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The Journal of Neuroscience, September 15, 2000, 20(18):7037-7042
Effects of Matrix Metalloproteinase-9 Gene Knock-Out on
Morphological and Motor Outcomes after Traumatic Brain Injury
Xiaoying
Wang1,
JaeChang
Jung2,
Minoru
Asahi1,
Wilson
Chwang1,
Laoti
Russo2,
Michael A.
Moskowitz3,
C. Edward
Dixon4,
M. Elizabeth
Fini2, and
Eng H.
Lo1
1 Neuroprotection Research Laboratory, Departments of
Neurology and Radiology, Massachusetts General Hospital, and Program in
Neuroscience, Harvard Medical School, Charlestown, Massachusetts 02129, 2 Vision Research Laboratories, New England Eye Center,
Tufts University School of Medicine, Boston, Massachusetts,
3 Stroke and Neurovascular Regulation Laboratory,
Massachusetts General Hospital, Harvard Medical School, Charlestown,
Massachusetts, and 4 Brain Trauma Research Center,
Department of Neurological Surgery, University of Pittsburgh,
Pittsburgh, Pennsylvania
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ABSTRACT |
Matrix metalloproteinases (MMPs) belong to a class of extracellular
proteinases responsible for maintaining and remodeling the
extracellular matrix. In addition to multiple functions in normal
physiology, abnormal MMP expression and activity may also participate
in the pathophysiology of cerebral disease. Here, we show that MMP-9
(gelatinase B; EC.3.4.24.35) contributes to the pathophysiology
of traumatic brain injury. After controlled cortical impact in mice,
MMP-9 was increased in traumatized brain. Total MMP-9 levels at 24 hr
were significantly increased as measured by a substrate cleavage assay.
Zymograms showed that MMP-9 was elevated as early as 3 hr after
traumatic brain injury, reaching a maximum at ~24 hr. Increased MMP-9
levels persisted for up to 1 week. Western blot analysis indicated
increased profiles of MMP-9 expression that corresponded with the
zymographic data. Knock-out mice deficient in MMP-9 gene expression
were compared with wild-type littermates in terms of morphological and
motor outcomes after trauma. Motor outcomes were measured at 1, 2, and 7 d after traumatic brain injury by the use of a rotarod device. MMP-9 knock-out mice had less motor deficits than wild-type mice. At
7 d, traumatic brain lesion volumes on Nissl-stained histological sections were significantly smaller in MMP-9 knock-out mice. These data
demonstrate that MMP-9 contributes to the pathophysiology of traumatic
brain injury and suggest that interruption of the MMP proteolytic
cascade may be a possible therapeutic approach for preventing the
secondary progression of damage after brain trauma.
Key words:
brain trauma; controlled cortical impact; extracellular
matrix; proteolysis; neurodegeneration; mouse
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INTRODUCTION |
Matrix metalloproteinases (MMPs)
form a family of zinc-dependent endopeptidases that are collectively
able to degrade or modify essentially all components of the
extracellular matrix (Nagase and Woessner, 1999 ). Target substrates
include collagens, gelatin, fibronectin, laminin, elastin, and
proteoglycans. Because MMPs can rapidly degrade critical protein
components in the extracellular matrix, their biological activity is
strictly regulated (Fini et al., 1998; Westermarck and Kahari, 1999).
Primary modes of regulation occur via gene transcription, proenzyme
activation, and dynamic inhibition by tissue inhibitors of
metalloproteinases. MMPs participate in a wide array of
important physiological processes including embryological remodeling,
wound healing, angiogenesis, bone remodeling, ovulation, and
implantation. Considering their central involvement in normal biology,
it is not surprising that overactivity of MMPs is also involved in
diverse disease processes (Lukashev and Werb, 1998). In the CNS,
MMPs have been implicated in degenerative disorders such as multiple
sclerosis and Alzheimer's disease (Yong et al., 1998). More recently,
evidence is accumulating to show that MMPs can be involved in acute
brain injury. MMP activity is upregulated after cerebral ischemia
(Rosenberg et al., 1996; Romanic et al., 1998; Gasche et al., 1999; Heo
et al., 1999) and edema (Morita-Fijimura et al., 1999).
In this study, we investigated the hypothesis that MMP-9 (gelatinase B;
EC.3.4.24.35) may be involved in the pathophysiological cascade
of neuronal damage after traumatic brain injury. This hypothesis was
tested by performing experiments using a standard controlled cortical
impact model of traumatic brain injury in mice. First, we documented
via enzyme activity assays, zymography, and Western blots that MMP-9
was upregulated after trauma. Then, we demonstrated that behavioral
motor deficits and cerebral lesion volumes were significantly reduced
in mutant mice with a targeted knock-out of the MMP-9 gene.
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MATERIALS AND METHODS |
Controlled cortical impact model of traumatic brain
injury. All experiments were performed following an
institutionally approved protocol in accordance with the NIH
Guide for the Care and Use of Laboratory Animals. For initial MMP
activity measurements, normal C57/B6 and CD1 mice were used. For all
other experiments, the MMP-9 knock-out strain and their corresponding
wild-type littermates (Vu et al., 1998) were used. The standard
controlled cortical impact model of traumatic brain injury (Dixon et
al., 1991; Smith et al., 1995; Whalen et al., 1999) was performed as
follows. Briefly, mice were anesthetized with 1-1.5% halothane in an
air/oxygen mixture via a face mask. An electronic thermostat-controlled
warming blanket was used to maintain the core temperature at 37.5°C.
