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J Cardiol 2003 Nov; 42（5）: 201 – 206

Involvement of Inflammation in
Acute Coronary Syndromes
Assessed by Levels of HighSensitivity C-Reactive Protein,
Matrix Metalloproteinase-9 andSoluble Vascular-Cell Adhesion
Molecule-1
Kazumiki NOMOTO, MD
Sumito

OGUCHI, MD

Ikuyoshi

WATANABE, MD

Toshio

KUSHIRO, MD

KatsuoKANMATSUSE, MD, FJCC＊

Abstract ─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
Objectives. Inflammation is important in the development of atherosclerosis. Matrix metalloproteinases（MMPs）and interferon-γ which participate in collagen degradation are pathological factors in plaque vulnerability as an important mechanism underlying acute coronary syndrome. This study investigatedwhether inflammation is related to the onset of acute coronary syndrome.
Methods. This study included 56 patients with acute coronary syndrome（ACS group）, 104 patients withchronic coronary artery disease（S group）, and 38 control subjects with no evidence of ischemic heart disease（C group）. High-sensitivity C-reactive protein（hs-CRP）, MMP-9, and interferon-γ were measured inperipheral blood samples. Soluble adhesion molecules（VCAM-1, ICAM-1）were also measured as inflammatory markers.
Results. The hs-CRP level was significantly higher in the ACS group（44.5 mg/l）than in the S group（2.1 mg/l）
and the C group（0.6 mg/l）（p ＜ 0.0001）. The MMP-9 level was also significantly higher in the
ACS group（333.8 ng/ml）than in the S group（110.8 ng/ml）and the C group（72.0 ng/ml）（p ＜ 0.0001）. The
VCAM-1 level was significantly higher in the ACS group（506.5 ng/ml）
than in the C group（448.8 ng/ml）（p ＜ 0.05）. The ICAM-1 level and the interferon-γ level did not differ between the groups. There was asignificant positive correlation between the level of hs-CRP and the level of the collagen degradation product MMP-9（r ＝ 0.52）in all subjects.
Conclusions. These results suggest that plaque destabilized by MMP-9 produced in response to inflammation participates in the mechanism of acute coronary syndrome.
─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────J Cardiol 2003 Nov ; 42（5）
: 201−206

Key Words
Coronary artery disease acute coronary syndrome

INTRODUCTION
Inflammation is important in the development of
atherosclerosis. Adhesion molecules, such as vascular-cell adhesion molecule-1（ VCAM-1）andPlaqueintercellular adhesion molecule-1（ICAM-1）,
cytokines and chemokines promote the progressionof this disease. Matrix metalloproteinases（MMPs）
and interferon-γ which participate in collagendegradation are pathological factors in plaque vul-──────────────────────────────────────────────
駿河台日本大学病院 循環器科 : 〒 101−8309 東京都千代田区神田駿河台 1−8−13 ; ＊日本大学医学部 内科学講座 2，東京
Department of Cardiology, Nihon University Surugadai Hospital, Tokyo ; ＊ The Second Department of Medicine, Nihon University,
School of Medicine, Tokyo
Address for correspondence : OGUCHI S, MD, The Department of Cardiology, Nihon University Surugadai Hospital, KandaSurugadai 1−8−13, Chiyoda-ku, Tokyo 101−8309
Manuscript received July 13, 2003 ; revised September 5, 2003 ; accepted September 5, 2003

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Nomoto, Oguchi, Watanabe et al

nerability as an important mechanism underlying
acute coronary syndromes1）.
Systemic inflammation increases the productionof cytokines, oxidized low-density lipoproteins（ LDL）and lipopolysaccharide（ endotoxin）.
Pathogens such as chlamydia and viruses stimulate
macrophages, T lymphocytes and other types ofinflammatory cells in atherosclerotic lesions torelease atherogenic reactants, such as adhesion
molecules, cytokines and chemokines2）.
Systemic inflammation also activates T lymphocytes and macrophages, inflammatory cells residing
in plaque. T lymphocytes release interferon-γ,
which inhibits smooth muscle cell proliferation anddecreases collagen synthesis. Interferon-γalso
increases the production of MMPs by macrophages,
leading to degradation of the extracellular matrix ofthe fibrous cap of plaque. The fibrous cap weakens,
finally resulting in plaque disruption3）.
Consequently, patients with vulnerable plaques
may show elevated peripheral blood levels of interferon-γ and MMPs. Therefore, MMP-9 and interferon-γ levels were measured in patients withacute coronary syndrome. The blood levels of highsensitivity C-reactive protein（hs-CRP）were measured to examine the relationship between inflammation and the onset of acute coronary syndrome.
Soluble adhesion molecules（VCAM-1, ICAM-1）
were also measured as inflammatory markers.
SUBJECTS AND METHODS
Study population
This study included 56 patients with acute coronary syndromes admitted within 6 hr after symptom
onset（ACS group, 48 with acute myocardial infarction and 8 with unstable angina）, 104 patients withchronic coronary artery disease（S group, 46 withold myocardial infarction and 58 with stableangina）, and 38 control subjects with no evidenceof ischemic heart disease（C group）. The following
clinical characteristics of the subjects were recorded : age, sex, presence or absence of hypertension,
diabetes mellitus, hyperlipidemia and smoking. All
subjects gave written informed consent before
enrollment in the study.
Measurement of inflammatory markers
Hs-CRP, MMP-9 and interferon-γ levels were
measured in peripheral blood samples. Soluble
adhesion molecule（VCAM-1, ICAM-1）levels werealso measured as inflammatory markers. Hs-CRP

