b-Blocker Improves Cardiac
Function by Reducing Oxidative Stress and Metalloproteinase Activity After Myocardial Infarction*
Mauricio Bernstein, MD
Suresh C. Tyagi, PhD
of Physiology and Biophysics,
University of Mississippi Medical Center,
*This work was supported in part by NIH grant GM-48595,
HL-51971, and a grant-in-aid from American Heart Association-Mississippi
Affiliate. A part of this study was presented at the 53rd Annual Fall Conference
and Scientific Sessions of the American Heart Association Council of High Blood
Pressure Research, September 13-16, 1999, Orlando, FL.
KEY WORDS: extracellular matrix,
MMP, TIMP-4, collagen, remodeling, muscarinic receptor, catecholamine,
norepinephrine, diastolic dysfunction, heart failure
b-blockers have been shown to reduce oxidative
stress and improve cardiovascular function. It is unclear, however, whether b-blockers improve cardiac remodeling by
inhibiting metalloproteinase and oxidative stress. The aims of this study were
to determine the effects of a b-adrenergic
blocker (metoprolol [M]) on matrix metalloproteinase (MMP) expression and
activity, tissue inhibitor of metalloproteinase-4 (TIMP-4) expression, collagen
degradation, and diastolic function in a rat model of myocardial infarction
(MI). Sprague Dawley rats were divided into four groups: (1) sham, (2) sham+M,
(3) MI, and (4) MI+M (n=6). Two days prior and continuously for 2 weeks after
ligating the left anterior descending artery, rats were given 10 mg/day
metoprolol by gavage. Hemodynamic parameters, serum, and cardiac specific
creatine phosphokinases were measured. Left ventricle (LV) systolic and
diastolic function were measured in anaesthetized rats. LV MMP-2 was measured by
Northern-blot and zymography. The levels of TIMP-4 were measured by
Northern-blot and Western-blot analyses. The scanned intensity data of MMP-2
and TIMP-4 mRNA and protein were normalized with 18S RNA and b-actin, respectively. In sham, sham+M, MI, and
MI+M groups, respectively, the following data were obtained: The mean arterial
pressures (MAP) were 111+3, 109+8, 99+16, and 88+21
mm Hg (P > .05). The end-diastolic
pressures were 4.15+1.4, 3.85+0.95, 12.9+2.0, and 9.9+1.0
mm Hg (P < .05). Heart rates were
339+13, 331+9, 310+43, and 256+29 beats/min. The
(-dP/dt)/MAP were 45+9, 46+6, 30+3, and 38+4 sec-1.
The 66 kDa MMP-2 activity was 0.04+0.02, 0.03+0.01, 0.57+0.02,
and 0.25+0.03 (scan unit). The 72 kDa gelatinase was 0.28+0.08,
0.24+0.03, 0.68+0.07, and 0.38+0.08 (scan unit). There was
no significant change in the protein levels of MMP-9 and TIMP-4 activity in
either group. Total reduction-oxidation (redox) disulfides, a marker of
oxidative stress, were 0.066+0.05, 0.06+0.02, 0.095+0.02,
and 0.055+0.01 mg/mg of tissue. A negative correlation between
total MMP-2/TIMP-4 activity and (-dP/dt)/MAP was obtained. The results
suggested that treatment with metoprolol improves cardiac function by
inhibiting metalloproteinase and decreasing oxidative stress after MI.
During protracted cycles of
ischemia/reperfusion,1 the oxygen produces oxyradical: 2O2
+ 2H2O = 2H2O2 + O2-
(toxic oxygen), dependent or independent of NADH/NAD oxidase,2 and
masks the activity of superoxide dismutase and catalase.3-5 Therefore,
during myocardial infarction (MI) oxygen tension and oxidative stress are
robustly increased.6 Oxidative stress increases the levels of
cytokines, growth factors, and neurohormones.7,8 This starts a
vicious cycle of oxidative stress in which neurohormone such as angiotensin II10
increases further oxidative stress by decreasing the levels of bradykinin and
prostaglandins. Otherwise, these molecules mediate antioxidation by increasing
nitric oxide production.11 In parallel, angiotensin II also induces NADH/NAD
oxidase.12 Therefore, increased oxidative stress may be the initial
cause of alteration in remodeling, structure, and function.