Mice were placed into the head holder within the device, and a 5 mm craniotomy was performed over the right cerebral hemisphere between the
bregma and lambda by the use of a trephine drill, taking care to keep
the dura intact. A 3 mm flat-tipped impactor was placed on the dural
surface at a 20° angle, and injury was induced by the use of 4 m/sec
impact velocity, 1 mm impact depth, and 150 msec impact dwell time.
After traumatic brain injury, the bone flap was replaced over the
craniotomy, and mice were allowed to recover back in their cages.
Because the duration of the entire cortical impact procedure is ~10
min, it was believed that it was unnecessary to prolong
anesthesia/surgical time to insert catheters for measuring blood
pressure, pH, and gases. However, measurements from previous series
demonstrated that all physiological parameters remained within the
normal range for this model in our laboratory.
MMP activity assay. At 24 hr after traumatic brain
injury, mice were killed with a lethal overdose of sodium pentobarbital intraperitoneally and transcardially perfused with cold saline (4°C).
MMP-9 activity present in supernatants from brain homogenates was
measured by the use of a colorimetric antibody-specific
substrate cleavage method (Amersham Pharmacia Biotech, Piscataway,
NJ). Briefly, MMP-9 was captured in microtiter wells coated with
anti-MMP-9 antibody. Total MMP-9 activity is measured by converting
MMP-9 proforms into active forms by the use of
p-aminophenylmercuric acetate. Note that this method does
not distinguish between latent zymogen versus cleaved active forms of
the enzyme; therefore this assay measures total MMP-9 that can be
activated. MMP-9 enzyme activity was then assessed by cleavage of a
chromogenic peptide substrate (S-2444) and quantified at 405 nm with a
spectrophotometric plate reader (Bio-Tek Instruments).
Traumatized brains (n = 5) were compared with
sham-operated controls (n = 3).
MMP zymography. At 1 hr, 3 hr, 6 hr, 1 d, 3 d,
5 d, and 7 d after trauma, mice were killed with an overdose
of sodium pentobarbital (100 mg/kg, i.p.) and transcardially perfused
with chilled (4°C) PBS, pH 7.4. The brains were rapidly
removed, and damaged brain tissue within the traumatized hemisphere
(~100-150 mg) was homogenized in lysis buffer (50 mM
Tris-HCl, pH 7.4, 150 mM NaCl, 1% Nonidet P-40, 0.1%
SDS, and 0.1% deoxycholic acid) including protease inhibitors
(2 µg/ml leupeptin, 2 µg/ml aprotinin, and 1 mM PMSF) for 30 min on ice. The homogenate was then centrifuged at 14,000 × g for 10 min at 4°C. Protein concentrations in the
supernatants were measured with the Bradford assay (Bio-Rad, Hercules,
CA). Three brains were used per lane. Approximately 10 µg of each
sample was loaded per lane into the wells of precast gels (10%
polyacrylamide minigels containing 0.1% gelatin; Novex) with SDS
sample buffer (2×; Novex). Electrophoresis was performed with a
Tris-glycine running buffer at 125 V constant voltage for 1.5-2 hr.
The gel was removed and incubated for 1 hr at room temperature in 100 ml of 2.7% Triton X-100 on a rotary shaker. Each gel was incubated with 100 ml of development buffer (50 mM Tris
base, 40 mM HCl, 200 mM
NaCl, 5 mM CaCl2, and 0.2%
Brij 35; Novex) at 37°C for 14-18 hr on a rotary shaker. Staining
was performed with 100 ml of 0.5% Coomassie blue G-250 in 30%
methanol and 10% acetic acid for 1 hr, and gels were then destained
with three changes of solutions. Gelatinolytic activity was
demonstrated as clear zones or bands at the appropriate molecular
weights. Mouse MMP-9 and human MMP-2 (from Chemicon, Temecula, CA) were
used as standards.
Western blots. At 1 hr, 3 hr, 6 hr, 1 d, 3 d,
5 d, and 7 d after trauma, mice were killed with an overdose
of sodium pentobarbital (100 mg/kg, i.p.) and transcardially perfused
with chilled (4°C) PBS, pH 7.4. The brains were rapidly removed, and
supernatants from homogenates were prepared as described above for
Western blot analysis using a monoclonal antibody targeted toward the catalytic subunit of mouse MMP-9 (donated by Robert Senior, Washington University, St. Louis, MO). Three brains were used per lane.
Approximately 10 µg of each sample per lane was loaded onto 4-20%
Tris-glycine gels with equal volumes of SDS sample buffer (Novex) and
then transferred to polyvinylidene difluoride membranes (Novex).
Membranes were blocked for 1 hr at room temperature in PBS and 0.1%
Tween 20 with 10% low-fat dried milk and then incubated with
the primary anti-MMP-9 antibody for 1 hr at room temperature. After the
primary incubation, the membranes were washed and then incubated again with horseradish peroxidase-linked anti-rabbit IgG and developed by the
use of enhanced chemiluminescence (ECL; Amersham). Mouse MMP-9
(from Chemicon) was used as a standard.
