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Received: 14 August 2016 Accepted: 30 December 2016 DOI: 10.1111/cpr.12332
REVIEW ARTICLE
Lipopolysaccharide induced vascular smooth muscle cells proliferation: A new potential therapeutic target for proliferative vascular diseases Dehua Jiang1
| Yu Yang2 | Dongye Li1,2
1 Institute of Cardiovascular Disease Research, Xuzhou Medical University, Xuzhou, Jiangsu, China 2
Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, China Correspondence Dongye Li, MD, PhD, Institute of Cardiovascular Disease Research, Xuzhou Medical University, Xuzhou, Jiangsu, China. Email:
[email protected]
Abstract Vascular smooth muscle cells (VSMCs) proliferation is involved in vascular atherosclerosis and restenosis. Recent studies have demonstrated that lipopolysaccharide (LPS) promotes VSMCs proliferation, but the signalling pathways which are involved are not completely understood. The purpose of this review was to summarize the existing knowledge of the role and molecular mechanisms involved in controlling VSMCs proliferation stimulated by LPS and mediated by toll-like receptor 4 (TLR4) signalling pathways. Moreover, the potential inhibitors of TLR4 signalling for VSMCs proliferation in proliferative vascular diseases are discussed. KEYWORDS
vascular smooth muscle cells, lipopolysaccharide, proliferation, signaling pathways
1 | INTRODUCTION
clinical atherosclerosis, are the sources of inflammatory responses. Liu
There is clear evidence that vascular smooth muscle cells (VSMCs)
in rat VSMCs, and the results revealed that Ang II and LPS increased
proliferation is a key step in the progression of atherosclerosis, inti-
TLR4 expression of VSMCs in a concentration-dependent manner. In
mal hyperplasia and hypertension.1 VSMCs can be converted from the
addition, Ang II and LPS contribute to atherosclerosis through a pro-
contractile phenotype to the synthetic phenotype under physiolog-
inflammatory effect. Liu concluded that Ang II induced an inflammatory
ical and pathological conditions, such as vascular injury, mechanical
response partly via a TLR4-dependent signalling pathway in VSMCs.6
has examined whether or not Ang II directly induced TLR4 expression
stretch and growth factor stimulation. The VSMCs phenotypic modu-
Inflammation is a major event in the process of atherosclerosis and
lation is beneficial for VSMCs proliferation and a robust factor in the
restenosis after vascular injury.7 LPS, often referred to as endotoxin
development of proliferative vascular diseases.2
from Gram-negative bacteria, is a mitogen of sepsis. It is composed of
In recent years, it has been shown that VSMCs proliferation in vitro
three structural elements: a core oligosaccharide, an O-antigen and a
is stimulated by multiple growth factors, such as angiotensin (Ang) II,
lipid A. Marshall reported that LPS mediation actions could be modu-
platelet-derived growth factor (PDGF)-BB, oxidized low-density lipo-
lated at multiple levels.8 The LPS from different bacteria do the same
protein (oxLDL), lipopolysaccharide (LPS), transforming growth factor-β
role on cells. High levels of LPS have certain toxic effect on cells, while
(TGF)-β and fibroblast growth factor.3 These factors can interact with
low levels of LPS promote cells proliferation. Epidemiological studies
each other in an in vitro environment. For example, oxLDL promotes in-
have indicated that LPS is a risk factor in disorders, such as atheroscle-
flammatory responses in VSMCs in association with increased expres-
rosis9 and diabetes. For example, Bataller has reported that serum levels
4
sion of toll-like receptor (TLR) 4, and oxLDL acts synergistically with
of LPS can predict mortality in patients with alcoholic hepatitis and are
Ang II in inducing VSMCs proliferation.5 Ang II and LPS, predictors of
associated with a poor response to corticosteroids. Jayashree reported
Abbreviations: VSMCs, vascular smooth muscle cells; LPS, lipopolysaccharide; Ang II, angiotensin II; PDGF, platelet-derived growth factor; oxLDL, oxidized low-density lipoprotein; TLR, toll-like receptor; ERK, extracellular signal-regulated kinase; ApoE−/−, apolipoprotein E-deficient; IL-1, interleukin-1; PI3K/Akt, phosphatidylinositol 3-kinase/Akt; MAPKs, mitogen-activated protein kinase; IRAK, interleukin-1 receptor-associated kinase; IFN-γ, interferon-γ; EdU, 5-ethynyl-2-deoxyuridine; Rac1, Ras-related C3 botulinum toxin substrate 1; JNK/SAPKs, c-jun N terminal kinase/ stress-activated protein kinases; miRNAs, microRNAs; NF-κB, nuclear transcription factor kappa κB; CDKs, cyclin-dependent protein kinases; GK, Goto-Kakizaki; PCNA, proliferating cell nuclear antigen; SsnB, sparstolonin B; TNF-α, tumour necrosis factor-alpha α; PPARγ, peroxisome proliferator-activated receptor γ; siRNA, small-interfering RNA.
Cell Proliferation 2017;50:e12332; wileyonlinelibrary.com/journal/cpr https:doi.org/10.1111/cpr.12332
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T A B L E 1 LPS activates TLR4 and promotes VSMCs proliferation in vitro and vascular hyperplasia in vivo Mode
Material
Stimulator
Results and function
Level
Reference
Human
VSMCs
10 ng/mL LPS
Increased TLR4 expression
in vitro
14
Human
VSMCs
25 ng/mL LPS
Increased TLR4 expression
in vitro
27
Human
VSMCs
100 ng/mL LPS
Increased TLR4 expression
in vitro
16
Human
VSMCs
100 ng/mL LPS
Increased TLR4 expression
in vitro
30
Human
VSMCs
100 ng/mL LPS
Increased TLR4 expression
in vitro
43
Human
Macrovessels Tissue
1 μg/mL LPS
Increased TLR4 expression
in vitro
11
Sprague-Dawley rats
VSMCs
10 μg/mL LPS
Increased TLR4 expression Cell proliferation
in vitro
24
Wistar rats
VSMCs
10 μg/mL LPS
Increased TLR4 expression Cell proliferation
in vivo and in vitro
33
Wistar rats
VSMCs
(30 μg/mL LPS/10 ng/ mL) IFN
Increased TLR4 expression
in vitro
22
Wistar and GK rats
Mesenteric VSMCs
100 ng/mL LPS
Cell proliferation
in vitro
50
Mouse
VSMCs
100 ng/mL LPS
Increased TLR4 expression Cell proliferation
in vitro
14
Rabbits
Abdominal aortas
110 ng/kg LPS
Thickened neointima increased TLR4 expression
in vivo
27
Rabbits
Abdominal aortas
500 ng LPS/rabbits
Intimal hyperplasia
in vivo
15
LPS, lipopolysaccharide; VSMCs, vascular smooth muscle cells; TLR4, toll-like receptor 4.