was measured by nephelometric assay（DadeBehring）. MMP-9 was measured by enzyme
immunoassay（ Fuji Pharmaceutical Industries）.
VCAM-1 and ICAM-1 were determined byenzyme-linked immunosorbent assay（ R&D
Systems）, and interferon-γwas measured byenzyme immunoassay（Bio Source）.
Statistical analysis
Continuous data are expressed as mean ± SD.
The Kruskal-Wallis test was used to compare clinical characteristics between the three groups. Any
significant difference underwent the Mann-Whitney
U-test with Bonferroni s correction. Differences in
hs-CRP, MMP-9, soluble VCAM-1 and soluble
ICAM-1 levels between the three groups were compared by one-way analysis of variance. Significant
differences were tested by Fisher s protected leastsignificant difference. p values of less than 0.05
were considered to indicate statistical significance.
RESULTS
Baseline characteristics of patients
Mean age was similar in the ACS group（64.9 ±9.5 years）, the S group（60.1 ± 10.2 years）, and theC group（59.6 ± 9.7 years）. The proportion of men
was also similar in the three groups（ACS group,
78.6% ; S group, 77.9% ; C group, 73.7%）. The
proportion of patients with hyperlipidemia washigher in the ACS group（60.7%）and the S group（68.3%）
than in the C group（28.9%）, but the proportions of patients with other risk factors, such as
hypertension, diabetes mellitus, and smoking did
not differ significantly（Table 1）.
Inflammatory markers
The hs-CRP level was 44.5 mg/l in the ACS
group, significantly higher than 2.1 mg/l in the S
group or 0.6 mg/l in the C group（p ＜ 0.0001）. The
MMP-9 level was 333.8 ng/ml in the ACS group,
significantly higher than 110.8 ng/ml in the S groupor 72.0 ng/ml in the C group（p ＜ 0.0001 ; Fig. 1）.
The VCAM-1 level was 506.5 ng/ml in the ACS
group, significantly higher than 448.8 ng/ml in the
C group（p ＜ 0.05, ACS group vs C group）. The
ICAM-1 was not different between the three groups（Fig. 2）. The interferon-γ level was low in all
three groups and did not differ significantly.
All subjects showed a significant positive correlation between the level of hs-CRP and the level ofthe collagen degradation product MMP-9（r ＝ 0.52,
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Involvement of Inflammation in Acute Coronary Syndromes

Table 1 Baseline characteristics of patients
ACS group（n＝56）

S group（n＝104）

C group（n＝38）

Age（yr, mean±SD）64.9±9.560.1±10.2

59.6±9.7

Male

44（78.6）

81（77.9）28（73.7）

Hypertension

28（50.0）67（64.4）25（65.8）

Diabetes mellitus

16（28.6）29（27.9）4（10.5）Hyperlipidemia＊

34（60.7）＊

71（68.3）

11（28.9）

Smoking20（35.7）

53（51.0）14（36.8）

Coronary risk factors＊（ ）: %. p＜0.05 vs C group.
ACS group : With acute coronary syndrome. S group : With chronic coronary artery disease. C group : Without
evidence of ischemic heart disease.

hs−CRP（mg/l）
100

MMP−9（ng/ml）

＊
＊

＊
＊

600
400

50
200

ACS group

S groupC group

ACS group

S groupC groupFig. 1 Levels of high-sensitivity C-reactive protein and matrix metalloproteinase-9 in the ACS
group, S group and C group
The levels of hs-CRP（left）and MMP-9（right）were significantly higher in the ACS group than in the S andC groups. The box represents the interquartile range（between the 25th and 75th percentiles）; the median isshown as a horizontal bar within each box. The bars outside each box show the range of 95% of all values.
＊
p ＜ 0.0001.
hs-CRP ＝ high-sensitivity C-reactive protein ; MMP-9 ＝ matrix metalloproteinase-9.
Explanation of the groups as in Table 1.