Rotarod motor performance tests. To assess behavioral
deficits after traumatic brain injury, the standard rotarod test (Hamm et al., 1994) was performed at 1, 2, and 7 d after controlled cortical impact. All mice were initially trained on the rotarod for
2 d before the day of trauma. One hour before traumatic brain injury, mice were assessed on the rotarod to obtain preinjury baselines. Thereafter, all rotarod scores were expressed as a percentage of preinjury baselines to reduce interanimal variability. Scores were measured as the latency or time successfully spent running
on the rotating rod (35 rpm); 10-13 animals were measured for each
time point. A repeated measures ANOVA was used for multiple comparisons over time between wild-type littermates and MMP-9 knock-out
mice. Comparisons at each time point was performed by the use of
Fisher's PLSD test.
Traumatic lesion volume quantitation. After traumatic brain
injury, mice were allowed to survive for 7 d before being killed with a lethal overdose of sodium pentobarbital intraperitoneally. All
mice were transcardially perfused with chilled (4°C) PBS, pH 7.4, followed by 4% paraformaldehyde in 0.1 M PBS. The brains were rapidly removed and fixed in fresh paraformaldehyde solution overnight at 4°C and then stored in 30% sucrose and 0.1 M PBS. Brains were sectioned by the use of a freezing
microtome into 25-µm-thick coronal slices. Every 20th section was
mounted onto a glass slide and stained with 0.1% cresyl violet.
Histological lesion areas were quantified with a standard
computer-assisted image analysis program, and lesion areas were then
integrated to obtain total lesion volumes in cubic millimeters.
Differences between wild-type littermates (n = 11) and
MMP-9 knock-out mice (n = 9) were assessed with
two-tailed t tests.
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RESULTS |
MMP-9 is upregulated after traumatic brain injury
Traumatic brain injury induced via controlled cortical impact
resulted in significant elevations of MMP-9 protein levels. At 24 hr
after trauma, total enzyme measured by colorimetric detection of
substrate cleavage showed that MMP-9 levels were increased by almost
threefold compared with that in the contralateral cortex (Fig.
1). Interestingly, MMP-9 was slightly
elevated in contralateral brain as well, suggesting that after trauma,
perturbations in cerebral status was not restricted to the impacted
hemisphere alone and subtle mechanical- and biochemical-induced
alterations may propagate across to the opposite hemisphere (Fig. 1).
In sham-operated brains, the craniotomy procedure alone (without impact
trauma) also appeared to increase MMP-9 protein levels slightly,
although this did not reach statistical significance (Fig. 1).
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Figure 1.
MMP-9 enzyme activity (mean ± SEM) in C57/B6
mouse brain at 24 hr after trauma or sham operation. In sham-operated
controls (n = 3), no constitutive MMP-9 activity
was detected in the contralateral hemisphere. In the ipsilateral side,
the craniotomy procedure alone appeared to induce a slight elevation in
enzyme activity. However, this increase was not statistically
significant (p = 0.16). In mice subjected to
brain trauma (n = 5), MMP-9 activity was
significantly higher in the traumatized hemisphere
(*p < 0.05). Interestingly, however, MMP-9 enzyme
activity was also significantly elevated in the contralateral side
compared with that in the shams (p < 0.05).
CCI, Controlled cortical impact.
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Alterations in MMP-9 was assessed over the course of 1 week after
trauma by the use of zymography. MMP-9 levels in traumatized brain
appeared to be elevated beginning as early as 3 hr after trauma and
remained elevated for the entire 1 week period of analysis (Fig.
2A). MMP-9 was
primarily expressed as the higher molecular weight zymogen (105 kDa).
No clear evidence of the lower molecular weight cleaved (activated)
form of MMP-9 was observed. MMP-9 was not detected in normal brains
from unoperated mice, but sham-operated control brains subjected to
craniotomy alone appeared to show slight elevations in MMP-9 levels
(Fig. 2A). Faint bands of zymographic digestion were
also observed at a level close to that of the human MMP-2 standard (72 kDa), suggesting a possible presence of MMP-2 (gelatinase A)
activity.
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Figure 2.
A, Representative zymograms of
brain homogenates from wild-type CD1 mice. No constitutive MMP-9
activity was detected in normal brains from unoperated mice. Slight
induction of MMP-9 was detected in sham-operated controls at 24 hr
after craniotomy alone without brain trauma. In traumatized brain,
increased activity was present by 3 hr after cortical impact. Elevated
MMP-9 levels persisted until the last time point measured at 7 d
after trauma. Primarily MMP-9 zymogen (105 kDa) was detected, and only
faint bands were present for the cleaved active forms (97 kDa).
Controls included normal brains from unoperated mice, brains from
sham-operated mice subjected to craniotomy without cortical impact, the
mouse MMP-9 standard (Chemicon), and the human MMP-2 standard
(Chemicon). Samples derived from three brains were used per
lane. Slight induction of gelatinolytic activity was
also observed close to the human MMP-2 standard, suggesting a possible
induction of MMP-2 after trauma. Note that (1) mouse MMP-9 has a
higher molecular weight (105 kDa) than human MMP-9 (92 kDa) and (2)
human and mouse MMP-2 has a molecular weight of 72 kDa but is typically
detected at 65 kDa when run with a nonreducing buffer.
B, Western blots showing that protein expression of
MMP-9 is increased after brain trauma in CD1 mice. MMP-9 was not
detectable in either normal brains from unoperated mice or
sham-operated controls. In all cases, only MMP-9 zymogen was detected.
Samples derived from three brains were used for each
lane.
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Western blot analysis showed that MMP-9 protein in the brain was
increased beginning as early as 3 hr after trauma, with a maximum
occurring at ~24 hr. However, MMP-9 levels remained clearly elevated
for the entire 1 week experimental period (Fig. 2B). Once again, only the 105 kDa zymogen was seen, although the antibody recognizes both the zymogen and the cleaved forms of MMP-9 (R. Senior,
personal communication).
