Possible Role of Parathyroid Hormone–Related Protein as a
Proinflammatory Cytokine in Atherosclerosis
José Luis Martín-Ventura, BS; Mónica Ortego, PhD; Pedro Esbrit, PhD;
Miguel Angel Hernández-Presa, PhD; Luis Ortega, MD; Jesús Egido, MD
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Background and Purpose—Parathyroid hormone–related protein (PTHrP) is a vasodilator peptide. In addition, PTHrP
appears to affect vascular growth and to be a mediator of inflammation in rheumatic and brain disorders. We examined
the possible role of PTHrP in the inflammatory process in atherosclerosis
Methods—We immunohistochemically analyzed the cellular localization of PTHrP, the type 1 PTH/PTHrP receptor
(PTH1R), and monocyte chemoattractant protein-1 (MCP-1) in 26 human carotid atherosclerotic plaques.
Results—The inflammatory region of plaques was characterized by high PTHrP, PTH1R, and MCP-1 immunostaining in
relation to the cap (0.75⫾0.1 versus 0.29⫾0.04, 0.5⫾0.1 versus 0.25⫾0.05, 0.72⫾0.2 versus 0.29⫾0.05, respectively;
P⬍0.05). PTHrP and MCP-1 were colocalized in both resident and inflammatory cells in the plaque. Moreover, in
cultured vascular smooth muscle cells (VSMC), PTHrP(1–36) increased MCP-1 mRNA (3-fold at 6 hours) and MCP-1
protein (2.5-fold at 24 hours). This effect was inhibited by either PTHrP(7–34) or various protein kinase A inhibitors
and by the nuclear factor-␬B (NF-␬B) inhibitor parthenolide. Furthermore, PTHrP(1–36) elicited an increase in NF-␬B
activation in VSMC. The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor simvastatin inhibited the
PTHrP(1–36) induction of both NF-␬B activity and MCP-1 overexpression, and this was reversed by mevalonate.
Conclusions—PTHrP appears to be a novel proinflammatory mediator in the atheroma lesion and may contribute to the
instability of carotid atherosclerotic plaques. Our data provide a new rationale to understand the mechanisms involved
in the beneficial effects of statins in atherosclerosis. (Stroke. 2003;34:●●●-●●●.)
Key Words: atherosclerosis 䡲 carotid arteries 䡲 inflammation
䡲 monocyte chemoattractant protein-1 䡲 parathyroid hormone–related protein
T
he pathophysiological aspects of atherosclerosis include
an inflammatory process and increased vascular smooth
muscle cell (VSMC) growth. While the latter is a key event
for vascular occlusion, the inflammatory process has been
related to plaque disruption.1 In this sense, studies on coronary arteries of patients suffering myocardial infarction demonstrated that the rupture of atheroma usually takes place in
the shoulder region, an area characterized by a high inflammatory content.2 A possible explanation was the increased
collagenolysis mediated by metalloproteinases (MMPs),
whose expression was mostly confined to the shoulder region
of plaques.3 In contrast, the mechanisms by which macrophages accumulate in this region still remain undefined.
Recent clinical trials have established that lipid lowering
with 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA)
reductase inhibitors (statins) reduces the incidence of cardiovascular disease.4 Some of the beneficial effects of these
drugs may involve nonlipid mechanisms because they have
been shown to reduce blood thrombogenicity and inflammation in humans.5,6 Moreover, C-reactive protein levels de-
crease after treatment with statins.7 In this regard, in a rabbit
model of atherosclerosis, atorvastatin inhibited the nuclear
factor-␬B (NF-␬B)– dependent increase of monocyte chemoattractant protein-1 (MCP-1) expression, and this effect
was associated with a decrease in both macrophage infiltration and neointima formation.8
Both parathyroid hormone (PTH)–related protein (PTHrP)
and the type 1 PTH/PTHrP receptor (PTH1R) are abundant in
the vascular system.9,10 Different vasoconstrictors, such as
angiotensin II, stimulate PTHrP and the PTH1R expression in
rat aortic VSMC.11,12 The N-terminal fragment of PTHrP is a
potent vasodilator and can inhibit VSMC growth when acting
in an autocrine/paracrine fashion.10,13 However, PTHrP can
also be internalized into the nucleus of VSMC and thus
increase their growth.13
Therefore, the true role of PTHrP in the vascular system
has not yet been established. Recent studies suggest that
PTHrP may also act as a proinflammatory cytokine in some
clinical settings.14,15 PTHrP overexpression occurs in human
and experimental atherosclerotic lesions related to the sever-
Received November 8, 2002; final revision received February 10, 2003; accepted February 26, 2003.