that circulatory levels and activity of LPS were significantly increased
(PI3K/Akt), mitogen-activated protein kinase (MAPK s) and interleu-
in patients with type 2 diabetes. Particular attention has focused on
kin-1 receptor-associated kinase (IRAKs), and all of these pathways
the link between LPS-mediated inflammation and VSMCs prolifera-
involve cell proliferation. The precise molecular mechanisms by which
10–13
tion.
LPS, a widely used exogenous ligand that activates TLR4, can
promote a pro-inflammatory phenotype of VSMCs14 and induce neoin-
these signalling pathways are involved in VSMCs proliferation induced by LPS are in need of further clarification.
timal formation in vitro and in vivo (Table 1). Yang has reported that LPS induces phosphorylation of extracellular signal-regulated kinase (p- ERK) 1/2 expression, as well as interleukin (IL)-1 and IL-6 production in
2.1 | LPS and the PI3K/Akt signalling pathway
human and murine VSMCs.14 Furthermore, LPS-induced p-ERK1/2 ex-
As a major transducer of mitogenic signals in a variety of cells, Akt is
pression was attenuated in TLR4 signalling-deficient mice. Danenberg
activated by arterial injury and contributes to neointimal formation.21
has reported that LPS increases neointimal formation in rabbits after
Akt is a main downstream effector of PI3K-mediated cell survival,
15
It
and the PI3K/Akt signalling pathway is required for VSMCs prolifera-
has been reported that TLR4 expression and nitric oxide production are
balloon and stent injury in association with systemic inflammation.
tion. Inhibition of the PI3K/Akt signalling pathway has been shown to
increased by LPS in human aortic VSMCs.16 Moreover, TLR4 is strongly
limit neointimal formation in rat vascular injury models. Hattori22 re-
expressed in human atherosclerotic vessels, and antagonizing TLR4 is
ported that LPS plus interferon-γ (LPS/IFN) stimulation of VSMCs led
− −
shown to reduce atherosclerosis in apolipoprotein E-deficient (ApoE / )
to PI3K/Akt pathway activation. Hattori examined the phosphoryla-
mice.17 Furthermore, downstream effectors of TLR4 have been shown
tion of Akt (p-Akt) and total Akt for 4 hours in VSMCs after LPS/IFN
to participate in VSMCs proliferation.18 Studies involving TLR signalling
stimulation, and showed that expression of p-Akt and total Akt was
have mainly focused on pathways activated in macrophages, mono-
time-dependent. Pre-incubation with LY294002, a PI3K/Akt signal-
19,20
In this review, we will summa-
ling pathway inhibitor, significantly down-regulate p-Akt expression
rize the remarkable effects and molecular mechanisms of LPS in VSMCs
cytes and vascular endothelial cells.
in VSMCs. These data indicated that the PI3K/Akt signalling pathway
proliferation. In addition, the potential inhibitors of TLR4 signalling for
could be activated in VSMCs stimulated by LPS.
VSMCs proliferation in proliferative vascular diseases will be discussed.
Phosphorylation of Ser473 and Thr308 sites is essential for Akt activation, which is involved in VSMCs proliferation associated with
2 | MECHANISMS AND POTENTIAL SIGNALLING PATHWAYS
inflammatory stimuli, such as AngII and PDGF in vitro and mechanical vascular injury in vivo. A previous study has suggested that LPS induced lung fibroblast proliferation through TLR4 signalling and the PI3K/Akt signalling pathway.23 Our previous study has shown p-Akt
It is well-known that LPS-stimulated TLR4 activation involves many
expression after LPS stimulation in rat VSMCs.24 In our experiments,
signal cascade reactions; including phosphatidylinositol 3-kinase/Akt
VSMCs were stimulated with LPS for 24 hours before cell counts and
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the 5-ethynyl-2-deoxyuridine (EdU) staining assays. These results
pre-treatment with SB203580, SP600125 and PD98059. These re-
showed that pre-incubation with LY294002 partially blocked VSMCs
sults suggest that ERK1/2, SAPK/JNK and p38 MAPK are different
proliferation stimulated by LPS. Moreover, Western blotting demon-
regulatory signalling mechanisms. Lin also reported that LPS admin-
strated that the levels of p-Akt (308) and p-Akt (473) protein expres-
istration affects TLR4 expression in vivo. Indeed, intravenous injec-
sion were up-regulated and achieved a peak 60 minutes after LPS
tions of LPS significantly elevated neointimal hyperplasia and TLR4
stimulation. Taken together, these results suggest that the PI3K/Akt
expression in New Zealand White rabbit aortas induced by balloon
pathway mediates VSMCs proliferation after LPS stimulation.
injury compared with the control group. However, whether or not the MAPKs signalling pathway is directly required for VSMCs proliferation stimulated by LPS warrants further investigation.