critical balance between matrix metalloproteinase (MMP) and tissue inhibitor of
metalloproteinase (TIMP) is necessary for normal tissue constitution.13
In the normal heart most of the MMPs are latent, and the MMP:TIMP ratio is 0.15
to 0.6,14 but in end-stage heart failure this ratio increases to
approximately 6 to 715. In vitro treatment of normal cardiac extract
with oxidants and inflammatory cell proteinase increases the ratio to
approximately 5 to 6.14 In ischemic heart disease, inflammatory
cytokines, neurohumoral factors and oxidative stress are elevated.16,17
Oxidative stress and norepinephrine produce collagenolysis and cardiac
dilatation.18,19 The sympathometric blockade is associated with
decreased oxidative stress and improved cardiac function after MI.20-23
It is unclear, however, whether beta-sympathometric blockade improves cardiac
function, in part, by inhibiting oxidative stress and matrix remodeling. The
hypothesis is that b-adrenergic blockade improves cardiac function,
in part, by inhibiting MMP after MI.
model of myocardial infarction:
Harlan Sprague-Dawley rats, weighing 300 to 375 g, were intubated, and
respiration was maintained during thoracotomy by intermittent positive
pressure. Ventilation was delivered by a small animal ventilator. Rats were
anesthetized with pentobarbital (50 mg/kg intraperitoneal). The left side
thorax was opened through 3 to 4 ribs, the heart was exteriorized, and the left
main coronary artery was ligated 2 mm from its origin29. The chest
was closed, intrathoracic negative pressure was reestablished, and the animals
were allowed to recover. Rats were divided into four groups: (1) rats were
subjected to sham-operation, and surgery was performed but the ligature was not
tied around the coronary artery (Sham); (2) sham received daily gavage with
metoprolol (Sham+M); (3) surgery was performed, and the ligature was tied
around the coronary artery (MI); and (4) rats were given metoprolol (10 mg/day)
gavage 2 days prior to creation of MI and continued for 2 weeks (MI+M). A
minimum of 6 rats (n = 6) was used in
each group. At the end of 2 weeks treatment the serum creatine phosphokinase
(CK) and degree of MI were measured. All studies conformed to the principles of
the National Institutes of Health Guide
for the Care and Use of Laboratory Animals and the protocols were approved
by our Institution's Animal Care and Use Committee.
Molecular assessment of heart
failure: To determine plasma CK
MB (myocardial) activity, blood (0.25 mL was collected from the tail vein by
producing a small excision in the tail of each animal on days 1 and 12
following coronary ligation. Because specific
CK MB isoenzyme is released in plasma following
myocardial injury in patients with MI,24,25 we measured CK MB
activity by agarose substrate gel electrophoresis.26 The bands due
to CK MB activity were scanned and the intensity (I) was used to estimate the
amount of CK MB. The amount of CK MB in the serum of MI rats (sample) was
determined as follows: Amountsample=AmountST/IST
x Isample; where ST is standard isoenzyme MB (Sigma). A criteria of
serum CK activity >10 mg/mL was applied to determine the severity of
Measurements of plasma redox-thiols: Total plasma redox-thiols were measured by
titrating the -SH group with dithio-bis-nitrobenzoate (DTNB) in the presence of
a minimal reducing agent. After incubation at 37oC for 3.5 hours,
all thiol and disulfides were exchanged to DTNB and produced color at 412 nm.
The concentration of thiols was calculated using an extinction coefficient of
13,600 M-1cm-1 at 412 nm.27
In vivo assessment of hemodynamic
parameters and left ventricular function: Mean arterial pressure (MAP), heart rate (HR), systolic and
diastolic blood pressure (SBP and DBP), left ventricular pressure (LVP) and
maximum fall in LVP, -dP/dt, were measured in anesthetized rats with Inactin
(Sigma Chemical Co, St. Louis, MO) (100 mg/kg intraparitoneal)26.
This anesthesia had minimal effect on cardiovascular function.28 For
MAP, a fluid-filled catheter (PE-50 tubing) was inserted into the right femoral
artery. The arterial catheter was connected to a pressure transducer (Micro-Med,
Corp) positioned at the level of the heart. Pulsatile arterial pressure was
recorded by a personal computer using customized software. For LVP, the
catheter was advanced to LV via right carotid artery, and the LVP was recorded.