From the Vascular Research Laboratory (J.L.M-V., M.O., M.A.H-P., J.E.) and Bone and Mineral Research Laboratory (P.E.), Fundación Jiménez Díaz,
Autónoma University; and Department of Pathology, Hospital Clínico San Carlos (L.O.), Madrid, Spain.
Correspondence to Jesús Egido, MD, Vascular Research Laboratory, Fundación Jiménez Díaz, Avenida Reyes Católicos 2, 28040 Madrid, Spain.
E-mail [email protected]
© 2003 American Heart Association, Inc.
Stroke is available at http://www.strokeaha.org
DOI: 10.1161/01.STR.0000078371.00577.76
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Figure 1. PTHrP, PTH1R, and MCP-1
immunodetection in human atherosclerotic plaques. Positivity for PTHrP and
PTH1R is increased in the shoulder
region (B, D), an area in the plaque with
a high inflammatory content, related to
the cap (A, C). MCP-1 positivity was also
increased in the shoulder region (F) compared with the cap (E). G, Schematic
representation of a human carotid
plaque, showing the atheroma region by
1 asterisk and the cap region by 2 asterisks. The shoulder region is shown by 2
triangles.
ity of the disease.16,17 However, the putative role of PTHrP in
the pathogenesis of atherosclerosis remains unclear. In the
present study we examined whether PTHrP might be involved in the inflammatory process associated with
atherosclerosis.
Methods
In Vivo Studies
Tissue Sampling
Twenty-six consecutive patients undergoing carotid endarterectomy
at our institution were included in the study, and informed consent
was obtained before enrollment (Table, available online at http://
stroke.ahajournals.org). The study was approved by the local ethical
committee in accordance with the institutional guidelines. For
analysis, we selected the carotid artery with its bifurcation, the
predilection site for plaque formation. We studied carotid atherosclerotic plaques in 2 different areas (shoulder and cap). The shoulder
region was composed of the plaque area at both sides of the lipid
core, and the fibrous cap was the rim over atheroma. Specimens were
collected and stored in 4% p-formaldehyde for 24 hours and then in
ethanol until paraffin embedding.
Immunohistochemistry
Paraffin-embedded carotid arteries were cross-sectioned into 4-␮mthick pieces at 5-mm intervals and then were dewaxed and rehy-
drated. Tissue samples were incubated with trypsin (0.01%) and then
incubated with 6% swine (or goat) serum/4% bovine serum albumin
(BSA) in phosphate-buffered saline (PBS) for 1 hour to block
nonspecific staining. The following primary antibodies were used:
monoclonal anti-human macrophage antibody HAM-56 (Dako),
monoclonal anti–␣-smooth muscle actin antibody HHF-35 (Sigma),
rabbit anti-human CD3 antibody (Dako), and a polyclonal rabbit
anti-human MCP-1 (Immugenex), at 1:100 dilution in BSA/PBS.
PTHrP and PTH1R staining was performed with either the rabbit
polyclonal anti-PTHrP antiserum C13 recognizing the (24 –35)
epitope in the PTHrP molecule18 or affinity-purified antibody AbVII (Babco)12 at 1:200 dilution in BSA/PBS. After overnight
incubations, biotinylated swine or goat anti-rabbit IgG, at 1:200
dilution, was added for 1 hour. The avidin-biotin-peroxidase complex (Dako) was added for an additional 30-minute period. Sections
were then stained for 10 minutes with 3,3⬘-diaminobenzidine (Dako),
counterstained with hematoxylin, and mounted in Pertex (Medite).
For colocalization studies, after immunohistochemistry was performed for macrophages and VSMC, immunofluorescence for
PTHrP was performed on the same tissue sections. As secondary
antibody, fluorescein isothiocyanate– conjugated goat anti-rabbit IgG
was used, and slides were mounted in 90% glycerol in PBS. In each
experiment, negative controls either without the primary antibody or
with the corresponding IgG were included to check for nonspecific
staining. In addition, for PTHrP, we also used preincubation of the
primary antibody C13 with [Cys23]human PTHrP(24 –25) amide, the
immunogen used to raise this antibody.18
Martín-Ventura et al
Role of PTHrP in Atherosclerosis
3
Figure 2. Colocalization studies. Double immunostaining
was performed with specific antibodies for either VSMC
(A) or macrophages (C) and anti-PTHrP antiserum C13
(B, D). The arrows show the double staining for PTHrP
(green) and for either VSMC or macrophages (brown).