MMP-9-deficient knock-out mice are resistant to traumatic
brain injury
The motor response to traumatic brain injury in MMP-9 knock-out
mice was compared with that in wild-type littermates. Initial pretrauma
performance on the rotarod device seemed to suggest that the MMP-9
knock-outs had somewhat lower motor endurance compared with that of the
wild-type littermates, although the difference did not reach
statistical significance (latencies were 63 ± 12 sec for
knock-outs and 87 ± 14 sec for wildtypes; p = 0.21; Fig. 3A). However, to
normalize for this potential difference in pretrauma performance, all
post-trauma latencies were also calculated as a percentage of preinjury
baselines. After traumatic brain injury induced by controlled cortical
impact, rotarod performance was significantly reduced in all mice.
However, over 1, 2, and 7 d after injury, a repeated measures
ANOVA demonstrated that knock-out mice had significantly fewer deficits
compared with that of wild-type mice (p < 0.05;
Fig. 3).
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Figure 3.
Motor performance (mean ± SEM) on a rotarod
device after brain trauma expressed either as the absolute time in
seconds (A) or a percent of pretrauma latency
(B) on the rotating rod. After brain injury,
latencies were significantly reduced in all mice. A repeated measures
ANOVA showed that overall rotarod performance was significantly
improved in knock-outs (KO) versus wild-type littermates
(WT). However, single time point comparisons
showed significantly improved performance in the MMP-9 knock-out mice
versus wild-type littermates only at 2 d after trauma
(*p < 0.05). Although the average rotarod latency
was also improved in knock-outs at 1 and 7 d, the difference did
not reach statistical significance (p = 0.09 at day 1, p = 0.18 at day 7 for percentage
comparisons). This may be caused by the somewhat variable rotarod
response after trauma and the need for larger numbers of mice to
increase the statistical power (n = 10-13 per time
point).
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At 7 d after injury, traumatized brains showed well demarcated
lesions with cavitations comprising the cortex as well as underlying hippocampal structures (Fig.
4A). Parenchyma
immediately surrounding the necrotic cavitation also showed decreased
cresyl violet staining. Although hippocampal structures were disrupted,
neuronal loss could also be discerned in CA1 and CA3 regions that
remained. Overall traumatic lesion volumes were significantly smaller
in the MMP-9 knock-outs compared with wild-type littermates (7.44 ± 0.5 mm3 in wildtypes vs 5.67 ± 0.6 mm3 in knock-outs; p < 0.05; Fig. 4B).
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Figure 4.
A, Representative Nissl-stained
brain sections showing that MMP-9 knock-outs (KO) suffer
less brain injury compared with that in wild-type littermates
(WT) at 7 d after trauma. B,
Lesion volumes at 7 d after traumatic brain injury (in cubic
millimeters; mean ± SEM). MMP-9 KO
(n = 9) had significantly smaller lesion volumes
compared with that of WT (n = 11;
*p < 0.05).
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DISCUSSION |
In addition to primary damage induced by the initial mechanical
impact, secondary mechanisms of cell death can significantly contribute
to traumatic brain injury (McIntosh et al., 1998a,b). The progression
of nervous tissue damage after trauma involves a multifactorial cascade
of secondary pathophysiology including excitotoxicity (Hayes et al.,
1988; Faden et al., 1989; Palmer et al., 1993), oxidative stress
(Kontos and Povlishock, 1986), inflammation (Arvin et al., 1996), and
abnormal apoptosis (Rink et al., 1995; Colicos and Dash, 1996;
Pravdenkova et al., 1996; Clark et al., 1997; Crowe et al., 1997; Liu
et al., 1997; Yakovlev et al., 1997; Conti et al., 1998; Fox et al.,
1998; Kaya et al., 1999; Springer et al., 1999). However, in this
report, we demonstrate that upregulation of MMP-9 may participate in
the pathophysiology of traumatic brain injury. In normal mouse brain,
cortical impact injury induced a significant upregulation of MMP-9
levels as measured by a variety of methods including colorimetric
substrate cleavage assay, zymography, and Western blot analysis. The
role for MMP-9 was further explored by the use of knock-out mice
deficient in MMP-9 gene expression. These studies suggested that MMP-9
may play a deleterious role in traumatic brain injury because knock-out mice had significantly smaller lesions compared with that in wild-type littermates. Importantly, motor deficits measured by the use of a
rotarod device also showed that MMP-9 knock-out mice had less behavioral injury compared with that in the wild-type mice.
As expected, no significant MMP-9 was detectable in normal brain,
consistent with the understanding that MMP-9 is not constitutively expressed in mammalian brain (Rosenberg et al., 1996; Gasche et al.,
1999; Heo et al., 1999). However, after traumatic brain injury, MMP-9
levels were observed to increase as early as 3 hr after injury,
reaching an apparent maximum at ~24 hr and remaining elevated for up
to 1 week. It will be important to document carefully the temporal
profile of MMP-9 levels over longer periods of time in future studies
to understand fully its contribution to long-term pathophysiology.