The pressure transducers were calibrated and electronically interfaced to a
personal computer for analog-to-digital conversion, storage, and analysis of
data. Ten minutes after insertion of the arterial and ventricular catheters,
respectively, resting measurements of arterial BP, heart rate, and LVP were
taken. The maximum derivative of fall in LVP (-dP/dt) and rise (+dP/dt) were
estimated. The -dP/dt is afterload-dependent; to correct for the afterload,
-dP/dt was divided by MAP.26 After functional measurements,
anesthetized animals were prepared for excision of the heart.
Identification of infarction: The heart was removed under sterile conditions
and weighed. The LV and RV were separated. The ratio LV weight (g)/body weight
(g) was employed to evaluate the increase in mass of the ventricle. The MI was
identified by observing discoloration and Evan's blue staining of the ischemic
muscle. The MI tissue was dissected and weighed. The percentage of MI was
calculated as follows: MI tissue weight/LV weight x 100. The rest of the tissue
was divided into three subgroups: (1) fixed in 10% buffered formalin for
histologic analysis, (2) tissue cooled in isopentane and stored at -80oC
for immuno- and in situ labeling, and (3) directly frozen tissue for mRNA
Zymography: The MMP activity was measured by zymography as
described.14 In brief, LV extract were prepared. The extracts (25 mg of protein in each lane) were loaded onto
nonreducing (1%) gelatin-SDS-PAGE. Gels were incubated overnight and stained
with Coomassie blue. To ensure that no significant gel-to-gel variation
occurred, standard rat heart MMP-2 (purified in our laboratory) was used in
each gel. The lytic bands were scanned and normalized with actin. Actin was
detected by coomassie blue at 42 kDa.
Western blots: The levels of TIMP-4 were specifically measured
by Western-blot analysis using anti-TIMP-4 antibody (Chemicon Corp). Intrinsic
activation of MMP produces soluble collagen fragments. Collagen-degradation was
measured by immuno-blot analysis using anti-collagen antibody (Sigma Chemical
Co). Cardiac extracts were prepared. The LV extracts were loaded onto reducing
SDS-PAGE. The gels were transferred onto nitrocellulose membrane. The membranes
were blotted with anti-TIMP-4 antibody (1:200) or anti-collagen antibody
(1:150). To detect the labeling, secondary antibody conjugated with alkaline
phosphatase was used. The bands below 100 kDa for alpha chain of collagen were
identified as collagen breakdown fragments.15 The scanned value of
3/4 fragment was used as measure of collagen degradation.
Expression of MMP-2 and TIMP-4: The mRNA analysis of cardiac MMP-2 and TIMP-4
was performed at days 1, 4, and 12 following coronary ligation and sham
operation at day 12 by Northern-blots as described.29 The
plasmid-containing collagenase IV cDNA probe was obtained from ATCC. The cDNA
probe for MMP-2 was 2.119 kb and was isolated by EcoRI enzyme digestion. The
mRNA levels for TIMP-4 were analyzed by Northern-blot using cDNA probe isolated
from RT-PCR. Primers for TIMP-4 were: sense 5'-GTGACGAGAAGGAGGTGGATTCC and
anti-sense 5'-CTTGATGCAGGCAAAGAACTTGGC (GenBank No. U76456). Isolated cDNA was
radio-labeled by random primer labeling using [32P]ATP and used as a
probe for mRNA labeling. A 4.5 kb EcoRI fragment of 18SR gene (a gift from Dr.
R. Guntaka) was used as an internal control. Same blots were stripped and
reprobed for different mRNA analysis.
Statistical Analysis: Because the data in each experimental group was
collected from different animals (ie, sham; sham+M; MI; and MI+M), the
significance of data between the groups was determined using a 2-way ANOVA
analysis of variance. In each group, a minimum of six animal data was used to
determine the significance. The SEM and mean are reported.
oxidative stress, and cardiac injury after MI: The LV and RV weights/body weight ratios were
increased in MI. Metoprolol had no significant effect on LV and RV weights/body
weight (Table 1). There was robust increase in the oxidative thiols in the MI
group. The treatment with metoprolol decreases the levels of oxidative stress
(Table 1). To determine the degree of cardiac muscle injury, plasma levels of
CK MB activity after MI were measured. Day 1 after MI, CK MB levels were
minimal. However, day 12 CK MB as well as MM and BB were increased. This
suggested severe tissue injury after MI (Figure 1). The treatment with
metoprolol decreases cardiac injury by reducing CK MB activity (Table 1).
