
fits very well with the selective cardiac β1-AR downregulation observed in our studies. These findings in
conjunction with the previously demonstrated agonist-like
short-term effects of our rat anti-β1-ECII in vivo (modest
increases in contractility and in blood pressure upon injection
of stimulatory anti-β1-ECII into naive control rats [41])
suggest that the induced and the transferred cardiomyopathic
phenotypes have to be attributed mainly to the mild but
sustained receptor activation by stimulatory anti-β1-ECII. As
a consequence, this type of anti-β1-AR antibody-induced
DiCM should now be categorized with other established
receptor-directed autoimmune diseases, such as myasthenia
gravis, Grave's disease, and type B insulin-resistant diabetes
mellitus [17,53].
5. Clinical and therapeutic perspectives
Although the above presented animal experiments
strongly suggest a cause-and-effect relationship between
functionally active anti-β1-AR (auto-)antibodies and the
initiation and/or course of dilated cardiomyopathy, the true
clinical relevance of these antibodies in human heart disease
remains to be determined. With respect to stimulatory antiβ1-ECII autoantibodies, however, we have previously shown
that the prevalence of such antibodies in healthy individuals
was rather low (< 1%), using an antibody-screening algorithm based on cell systems which present the human β1-AR
in its natural conformation [4]. In patients with a known
cause of heart failure, by using the same screening strategy,
we were able to exclude significant amounts of anti-β1-AR
in smaller patient-cohorts with valvular or hypertensive heart
disease [54]. In contrast, we and others have detected
significant amounts of stimulatory anti-β1-ECII in patients
with ischemic cardiomyopathy (ICM, about 10% prevalence), in Chagas cardiomyopathy (CCM, about 30%
prevalence [8]), and, most notably, in DCM with a
prevalence varying from 26% to 95% of the patients,
depending on screening strategy [4,12,55,56]. Differences in
the screening modalities for functionally active anti-β1-AR
12
R. Jahns et al. / International Journal of Cardiology 112 (2006) 7–14
autoantibodies (which may comprise antibodies targeting
β1-ECII, β1-ECI, or both epitopes [55]), most probably
account for the relatively wide range of antibody-prevalences reported in the literature. One prerequisite for future
clinical trials would thus be a standardized screening
algorithm for functionally active (conformational) human
anti-β1-AR autoantibodies, utilizing cell systems which
present the target receptor in its native conformation [16].
Recent clinical observations indicate that the presence of
stimulatory anti-β1-AR autoantibodies in patients with DCM
might be associated with poorer left ventricular function [4],
the occurrence of more severe ventricular arrhythmia [57],
and a higher incidence of sudden cardiac death [56].
Concordant with these observations, in our recently
accomplished 10-year follow-up study of the DCM collective described in 1999 [4], we found a higher prevalence of
ventricular premature capture beats and Lown class III-IV
arrhythmia in anti-β1-ECII-positive compared with antibodynegative patients. In addition, analysis of the demographic
data revealed that in our collective the presence of
stimulatory anti-β1-ECII was associated with an almost
three-fold increase in all-cause and cardiovascular mortalityrisk after adjustment for other prognostic factors [58]. These
clinical data underscore the prognostic relevance of
stimulatory anti-β1-AR in DCM, and encourage further
research in the evolving field of antibody-directed strategies
as a therapeutic principle [17,53,59].
One (today generally accepted) pharmacologic strategy
would be the use of beta-blocking agents in order to attenuate
or even abolish the autoantibody-mediated stimulatory
effects, at least if β-blockers can indeed prevent the
antibody-induced activation of β1-AR [17,30,60]. New
therapeutic approaches include elimination of stimulatory
anti-β1-AR by non-selective or selective immunoadsorption
[53,61], or direct targeting of the anti-β1-ECII antibodies and/
or the anti-β1-ECII producing B-cells themselves (that is,
induction of immune tolerance) [62]. In our rat model,
prophylactic application of a newly developed β1-ECIIhomologous cyclopeptide (β1-ECII-CP) 6 weeks after the
active induction of stimulatory anti-β1-ECII antibodies
significantly reduced the amount of circulating anti-β1-ECII,
and effectively prevented development of cardiac dilatation
and dysfunction [63]. The beneficial effects of the new
cyclopeptide were similar to those achieved by prophylactic
application of the cardioselective β-blocker bisoprolol.
However, compared with bisoprolol, β1-ECII-CP did reduce
neither heart rate nor blood pressure, which might be
advantageous in a clinical condition. Moreover, β1-ECII-CP
not only induced a rapid decrease in anti-β1-ECII-titers, but –
within a few months – also induced a complete cessation of
anti-β1-ECII antibody-production despite continued boosts of
the animals with the β1-ECII-immunogen (i.e., induced a kind
of immunological anergy) [63]. Future research will show,
whether this promising new experimental approach proves to
be efficient also in the treatment of advanced anti-β1-ECIIinduced cardiomyopathy and heart failure.