Long-term changes have been described after traumatic brain injury
(Dixon et al., 1999) so chronic MMP activity may be involved. Although
the results of our study make a mechanistic connection between
increased levels of MMP-9 protein and brain tissue damage, we have not
directly measured proteolytic activity. Therefore, we cannot say
whether tissue damage is caused by proteolysis by MMP-9 or whether some
undocumented activity of MMP-9 is involved. The MMP-9 protein detected
by the various methods used in this study was the 105 kDa proenzyme
form; none of the truncated forms of the enzyme associated with
proteolytic activity in vitro was detectable. This in
vivo finding is often reported (Matsubara et al., 1991; Fini et
al., 1996; Mohan et al., 2000) and is not inconsistent with
functionality of MMP-9 as a protease. A number of studies suggest that
enzymatic activation of MMP-9 proenzyme occurs by binding at the cell
surface and that activated enzyme is then rapidly degraded (Yu and
Stamenkovic, 1999). Therefore, little active MMP-9 may be present in
tissue at any given time.
Our zymographic data showed that after traumatic brain injury, the
primary gelatinase elevated was MMP-9. Faint zones of activity were
observed at a level close to that of the human MMP-2 standard (72 kDa),
suggesting that small elevations in MMP-2 may also occur in our model.
This is in contrast to studies of cerebral ischemia in which large
elevations in MMP-2 activity were observed (Rosenberg et al., 1996;
Romanic et al., 1998; Gasche et al., 1999; Heo et al., 1999). Although
traumatic brain injury shares many common pathways with cerebral
ischemia, there are critical differences in pathophysiology (McIntosh
et al., 1998a,b), and the present data are consistent with this idea.
On the other hand, focal regions of tissue ischemia can accompany
traumatic brain injury (Bryan et al., 1995; Dietrich et al., 1998) so
common upstream triggers of MMP upregulation may also be involved.
Although the present data suggest that MMP-9 contributes to brain
damage after trauma, the precise mechanisms involved remain to be
defined. In cerebral ischemia, an emphasis has been placed on the fact
that MMP-9 can digest matrix proteins present in the vascular basal
lamina including collagen, fibronectin, and laminin. Damage to vascular
integrity would then lead to disrupted blood-brain barrier function
and increased vasogenic edema (Rosenberg et al., 1996; Gasche et al.,
1999; Heo et al., 1999). Because edema can play a critical role in
traumatic brain injury, this specific pathway may be involved here as
well. However, it is important to recognize that matrix proteins such
as laminin are also widely disseminated throughout the brain
parenchyma, and loss of parenchymal laminin may affect cell-matrix
interactions and cell survival (Hagg et al., 1989; Murtomaki et al.,
1995; Chen and Strickland, 1997; Tsirka et al., 1997). Therefore, it
remains conceivable that MMP-mediated matrix protein degradation may
disrupt cell-matrix interactions beyond the vascular compartment as
well and further contribute to neuronal cell death. It must be
acknowledged, however, that laminin can be degraded by other enzymes
[e.g., plasmin (Tsirka et al., 1997)]. Cascades of extracellular
proteolysis after traumatic brain injury may involve other proteases
besides MMPs.
There are a few caveats associated with the present study. First, we
measured traumatic lesion volumes at a relatively early time point (1 week) after cortical impact. We cannot exclude the possibility that
long-term effects may occur that overwhelm the acute protective effects
of MMP-9 gene knock-out. It has been shown that degenerative and/or
regenerative processes may extend for periods up to a year after
traumatic brain injury (Dixon et al., 1999). During these prolonged
periods, MMPs may play critical roles in cerebral reorganization. The
possibility of biphasic responses to traumatic brain injury has been
demonstrated recently in the tumor necrosis factor- (TNF-) and
TNF receptor-deficient mutant mice, in which absence of the gene
appeared to protect the brain during acute time frames but retard
functional recovery during prolonged periods after injury (Scherbel et
al., 1999; Sullivan et al., 1999). Second, we only used a primarily
motor behavioral task (i.e., the rotarod assay). It is known that
cognitive and/or memory deficits are an important part of the
controlled cortical impact model of traumatic brain injury (Dixon et
al., 1999). Indeed, we find that lesion volumes tend to include
extensive destruction of hippocampal structures, especially in the
wild-type mice. It will be important to determine whether cognitive
deficits are also improved by MMP-9 gene deletion; these studies are
being pursued in our laboratory presently. Third, we do not have data on the cell types that serve as sources for MMP-9. It is known that
macrophages and neutrophils can be an important source for MMPs and
other deleterious proteases (Pagenstecher et al., 1998), and
inflammatory macrophage and neutrophil infiltration is clearly an
important event after trauma (Carlos et al., 1997; Bethea et al., 1998;
Chatzipantelli et al., 2000). However, it has been shown that resident
brain cells (neurons, astrocytes, and oligodendrocytes) can also
produce MMPs (Gottschall and Deb, 1996; Zuo et al., 1998; Oh et al.,
1999). It will be important to define carefully the cellular sources of
deleterious MMP activity after traumatic brain injury. Finally, the MMP
family comprises many other members besides MMP-9. MMPs (along with
plasminogen activators) form a protease cascade that bears some
similarity to the caspase cascade in terms of amplifying cell death
(Cuzner and Opdenakker, 1999). Much like the caspase cascade in which
caspase-3 may be a possible final executioner, it has also been
proposed that MMP-9 may be a terminal member of the MMP cascade (Cuzner
and Opdenakker, 1999). Nevertheless, it will be critical to assess the
roles for more upstream MMPs by the use of other specific antibodies
and knock-out mouse models.