MMP-2 and TIMP-4 after MI: The levels of TIMP-4 were elevated at day 1
after MI (Figure 2). TIMP-4 was induced early in response to ischemic insult.
The results may suggest compensatory response of TIMP-4 after MI. However, at
days 4 through 12 MMP-2/TIMP-4 ratio increased significantly (P < .01) in the MI group compared
with the sham control (Figure 2). The treatment with metoprolol decreases
MMP-2/TIMP-4 ratio after MI (Table 2). The MMP-2 expression was decreased in MI
rats treated with metoprolol for 12 days (data not shown). The metoprolol had
no significant effect on sham animals (Table 2).
Collagen degradation: To determine whether interstitial fibrillar
collagen is degraded after MI, collagenolytic activity was determined by
measuring 3/4 and 1/4 collagen fragments in cardiac tissue homogenates at 12
days after MI. Results suggested collagen degradation after MI. The generation
of these fragments was inhibited in rats treated with metoprolol after MI
(Figure 3). MMP-2 and TIMP-4 activity was measured by zymography and Western
blot analysis, respectively (Figure 4). The levels of TIMP-4 protein did not
change significantly in either groups compared with sham controls. MMP-2
activity at 66 and 72, and MMP-9 at 92 kDa was increased significantly after MI
(P < .05). The activity at 66 and
72 kDa MMP was significantly decreased in rats treated with metoprolol (P < .05). However, there was no
significant effect of metoprolol on MMP activity at 92 kDa (P > .05; Figure 5).
Hemodynamic and cardiac function: MI rats with >10 mg/mL of plasma CK MB activity demonstrated
significant alterations in hemodynamic and LV function (Tables 1 and 2).
Arterial pressure was reduced in rats with MI. Metoprolol has no significant
effect on MAP but decreases heart rate in MI rats compared with controls (Table
1). LV function, -dP/dt, and end-diastolic pressure were impaired after MI and
improved following metoprolol treatment (Table 2). Based on MMP activity and LV
function, a relationship between (-dP/dt)/MAP versus levels of MMP-2/TIMP-4
ratio was delineated (Figure 6). The cardiac MMP-2/TIMP-4 ratio was reduced, from
1.10 + 0.17 in the MI group to 0.61 + 0.08 in the MI+M group.
This decrease was associated with improved LV function by metoprolol.
Our results suggest that the b-blocker prevents oxidative damage to the
myocardium and alters ventricular loading conditions so that the stimulus for
remodeling was attenuated. There is an association between b-blocker, oxidative stress, and MMP-2 activity.
Metoprolol decreases MMP-2 in virtue of an antioxidant effect, and the decrease
of oxidative stress and MMP-2 were parallel.
three creatine phosphokinase isoforms (BB, MB, MM) were induced after MI
(Figure 1). These enzymes are also induced in hypertrophic heart disease.26,30
In humans, the functional exercise capacity of survivors of MI patients was
inversely related to serum creatine phosphokinase.31,32 Our results
suggested that treatment with metoprolol decreases the levels of CK isoenzymes
and reduces the cardiac injury after MI.
and colleagues33 treated MI mice with either a placebo or nonspecific
MMP inhibitor. The results were mixed in that both groups had mice that
experienced no change (30% of placebo versus 18% receiving drug), an increase
(50% placebo versus 30% drug), or a decrease (20% placebo and 52% drug) in the
chamber area. Unfortunately, infarct size was not measured in that study and
one could never be certain that the differences between the two groups were not
the result of variations in infarct size. Peterson and coworkers34
have demonstrated that some MMPs were significantly elevated during the first
week after MI and another was not until 16 weeks after MI. Previously in the
human heart15 a dissociation was demonstrated between LV MMP/TIMP
mRNA and protein levels, suggesting posttranslational processing after MI in
which MMP is activated. Cleutjens and colleagues,35 using a rat
model of MI, demonstrated that TIMP-1 mRNA was increased 6 hours after coronary
ligation and reached a maximum level on day 2, remaining high by day 7. They
also showed that mRNA for MMP-1 was transiently induced only at day 7 after MI.