Acknowledgements
Grant support: The presented work was supported by the
Deutsche Forschungsgemeinschaft (Grants Ja 706/2-3 and Ja
706/2-4).
References
[1] Richardson P, McKenna W, Bristow M, et al. Report of the WHO/ISFC
task force on the definition and classification of cardiomyopathies.
Circulation 1996;93:841–2.
[2] American Heart Association, Dallas; Heart Disease and Stroke
Statistics - 2005 Update.
[3] Morita H, Seidman J, Seidman CE. Genetic causes of human heart
failure. J Clin Invest 2005;115:518–26.
[4] Jahns R, Boivin V, Siegmund C, Inselmann G, Lohse MJ, Boege F.
Autoantibodies activating human β1-adrenergic receptors are associated with reduced cardiac function in chronic heart failure.
Circulation 1999;99:649–54.
[5] Liao L, Sindhwani R, Rojkind M, Factor S, Leinwand L, Diamond
B. Antibody-mediated autoimmune myocarditis depends on genetically determined target organ sensitivity. J Exp Med 1995;
181:1123–31.
[6] Luppi P, Rudert WA, Zanone MM, et al. Idiopathic dilated
cardiomyopathy. A superantigen-driven autoimmune disease. Circulation 1998;98:777–85.
[7] Noutsias M, Seeberg B, Schultheiss HP, Kühl U. Expression of cell
adhesion molecules in dilated cardiomyopathy: evidence for endothelial activation in inflammatory cardiomyopathy. Circulation 1999;99:
2124–31.
[8] Elies R, Ferrari I, Wallukat G, et al. Structural and functional analysis
of the B cell epitopes recognized by anti-receptor autoantibodies in
patients with Chagas' disease. J Immunol 1996;157:4203–11.
[9] Caforio AL, Mahon NJ, Tona F, McKenna WJ. Circulating cardiac
autoantibodies in dilated cardiomyopathy and myocarditis: pathogenetic and clinical significance. Eur J Heart Fail 2002;4:411–7.
[10] Rose NR. Infection, mimics, and autoimmune disease. J Clin Invest
2001;107:943–4.
[11] Fu MLX, Magnusson Y, Bergh CH, Waagstein F, Hjalmarson Å,
Hoebeke J. Localization of a functional autoimmune epitope on the
second extracellular loop of the human muscarinic receptor in patients
with idiopathic DCM. J Clin Invest 1993;91:1964–8.
[12] Magnusson Y, Wallukat G, Waagstein F, Hjalmarson Å, Hoebeke J.
Autoimmunity in idiopathic DCM. Characterization of antibodies
against the β1-adrenoceptor with positive chronotropic effect.
Circulation 1994;89:2760–7.
[13] Schulze K, Becker BF, Schauer R, Schultheiss HP. Antibodies to ADPATP carrier – an autoantigen in myocarditis and dilated cardiomyopathy-impair cardiac function. Circulation 1990;81:959–69.
[14] Eriksson U, Ricci R, Hunziker L, et al. Dendritic cell-induced
autoimmune heart failure requires cooperation between adaptive and
innate immunity. Nat Med 2003;9(12):1484–90.
[15] Okazaki T, Tanaka Y, Nishio R, et al. Autoantibodies against cardiac
troponin I are responsible for dilated cardiomyopathy in PD-1-deficient
mice. Nat Med 2003;9(12):1477–83.
[16] Jahns R, Boivin V, Lohse MJ. Beta1-adrenergic receptor function,
autoimmunity, and pathogenesis of dilated cardiomyopathy. Trends
Cardiovasc Med 2006;16:20–4.
[17] Freedman NJ, Lefkowitz RJ. Anti-β1-adrenergic receptor antibodies
and heart failure: causation, not just correlation. J Clin Invest
2004;113:1379–82.
[18] Engelhardt S, Hein L, Dyachenkow V, Kranias EG, Isenberg G, Lohse
MJ. Altered calcium handling is critically involved in the cardiotoxic
effects of chronic β-adrenergic stimulation. Circulation 2004;109:
1154–60.
R. Jahns et al. / International Journal of Cardiology 112 (2006) 7–14
[19] Frielle T, Collins S, Daniel KW, Caron MG, Lefkowitz RJ, Kobilka
BK. Cloning of the cDNA for the human β1-adrenergic receptor. Proc
Natl Acad Sci U S A 1987;84:7920–4.
[20] Hein L, Kobilka BK. Adrenergic receptor signal transduction and
regulation. Neuropharmacology 1995;34(4):357–66.
[21] Bywater RP. Location and nature of the residues important for ligand
recognition in G-protein coupled receptors. J Mol Recognit
2005;18:60–72.