In conclusion, the present study demonstrated that MMP-9 activity was
increased in a mouse model of traumatic brain injury, and knock-out
mice deficient in MMP-9 gene expression showed reduced morphological
damage and motor deficits compared with that in wild-type mice. These
data demonstrate that MMP-9 contributes to the pathophysiology of
traumatic brain injury. Interrupting the MMP cascade may be a relevant
therapeutic approach for preventing the devastating progression of
secondary injury.
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FOOTNOTES |
Received April 28, 2000; revised June 14, 2000; accepted June 26, 2000.
This work was funded in part by National Institutes of Health Grants
R01-NS37074, R01-NS38731, R01-NS40529, and R01-EY12651. M.E.F. is a
Stein Research to Prevent Blindness Professor. We thank Drs. Robert
Senior and J. Michael Shipley for kindly donating the anti-mouse MMP-9
antibody and for permission to use the MMP-9 knock-out mouse in these
studies. Drs. Michael Schwartzchild and Jiang-Fan Chen provided
critical advice on the rotarod motor test, and we are grateful to Dr.
Michael Whalen for critical discussions on the pathophysiology of
traumatic brain injury.
Correspondence should be addressed to Dr. Eng H. Lo, Neuroprotection
Research Laboratory, Departments of Neurology and Radiology, Harvard
Medical School, Massachusetts General Hospital East 149-2322, Charlestown, MA 02129. E-mail: Lo{at}helix.mgh.harvard.edu.
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REFERENCES |
-
Arvin B,
Neville LF,
Barone FC,
Feuerstein GZ
(1996)
The role of inflammation and cytokines in brain injury.
Neurosci Biobehav Rev
20:445-452[Web of Science][Medline].
-
Bethea JR,
Castro M,
Keane RW,
Lee TT,
Dietrich WD,
Yezierski RP
(1998)
Traumatic spinal cord injury induces nuclear factor kappa B activation.
J Neurosci
18:3251-3260[Abstract/Free Full Text].
-
Bryan RM,
Cherian L,
Robertson C
(1995)
Regional cerebral blood flow after controlled cortical impact.
Anesth Analg
80:687-695[Abstract].
-
Carlos TM,
Clark RSB,
Higgins DF,
Schiding JK,
Kochanek PM
(1997)
Expression of endothelial adhesion molecules and recruitment of neutrophils after traumatic brain injury in rats.
J Leukoc Biol
61:279-285[Abstract].
-
Chatzipantelli K,
Alonso OF,
Kraydieh S,
Dietrich WD
(2000)
Importance of posttraumatic hypothermia and hyperthermia on the inflammatory response after fluid percussion brain injury: biochemical and immunocytochemical studies.
J Cereb Blood Flow Metab
20:531-542[Web of Science][Medline].
-
Chen ZL,
Strickland S
(1997)
Neuronal death in the hippocampus is promoted by plasmin-catalyzed degradation of laminin.
Cell
91:917-925[Web of Science][Medline].
-
Clark RSB,
Chen J,
Watkins SC,
Kochanek PM,
Chen M,
Stetler RA,
Loeffert JE,
Graham SH
(1997)
Apoptosis-suppressor gene bcl-2 expression after traumatic brain injury in rats.
J Neurosci
17:9172-9182[Abstract/Free Full Text].
-
Colicos MA,
Dash PK
(1996)
Apoptotic morphology of dentate gyrus granule cells following experimental cortical impact injury in rats: possible role in spatial memory deficits.
Brain Res
739:120-131[Web of Science][Medline].
-
Conti AC,
Raghupathi R,
Trojanowski JQ,
McIntosh TK
(1998)
Experimental brain injury induces regionally distinct apoptosis during acute and delayed post-traumatic period.
J Neurosci
18:5663-5672[Abstract/Free Full Text].
-
Crowe MJ,
Bresnahan JC,
Shuman SL,
Masters JN,
Beattie MS
(1997)
Apoptosis and delayed degeneration after spinal cord injury in rats and monkeys.
Nat Med
3:73-76[Web of Science][Medline].
-
Cuzner ML,
Opdenakker G
(1999)
Plasminogen activators and matrix metalloproteinases, mediators of extracellular proteolysis in inflammatory demyelination of the central nervous system.
J Neuroimmunol
94:1-14[Web of Science][Medline].
-
Dietrich WD,
Alonso O,
Busto R,
Prado R,
Zhao W,
Dewanjee MK,
Ginsberg MD
(1998)
Posttraumatic cerebral ischemia after fluid percussion brain injury: an autoradiographic and histopathological study in rats.
Neurosurgery
43:585-593[Medline].
-
Dixon CE,
Clifton GL,
Lighthall JW,
Yaghmai AA,
Hayes RL
(1991)
A controlled cortical impact model of traumatic brain injury in the rat.
J Neurosci Methods
39:253-262[Web of Science][Medline].
-
Dixon CE,
Kochanek PM,
Yan HQ,
Schiding JK,
Griffith RG,
Baum E,
Marion DW,
DeKosky ST
(1999)
One year study of spatial memory performance, brain morphology, and cholinergic markers after controlled cortical impact injury.
J Neurotrauma
16:109-122[Web of Science][Medline].
-
Faden AI,
Demediuk P,
Panter SS,
Vink R
(1989)
The role of excitatory amino acids and NMDA receptors in traumatic brain injury.
Science
244:798-800[Abstract/Free Full Text].
-
Fini ME,
Parks WC,
Rinehart WB,
Girard MT,
Matsubara M,
Cook JR,
West-Mays JA,
Sadow PM,
Burgeson RE,
Jeffrey JJ,
Raizman MB,
Krueger RR,
Zieske JD
(1996)
Role of matrix metalloproteinases in failure to re-epithelialize after corneal injury.