Our data suggest that MMP-2 induced between days 4 and 7 after MI and
cardiospecific TIMP-436 induced day 1 up to day 12 (Figure 2). MMP-2
activity increased and TIMP-4 protein levels remained constant up to 2 weeks
after MI (Figure 4), suggesting an increased MMP-2/TIMP-4 ratio after MI.
significant fibrosis in both ventricles after MI, collagen content is reduced
and collagen is continuously being degraded in 3- to 8-month-old infarcted rat
heart.37 Since rat heart does not contain MMP-138 and
MMP-2 degrades interstitial collagen,39 we analyzed degradation of
cardiac collagen into 3/4 and 1/4 fragments. Results suggested collagen
degradation (Figure 3) and activation of MMP-2 in MI heart (Figure 4). A
48-hours tachypacing model in dogs showed that increased LV chamber stiffness
and increased gelatinase activity can be inhibited by b-blockade.40 However, this study did
not elucidate the interplay of oxidative stress, MMP-2 and -9 activation,
levels of TIMP-4, and collagenolysis in regard to cardiac function. To
determine whether MMP activity and collagen degradation in MI heart can be
inhibited by metoprolol, we analyzed cardiac extracts from MI rats treated with
metoprolol. Results suggested that metoprolol was able to inhibit
collagenolytic activity after MI (Figure 3 and 4). Rats on metoprolol showed
reduced MMP-2 activity (Figures 4 and 5). The levels of TIMP-4 did not change
significantly by metoprolol treatment (Table 2). Cardiac MMP-2 at 66 and 72 kDa
(ie, gelatinase a) were inhibited in metoprolol treated rats, and there was no
effect on gelatinase b (92 kDa; Figure 5, Table 2), suggesting that metoprolol
treatment decreases MMP-2/TIMP-4 ratio after MI.
humans, serum levels of MMP-1 and TIMP-1 were negatively correlated to left
ventricle end-systolic volume index.41 A negative relationship
between cardiac MMP-2/TIMP-4 ratio and cardiac index, (-dP/dt)/MAP, in a rat
model of MI is shown in Figure 6, suggesting activation of MMP may be one of
the causes of cardiac dysfunction after MI, and metoprolol improves cardiac
index in part by inhibiting MMP.
Perspective: A study of the treatment of animal with
catecholamine demonstrated collagenolysis and LV dilatation.18 Our
results suggest that MMP-2/TIMP-4 ratio is reduced in the metoprolol group
compared with MI and may in part be responsible for the improvement of cardiac
function. However, it does not differentiate whether MMP inhibition by
metoprolol is, in part, due to its effect on the reduction of blood pressure or
decreased levels of norepinephrine. It would be of great interest to determine
whether other b-blockers, independent of lowering blood
pressure, and antioxidants improve cardiac function by inhibiting extracellular
matrix (ECM) remodeling. These studies are in progress.
1. Plasma creatinine phosphokinase isoform in sham control and day 1
and 12 following ligation: Lanes 1 and 2 are plasma from rats on day 12
following ligation. Lane 3 is standard CK isoforms. Lanes 4 through 7 are day 1
after ligation. Lanes 8 through 11, plasma from sham controls. CK MM
(skeletal), MB (cardiac) and BB (nerve and kidney) activity was analyzed on
agarose gel electrophoresis using kinase substrate as described in Materials
2. Northern-blot analysis of
temporal changes in MMP-2 and TIMP-4 mRNA following MI: Lane 1, sham surgery;
lane 2, 1 day after creation of MI; lane 3, 4 days after MI; and lane 4, 12
days after MI. The 18S RNA was used as internal control. The size of transcript
was 3.5 kb for MMP-2 and 1.5 kb for TIMP-4.
3. Cardiac collagen degradation in tissue extract prepared from MI,
metoprolol treated, and sham rats: After SDS-PAGE immuno-blot was performed
using anti-collagen I antibody. Collagen 3/4 and 1/4 fragments are representative
of collagen degradation. Lanes 1 through 4, extracts from MI; lanes 5 through
6, metoprolol treated-MI; lane 7, sham. Relative amounts of collagen-degraded
fragments are reported on top of the blot.