[22] Hoffmann C, Leitz MR, Oberdorf-Maass S, Lohse MJ, Klotz KN.
Comparative pharmacology of human β-adrenergic receptor subtypes:
characterization of stably transfected receptors in CHO cells. NaunynSchmiedeberg's Arch Pharmacol 2004;362:151–9.
[23] Lohse MJ, Engelhardt S, Eschenhagen T. What is the role of βadrenergic signaling in heart failure? Circ Res 2003;93:896–906.
[24] Wieland K, Zuurmond HM, Andexinger S, Ijzerman AP, Lohse MJ.
Stereospecificity of agonist binding to β2-adrenergic receptors
involves Asn-293. Proc Natl Acad Sci U S A 1996;93:9276–81.
[25] Gether U, Lin S, Ghanouni P, Ballesteros JA, Weinstein H, Kobilka
BK. Agonists induce conformational changes in transmembrane
domains III and VI of the β2-adrenoceptor. EMBO J 1997;16:
6737–47.
[26] Dohlman HG, Caron MG, De Blasi A, Frielle T, Lefkowitz RJ. Role of
extracellular disulfide-bonded cysteines in the ligand binding function
of the β2-adrenergic receptor. Biochemistry 1990;29:2335–42.
[27] Noda K, Saad Y, Graham RM, Karnik SS. The high affinity state of the
β2-adrenergic receptor requires unique interaction between conserved
and non-conserved extracellular loop cysteines. J Biol Chem
1994;269:6743–52.
[28] Lin S, Gether U, Kobilka BK. Ligand stabilization of the β2-adrenergic
receptor: effect of DTT on receptor conformation monitored by circular
dichroism and fluorescence spectroscopy. Biochemistry 1996;
35:14445–51.
[29] Vauquelin G, Bottari S, Kanarek L, Strosberg A. Evidence for essential
disulfide bonds in β1-adrenergic receptors of turkey erythrocyte
membranes. J Biol Chem 1978;254:4462–9.
[30] Jahns R, Boivin V, Krapf T, Wallukat G, Boege F, Lohse MJ.
Modulation of β1-adrenoceptor activity by domain-specific antibodies
and heart failure-associated autoantibodies. J Am Coll Cardiol
2000;36:1280–7.
[31] Hoebeke J. Structural basis of autoimmunity against G protein-coupled
membrane receptors. Int J Cardiol 1996;54:103–11.
[32] Mobini R, Magnusson Y, Wallukat G, Viguier M, Hjalmarson Å,
Hoebeke J. Probing the immunological properties of the extracellular
domains of the human β1-adrenoceptor. J Autoimmun 1999;13
(2):179–86.
[33] Rose NR. Viral damage or molecular mimicry-placing the blame in
myocarditis. Nat Med 2000;6:631–2.
[34] Brown JH, Jardetzky TS, Gorga JC, et al. Three-dimensional structure
of the human class II histocompatibility antigen HLA-DR1. Nature
(Lond) 1993;364:33–9.
[35] Guillet JG, Hoebeke J, Lengagne R, Borras-Herrera F, Strosberg AD,
Borras-Cuesta F. Haplotype specific homology scanning algorithm to
predict T cell epitopes from protein sequences. J Mol Recognit
1991;4:17–25.
[36] Magnusson Y, Hoyer S, Lengagne R, et al. Antigenic analysis of the
second extracellular loop of the human β-adrenergic receptors. Clin
Exp Immunol 1989;78:42–8.
[37] Tate K, Magnusson Y, Viguier M, et al. Epitope-analysis of T- and Bcell response against the human beta 1-adrenoceptor. Biochimie
1994;76:159–64.
[38] Jahns R, Siegmund C, Jahns V, et al. Probing human β1- and β2adrenoceptors with domain-specific fusion protein antibodies. Eur J
Pharmacol 1996;316:111–21.
[39] Matsui S, Fu M, Katsuda S, et al. Peptides derived from
cardiovascular G-protein-coupled receptors induce morphological
cardiomyopathic changes in immunized rabbits. J Mol Cell Cardiol
1997;29:641–55.
13
[40] Iwata M, Yoshikawa T, Baba A, et al. Autoimmunity against the
second extracellular loop of β1-adrenergic receptors induces βadrenergic receptor desensitization and myocardial hypertrophy in
vivo. Circ Res 2001;88:578–86.
[41] Jahns R, Boivin V, Hein L, et al. Direct evidence for a β1-adrenergic
receptor directed autoimmune attack as a cause of idiopathic dilated
cardiomyopathy. J Clin Invest 2004;113:1419–29.
[42] Larsson L, Bollano E, Haugen E, Fu M. Phenotype of early
cardiomyopathic changes induced by active immunization of rats
with a synthetic peptide corresponding to the second extracellular loop
of the human β1-AR. Circulation 2004;110(Suppl III):598 (2779).