VCAM−1（ng/ml）
1000

ICAM−1（ng/ml）
400

500

200

P＜0.05

ACS group

S group C group

ACS groupNS

S groupC groupFig. 2 Levels of vascular-cell adhesion molecule-1 and intercellular adhesion molecule-1 in the ACS
group, S group and C group
The level of VCAM-1（left）was significantly higher in the ACS group than in the C group. The level of
ICAM-1（right）did not differ between the groups. The box represents the interquartile range（between the
25th and 75th percentiles）; the median is shown as a horizontal bar within each box. The bars outside eachbox show the range of 95% of all values.
VCAM-1 ＝ vascular-cell adhesion molecule-1 ; ICAM-1 ＝ intercellular adhesion molecule-1.
Explanation of the groups in Table 1.

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Nomoto, Oguchi, Watanabe et alhs−CRP（mg/l）

150
r＝0.52

100

50

0

250

500
MMP−9（ng/ml）

750

Fig. 3 Scatterplot of high-sensitivity C-reactive protein
and matrix metalloproteinase-9 values in all
subjects
The levels of hs-CRP and MMP-9 were significantly
correlated（r ＝ 0.52）.
Abbreviations as in Fig. 1.

p ＜ 0.0001 ; Fig. 3）.
DISCUSSION
Acute coronary syndromes such as unstableangina and acute myocardial infarction are linked
to disruption of plaque. Since elevated concentrations of CRP, serum amyloid A and other acutephase proteins occur in the blood of patients withunstable angina, the involvement of inflammation
has received considerable attention in acute coronary syndromes4）. Inflammatory markers found inincreased concentrations in patients with acutecoronary syndrome include acute-phase proteinsand cytokines, such as CRP, serum amyloid A,
plasminogen activator inhibitor-1, MMPs, interleukin-6 and interleukin-84−8）.
MMPs degrade collagen and other components
of extracellular matrix and so are important in thedestabilization of plaque and the onset of acutecoronary syndrome. Our study showed that hs-CRP
and MMP-9 levels were significantly higher in the
ACS group than in the other groups. This elevationof MMP-9 levels may be associated with increased
production of MMP, probably in activatedmacrophages or vascular smooth muscle cells inplaque prone to rupture. Vulnerable plaque is characterized by a large lipid core, a thin fibrous cap
covering the plaque, sparse smooth muscle cells
and aggressive macrophage infiltration 2） .
Constitutive expression of MMP occurs9）in vascular smooth muscle cells in normal arteries, and
MMP expression is increased in vascular smoothmuscle cells in atherosclerotic arteries.
Recently, a relationship has been found between

blood levels of MMPs and acute coronary syndrome, but mostly in small studies. Serial changes
occur in the peripheral blood levels of MMPs inpatients with acute coronary syndrome6）. Great cardiac vein-aortic root differences in plasma MMP-9levels are elevated in patients with acute coronary
syndrome, but no significant differences weredetected in the plasma MMP-9 levels in the aortic
root 10）. Our study of 208 patients showed thatperipheral blood levels of MMP-9 in patients withacute coronary syndrome were significantly higher
than those in patients with chronic coronary arterydisease and control subjects. We also demonstrated
a significant positive correlation between hs-CRP
levels and MMP-9 levels in all subjects. These findings suggest that inflammation is important in theonset and progression of acute coronary syndromes.
MMPs are produced by endothelial cells andsmooth muscle cells, as well as many other types ofcells including neutrophils, macrophages and tumor
cells. MMP-9 levels are increased in the coronary
circulation of patients with acute coronary syndrome10）. These findings indicate that MMP-9 isformed in the coronary circulation. Therefore,
increased MMP-9 levels in acute coronary syndrome patients are related to plaque rupture and do
not result from systemic inflammation.
Our study showed that hs-CRP levels were higher in the coronary artery disease group than in thecontrol group. These findings may indicate that thehs-CRP level is useful for identifying chronic
inflammation and may improve risk management inpatients with atherosclerotic disease. The hs-CRP
concentration is correlated with the risk of myocardial infarction and predicts the risk of coronary
events11）. Other studies have shown that elevated
CRP concentration on admission for myocardial
infarction is related to increased risk of unstableangina 12）and a CRP concentration of more than
5 mg/l is associated with increased mortality13）.
Our study found no significant difference ineither the hs-CRP level or the MMP-9 level
between patients with acute myocardial infarction
and unstable angina. This observation suggests thatelevated concentrations of hs-CRP and MMP-9 aresomehow related to the development of acute coronary syndromes and do not result from tissue damage associated with acute myocardial infarction.
VCAM-1 level was significantly elevated in the
ACS group, suggesting that patients with acutecoronary syndrome have an increased risk of atherJ Cardiol 2003 Nov; 42（5）: 201 – 206