PTHrP (E) and MCP-1 (F) immunostaining was performed in serial atheroma sections.
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In Vitro Studies
Sepharose beads (Pharmacia Biotech) were added to the lysate for 4
hours at 4°C. After they were washed with lysate buffer (⫻3) and
with kinase buffer (20 mmol/L HEPES, pH 7.6; 20 mmol/L MgCl2;
20 mmol/L ␤-glycerophosphate; 10 mmol/L NaF; 0.2 mmol/L
Na3VO4; 0.2 mmol/L dithiothreitol) (⫻2), Sepharose beads were
resuspended in sodium dodecyl sulfate–polyacrylamide gel electrophoresis sample buffer, boiled for 5 minutes, and subjected to
electrophoresis. The detection was made with the use of the anti-rat
MCP-1 antibody and enhanced chemiluminescence (ECL, Amersham), as described.12
Cell Culture
Electrophoretic Mobility Shift Assay
Quantification
Computer-assisted morphometric analysis was performed with the
Olympus semiautomatic image analysis system with Micro Image
software (version 1.0 for Windows). Because of the different number
of cells in the plaques analyzed, results were expressed as an index
of protein expression (percentage of positive staining for PTHrP,
PTH1R, or MCP-1/percentage of total cell positive staining) in both
shoulder and cap regions.
Rat aortic VSMC were isolated and cultured as previously described.19 Cells were growth-arrested by incubation in serum-free
medium for 48 hours and then incubated with human PTHrP(1–36),
kindly provided by A.F. Stewart (Division of Endocrinology, University of Pittsburgh, Pittsburgh, Pa). In some experiments,
(Asn10,Leu11,D-Trp12)PTHrP(7–34) amide [PTHrP(7–34)] (Bachem),
simvastatin (MSD), RpcAMPS (Biolog Life Science Institute), H89
(Calbiochem), parthenolide, or mevalonate (Sigma) was added to the
culture medium 1 or 2 hours before PTHrP(1–36).
RNA Extraction and Northern Blot Analysis
Twenty micrograms of VSMC total RNA, obtained by a standard
method (Trizol, Life Technologies), was denatured, electrophoresed
on a l% agarose-formaldehyde gel, and then transferred to nylon
membranes (Genescreen, Perkin Elmer). Rat MCP-1 and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) probes, obtained
from preparative reverse transcription–polymerase chain reaction
with the use of total RNA and specific primers, were labeled with
[␣32P]dCTP (Amersham), as previously described.19 Films were
scanned with the use of the ImageQuant densitometer program.
Immunoprecipitation and Detection of Rat MCP-1
Cells were washed with PBS buffer containing 400 mmol/L sodium
orthovanadate (Na3VO4) and 10 mmol/L NaF. This reaction was
stopped by the addition of 200 ␮L of lysis buffer (1% Igepal;
50 mmol/L HEPES, pH 7.5; 100 mmol/L NaCl; 2 mmol/L EDTA;
1 mmol/L pyrophosphate; 10 mmol/L Na3VO4; 1 mmol/L phenylmethylsulfonyl fluoride; and 100 mmol/L NaF). For MCP-1 immunoprecipitation, cell lysates (400 ␮g of whole protein) were incubated with 1 ␮g of rabbit polyclonal anti-rat MCP-1 (Ab7202,
Abcam) overnight at 4°C in lysis buffer. Then 50 ␮L of protein A
Electrophoretic mobility shift assay for NF-␬B binding activity was
performed with protein extracts from VSMC as described.19 The
specificity of the assay was tested with a 100-fold excess of
unlabeled NF-␬B consensus oligonucleotide added to the 32P-labeled
probe-binding reaction.
Statistical Analysis
Statistical analysis was performed with GraphPAD InStat software.
Immunohistochemistry and Northern blot analysis data are
mean⫾SEM and were analyzed by either Mann-Whitney or
ANOVA test when appropriate. Significant differences were considered for P⬍0.05.
