Lung Matrix Metalloproteinase Activation following Partial Hepatic Ischemia/Reperfusion Injury in Rats

Abstract

Purpose:
Warm hepatic ischemia-reperfusion (I/R) injury can lead to multiorgan dysfunction. The aim of the present study was to investigate whether acute liver I/R does affect the function and/or structure of remote organs such as lung, kidney, and heart via modulation of extracellular matrix remodelling.

Methods:
Male Sprague-Dawley rats were subjected to 30 min partial hepatic ischemia by clamping the hepatic artery and the portal vein. After a 60 min reperfusion, liver, lung, kidney, and heart biopsies and blood samples were collected. Serum hepatic enzymes, creatinine, urea, Troponin I and TNF-alpha, and tissue matrix metalloproteinases (MMP-2, MMP-9), myeloperoxidase (MPO), malondialdehyde (MDA), and morphology were monitored.

Results:
Serum levels of hepatic enzymes and TNF-alpha were concomitantly increased during hepatic I/R. An increase in hepatic MMP-2 and MMP-9 activities was substantiated by tissue morphology alterations. Notably, acute hepatic I/R affect the lung inasmuch as MMP-9 activity and MPO levels were increased. No difference in MMPs and MPO was observed in kidney and heart.

Conclusions:
Although the underlying mechanism needs further investigation, this is the first study in which the MMP activation in a distant organ is reported; this event is probably TNF-alpha-mediated and the lung appears as the first remote organ to be involved in hepatic I/R injury.

Full text

Research Article
Lung Matrix Metalloproteinase Activation following Partial
Hepatic Ischemia/Reperfusion Injury in Rats
Giuseppina Palladini,1Andrea Ferrigno,1Vittoria Rizzo,2
Eleonora Tarantola,3Vittorio Bertone,3Isabel Freitas,3,4 Stefano Perlini,1
Plinio Richelmi,1and Mariapia Vairetti1
1Department of Internal Medicine and erapeutics, Fondazione IRCCS Policlinico S. Matteo, University of Pavia,
Via Ferrata 9A, 27100 Pavia, Italy
2Department of Molecular Medicine, Fondazione IRCCS Policlinico S. Matteo, University of Pavia, 27100 Pavia, Italy
3Department of Biology and Biotechnology “Lazzaro Spallanzani,” University of Pavia, 27100 Pavia, Italy
4Institute of Molecular Genetics of the C.N.R. (IGM-CNR), Histochemistry and Cytometry Section, University of Pavia,
27100Pavia,Italy
Correspondence should be addressed to Mariapia Vairetti; mariapia.vairetti@unipv.it
Received  August ; Accepted  November ; Published  January 
Academic Editors: A. K. Nussler and G. Ramadori
Copyright ©  Giuseppina Palladini et al. is is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
cited.
Purpose. Warm hepatic ischemia-reperfusion (I/R) injury can lead to multiorgan dysfunction. e aim of the present study
was to investigate whether acute liver I/R does aect the function and/or structure of remote organs such as lung, kidney, and
heart via modulation of extracellular matrix remodelling. Methods. Male Sprague-Dawley rats were subjected to  min partial
hepatic ischemia by clamping the hepatic artery and the portal vein. Aer a  min reperfusion, liver, lung, kidney, and heart
biopsies and blood samples were collected. Serum hepatic enzymes, creatinine, urea, Troponin I and TNF-alpha, and tissue matrix
metalloproteinases (MMP-, MMP-), myeloperoxidase (MPO), malondialdehyde (MDA), and morphology were monitored.
Results. Serum levels of hepatic enzymes and TNF-alpha were concomitantly increased during hepatic I/R. An increase in hepatic
MMP- and MMP- activities was substantiated by tissue morphology alterations. Notably, acute hepatic I/R aect the lung
inasmuch as MMP- activity and MPO levels were increased. No dierence in MMPs and MPO was observed in kidney and heart.
Conclusions. Although the underlying mechanism needs further investigation, this is the rst study in which the MMP activation in
a distant organ is reported; this event is probably TNF-alpha-mediated and the lung appears as the rst remote organ to be involved
in hepatic I/R injury.
1. Introduction
Reperfusionfollowingprolongedischemiamaycausepara-
doxical damage at several levels. is phenomenon, dened
as ischemia-reperfusion (I/R) injury, has been described in
the heart as well in other organs, such as the liver []. Among
theseveralinvolvedmechanisms,oxygentoxicityandfree
radical production play an important role []. Warm hepatic
I/Rinjurymayoccurnotonlyduringlivertransplantation,
but also following surgical resections requiring hepatic inow
occlusion for bleeding control. Via systemic yet poorly
understood mechanisms, I/R injury in one organ can also
lead to multiorgan dysfunction that is to tissue damage in
remote organs away from the body district where the I/R
damage is taking place. For example, I/R intestine damage
has been described to cause multiple organ dysfunction due
to uncontrolled production and release of cytokines and
other proinammatory molecules []. Recent data suggested
that also hepatic I/R injury may cause damage to remote
organs such as kidney [], heart [], and lung []. Indeed,
damaged liver tissue releases destructive proinammatory
cytokines and oxygen-derived radicals into the circulation
thatarelikelycausingfurtherdamagetoremoteorgans[].
In an experimental model, Colletti et al. [], showed that
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Volume 2014, Article ID 867548, 10 pages
http://dx.doi.org/10.1155/2014/867548

