The gp130
⁄
STAT3 signaling pathway mediates
b-adrenergic receptor-induced atrial natriuretic
factor expression in cardiomyocytes
Hui Zhang, Wei Feng, Wenqiang Liao, Xiaowei Ma, Qide Han and Youyi Zhang
Institute of Vascular Medicine, Peking University Third Hospital and Key Laboratory of Molecular Cardiovascular Sciences, Ministry of
Education, Beijing, China
b-Adrenergic receptor (b-AR), an archetypal member
of the G-protein-coupled receptor (GPCR) super-
family, has roles in a variety of cardiovascular patho-
logical and physiological processes. There are three
known subtypes in the heart – b
1
-AR, b
2
-AR and
b
3
-AR. Of these, the b
1
-AR subtype stimulates the
classic Gs–adenylyl cyclase–cAMP–protein kinase A
signaling pathway, whereas b
2
-AR activates bifurcated
signaling pathways through both Gs and Gi proteins
[1,2]. It is well established that stimulation of myo-
cardial b-AR results in cardiac remodeling, which is
characterized by increased cell size and initiation of
the ‘fetal gene’ program, such as atrial natriuretic

E-mail:
(Received 31 March 2008, revised 8 May
2008, accepted 13 May 2008)
doi:10.1111/j.1742-4658.2008.06504.x
b-Adrenergic receptor (b-AR)-induced cardiac remodeling is closely linked
with the re-expression of the atrial natriuretic factor (ANF) gene. How-
ever, the exact molecular mechanism of this response remains elusive.
Here, we demonstrate that the b-AR agonist isoproterenol potently evokes
the tyrosine phosphorylation of STAT3 and increases its transcriptional
activity in an extracellularly regulated kinase 1 ⁄ 2 and glycoprotein (gp)130
signaling-dependent manner in rat cardiomyocytes. Interestingly, both
specific silencing of signal transducers and activators of transcription 3
(STAT3) expression by lentivirus-mediated RNA interference and anta-
gonism of gp130 signaling lead to significant inhibition of isoproterenol-
stimulated ANF expression. Together, these results indicate that
gp130 ⁄ STAT3 signaling has an essential role in ANF expression by b-AR
stimulation.
Abbreviations
ANF, atrial natriuretic factor; b-AR, b-adrenergic receptor; ERK, extracellularly regulated kinase; GFP, green fluorescent protein; gp,
glycoprotein; GPCR, G-protein-coupled receptor; IL-6, interleukin-6; ISO, isoproterenol; JAK, Janus kinase; JNK, Jun N-terminal kinase; LIF,
leukemia inhibitory factor; MAPK, mitogen-activated protein kinase; MOI, multiplicity of infection; NRCM, neonatal rat cardiomyocyte; NS,
nonsilencing; qRT-PCR, quantitative real-time RT-PCR; shRNA, short hairpin RNA; siRNA, small interfering RNA; STAT3, signal transducers
and activators of transcription 3.
3590 FEBS Journal 275 (2008) 3590–3597 ª 2008 The Authors Journal compilation ª 2008 FEBS
ANF expression in cardiomyocytes [10]. By contrast,
although STAT3 could associate with the endogenous
ANF gene in type I angiotensin II receptor-activated
cardiomyocytes, no modulation of ANF promoter
activity by STAT3 with angiotensin II stimulation was
observed [11]. These reports revealed that regulation of

was proven to have no statistical significance (data not
shown). These results support the notion that STAT3
activation has high specificity under different stimula-
tion conditions.
To investigate whether ISO-induced STAT3 phos-
phorylation is a specific action of b-AR, antagonists of
b-AR were employed. As shown in Fig. 1B, the b-AR
A
B
CD
Fig. 1. Activation of b-AR induced STAT3 tyrosine phosphorylation and increased its transcriptional activity in NRCMs. (A) NRCMs were
serum-starved for 24 h, and then treated with 10 l
M ISO. The cell lysates were harvested at the indicated time and analyzed by western
blot assays using anti-phospho-tyr705-STAT3. The same membranes were stripped and reprobed with total STAT3 antibody (n = 3). (B, C)
Cardiomyocytes were serum-starved, treated with 10 l
M ISO for 60 min after pretreatment with 10 lM propranolol, 5 lM CGP 20712A or
5 l
M ICI 118551, and then harvested for western blot analysis (n = 3). **P < 0.01 versus control,
#
P < 0.05 versus ISO,
##
P < 0.01 versus
ISO. (D) Cardiomyocytes were cotransfected with STAT3-driven promoter and renilla luciferase plasmid for 24 h, starved, and then stimu-
lated with 10 l
M ISO for 8 h with or without pretreatment with 10 lM propranolol. The data were converted to relative luciferase activity.
*P < 0.05 versus control,
#
P < 0.05 versus ISO (n = 3). Prop, propranolol; CGP, CGP 20712A; ICI, ICI 118551.
H. Zhang et al. gp130 ⁄ STAT3 mediates ANF expression by b-AR
FEBS Journal 275 (2008) 3590–3597 ª 2008 The Authors Journal compilation ª 2008 FEBS 3591