Results
In Vivo Studies
PTHrP, PTH1R, and MCP-1 Immunostaining in Human
Atherosclerotic Plaques
We found that human atherosclerotic plaques contain higher
macrophage and T-cell infiltration and lower VSMC in the
shoulder region than in the cap (not shown). This is consistent
with the presence of a high inflammatory content in the former
region.2 However, there were no significant differences in total
cell positive staining for both macrophages and VSMC when
these 2 regions were compared. Immunostaining for PTHrP,
PTH1R, and MCP-1 was significantly higher in the shoulder
region than in the cap (0.75⫾0.1 versus 0.29⫾0.04, 0.5⫾0.1
versus 0.25⫾0.05, 0.72⫾0.2 versus 0.29⫾0.05, respectively;
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Figure 3. Time course of PTHrP(1–36)induced increase of MCP-1 expression
in VSMC. VSMC were serum-depleted
for 48 hours and then were treated with
PTHrP(1–36) (10⫺8 mol/L) at different
time periods. Lipopolysaccharide (LPS)
(1 ␮g/mL) was used as a positive control. A, Representative Northern blots
corresponding to MCP-1 and GADPH
mRNA and relative densitometric values
from 3 independent experiments in
each case are shown. *P⬍0.05 vs basal
value. B, Representative Western blot
with a specific anti-rat MCP-1 antibody
is shown.
P⬍0.05 for all) (Figure 1). To ensure the specificity of the
technique, we performed negative controls by omitting the
corresponding primary antibodies or using the corresponding
IgG. In addition, for PTHrP, we also used preincubation of the
primary antibody C13 with [Cys23]human PTHrP(24 –25)
amide, the immunogen used to raise this antibody,18 and there
was no staining in any of the cases (not shown).
In addition, we performed a double-staining procedure,
using immunoperoxidase/immunofluorescence, to determine
the cell type(s) contributing to PTHrP overexpression in
human atherosclerotic plaques. By this manner, PTHrP staining was detected in both VSMC (Figure 2A and 2B) and
macrophages (Figure 2C and 2D). Moreover, immunostaining for PTHrP and MCP-1 in serial tissue sections showed the
presence of both proteins in the same cells (Figure 2E and
2F). Taken together, these results suggest that both PTHrP
and MCP-1 are likely to be involved in the inflammatory
process in the vulnerable region of human atheroma.
In Vitro Studies
PTHrP(1–36) Stimulates MCP-1 Expression in VSMC
Since MCP-1 and PTHrP were colocalized in human atherosclerotic plaques, we explored the potential proinflammatory
effect of PTHrP in cultured VSMC. PTHrP(1–36) at 10⫺8
mol/L increased MCP-1 mRNA (with a maximal stimulation
at 6 hours, representing 3-fold over control) and MCP-1
protein (approximately 2.5-fold over control at 24 hours)
(Figure 3). These results suggest that PTHrP may be a novel
mediator involved in the recruitment of mononuclear cells
into the atheroma lesion through the induction of MCP-1.
Mechanisms Involved in PTHrP(1–36)-Induced MCP-1
Expression in VSMC
In the next set of experiments, we analyzed the possible
mechanisms involved in MCP-1 mRNA induction by
PTHrP(1–36). Since this peptide can stimulate cAMP in
VSMC,20 we initially tested the effect of protein kinase A
(PKA) inhibitors. Both RpcAMPS and H89, at 5⫻10⫺5 and
10⫺7 mol/L, respectively, prevented the PTHrP-induced
MCP-1 gene expression at 6 hours in these cells (Figure 4).
Moreover, pretreatment with PTHrP(7–34), at 10⫺6 mol/L,
which stimulates protein kinase C but not PKA by interacting
with the PTH1R,21 abrogated the PTHrP(1–36)-induced
MCP-1 mRNA, while it was inefficient by itself (Figure 4).