Am J Pathol
149:1287-1302[Abstract].
-
Fini ME,
Cook JR,
Mohan R,
Brinckerhoff CE
(1998)
Regulation of matrix metalloproteinase gene expression.
In: Matrix metalloproteinases (Parks WC,
Mecham RP,
eds), pp 299-356. New York: Academic.
-
Fox GB,
Fan L,
Levasseur RA,
Faden AI
(1998)
Sustained sensory/motor and cognitive deficits with neuronal apoptosis following controlled cortical impact brain injury in the mouse.
J Neurotrauma
15:599-614[Web of Science][Medline].
-
Gasche Y,
Fujimura Y,
Copin J,
Kawase M,
Masengale J,
Chan PH
(1999)
Early appearance of activated MMP-9 after focal cerebral ischemia in mice.
J Cereb Blood Flow Metab
19:1020-1028[Web of Science][Medline].
-
Gottschall PE,
Deb S
(1996)
Regulation of matrix metalloproteinase expression in astrocytes, microglia and neurons.
Neuroimmunomodulation
3:69-75[Web of Science][Medline].
-
Hagg T,
Muir D,
Engvall E,
Varon S,
Manthorpe M
(1989)
Laminin antigens in rat CNS: distribution and changes upon brain injury.
Neuron
3:721-732[Medline].
-
Hamm RJ,
Pike BR,
O'Dell DM,
Lyeth BG,
Jenkins LW
(1994)
The rotarod test: an evaluation of its effectiveness in assessing motor deficits after traumatic brain injury.
J Neurotrauma
11:187-196[Web of Science][Medline].
-
Hayes RL,
Jenkins LW,
Lyeth BG,
Balster RL,
Robinson SE,
Clifton GL,
Stubbins JF,
Young HF
(1988)
Pretreatment with phencyclidine, an NMDA antagonist attenuates long term behavioral deficits in the rat produced by traumatic brain injury.
J Neurotrauma
5:259-274[Medline].
-
Heo JH,
Lucero J,
Abumiya T,
Koizol JA,
Copeland BR,
del Zoppo GJ
(1999)
Matrix metalloproteinases increase very early during experimental focal cerebral ischemia.
J Cereb Blood Flow Metab
19:624-633[Web of Science][Medline].
-
Kaya SS,
Mahmood A,
Li Y,
Yavuz E,
Goskel M,
Chopp M
(1999)
Apoptosis and expression of p53 proteins and cyclin D1 after cortical impact in rat brain.
Brain Res
818:23-33[Medline].
-
Kontos HA,
Povlishock JT
(1986)
Oxygen radicals in brain injury.
Cent Nerv Syst Trauma
3:257-263[Medline].
-
Liu XZ,
Xu XM,
Hu R,
Du C,
Zhang SX,
McDonald JW,
Dong HX,
Wu YJ,
Fan GS,
Jacquin MF,
Hsu CY,
Choi DW
(1997)
Neuronal and glial apoptosis after traumatic spinal cord injury.
J Neurosci
17:5395-5406[Abstract/Free Full Text].
-
Lukashev ME,
Werb Z
(1998)
ECM signalling: orchestrating cell behavior and misbehavior.
Trends Cell Biol
8:437-441[Web of Science][Medline].
-
Matsubara M,
Girard MT,
Kublin CL,
Cintron C,
Fini ME
(1991)
Differential roles for two gelatinolytic enzymes of the matrix metalloproteinase family in the remodelling cornea.
Dev Biol
147:425-432[Web of Science][Medline].
-
McIntosh TK,
Juhler M,
Wieloch T
(1998a)
Novel pharmacologic strategies in the treatment of experimental traumatic brain injury.
J Neurotrauma
15:731-769[Web of Science][Medline].
-
McIntosh TK,
Saatman RE,
Raghupathi R,
Graham DI,
Smith DH,
Lee VM,
Trojanowski JQ
(1998b)
Molecular and cellular sequelae of experimental traumatic brain injury: pathogenetic mechanisms.
Neuropathol Appl Neurobiol
24:251-267[Web of Science][Medline].
-
Mohan R,
Sivak J,
Ashton P,
Russo LA,
Pham BT,
Raizman MB,
Fini ME
(2000)
Curcuminoids inhibit the angiogenic response stimulated by FGF-2 including expression of matrix metalloproteinase gelatinase B.
J Biol Chem
275:10405-10412[Abstract/Free Full Text].
-
Morita-Fijimura Y,
Fujimura M,
Gasche Y,
Copin J,
Chan PH
(1999)
Overexpression of copper and zinc superoxide dismutase in transgenic mice prevents the induction and activation of matrix metalloproteinases after cold injury induced brain trauma.
J Cereb Blood Flow Metab
20:130-138.
-
Murtomaki S,
Trekner E,
Wright J,
Saksela O,
Liesi P
(1995)
Increased proteolytic activity of the granule neurons may contribute to neuronal death in the weaver mouse cerebellum.
Dev Biol
168:635-648[Web of Science][Medline].
-
Nagase H,
Woessner JF
(1999)
Matrix metalloproteinases: a minireview.
J Biol Chem
274:21491-21494[Free Full Text].
-
Oh LYS,
Larsen PH,
Krekoski CA,
Edwards DR,
Donovan F,
Werb Z,
Yong VW
(1999)
Matrix metalloproteinase-9/gelatinase B is required for process outgrowth by oligodendrocytes.