2.2 | LPS and the Rac1 signalling pathway The previous study has summarized the role of Ras-related C3 botulinum toxin substrate 1 (Rac1) in cardiovascular and cerebrovascular diseases.25 It has been reported that Rac1 promotes pulmonary artery 26
VSMCs proliferation,
and is essential in mediating VSMCs prolifera-
2.4 | LPS and the IRAKs signalling pathway It is well-known that activity of IRAK1 and IRAK4 kinases is indispensable in TLR signalling.31 Barthwal32 reported that IRAK1 mediates
tion induced by PDGF in rats. It has been reported that LPS treatment
VSMCs proliferation and neointimal formation via the protein kinase
rapidly induces the activation of Rac1 in a time-dependent manner in
C-ε-IRAK1-ERK signalling pathway. Our previous studies have inves-
VSMCs.27 Because Rac1 is involved in cell proliferation, we evaluate
tigated the effect of IRAK1 and IRAK4 kinase activities on neointimal
24
whether Rac1 is also required for LPS-induced VSMCs proliferation.
formation in Wistar rats. In in vivo studies, inhibition of IRAK1 and
As seen in our previous study,24 VSMCs were stimulated with LPS for
IRAK4 attenuated neointimal formation and fibrotic remodelling after
24 hours. Cell counts and the EdU staining assays revealed that pre-
injury, which was monitored by elastic-van Gieson staining. Inhibition
treatment with NSC23766, a novel selective Rac1 inhibitor, partially
of IRAK1 and IRAK4 also attenuated cell proliferation as characterized
abolished VSMCs proliferation stimulated by LPS, suggesting that
by EdU incorporation. In in vitro studies, VSMCs were stimulated with
Rac1 mediated VSMCs proliferation. Glutathione-S-transferase pull-
LPS for 24 hours before the EdU staining assay. It was shown that
down assays demonstrated that Rac1 activity is up-regulated after LPS
pre-incubation with N-(2-morpholinylethyl)-2-(3-nitrobenzoylamido)-
stimulation. Moreover, Rac1 activity was essential for LPS-induced p-
benzimidazole, an IRAK1/4 inhibitor, partially blocked VSMCs prolif-
Akt expression. Inhibition of Rac1 partially reduced p-Akt (308) and
eration stimulated by LPS. Furthermore, the IRAK1 and IRAK4 kinase
p-Akt (473) protein expression in VSMCs. These results suggest that
activities were suppressed by pre-incubation with an IRAK1/4 inhibi-
Rac1 signalling pathway mediates LPS-induced VSMCs proliferation.
tor in vivo and in vitro.33–35 These results suggest that IRAK1/4 participates in VSMCs proliferation and neointimal formation. Whether
2.3 | LPS and the mitogen-activated protein kinases signalling pathway
or not the IRAK1 and IRAK4 signalling pathway is directly required for VSMCs proliferation stimulated by LPS via the TLR4 signalling pathway warrants further investigation.
As a classical signalling pathway, MAPKs are involved in cardiovascular disorders.28 MAPKs are phosphorylated on serine and tyrosine residues by dual-specific kinases. The kinase family has three mem-
2.5 | LPS and MicroRNAs
bers, including ERKs, c-jun N terminal kinase/stress-activated protein
MicroRNAs (miRNAs) are small, long chain, non-coding RNAs with
kinases (JNK/SAPKs) and the protein kinase, p38. Downstream effec-
regulatory effects on biological process, such as cell proliferation and
tors of MAPKs, including ERK1/2, JNK1/2 and p38MAPK, are rapidly
cell apoptosis. It has been reported that TLR induces differential ex-
activated by balloon injury in rat carotid arteries.29 The proliferative
pression of miRNAs and immune responses against infections.36 Study
effect of the MAPKs pathway in VSMCs is an increasing concern.
has indicated that the expressions of miRNAs are changeable stimu-
Kim investigated the effects of TLR4 signalling and the involvement
lated by LPS via TLR signalling pathways in mouse macrophages.37 In
of MAPKs in VSMCs induction by LPS.30 Compared with the control
recent years, miRNAs are involved in VSMCs phenotypic modulation
group, the levels of p-ERK and p-p38 MAPK expression were elevated
and proliferation in some diseases.38 Li39 has reviewed that some
in response to LPS stimulation, and the level of p-JNK expression
miRNAs regulate VSMCs functions in atherosclerosis. For example,
was transiently increased at early time points in the LPS-stimulated
miR-21 has been shown to have a role in VSMCs proliferation, and
27
reported that LPS-promoted TLR4 expres-
inhibition of miR-21 decreases the proliferation of VSMCs. Zhang40
sion in VSMCs was associated with activation of intracellular MAPKs
has reported that the expression of ssc-miR-146a-5p and ssc-miR-
groups. Meanwhile, Lin
signalling pathway. Western blotting demonstrated that the levels of
221-5p is up-regulated in pig skeletal muscle after LPS stimulation.
p-ERK1/2, p-SAPK/JNK and p-p38 MAPK were up-regulated after
Wang has reported that the expression of miR-152 is down-regulated
LPS stimulation. LPS-induced TLR4 mRNA expression was reduced by
in LPS-stimulated VSMCs. The over-expression of miR-152 decreases
pre-treatment with SP600125 (an SAPK/JNK inhibitor) or PD98059
VSMCs proliferation stimulated by LPS.41 As new regulators of TLR,
(an ERK1/2 inhibitor), but not by SB203580 (a p38MAPK inhibitor).
further investigations should focus on the potential function of miR-
LPS-induced TLR4 protein expression was significantly reduced by
NAs in VSMCs proliferation induced by LPS.
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2.6 | LPS and other signalling pathways
phenotype-related proteins in VSMCs induced by LPS were investigated. Compared to control Wistar rats, the expression of proliferat-
As a classical transcription factor, nuclear transcription factor kappa B
ing cell nuclear antigen (PCNA), a marker of cell proliferation, was
(NF-κB) activation plays a critical role in LPS-induced VSMCs prolif-
increased, whereas the expression of calponin was decreased in GK
eration.22 Our previous study has involved the TLR4-mediated NF-κB
rats. Mesenteric VSMCs from diabetic GK rats exhibited increased
signalling pathway by microarrays analysis in rats with carotid artery
levels of p-ERK1/2 expression compared to controls. Furthermore,
balloon injury.34 It has been reported that VSMCs proliferation and
LPS enhanced p-ERK1/2 levels to a greater extent in GK rats’ VSMCs
neointimal formation in balloon-injured rat carotid arteries are as-
than controls. In addition, high glucose levels significantly increased
sociated with activation of cyclin-dependent protein kinases (CDKs)
PCNA and decreased calponin expression in mesenteric VSMCs in
and are cyclin-dependent,42 suggesting that CDKs regulated prolif-
a time-dependent manner. These results suggest that mesenteric
erative vascular diseases. James43 compared the genes of quiescent
VSMCs from GK rats undergo phenotypic modulation. However, the
human coronary artery smooth muscle cells with cells treated by LPS.
precise mechanisms underlying VSMCs phenotypic modulation and
Treatment of VSMCs with LPS resulted in up-regulation of several cell
the direct relationship with proliferation in GK rat mesenteric VSMCs
cycle-dependent genes such as CDK5 and CDK10, while several CDK
have not been described. Thus, future experiments are needed to de-
inhibitors such as p27, p21 and p16 were repressed. Whether or not
termine whether or not LPS regulates VSMCs proliferation and rel-
CDKs and CDK inhibitory proteins are directly required for VSMCs
evant signalling pathways in diabetic rats.
proliferation stimulated by LPS warrants further investigation.