4. Zymographic and Western-blot
analysis of MMP-2 and TIMP-4, respectively, in cardiac tissue extracts from
lane 1, sham; lanes 2 through 5, MI; and lanes 6 and 7, MI rats treated with
metoprolol for 2 weeks. Actin was used as internal control. Molecular weight
marker for MMP are shown on the right.
5. Histographic presentation of MMP 66 kDa, 72 kDa, and 92 kDa in
the sham, MI, and MI+metoprolol groups: The bands from zymographic gels were
scanned. To minimize gel-to-gel variation, a standard gelatinase was loaded
onto each gel. The intensity (arbitrary unit) was compared with standard
gelatinase and was normalized for actin. The mean + SEM is reported.
6. A correlation between MMP-2/TIMP-4 ratio versus active cardiac
diastolic function, (-dD/dt)/MAP (r = 0.90; P
= .01): Cardiac function in sham, sham+M, MI, and MI plus metoprolol, was
recorded. The MMP-2 and TIMP-4 activity (intensity) was measured in cardiac
tissue homogenates prepared from respective animals. Data from all groups were
combined. The metoprolol group is on the left. The mean + SEM is
1. Body, LV and RV weights, cardiac tissue reduction-oxidation
(redox)-thiols, hemodynamic parameters, and activity of plasma creatine
phosphokinase cardiac isoform (CK MB) in sham, sham + M, MI, and MI + M groups
of rats at day 12: Each rat was anesthetized by Inactin (100 mg/kg
intraparitoneal). Heart rate (HR), mean arterial pressure (MAP), systolic blood
pressure (SBP), and diastolic blood pressure (DBP) were measured. After
hemodynamic and cardiac function measurements, tissue was isolated and MI was
identified. The mean + SEM are reported.
Sham Sham+M MI MI+M
n 6 6 6 6
Body Weight (BW), g 392+9 385+12 335+34 313+47
Left Ventricle Weight (LVW), g 0.86+0.04 0.85+0.02 0.85+0.05 0.84+0.07
Right Ventricle Weight (RVW), g 0.19+0.03 0.18+0.04 0.18+0.03 0.16+0.06
LVW/BW, x 103 2.19+0.04 2.20+0.06 2.54+0.05 2.68+0.07
RVW/BW, x 103 0.48+0.03 0.47+0.02 0.54+0.03 0.51+0.06
% MI 0-5% 0-5% 27.6+9.3 18.4+6.0*
Redox-thiols, mg/mg of tissue 0.066+0.050 0.06+0.02 0.095+0.02 0.055+0.01*
of plasma 0.010+0.008 0.011+0.006 12.5+2.7 4.8+1.2*
MAP, mm Hg 111+3 109+8 99+16 89+21
HR, beats/min 339+13 331+9 310+43 256+28*
SBP, mm Hg 135+8 132+6 126+16 108+27
DBP, mm Hg 93+3 91+7 83+12 72+17
*P value was < .05 when MI+M group was compared
with MI group.
2. Cardiac MMP activity at 66, 72, and 92 kDa, TIMP-4 (arbitrary
unit), end-diastolic pressure (EDP) and cardiac output, (-dP/dt)/MAP of sham,
sham+M, MI and MI+M groups of rats: Each rat was anesthetized with Inactin (100
mg/kg, intraparitoneal). Left ventricle-EDP and -dP/dt were measured. The mean +
SEM are reported.
Sham Sham+M MI MI+M
n 6 6 6 6
MMP-2; 66 kDa 0.04
+ 0.02 0.03 + 0.01 0.57 + 0.02 0.25 + 0.03*
MMP-2; 72 kDa 0.28
+ 0.08 0.24 + 0.03 0.67 + 0.07 0.38 + 0.08*
MMP-9; 92 kDa 0.01
+ 0.01 0.01 + 0.01 0.06 + 0.07 0.09 + 0.11
+ 0.04 0.55 + 0.06 0.62 + 0.05 0.62 + 0.07
Cardiac Diastolic Function
(-dP/dt)/MAP, sec-1 45+9 46+6 30+3 39+4*
EDP, mm Hg 4+1 3.85+0.95 13+2 9.9+1.0*
*P value was < .05 when the MI+M group was
compared with MI group.