synergistic effect in ISO-induced STAT3 activation.
The STAT3 transcriptional activity was also exam-
ined by transfection of the STAT3-driven promoter
luciferase plasmid. Consistent with the result of STAT3
tyrosine phosphorylation, ISO significantly increased
the transcriptional activity of STAT3, and this increase
was completely inhibited by propranolol, further con-
firming a b-AR-dependent mechanism (Fig. 1D).
We previously demonstrated that intraperitoneal
injection of ISO caused delayed phosphorylation of
STAT3 in mouse heart [14]. In the present study, we
found that b-AR stimulation in rat cardiomyocytes
per se is able to not only cause phosphorylation of
STAT3 on tyrosine but also promote its transcriptional
activity. Despite different internal mechanisms due to
species differences, the two findings indicate an exten-
sive and striking interaction between b-AR and
STAT3. Furthermore, our finding strengthens the
implication, which has not been investigated before,
that STAT3 has an important role in the induction of
the specific cardiac phenotype of b-AR.
Extracellularly regulated kinase (ERK)1 ⁄ 2 but not
p38 or Jun N-terminal kinase (JNK) played an
important role in b-AR-induced STAT3 activation
We further investigated the signaling pathway of b-AR-
induced STAT3 activation. It is well known that b-AR
stimulation can activate the mitogen-activated protein
kinase (MAPK) signaling pathway [15,16]. On the other
hand, the MAPK pathway has been shown to have an
important role in the regulation of STAT3 signaling

ven promoter together with renilla luciferase plasmid, starved, and
then stimulated with 10 l
M ISO after pretreatment with 10 lM
SB203580, 10 lM SP600125 or 10 lM U0126. *P < 0.05 versus
control;
#
P < 0.05 versus ISO; NS, no statistical significance versus
ISO (n = 3). SB, SB203580; SP, SP600125.
gp130 ⁄ STAT3 mediates ANF expression by b-AR H. Zhang et al.
3592 FEBS Journal 275 (2008) 3590–3597 ª 2008 The Authors Journal compilation ª 2008 FEBS
STAT3 activation is a complicated process. We specu-
lated that some new secreted cytokines, particularly the
gp130 family cytokines, might contribute to the delayed
STAT3 activation. Blockade of the gp130 receptor
using neutralizing antibody to gp130 markedly
inhibited STAT3 tyrosine phosphorylation and its tran-
scriptional activity with ISO stimulation (Fig. 3A,B),
confirming that the STAT3 activation is gp130-depen-
dent. Consistent with this, inhibition of new RNA
transcription by actinomycin D significantly suppressed
ISO-induced STAT3 tyrosine phosphorylation
(Fig. 3C), supporting the requirement for a de novo
transcriptional process. In addition, because gp130, as
the coreceptor of gp130 family cytokines, promotes the
recruitment and activation of JAK (Janus kinase) tyro-
sine kinases, thereby activating STAT3 [7], the poten-
tial role of JAK was also determined. As shown in
Fig. 3D, a specific JAK2 inhibitor, AG490, dramati-
cally attenuated b-AR-induced STAT3 activation.
Taken together, these results indicate that autocrine

STAT3 signaling pathway mediated
b-AR-induced ANF expression
b-AR-induced cardiac remodeling is closely linked to
ANF expression. To determine the role of activated
STAT3 in ANF expression resulting from b-AR stimu-
lation, we constructed a lentiviral vector derived from
HIV-1 to express short hairpin RNA (shRNA) dire-
cted against rat STAT3 (rST3 lentivirus). Fluorescent
microscopy analysis showed that the transfection effi-
ciency was more than 90% in cardiomyocytes, with a
multiplicity of infection (MOI) of 150. [The lentiviral
infection efficiency was visualized by the expression of
green fluorescent protein (GFP), the gene for which is
a marker gene contained within the lentiviral vector.)
A
∗
#
B
C
∗∗
##
D
Fig. 3. gp130 family cytokines were
involved in b-AR-induced STAT3 activation.
(A, C) Cardiomyocytes were stimulated with
10 l
M ISO for 60 min after pretreatment
with 4 lgÆmL
)1
gp130 neutralizing antibody