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Involvement of Inflammation in Acute Coronary Syndromes

osclerosis. The expression of adhesion molecules
such as VCAM-1 and ICAM-1 is induced byinflammatory cytokines, including interleukin-1
and tumor necrosis factor, and by endotoxins.
These molecules are implicated in the local infiltration of inflamed tissue by various types of leukocytes. Oxidized LDL is thought to be very important role in the development of atherosclerosis.
Lysophosphatidylcholine, considered the major
active component of oxidized LDL, acts on cultured endothelial cells, selectively enhances theexpression of VCAM-1, ICAM-1 and P-selectin on
the cell surface, and strengthens the adhesion of
monocytes to endothelium 14,15）. These adhesion
molecules are thus thought to promote atherosclerosis.
Study limitations
This study had several limitations. Not all serum
inflammatory marker levels differed significantly
between the study groups. The serum level of interferon-γ was often below the detection limit, so
assay sensitivity should be improved by the devel要

opment of high-sensitive assays. Levels of interferon-γ in the coronary sinus blood（rather than the
peripheral blood）should also be measured. Anotherlimitation was that inflammatory marker levels
were measured after the onset of symptoms in the
ACS group, and we could not determine whether
elevation of these markers was a cause or an effectof coronary events. However, because the patientswith acute coronary syndrome were admitted within 6 hr after symptom onset, time-related effects on
inflammatory marker levels were considered minimal.
CONCLUSIONS
Acute coronary syndromes are associated withsignificantly increased levels of hs-CRP, VCAM-1
and MMP-9 as compared with chronic coronary
artery disease and control subjects with no evidenceof ischemic heart disease. Our results suggest thatplaque destabilized by MMP-9 produced in
response to inflammation participates in the mechanism of acute coronary syndromes.

約

急性冠症候群の発症と炎症との関連: 高感度 C 反応性蛋白とマトリックス・メタロ
プロテアーゼ-9 および可溶性 Vascular-Cell Adhesion Molecule-1 の測定による検討
野本
目

和幹

大口

純人

渡辺

郁能

久代登志男

上松瀬勝男

的 : 動脈硬化の進展には炎症が大きな役割を果たしている．急性冠症候群発症の機序の一つであるプラークの不安定化には，コラーゲン分解に関与するマトリックス・メタロプロテアーゼ（MMP）やインターフェロンγなどの物質が関係していることが病理学的に考えられている．本研
究の目的は，急性冠症候群の発症と炎症との関連を明らかにすることである．
方法 : 当院に来院した発症 6 時間以内の急性冠症候群（急性群）56 例，慢性冠動脈疾患（慢性群）

104 例，虚血性心疾患を有さない対照患者（対照群）
38 例を対象とし，末梢血の高感度 C 反応性蛋白，MMP-9 およびインタ ーフ ェロンγを測定した．さらに，炎症関連物質として可溶性接着分子（VCAM-1，ICAM-1）も測定した．
結果 : 高感度 C 反応性蛋白は，それぞれ急性群 44.5 mg/l，慢性群 2.1 mg/l，対照群 0.6 mg/l で，急性群は慢性群と対照群に比較して有意に高値を示した（p ＜ 0.0001）．MMP-9 も急性群 333.8 ng/ml，
慢性群 110.8 ng/ml，対照群 72.0 ng/ml で，急性群は慢性群と対照群に比較して有意に高値を示した（p ＜ 0.0001）．VCAM-1 は急性群 506.5 ng/ml，対照群 448.8 ng/ml で，急性群は対照群に比較して有意に高値を示した（p ＜ 0.05）．ICAM-1 とインターフェロンγは各群間で差は認められなかった．
全例で検討すると，高感度 C 反応性蛋白値と MMP-9 値との両値間に r ＝ 0.52 の有意な相関がみられた．
結論 : 急性冠症候群の発症には，炎症に基づく MMP-9 の産生を介したプラークの不安定化が関与していることが示唆された．

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