1. Belch JJF, Chopra M, Hutchinson S, et al:
Free radical pathology in chronic arterial disease. Free Radical Biol Med 6:375-378, 1989.
2. Babior BM: NADPH oxidase: An update. Blood 93:1464-1476, 1999.
3. McCord JM, Fridovich I: Superoxide dismutase:
An enzymatic function for erythrocuprein (hemocuprein). J Biol Chem 244:6049-6055, 1969.
4. Lawrence RA, Burk RF: Species, tissue and
subcellular distribution of selenium dependent, glutathione peroxidase
activity. J Nutr 108:211-215, 1978.
5. Ross D, Wening RS, Wyss SR: Protection of
human neutrophils by endogenous catalase: Studies with cells from
catalase-deficient individuals. J Clin
Invest 65:1515-1522, 1980.
6. Zweier HL, Flaherty JT, Weisfelt ML: Direct
measurement of free radical generation following reperfusion of ischemic
myocardium. Proc Natl Acad Sci (USA)
7. Laycock SK, McMurray J, Kane KA, Parratt JR:
Effects of chronic norepinephrine administration on cardiac function in rats. J Cardiovasc Pharmacol 26:584-589, 1995.
8. Givertz MM, Colucci WS: New targets for
heart-failure therapy: Endothelin, inflammatory cytokines, a oxidative stress. Lancet 352:SI34-SI38, 1998.
9. Chen CY, Huang YL, Lin TH: Association
between oxidative stress and cytokine production in nickel-treated rats. Arch Biochem Biophys 15:356(2):127-132,
10. Tyagi SC, Smiley LM, Mujumdar VS, et al:
Reduction-oxidation (redox) and vascular tissue level of homocyst(e)ine in
human coronary atherosclerotic lesions and role in vascular extracellular
matrix remodeling and vascular tone. Mol
Cell Biochem 181:107-116, 1998.
11. Varin R, Mulder P, Tamion F, et al:
Improvement of endothelial function by chronic ACEI in heart failure: Role of
NO, prostanoids, oxidant stress and bradykinin. Circulation 102:351-356, 2000.
12. Zhang H, Schmeisser A, Garlichs CD, et al:
Angiotensin II-induced superoxide anion generation in human vascular
endothelial cells: Role of membrane-bound NADH/NADPH-oxidases. Cardiovasc Res 44:215-222, 1999.
13. Tyagi SC, Kumar SG, Banks J, Fortson W:
Co-expression of tissue inhibitor and matrix metalloproteinase in myocardium. J Mol Cell Cardiol 27:2177-2189, 1995.
14. Tyagi SC, Ratajska A, Weber KT: Myocardial
matrix metalloproteinases: Localization and activation. Mol Cell Biochem 126:49-59, 1993.
15. Tyagi SC, Kumar SG, Haas SJ, et al:
Posttranscriptional regulation of matrix metalloproteinase in human heart
end-stage failure secondary to ischemic cardiomyopathy. J Mol Cell Cardiol 28:1415-1428, 1996.
16. Streeten DH, Anderson GH: Secondary
hypertension: An overview of its causes and management. Drugs 43:805-819, 1992.
17. Senzaki H, Gluzband YA, Pak PH, et al:
Synergistic exacerbation of diastolic stiffness from short-term
tachycardia-induced cardiodepression and angiotensin II. Cir Res 82:503-512, 1998.
18. Illyes G, Hamar J, Tanka D: Myocardial
collagen degradation: Morphological and biochemical correlation. Acta Biol Hungar 42:275-283, 1991.
19. Movahed A, Reeves WC, Mehta PM, et al:
Norepinephrine-induced left ventricular dysfunction in anesthetized and
conscious, sedated dogs. Intern J Cardiol
20. Mak IT, Weglicki WB: Protection by beta
blocking agents against free radical-mediated sarcolemmal lipid peroxidation. Cir Res 63:262-266, 1988.
21. Mak IT, Kramer JH, Freedman AM, et al:
Oxygen radical-mediated injury of myocyte-protection by propranolol. J Mol Cell Cardiol 22:687-695, 1990.