lencing (NS) lentivirus, rST3 lentivirus markedly
suppressed the b-AR-promoted ANF promoter tran-
scriptional activity (Fig. 4B). In addition, we also
examined the levels of endogenous ANF mRNA using
qRT-PCR. The result showed similar trends to that of
the ANF promoter luciferase reporter assay (supple-
mentary Fig. S3). On the other hand, we also assessed
the ANF protein expression by ELISA. Consistent
with the result of ANF transcription, knock-down of
STAT3 significantly inhibited ISO-induced ANF pro-
tein production in the NRCM culture medium
(Fig. 4C).
The involvement of STAT3 in b-AR-induced ANF
expression was further supported by investigation of
the instant upstream signaling of STAT3, in that both
inhibition of gp130 and inhibition of JAK2 markedly
suppressed b-AR-promoted ANF promoter transcrip-
tional activity (Fig. 5A,B). It is thus easy to infer that
gp130 ⁄ STAT3 signaling acts virtually as an integral
pathway in b-AR-induced ANF expression.
Both STAT3 and ANF are important in cardiac
remodeling and cardioprotection [4,5,24,25]. However,
there are only a few reports describing their relation-
ships, and few of these are in the context of GPCRs.
In the present study, we unequivocally demonstrated
that STAT3 activation is required for ANF expression
with b-AR stimulation. Given that STAT3 can associ-
ate with the endogenous ANF gene in vitro [11], its
effects on b-AR-induced ANF expression may result
from direct transcriptional regulation. STAT3 may

As ANF transcription is often activated in many
types of cardiac hypertrophy and remodeling, the
results of this investigation can be compared with
those studies investigating the regulation of ANF
expression by GPCRs and cytokines. On the other
hand, although ANF is a marker of hypertrophy, sepa-
ration of re-emergence of ANF from cardiac growth
has been recently demonstrated by some researchers
[11,26]. Thus, understanding how ANF is regulated
may lead to therapeutic strategies that prevent hyper-
trophy while allowing for the beneficial effects of ANF
production. Furthermore, this study will further our
understanding of b-AR signaling and provide potential
therapeutic targets for the treatment of heart disease.
Experimental procedures
Isolation and culture of rat cardiomyocytes
One-day-old Sprague–Dawley rats were obtained from the
Medical Experimental Animal Center of Peking University
Health Science Center. Before their hearts were taken, neo-
natal rats were put into a glass beaker containing a cotton
mass wetted with ethyl ether. After anesthesia and decapi-
tation, hearts were taken out immediately and put into
ice-cold NaCl ⁄ P
i
, and then cut into pieces. The NRCMs
were prepared as previously described [27]. Experiments
were carried out in accordance with the guidelines laid
down by the NIH in the USA.
Western blot analysis
Western blot analyses were performed as previously

CA, USA). The optimal sequence of siRNA against rat
STAT3 (5¢-CTTCAGACCCGCCAACAAA-3¢) was then
cloned into the plasmid pGCL–GFP, which encodes an
HIV-derived lentiviral vector containing a multiple cloning
site for insertion of shRNA constructs to be driven by an
upstream U6 promoter and a downstream cytomegalovirus
promoter–GFP fluorescent protein (marker gene) cassette
flanked by loxP sites. Lentivirus preparations were
A
B
Fig. 5. gp130 ⁄ JAK2 signaling pathway was involved in b-AR-
induced ANF expression. (A, B) Cardiomyocytes were transfected
with ANF promoter (a luciferase reporter plasmid containing the
ANF promoter region) together with renilla luciferase plasmid,
starved, and then stimulated with 10 l
M ISO after pretreatment with
4 lgÆmL
)1
gp130 neutralizing antibody or 10 lM AG490. *P < 0.05,
**P < 0.01 versus control,
#
P < 0.05,
##
P < 0.01 versus ISO.
H. Zhang et al. gp130 ⁄ STAT3 mediates ANF expression by b-AR
FEBS Journal 275 (2008) 3590–3597 ª 2008 The Authors Journal compilation ª 2008 FEBS 3595
produced by the Shanghai GeneChem, Co. Ltd, China. The
resulting lentiviral vector containing rat STAT3 shRNA
was named rST3 lentivirus, and its sequence was confirmed
by PCR and sequencing analysis. A negative control lentivi-

Data are expressed as means ± SE. The statistical signifi-
cance of the differences between the means of the groups
was determined by one-way anova or t-tests. A P-value
< 0.05 was considered to be significant.
Acknowledgements
This work was supported by the National Key
Basic Research Program (NKBRP) of China
(2006CB503806) and the Natural Science Foundation
of China (30470691, 30672466). We thank Dr Guang-
ming Wang (Peking University Health Science Center,
China) for providing the pGL3–TATA, and Prof. John
G. Edwards (New York Medical College, USA) for
providing rat ANF promoter reporter plasmid
[pANF(-638)-Luc].
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Supplementary material
The following supplementary material is available
online:
Fig. S1. Relative IL-6 mRNA copy number as a result
of b-AR stimulation.
Fig. S2. b-AR stimulation of IL-6 production.
Fig. S3. STAT3-specific lentivirus-mediated RNA inter-
ference inhibited b-AR-induced endogenous ANF
mRNA expression.
This material is available as part of the online article
from
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H. Zhang et al. gp130 ⁄ STAT3 mediates ANF expression by b-AR
FEBS Journal 275 (2008) 3590–3597 ª 2008 The Authors Journal compilation ª 2008 FEBS 3597