In all, we discuss some relevant signalling pathways activated by TLR4 stimulated with LPS in VSMCs. How TLR4 is activated by LPS in
2.7 | LPS and phenotypic modulation
VSMCs is rarely investigated. Lin27 has reported that nicotinamide adenine dinucleotide phosphate oxidase activation, mRNA stabilization
Phenotypic modulation of VSMCs from the contractile phenotype to
and MAPKs signalling pathways play critical roles in LPS-enhanced
the synthetic phenotype has been shown to be regulated in different
TLR4 expression in HASMCs. Our previous study has revealed that
stimulations.44 Bae has described the regulatory mechanism under-
PI3K/Akt and Rac1 are involved in TLR4 expression in VSMCs stim-
lying PDGF-induced phenotypic modulation of VSMCs. It has dem-
ulated by LPS.24 However, whether internalization or translocation of
onstrated that the levels of p-Akt, p-ERK1/2 and p-p38 MAPK are
TLR4 is activated by LPS in VSMCs needs further investigation. By the
up-regulated after PDGF stimulation in VSMCs, and are significantly
way, whether or not LPS activates these signalling pathways via non-
reduced by pre-treatment with U0126 (an ERK inhibitor), LY294002
TLR4 in VSMCs needs to be discussed.
and PD98059 respectively. Pharmacologic inhibition of ERK and Akt blocks PDGF-induced phenotypic modulation of VSMCs. Taken together, PDGF regulates VSMCs phenotypic modulation.45 We re-
3 | POSSIBLE THERAPEUTIC TARGETS
cently published our findings on IRAK4 and modulation of the VSMCs phenotype in diabetic rats.46 The result showed that an IRAK1/4
To date, some experimental animal models and clinical study have
inhibitor increased LPS-mediated smooth muscle 22α protein and
suggested that TLRs have a crucial role in cardiovascular diseases.51
mRNA expression, which define the contractile phenotype of VSMCs.
A previous study has investigated the role of TLR4 on atherosclero-
Whether or not LPS directly regulates VSMCs phenotypic modulation
sis stimulated by LPS in ApoE−/− mice and reported that TLR4 may
involved in VSMCs proliferation is unknown.
be a therapeutic target in atherosclerosis. Thus, regulation of TLR4 signalling may be a novel therapeutic approach for treating these
2.8 | LPS and signalling pathways in diabetic rats
diseases.52 However, it remains uncertain whether treatment with a TLR4 inhibitor may attenuate atherosclerosis and proliferative vas-
We and others have discussed the proliferative effect and underly-
cular diseases. Because TLR4 is predominated in VSMCs stimulated
ing mechanism of LPS on VSMCs in non-diabetic rats. A previous
by LPS, TLR4 has been employed as the primary pharmacological
study has showed that the circulatory LPS levels and activities were
approach in experimental models of VSMCs proliferation and prolif-
increased in patients with type 2 diabetes.47 Maria has reported high
erative vascular diseases. Pharmacological approaches of TLR4 sig-
glucose-induced TLR4 activation in VSMCs.48 Wang49 has concluded
nalling inhibition include TLR4 antagonists, neutralizing antibodies,
that TLR4 may become a new potential pharmacological target for
small molecules, natural chemicals and agents. Table 2 summarizes
treating diabetic retinopathy. Thus, we have detected DNA synthe-
the current applications of TLR 4 inhibition mainly at the experimen-
sis and neointimal formation after catheter balloon injury in Goto-
tal level.
Kakizaki (GK) and matched control Wistar rats. After balloon injury, DNA synthesis and neointimal formation in GK rats were more apparent than in Wistar rats.34 In a recent study, mesenteric VSMCs were isolated from GK rats and age-matched control Wistar rats.50
3.1 | Chemicals Several studies have been performed using inhibitors of TLR4 acti-
Mesenteric VSMCs were synchronized before stimulation with LPS
vation. TAK-242, a small-molecule agent, has been shown to inhibit
for 15 minutes. The effects of VSMCs phenotypic modulation and
LPS-induced inflammation by targeting TLR4 signalling. TAK-242 also
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T A B L E 2 TLR4-targeting therapeutic strategies
Therapeutic strategies
Model and effect
References number
Chemicals A promising therapeutic agent for sepsis
54,55
Reduces macrophages recruitment to atherosclerotic plaques in vivo and murine peritoneal foam cell formation in vitro
56
Attenuates the development of cardiac hypertrophy
57
Reduces myocardial ischaemia-reperfusion injury
58
Prevents LPS-induced loss of vascular contractility
59
Inhibits TNF-α production in cultured VSMCs
60
Sparstolonin B
Inhibits VSMCs proliferation
61
Kolaviron
Decreases VSMCs proliferation
62
Hydroxysafflor yellow A
Attenuates VSMCs proliferation
63
Lithospermic acid
Reduces VSMCs proliferation
64
Atorvastatin
Inhibits phenotype modulation in VSMCs
65
Rosiglitazone
Atenuates intmal hyperplasia ameliorates LPS- induced infammaton in VSMCs
66, 67
Probucol
Suppressed LPS-accelerated atherosclerosis
68
Anti-TLR4 Antibody
Antagonizes inflammatory responses in VSMCs
67
NI-0101
Significantly suppress cytokine release in rheumatoid arthritis patients
69
Inhibits inflammatory responses in VSMCs
67
TAK-242 (CLI-095)
Eritoran
Rapamycin Natural chemicals
Clinical drugs
Antibody
RNAi TLR4 siRNA
inhibits LPS-induced phosphorylation of MAPKs.53 Ii54 has examined
contractility which could be effectively antagonized by eritoran. They
the therapeutic effect of TAK-242 in a mouse sepsis model. TAK-242
concluded inhibition of TLR4 by eritoran might serve as a novel ther-
is a promising therapeutic agent for sepsis and immune-mediated lung
apeutic concept to prevent cardiac dysfunction and hypotension after
injury.55 TAK-242, also known as CLI-095 or resatorvid, is a small-
endotoxemia. Eritoran has failed in treating sepsis, but perhaps it
molecule inhibitor of TLR4 signalling that acts by binding to the intra-
has positive outcomes in proliferative vascular diseases. However, it
cellular domain of TLR4. Wang examined whether CLI-095 attenuated
is still unclear whether eritoran prevents atherosclerosis in vivo and
the progression of atherosclerosis.56 The results showed that CLI-095
LPS-dependent VSMCs proliferation in vitro. Further investigations
reduced macrophages recruitment to atherosclerotic plaques in vivo
regarding the impact of eritoran on proliferative vascular diseases are
and murine peritoneal foam cell formation in vitro. They concluded
necessary.