[43] Fukuda Y, Miyoshi S, Tanimoto K, et al. Autoimmunity against the
second extracellular loop of β1-adrenergic receptors induces early
afterdepolarization and decreases in K-channel density in rabbits. J Am
Coll Cardiol 2004;43:1090–100.
[44] Magnusson Y, Hjalmarson Å, Hoebeke J. β1-adrenoceptor autoimmunity in cardiomyopathy. Int J Cardiol 1996;54:137–41.
[45] Wallukat G, Kaiser A, Wollenberger A. The β1-adrenoceptor as
antigen: functional aspects. Eur Heart J 1995;16(Suppl 0):85–8.
[46] Mijares A, Lebesgue D, Argibay J, Hoebeke J. Anti-peptide antibodies
sensitive to the “active” state of the β2-adrenergic receptor. FEBS Lett
1996;399:188–91.
[47] Milligan G, Bond A. Inverse agonism and the regulation of receptor
number. TIPS 1997 (Dec.);18:468–74.
[48] Witebsky E, Rose NR, Terplan K, Paine JR, Egan RW. Chronic
thyreoiditis and autoimmunization. J Am Med Assoc 1957;164:
1439–47.
[49] Rose NR, Bona C. Defining criteria for autoimmune diseases
(Witebsky's postulates revisited). Immunol Today 1993;14:426–30.
[50] Matsui S, Fu M, Katsuda S, et al. Transfer of rabbit autoimmune
cardiomyopathy into severe combined immunodeficiency mice.
J Cardiovasc Pharmacol 2003;42(Suppl 1):S99–103.
[51] Omerovic E, Bollano E, Andersson B, et al. Induction of cardiomyopathy in severe combined immunodeficiency mice by transfer of
lymphocytes from patients with idiopathic dilated cardiomyopathy.
Autoimmunity 2000;32:271–80.
[52] D'Ambrosio A, Patti G, Manzoli A, et al. The fate of acute myocarditis
between spontaneous improvement and evolution to dilated cardiomyopathy. Heart 2001;85:499–504.
[53] Hershko AY, Naparstek Y. Removal of pathogenic autoantibodies by
immunoadsorption. Ann N Y Acad Sci 2005;1051:635–46.
[54] Jahns R, Boivin V, Siegmund C, Boege F, Lohse MJ, Inselmann G.
Activating β1-adrenoceptor antibodies are not associated with
cardiomyopathies secondary to valvular or hypertensive heart disease.
J Am Coll Cardiol 1999;34:1545–51.
[55] Wallukat G, Wollenberger A, Morwinski R, Pitschner HF. Anti-β1adrenoceptor autoantibodies with chronotropic activity from the serum
of patients with dilated cardiomyopathy: mapping of epitopes in the
first and second extracellular loops. J Mol Cell Cardiol 1995;27:
397–406.
[56] Iwata M, Yoshikawa T, Baba A, Anzai T, Mitamura H, Ogawa S.
Autoantibodies against the second extracellular loop of β1-adrenergic
receptors predict ventricular tachycardia and sudden death in patients
with idiopathic dilated cardiomyopathy. J Am Coll Cardiol 2001;37:
418–24.
[57] Chiale PA, Ferrari I, Mahler E, et al. Differential profile and
biochemical effects of antiautonomic membrane receptor antibodies
in ventricular arrhythmias and sinus node dysfunction. Circulation
2001;103:1765–71.
[58] Störk S, Boivin V, Horf R, et al. Activating autoantibodies against the
human β1-adrenoceptor predict increased mortality in dilated cardiomyopathy. Circulation 2004;110(Abst Suppl III):555 (2583).
[59] Ogawa S, Yoshikawa T. Autoantibodies: emerging upstream targets of
arrhythmias and sudden cardiac death in patients with dilated
cardiomyopathy. J Mol Cell Cardiol 2001;33:1761–3.
[60] Matsui S, Fu ML. Prevention of experimental autoimmune cardiomyopathy in rabbits by receptor blockers. Autoimmunity 2001;43:217–20.
14
R. Jahns et al. / International Journal of Cardiology 112 (2006) 7–14
[61] Wallukat G, Müller J, Hetzer R. Specific removal of β1-adrenergic
antibodies directed against cardiac proteins from patients with
idiopathic DCM. N Engl J Med 2002;347:1806.
[62] Anderton SM. Peptide-based immunotherapy of autoimmunity: a path
of puzzles, paradoxes, and possibilities. Immunology 2001;104:
367–76.
[63] Jahns R, Boivin V, Hein L, et al. A new cyclic receptor-peptide
prevents development of heart dilatation and failure induced by
antibodies activating cardiac β1-adrenergic receptors. Circulation
2005;102(Abst Suppl II):5 (120).