NF-␬B is a key regulatory factor of MCP-1 gene expression. We found that the NF-␬B inhibitor parthenolide22 (10⫺5
mol/L) abolished the increase of MCP-1 mRNA induced by
PTHrP(1–36) (10⫺8 mol/L) in VSMC (Figure 4). Thus, we
Martín-Ventura et al
Role of PTHrP in Atherosclerosis
5
Figure 4. Mechanisms involved in the
MCP-1 mRNA upregulation triggered by
PTHrP(1–36). SMC were pretreated with
2 different PKA inhibitors, RpcAMPS (2.5
to 5⫻10⫺5 mol/L) and H89 (10⫺7 mol/L) or
with the NF-␬B inhibitor parthenolide
(Parthe) (10⫺5 mol/L), and then PTHrP(1–
36) (10⫺8 mol/L) was added. Pretreatment
with PTHrP(7–34) (10⫺6 mol/L) abolished
the PTHrP-induced MCP-1 mRNA
expression, but it did not have any effect
alone (10⫺8 mol/L). Representative Northern blots corresponding to MCP-1 and
GADPH mRNA and relative densitometric
values from 3 independent experiments
are shown. *P⬍0.05 vs PTHrP-stimulated
value.
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examined whether PTHrP would have a direct effect on
NF-␬B activation in VSMC, as occurs in osteoblastic cells.23
PTHrP(1–36) (10⫺8 mol/L) was shown to induce an increase
in NF-␬B activation in a time-dependent manner (Figure 5A).
This effect was specific since a 100-fold excess of unlabeled
NF-␬B oligonucleotide probe abolished such effect.
Figure 5. Effect of PTHrP on NF-␬B activation in VSMC. A,
VSMC stimulated with PTHrP(1–36) (10⫺8 mol/L) for different
time periods induced NF-␬B activation with a maximal effect at
90 minutes. The 100-fold excess of cold NF-␬B oligonucleotide
abolished such effect. B, Pretreatment with simvastatin (SV)
(10⫺6 mol/L) diminished NF-␬B activation at 90 minutes, and this
effect was reversed by mevalonate (MVA) (10⫺4 mol/L). A representative electrophoretic mobility shift assay from 3 independent
experiments is shown.
Effect of the HMG-CoA Reductase Inhibitor Simvastatin
on PTHrP(1-36)-Induced MCP-1 mRNA
Since statins can decrease both MCP-1 upregulation and
NF-␬B activation both in vitro and in vivo,8,19 we explored
whether simvastatin could also downregulate the effect of
PTHrP(1–36) on MCP-1 mRNA and NF-␬B activation in
VSMC. We found that pretreatment with simvastatin, within
the therapeutic range (10⫺6 to 10⫺7 mol/L), inhibited the
PTHrP-induced MCP-1 mRNA overexpression. When
VSMC were treated with PTHrP and simvastatin in the
Figure 6. Effect of simvastatin (SV) on the PTHrP-induced
increase of MCP-1 mRNA in VSMC. VSMC were incubated with
PTHrP(1–36) (10⫺8 mol/L) for 6 hours in the presence of increasing concentrations of simvastatin (10⫺6 to 10⫺7 mol/L), with or
without mevalonate (MVA) (10⫺4 mol/L). Northern blots corresponding to MCP-1 and GADPH mRNA and relative densitometric values from 3 independent experiments are shown. *P⬍0.05
vs PTHrP-stimulated value. LPS indicates lipopolysaccharide.
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presence of mevalonate (10⫺4 mol/L), the metabolite that is
directly synthesized by the HMG-CoA reductase, these effects were reversed (Figure 6). Moreover, simvastatin (10⫺6
mol/L) diminished NF-␬B activation, and this effect was also
reversed by mevalonate (Figure 5B). These results suggest
that statins could downregulate MCP-1 expression, at least in
part, by interfering with the effect of PTHrP in VSMC.
Discussion
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In recent years, PTHrP has gained increasing interest because
of its diverse actions in the cardiovascular system.10 PTHrP
gene is overexpressed in rat and human vessels during
neointimal formation, and intensity of PTHrP staining in
VSMC has been shown to correlate with the severity of
coronary atherosclerosis.16,17 These findings raise the possibility that PTHrP may function, in a stimulatory or contributory manner, in the pathogenesis of arterial sclerosis and
restenosis. The N-terminal region of PTHrP has been shown
to inhibit migration and proliferation of VSMC both in vitro
and in vivo in atherosclerotic lesions.24,25 Consistent with
these findings, in the present study both PTHrP and the
PTH1R staining were increased in the more vulnerable area
in the human plaque, containing a lower VSMC number. In
marked contrast, PTHrP(1–141) stably transfected into A10
rat VSMC induced marked cell growth, and fetal aortic
VSMC from PTHrP (⫺/⫺) mice showed a decreased proliferation rate.13 The mechanism responsible for this proliferative effect involves PTHrP targeting to the nucleus. Interestingly, a recent study has shown that these opposite effects of
PTHrP on VSMC proliferation are reversed in spontaneously
hypertensive rats.26 Collectively, these data strongly suggest
that PTHrP may participate in the altered mechanisms of
VSMC growth in vascular pathology. However, the specific
impact of this suggested role of PTHrP in the atherosclerotic
process remains to be elucidated.