that CLI-095 was able to alleviate atherosclerotic plaque in ApoE−/−
Rapamycin is an important pharmacologic agent against athero-
mice by reducing foam cell formation. So CLI-095 may be a candidate
sclerosis by inhibiting VSMCs proliferation and neointimal thickening.
as a new anti-proliferative drug. Eritoran, a TLR4 antagonist, potently suppresses TLR4 signalling pathway. Baumgarten57 have demonstrated that application of the
It has been reported based on a clinical study that rapamycin inhibits tumour necrosis factor-alpha (TNF-α) production in cultured VSMCs obtained from saphenous vein segments.60 Therefore, rapamycin may
TLR4 antagonist eritoran attenuates the development of cardiac hy-
reduce in-stent restenosis via attenuation of inflammatory cytokine
pertrophy. Shimamoto reported that inhibition of TLR4 with eritoran
expression in VSMCs. Due to the established efficacy in the preven-
in an in situ murine model significantly reduced myocardial ischaemia–
tion of stent restenosis, rapamycin might be an interesting therapeutic
reperfusion injury.
58
Meyer has tested for eritoran impact on vascular
agent in cardiovascular disorders. However, whether or not rapamycin
contractility.59 The data demonstrated that LPS up-regulated cyto-
can directly treat VSMCs proliferation stimulated by LPS needs further
kine expression via TLR4 and induced attenuation of smooth muscle
investigation.
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VSMCs.65 Meanwhile, peroxisome proliferator-activated receptor γ (PPARγ) agonist attenuates intimal hyperplasia by inhibiting TLR4-mediated inflammation in VSMCs.66 Moreover, Ji67 tested the role of rosiglitazone in regulating LPS-induced vascular inflammation; the results showed that rosiglitazone exerted a potent anti- inflammatory action via decreasing TLR4 and increasing PPARγ in LPS-induced VSMCs. In addition, administration of probucol suppressed LPS-accelerated atherosclerosis and plaque instability in ApoE−/− mice.68
3.4 | Anti-TLR4 antibody and TLR4 small-interfering RNA (siRNA) As the first monoclonal antibody blocking TLR4 signalling, NI-0101 is well tolerated without safety concern in healthy volunteers. Hatterer F I G U R E 1 Possible mechanisms for lipopolysaccharide (LPS) exerting its proliferative effects on vascular smooth muscle cells (VSMCs) by signalling pathways. Multiple signalling pathways can be activated in VSMCs proliferation. LPS can induce signalling pathways such as PI3K/Akt, MAPKs, IRAK1/4 which further promotes the expression of NF-κB for proliferative effects on VSMCs. Further investigation is required to determine whether the mechanisms of proliferative effects of LPS on VSMCs involve CDK, microRNA and phenotypic modulation, which are not shown in the figure. Moreover, whether internalization or translocation of TLR4 is activated by LPS in VSMCs needs further investigation
3.2 | Natural chemicals
reported TLR4 inhibition using NI-0101 in an ex vivo model of rheumatoid arthritis pathogenesis can significantly modulate cytokine release.69 Ji67 has reported that the TLR4 blocker or TLR4 siRNA significantly antagonized the LPS-mediated inflammatory responses in VSMCs. Taken together, whether or not rapamycin, TAK-242, eritoran, PPARγ agonist and atorvastatin can be used directly to treat VSMCs proliferation stimulated by LPS warrants further investigate. It will likely be a long time before these agents, who are currently undergoing testing in animal models, enter human trials.
4 | CONCLUSION AND PERSPECTIVE
Pharmacologic intervention involves multiple signal transduction
Abnormal VSMCs proliferation plays an important role in prolifera-
pathways (mainly PI3K/Akt and ERK). However, which pathway
tive vascular diseases, such as atherosclerosis and restenosis,70 which
plays the major role in anti-proliferative is not determined. Due to
involve all stages of inflammation associated with complex immune
the complexity of signalling pathways involved in regulating VSMCs
responses. LPS is reported to be involved in the modulation of VSMCs
proliferation, it is essential to develop multi-targeted drugs for
proliferation and neointimal formation.71 As a TLR4 agonist, LPS is re-
anti-proliferative effect. As important therapeutic targets, the anti-
ported to be dominated by binding TLR4. Zhang72 has reported TLR4
proliferative effects of drugs have been utilized for inhibiting VSMCs
as potential clinical biomarker for in-stent restenosis in drug-eluting
proliferation. Sparstolonin B (SsnB), a selective TLR4 antagonist with
stent patients, so we figure out that TLR4 may be the main therapeu-
potent anti-inflammatory properties, has protective effects on en-
tic target able to block LPS action.