J Neurosci
19:8464-8475[Abstract/Free Full Text].
-
Pagenstecher A,
Stalder AK,
Kincaid CL,
Shapiro SD,
Campbell IL
(1998)
Differential expression of matrix metalloproteinase and tissue inhibitor of matrix metalloproteinase genes in mouse CNS in normal and inflammatory states.
Am J Pathol
152:729-741[Abstract].
-
Palmer AM,
Marion DW,
Botscheller ML,
Swedlow PE,
Styren SD,
DeKosky ST
(1993)
Traumatic brain injury induced excitotoxicity assessed in a controlled cortical impact model.
J Neurochem
61:2015-2024[Web of Science][Medline].
-
Pravdenkova SV,
Basnakian AG,
James JS,
Andersen BJ
(1996)
DNA fragmentation and nuclear endonuclease activity in rat brain after severe closed head injury.
Brain Res
729:151-155[Web of Science][Medline].
-
Rink A,
Fung KM,
Trojanowski JQ,
Lee VM,
Neugebauer E,
McIntosh TK
(1995)
Evidence of apoptotic cell death after experimental brain injury in the rat.
Am J Pathol
147:1575-1583[Abstract].
-
Romanic AM,
White RF,
Arleth AJ,
Ohlstein EH,
Barone FC
(1998)
Matrix metalloproteinase expression increases after cerebral focal ischemia in rats.
Stroke
29:1020-1030[Abstract/Free Full Text].
-
Rosenberg GA,
Navratil M,
Barone F,
Feuerstein G
(1996)
Proteolytic cascade enzymes increase in focal cerebral ischemia in rat.
J Cereb Blood Flow Metab
16:360-366[Web of Science][Medline].
-
Scherbel U,
Raghupathi R,
Nakamura M,
Saatman KE,
Trojanowski JQ,
Neugebauer E,
Marino MW,
McIntosh TK
(1999)
Differential acute and chronic responses of tumor necrosis factor deficient mice to experimental brain injury.
Proc Natl Acad Sci USA
96:8721-8726[Abstract/Free Full Text].
-
Smith DH,
Soares HD,
Pierce JS,
Perlman K,
Saatman K,
Meaney DF,
Dixon CE,
McIntosh TK
(1995)
A model of parasagittal controlled cortical impact in the mouse: cognitive and histological effects.
J Neurotrauma
12:169-178[Web of Science][Medline].
-
Springer JE,
Azhill RD,
Knapp PE
(1999)
Activation of caspase-3 apoptotic cascade in traumatic spinal cord injury.
Nat Med
5:943-946[Web of Science][Medline].
-
Sullivan PG,
Bruce-Keller AJ,
Rabchevsky AG,
Christakos S,
St Clair DK,
Mattson MP,
Scheff SW
(1999)
Execerbation of damage and altered NFkB activation in mice lacking TNF receptors after traumatic brain injury.
J Neurosci
19:6248-6256[Abstract/Free Full Text].
-
Tsirka SE,
Rogove AD,
Bugge TH,
Degen JL,
Strickland S
(1997)
An extracellular proteolytic cascade promotes neuronal degeneration in the mouse hippocampus.
J Neurosci
17:543-552[Abstract/Free Full Text].
-
Vu TH,
Shipley JM,
Bergers G,
Helms JA,
Hanahan D,
Shapiro SD,
Senior RM,
Werb Z
(1998)
MMP-9 is a key regulator of growth plate angiogenesis and apoptosis of hypertrophic chondrocytes.
Cell
93:411-422[Web of Science][Medline].
-
Westermarck J,
Kahari W
(1999)
Regulation of matrix metalloproteinase expression in tumor invasion.
FASEB J
13:781-792[Abstract/Free Full Text].
-
Whalen MJ,
Clarck RSB,
Dixon CE,
Robichaud P,
Marion DW,
Vagni V,
Graham SH,
Virag L,
Hasko G,
Stachlewitz R,
Szabo C,
Kochanek PM
(1999)
Reduction of cognitive and motor deficits after traumatic brain injury in mice deficient in poly-ADP-ribose polymerase.
J Cereb Blood Flow Metab
19:835-842[Web of Science][Medline].
-
Yakovlev AG,
Knoblach SM,
Fan L,
Fox GB,
Goodnight R,
Faden AI
(1997)
Activation of CPP32-like caspases contributes to neuronal apoptosis and neurological dysfunction after traumatic brain injury.
J Neurosci
17:7415-7424[Abstract/Free Full Text].
-
Yong VW,
Krekoski CA,
Forsyth PA,
Bell R,
Edwards DR
(1998)
Matrix metalloproteinases and disease of the CNS.
Trends Neurosci
21:75-80[Web of Science][Medline].
-
Yu Q,
Stamenkovic I
(1999)
Localization of metalloproteinase 9 to the cell surface provides a mechanism for CD44-mediated tumor invasion.
Genes Dev
13:35-48[Abstract/Free Full Text].
-
Zuo J,
Ferguson TA,
Hernandez YJ,
Stetler-Stevenson WG,
Muir D
(1998)
Neuronal matrix metalloproteinase 2 degrades and inactivates a neurite-inhibiting chondroitin sulfate proteoglycan.
J Neurosci
18:5203-5211[Abstract/Free Full Text].
Copyright © 2000 Society for Neuroscience 0270-6474/00/20187037-06$05.00/0
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