Previous studies suggest the view of PTHrP as a member
of the cytokine network involved in the inflammatory response in rheumatic and brain disorders.14,15 Inflammation is
involved in the genesis, rupture, and thrombosis of atherosclerotic plaques. The breakdown of the plaque occurs more
frequently at points where the fibrous cap is thinner and
where there is a great amount of inflammatory cells such as
macrophages and T lymphocytes.27 A possible explanation
was the increased collagenolysis mediated by MMP, whose
expression was mostly confined to the shoulder region of
plaques.3 In contrast, the mechanisms by which macrophages
accumulate in this region have not been totally defined. In the
present study we observed that PTHrP, PTH1R, and MCP-1
were overexpressed in the inflammatory region of human
carotid atherosclerotic plaques. Moreover, PTHrP and
MCP-1 staining localized to the same cells in these plaques.
Furthermore, PTHrP(1–36) was found to induce MCP-1
expression in cultured VSMC. Taken together, these findings
strongly suggest that PTHrP has a role in the inflammatory
process involved in atherosclerosis.
The N-terminal fragment of PTHrP signals by increasing
the production of cAMP in VSMC.20 We showed herein that
PKA inhibitors as well as PTHrP(7–34), which lacks cAMP-
inducing activity,21 blocked the effect of PTHrP(1–36) on
MCP-1 overexpression in VSMC. In this regard, MCP-1
upregulation by leptin in aortic endothelial cells has recently
been reported to depend on PKA activition.28 In addition, our
findings indicate that NF-␬B activation also seems to be
involved in the PTHrP(1–36)-induced increase of MCP-1
mRNA in VSMC. In fact, in a preliminary report, it was
shown that the shoulder region of human carotid atherosclerotic plaques, displaying an intense PTHrP staining as shown
herein, has augmented NF-␬B activity.29 Collectively, these
findings support the involvement of both PKA and NF-␬B in
the signaling mechanism of MCP-1 upregulation by
PTHrP(1–36) in VSMC.
HMG-CoA reductase inhibitors decrease the incidence of
acute coronary events.4 Previous studies have demonstrated
that these drugs decrease the extent of atherosclerosis in
experimental models without hyperlipidemia and in the absence of lipid reduction.30 In a rabbit model of atherosclerosis, atorvastatin decreased NF-␬B activity in femoral arteries,
coinciding with a decrease in MCP-1 expression, macrophage
content, and lesion size.8 Moreover, atorvastatin inhibited
NF-␬B activity and MCP-1 mRNA elicited by tumor necrosis
factor-␣ and angiotensin II in VSMC and mononuclear cells
in vitro.19 In the present study simvastatin prevented the
effect of PTHrP(1–36) on both NF-␬B activation and MCP-1
mRNA overexpression in cultured VSMC. These results
provide a new potential mechanism by which statins could
exert their known anti-inflammatory properties and then
contribute to plaque stabilization.
In conclusion, our findings suggest that PTHrP may be an
important regulator of some events involved in atherosclerotic plaque formation, such as macrophage accumulation.
Our data provide a new rationale to understand the mechanisms involved in the beneficial effects of statins in
atherosclerosis.
Acknowledgments
This work was supported by grants from CAM 08.4/0005.1/1998,
SAF 2001/0717, Fundación Ramón Areces (Madrid, Spain), and
Merck Sharp and Dhome Spain. J.L. Martín-Ventura and M. Ortego
are fellows of the Spanish Fondo de Investigación Sanitaria and
Comunidad Autónoma de Madrid.
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Possible Role of Parathyroid Hormone-Related Protein as a Proinflammatory Cytokine in
Atherosclerosis
José Luis Martín-Ventura, Mónica Ortego, Pedro Esbrit, Miguel Angel Hernández-Presa, Luis
Ortega and Jesús Egido
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