dotoxin shock. Fan has investigated the role of SsnB in VSMCs pro-
The present in vitro study has demonstrated that LPS induces
liferation and inflammatory responses and found that SsnB reduces
VSMCs proliferation, although the exact mechanism has not been
VSMCs proliferation, and TNF-α and IL-6 expression stimulated by
LPS in VSMCs.61 SsnB significantly inhibited ERK1/2 and Akt signal-
completely elucidated (Figure 1). Whether or not these data obtained via in vitro experiments can explain the mechanism underlying LPS-
ling pathways in VSMCs activated by LPS. Thus, SsnB significantly in-
induced vascular hyperplasia in vivo remains to be determined. Anti-
hibits VSMCs proliferation associated with inflammatory responses.
proliferative approaches by targeting the LPS/TLR4 pathway have
Together, these results suggest that SsnB may be a candidate as a new
shown promising prospects in inhibiting VSMCs proliferation and
anti-proliferative drug. Similarly, Kolaviron,62 Hydroxysafflor yellow
neointimal thickening. These findings further our understanding of the
A63 and lithospermic acid64 also significantly inhibits VSMCs prolifera-
function of LPS in vascular diseases, and suggest TLR4 as a prospec-
tion stimulated by LPS.
tive target for the preventive and therapeutic proliferative vascular diseases.
3.3 | Clinical drugs Atorvastatin can effectively reduce neointimal formation and stent
CONFLICTS OF INTEREST
restenosis via the TLR4/NF-κB signalling pathway. Moreover, Atorvastatin inhibits phenotype modulation of PDGF-BB-induced
The authors declare no conflict of interest.
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ACKNOWLE DG E MEN TS We thank Dr Haochen Xuan for his technical support in developing the figure.
REFERENCES 1. Lim S, Park S. Role of vascular smooth muscle cell in the inflammation of atherosclerosis. BMB Rep. 2014;47:1–7. 2. Shi N, Chen SY. Mechanisms simultaneously regulate smooth muscle proliferation and differentiation. J Biomed Res. 2014;28:40–46. 3. Muto A, Fitzgerald TN, Pimiento JM, et al. Smooth muscle cell signal transduction: implications of vascular biology for vascular surgeons. J Vasc Surg. 2007;45(suppl A):A15–A24. 4. Kiyan Y, Tkachuk S, Hilfiker-Kleiner D, Haller H, Fuhrman B, Dumler I. oxLDL induces inflammatory responses in vascular smooth muscle cells via urokinase receptor association with CD36 and TLR4. J Mol Cell Cardiol. 2014;66:72–82. 5. Watanabe T, Pakala R, Katagiri T, Benedict CR. Mildly oxidized low-density lipoprotein acts synergistically with angiotensin II in inducing vascular smooth muscle cell proliferation. J Hypertens. 2001;19:1065–1073. 6. Ji Y, Liu J, Wang Z, Liu N. Angiotensin II induces inflammatory response partly via toll-like receptor 4-dependent signaling pathway in vascular smooth muscle cells. Cell Physiol Biochem. 2009;23:265–276. 7. Ginnan R, Guikema BJ, Halligan KE, Singer HA, Jourd’heuil D. Regulation of smooth muscle by inducible nitric oxide synthase and NADPH oxidase in vascular proliferative diseases. Free Radic Biol Med. 2008;44: 1232–1245. 8. Marshall JC. Lipopolysaccharide: an endotoxin or an exogenous hormone? Clin Infect Dis. 2005;41(suppl 7):S470–S480. 9. Stoll LL, Denning GM, Li WG. Regulation of endotoxin-induced proinflammatory activation in human coronary artery cells: expression of functional membrane-bound CD14 by human coronary artery smooth muscle cells. J Immunol. 2004;173:1336–1343. 10. Li H, He Y, Zhang J, Sun S, Sun B. Lipopolysaccharide regulates toll- like receptor 4 expression in human aortic smooth muscle cells. Cell Biol Int. 2007;31:831–835. 11. Pryshchep O, Ma-Krupa W, Younge BR, Goronzy JJ, Weyand CM. Vessel-specific toll-like receptor profiles in human medium and large arteries. Circulation. 2008;118:1276–1284. 12. Hernanz R, Martinez-Revelles S, Palacios R, et al. Toll-like receptor 4 contributes to vascular remodelling and endothelial dysfunction in angiotensin II-induced hypertension. Br J Pharmacol. 2015;172:3159–3176. 13. Saxena A, Rauch U, Berg KE, et al. The vascular repair process after injury of the carotid artery is regulated by IL-1RI and MyD88 signalling. Cardiovasc Res. 2011;91:350–357. 14. Yang X, Coriolan D, Murthy V, Schultz K, Golenbock DT, Beasley D. Proinflammatory phenotype of vascular smooth muscle cells: role of efficient Toll-like receptor 4 signaling. Am J Physiol Heart Circ Physiol. 2005;289:H1069–H1076. 15. Danenberg HD, Welt FG, Walker M 3rd, Seifert P, Toegel GS, et al. Systemic inflammation induced by lipopolysaccharide increases neointimal formation after balloon and stent injury in rabbits. Circulation. 2002;105:2917–2922. 16. Heo SK, Yun HJ, Noh EK, Park WH, Park SD. LPS induces inflammatory responses in human aortic vascular smooth muscle cells via Toll- like receptor 4 expression and nitric oxide production. Immunol Lett. 2008;120:57–64. 17. Lu Z, Zhang X, Li Y, Jin J, Huang Y. TLR4 antagonist reduces early- stage atherosclerosis in diabetic apolipoprotein E-deficient mice. J Endocrinol. 2013;216:61–71. 18. Pi Y, Zhang LL, Li BH, et al. Inhibition of reactive oxygen species generation attenuates TLR4-mediated proinflammatory and
19. 20. 21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