22. Ruffolo RR, Feuerstein GZ: Neurohormonal
activation, oxygen free radicals, and apoptosis in the pathogenesis of
congestive heart failure. J Cardiovasc
Pharmacol 32(Suppl I):S22-S30, 1998.
23. MERIT-HF Study Group: Effect of metoprolol
CR/XL in chronic heart failure: Metoprolol CR/XL randomised intervention trial
in congestive heart failure (MERIT-HF). Lancet
24. Puleo PR: Sensitive, rapid assay of subforms
of creatine kinase MB in plasma. Clin
Chem 35:1452-1455, 1989.
25. Puleo PR, Meyer D, Wathen C, et al: Use of a
rapid assay of subforms of creatine kinases MB to diagnose or rule out acute
myocardial infarction. N Engl J Med
26. Mujumdar VS, Tyagi SC: Temporal regulation
of extracellular matrix components in transition from compensatory hypertrophy
to decompensatory heart failure. J
Hypertension 17:261-270, 1999.
27. Tyagi SC, Hayden MR, Hall JE: Role of
angiotensin in angiogenesis and cardiac fibrosis in heart failure, in Dhalla
NS, Zahradka P, Dixon IMC, Beamish RE (eds): Angiotensin II Receptor Blockade: Physiological and Clinical
Implications. Boston, Kluwer Academic Publishers, Progress in Experiential Cardiology 2:537-549, 1998.
28. Buelke SJ, Holson JF, Bazare JJ, Young JF:
Comparative stability of physiological parameters during sustained anesthesia
in rats. Lab Anim Sci 28:157-162,
29. Tyagi SC, Kumar SG, Cassatt S, Parker JL:
Temporal expression of extracellular matrix metalloproteinase and tissue
plasminogen activator in the development of collateral vessels in canine model
of coronary occlusion. Can J Physiol
Pharmacol 74:983-995, 1996.
30. Hina K, Kusachi S, Iwasaki K, et al: Use of
serum creatine kinase MM isoforms for predicting the progression of LV dilation
in patients with hypertrophic cardiomyopathy. Jpn Circulation J 61:315-322, 1997.
31. Carter CL, Amundsen LR: Infarct size and
exercise capacity after myocardial infarction. J Appl Physiol 42:782-785, 1977.
32. Dangas G, Mehran R, Peterson MA, et al.
Post-procedure CKMB enzyme elevation and baseline left ventricular dysfunction
are additive predictors of late mortality after percutaneous coronary
intervention. Circulation 100(18):I-779,
33. Rohde LE, Ducharme A, Arroyo LH, et al: MMP
inhibitors attenuates early LV enlargement in experimental MI in mice. Circulation 99:3063-3070, 1999.
34. Peterson JT, Li H, Dillon L, Bryant JW:
Evolution of matrix metalloproteinase and tissue inhibitor expression during
heart failure progression in the infarcted rat. Cardiovasc Res 46(2):307-315, 2000.
35. Cleutjens JP, Kandala JC, Guardo E, et al:
Regulation of collagen degradation in the rat myocardium after infarction. J Mol Cell Cardiol 27:1281-1292, 1995.
36. Leco KJ, Apte SS, Taniguchi GT, et al:
Murine tissue inhibitor of metalloproteinase-4 (TIMP-4): cDNA isolation and
expression in adult mouse tissues. FEBS
Lett 410:213-217, 1997.
37. Takahashi S, Barry AC, Factor SM: Collagen degradation
in ischemic rat hearts. Biochem J
38. Vincenti VP, Coon CI, Mengshol JA, et al:
Cloning of the gene for interstitial collagenase-3 (MMP-13) from rabbit
synovial fibroblasts: Differential expression with collagenase-1 (MMP-1). Biochem J 331:341-346, 1998.
39. Aimes RT, Quigley JP: MMP-2 is an
interstitial collagenase. J Biol Chem
40. Sensaki H, Paolocci N, Gluzband Y, et al:
ß-blockade prevents sustained metalloproteinase activation and diastolic
stiffening induced by angiotensin II combined with evolving cardiac
dysfunction. Circ Res 86:807-815,
41. Hirohata S, Kusachi S, Murakami M, et al:
Time dependent alterations of serum MMP-1 and TIMP-1 after successful
reperfusion of acute MI. Heart