proliferative phenotype of vascular smooth muscle cells. Lab Invest. 2013;93:880–887. Lu YC, Yeh WC, Ohashi PS. LPS/TLR4 signal transduction pathway. Cytokine. 2008;42:145–151. Dauphinee SM, Karsan A. Lipopolysaccharide signaling in endothelial cells. Lab Invest. 2006;86:9–22. Zhou RH, Lee TS, Tsou TC, et al. Stent implantation activates Akt in the vessel wall: role of mechanical stretch in vascular smooth muscle cells. Arterioscler Thromb Vasc Biol. 2003;23:2015–2020. Hattori Y, Hattori S, Kasai K. Lipopolysaccharide activates Akt in vascular smooth muscle cells resulting in induction of inducible nitric oxide synthase through nuclear factor-kappa B activation. Eur J Pharmacol. 2003;481:153–158. He Z, Gao Y, Deng Y, et al. Lipopolysaccharide induces lung fibroblast proliferation through Toll-like receptor 4 signaling and the phosphoinositide3-kinase-Akt pathway. PLoS ONE. 2012;7:e35926. Jiang D, Li D, Cao L, et al. Positive feedback regulation of proliferation in vascular smooth muscle cells stimulated by lipopolysaccharide is mediated through the TLR 4/Rac1/Akt pathway. PLoS ONE. 2014;9:e92398. Carrizzo A, Forte M, Lembo M, Formisano L, Puca AA, Vecchione C. Rac-1 as a new therapeutic target in cerebro- and cardio-vascular diseases. Curr Drug Targets. 2014;15:1231–1246. Diebold I, Djordjevic T, Hess J, Gorlach A. Rac-1 promotes pulmonary artery smooth muscle cell proliferation by upregulation of plasminogen activator inhibitor-1: role of NFkappaB-dependent hypoxia-inducible factor-1alpha transcription. Thromb Haemost. 2008;100:1021–1028. Lin FY, Chen YH, Tasi JS, et al. Endotoxin induces toll-like receptor 4 expression in vascular smooth muscle cells via NADPH oxidase activation and mitogen-activated protein kinase signaling pathways. Arterioscler Thromb Vasc Biol. 2006;26:2630–2637. Muslin AJ. MAPK signalling in cardiovascular health and disease: molecular mechanisms and therapeutic targets. Clin Sci (Lond). 2008;115:203–218. Tang B, Ma S, Yang Y, et al. Overexpression of angiotensin II type 2 receptor suppresses neointimal hyperplasia in a rat carotid arterial balloon injury model. Mol Med Rep. 2011;4:249–254. Son YH, Jeong YT, Lee KA, et al. Roles of MAPK and NF-kappaB in interleukin-6 induction by lipopolysaccharide in vascular smooth muscle cells. J Cardiovasc Pharmacol. 2008;51:71–77. Chaudhary D, Robinson S, Romero DL. Recent advances in the discovery of small molecule inhibitors of interleukin-1 receptor-associated kinase 4 (IRAK4) as a therapeutic target for inflammation and oncology disorders. J Med Chem. 2015;58:96–110. Jain M, Singh A, Singh V, Barthwal MK. Involvement of interleukin-1 receptor-associated kinase-1 in vascular smooth muscle cell proliferation and neointimal formation after rat carotid injury. Arterioscler Thromb Vasc Biol. 2015;35:1445–1455. Bai S, Li D, Zhou Z, et al. Interleukin-1 receptor-associated kinase 1/4 as a novel target for inhibiting neointimal formation after carotid balloon injury. J Atheroscler Thromb. 2015;22:1317–1337. Zhang X, Wang Y, Hu W, et al. Interleukin-1/toll-like receptor-induced nuclear factor kappa B signaling participates in intima hyperplasia after carotid artery balloon injury in goto-kakizaki rats: a potential target therapy pathway. PLoS ONE. 2014;9:e103794. Guo J, Li D, Bai S, Xu T, Zhou Z, Zhang Y. Detecting DNA synthesis of neointimal formation after catheter balloon injury in GK and in Wistar rats: using 5-ethynyl-2’-deoxyuridine. Cardiovasc Diabetol. 2012;11:150. Aalaei-andabili SH, Rezaei N. Toll like receptor (TLR)-induced differential expression of microRNAs (MiRs) promotes proper immune response against infections: a systematic review. J Infect. 2013;67:251–264. Chiu CC, Wu WS. Investigation of microRNAs in mouse macrophage responses to lipopolysaccharide-stimulation by combining
|
JIANG et al.
8 of 8
38.
39. 40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
51. 52. 53.
54.
55.
56.
gene expression with microRNA-target information. BMC Genom. 2015;16(suppl 12):S13. Satoh M, Takahashi Y, Tabuchi T, et al. Circulating Toll-like receptor 4-responsive microRNA panel in patients with coronary artery disease: results from prospective and randomized study of treatment with renin-angiotensin system blockade. Clin Sci (Lond). 2015;128:483–491. Yu X, Li Z. MicroRNAs regulate vascular smooth muscle cell functions in atherosclerosis (review). Int J Mol Med. 2014;34:923–933. Zhang J, Fu SL, Liu Y, Liu YL, Wang WJ. Analysis of MicroRNA expression profiles in weaned pig skeletal muscle after lipopolysaccharide challenge. Int J Mol Sci. 2015;16:22438–22455. Wang YS, Chou WW, Chen KC, Cheng HY, Lin RT, et al. MicroRNA-152 mediates DNMT1-regulated DNA methylation in the estrogen receptor alpha gene. PLoS ONE. 2012;7:e30635. Andres V. Control of vascular cell proliferation and migration by cyclin-dependent kinase signalling: new perspectives and therapeutic potential. Cardiovasc Res. 2004;63:11–21. Joe Minta J, Yun J, Sandy D, Shikha R. Microarray analysis of human vascular smooth muscle cell responses to bacterial lipopolysaccharide. American Journal of Immunology. 2007;3:56–73. Pei C, Qin S, Wang M, Zhang S. Regulatory mechanism of human vascular smooth muscle cell phenotypic transformation induced by NELIN. Mol Med Rep. 2015;12:7310–7316. Ha JM, Yun SJ, Kim YW, et al. Platelet-derived growth factor regulates vascular smooth muscle phenotype via mammalian target of rapamycin complex 1. Biochem Biophys Res Commun. 2015;464:57–62. Cao L, Pan D, Li D, et al. Relation between anti-atherosclerotic effects of IRAK4 and modulation of vascular smooth muscle cell phenotype in diabetic rats. Am J Transl Res. 2016;8:899–910. Jayashree B, Bibin YS, Prabhu D, et al. Increased circulatory levels of lipopolysaccharide (LPS) and zonulin signify novel biomarkers of proinflammation in patients with type 2 diabetes. Mol Cell Biochem. 2014;388:203–210. Carrillo-Sepulveda MA, Spitler K, Pandey D, Berkowitz DE, Matsumoto T. Inhibition of TLR4 attenuates vascular dysfunction and oxidative stress in diabetic rats. J Mol Med (Berl). 2015;93:1341–1354. Wang YL, Wang K, Yu SJ, et al. Association of the TLR4 signaling pathway in the retina of streptozotocin-induced diabetic rats. Graefes Arch Clin Exp Ophthalmol. 2015;253:389–398. Carrillo-Sepulveda MA, Matsumoto T. Phenotypic modulation of mesenteric vascular smooth muscle cells from type 2 diabetic rats is associated with decreased caveolin-1 expression. Cell Physiol Biochem. 2014;34:1497–1506. Vallejo JG. Role of toll-like receptors in cardiovascular diseases. Clin Sci (Lond). 2011;121:1–10. Peri F, Piazza M. Therapeutic targeting of innate immunity with Toll- like receptor 4 (TLR4) antagonists. Biotechnol Adv. 2012;30:251–260. Hussey SE, Liang H, Costford SR, et al. TAK-242, a small-molecule inhibitor of Toll-like receptor 4 signalling, unveils similarities and differences in lipopolysaccharide - and lipid-induced inflammation and insulin resistance in muscle cells. Biosci Rep. 2013;33:37–47. Takashima K, Matsunaga N, Yoshimatsu M, et al. Analysis of binding site for the novel small-molecule TLR4 signal transduction inhibitor TAK-242 and its therapeutic effect on mouse sepsis model. Br J Pharmacol. 2009;157:1250–1262. Ni JQ, Ouyang Q, Lin L, et al. Role of toll-like receptor 4 on lupus lung injury and atherosclerosis in LPS-challenge ApoE(-)/(-) mice. Clin Dev Immunol. 2013;2013:476856. Wang XQ, Wan HQ, Wei XJ, Zhang Y, Qu P. CLI-095 decreases atherosclerosis by modulating foam cell formation in apolipoprotein E-deficient mice. Mol Med Rep. 2016;14:49–56.
57. Ehrentraut H, Weber C, Ehrentraut S, et al. The toll-like receptor 4-antagonist eritoran reduces murine cardiac hypertrophy. Eur J Heart Fail. 2011;13:602–610. 58. Shimamoto A, Chong AJ, Yada M, et al. Inhibition of Toll-like receptor 4 with eritoran attenuates myocardial ischemia-reperfusion injury. Circulation. 2006;114:I270–I274. 59. Ehrentraut S, Frede S, Stapel H, et al. Antagonism of lipopolysaccharide- induced blood pressure attenuation and vascular contractility. Arterioscler Thromb Vasc Biol. 2007;27:2170–2176. 60. Adkins JR, Castresana MR, Wang Z, Newman WH. Rapamycin inhibits release of tumor necrosis factor-alpha from human vascular smooth muscle cells. Am Surg. 2004;70:384–387; discussion 387-388. 61. Liu Q, Li J, Liang Q, et al. Sparstolonin B suppresses rat vascular smooth muscle cell proliferation, migration, inflammatory response and lipid accumulation. Vascul Pharmacol. 2015;67–69:59–66. 62. Oyagbemi AA, Omobowale TO, Adedapo AA, Yakubu MA. Kolaviron, biflavonoid complex from the seed of Garcinia kola attenuated angiotensin II- and lipopolysaccharide-induced vascular smooth muscle cell proliferation and nitric oxiwde production. Pharmacognosy Res. 2016;8:S50–S55. 63. Yang G, Zhou X, Chen T, et al. Hydroxysafflor yellow A inhibits lipopolysaccharide-induced proliferation and migration of vascular smooth muscle cells via Toll-like receptor-4 pathway. Int J Clin Exp Med. 2015;8:5295–5302. 64. Chen L, Wang WY, Wang YP. Inhibitory effects of lithospermic acid on proliferation and migration of rat vascular smooth muscle cells. Acta Pharmacol Sin. 2009;30:1245–1252. 65. Chen S, Liu B, Kong D, et al. Atorvastatin calcium inhibits phenotypic modulation of PDGF-BB-induced VSMCs via down-regulation the Akt signaling pathway. PLoS ONE. 2015;10:e0122577. 66. Ji Y, Liu J, Wang Z, Liu N, Gou W. PPARgamma agonist, rosiglitazone, regulates angiotensin II-induced vascular inflammation through the TLR4-dependent signaling pathway. Lab Invest. 2009;89:887–902. 67. Ji Y, Liu J, Wang Z, Li Z. PPARgamma agonist rosiglitazone ameliorates LPS-induced inflammation in vascular smooth muscle cells via the TLR4/TRIF/IRF3/IP-10 signaling pathway. Cytokine. 2011;55:409–419. 68. Li JF, Chen S, Feng JD, Zhang MY, Liu XX. Probucol via inhibition of NHE1 attenuates LPS-accelerated atherosclerosis and promotes plaque stability in vivo. Exp Mol Pathol. 2014;96:250–256. 69. Hatterer E, Shang L, Simonet P, et al. A specific anti-citrullinated protein antibody profile identifies a group of rheumatoid arthritis patients with a toll-like receptor 4-mediated disease. Arthritis Res Ther. 2016;18:224. 70. Curcio A, Torella D, Indolfi C. Mechanisms of smooth muscle cell proliferation and endothelial regeneration after vascular injury and stenting: approach to therapy. Circ J. 2011;75:1287–1296. 71. Vink A, Schoneveld AH, van der Meer JJ, et al. In vivo evidence for a role of toll-like receptor 4 in the development of intimal lesions. Circulation. 2002;106:1985–1990. 72. Liang S, Aiqun M, Jiwu L, Ping Z. TLR3 and TLR4 as potential clinical biomarkers for in-stent restenosis in drug-eluting stents patients. Immunol Res. 2016;64:424–430.
How to cite this article: Jiang D, Yang Y, Li D. Lipopolysaccharide induced vascular smooth muscle cells proliferation: A new potential therapeutic target for proliferative vascular diseases. Cell Prolif. 2017;50:e12332, https://doi.org/10.1111/cpr.12332