e Scientic World Journal
hepatic I/R injury is associated with lung dysfunction such as
neutrophil inltration, edema, intraalveolar hemorrhage and
endothelial activation.
Inammatory cytokines such as TNF-alpha participate
to extracellular matrix (ECM) degradation following liver
injury, and hepatic TNF-alpha expression has been demon-
stratedtobeparallelwithinductionofmatrixmetallopro-
teinases (MMPs) [], collagenolytic zinc-dependent enzymes
that degrade several ECM constituents such as collagen,
gelatin, elastin, and bronectin []. A recent study []
reports increased liver MMP- expression following I/R
injury, and a correlation between serum MMP- and sever-
ity/progression of liver damage has been described in the
setting of I/R injury [], acute allogra rejection [], and
chronic viral hepatitis []. Also in the kidney, it has been
recently shown that MMPs play a role in the development
of endothelial damage during ischemia-reperfusion injury,
with increased MMP- activity paralleling degradation of
endothelial cells and the subsequent increase in vascular
permeability []. Cardiovascular dysfunction frequently
occurs aer major surgery or liver transplantation. Several
investigators have reported that liver ischemia is associated
with the release of vasoactive substance that inicts remote
cardiac damage [].
e mechanisms leading to the initiation of multior-
ganinjuryhavenotyetbeenelucidated.eaimofthe
present study was therefore to investigate whether acute liver
ischemia and reperfusion do aect the function and the
structure of remote organs such as kidney, heart, and lung via
the modulation of ECM remodelling. As indicators of remote
and local tissue damage and leukocyte inltration we used
malondialdehyde (MDA), an indicator of lipid peroxidation
rate, and myeloperoxidase (MPO), a neutrophil marker.
2. Material and Methods
2.1. Animals. e use of animals in this experimental study
was approved by the National Institute for Research, and the
animals were cared for according to its guidelines. irty-
two Male Sprague-Dawley rats (– g) with free access
to water and food were used.
2.2. Materials. All reagents were of the highest grade of purity
available and were purchased from Sigma Aldrich.
2.3. Ischemia-Reperfusion (I/R) Procedure. e eects of I/R
were studied in vivo in a partial normothermic hepatic I/R
model that has been previously reported [,]. Briey, the
abdomen was opened by a median incision while the rats
were anesthetized with pentobarbital ( mg/kg). Ischemia
totheleandmedianlobewasinducedbyclampingthe
portal vein and hepatic artery with microvascular clips for
 min, and the abdomen was temporary closed with a suture.
Aer  min of ischemia, the abdomen was reopened, the
clips were removed, the abdomen was closed again, and the
liverwasreperfusedformin.Topreventpostsurgicaldehy-
dration and hypotension mL of normal saline was injected
in the inferior vena cava immediately aer the removal of
the clips. e duration of the injection was approximately
 s. During I/R the animals (𝑛=17) were maintained on
warm support to prevent heat loss: rectal temperature was
maintained at 37 ± 0.1∘C. Sham-operated control animals
(𝑛=15) were similarly treated as compared with I/R
group for all the aspects of the experimental model: rats
were maintained under heat support during anaesthesia of
equal length of time, injected with cc saline and submitted
tosimilarmanipulationoftheliverhiluswithoutvascular
occlusion. Blood samples were obtained aer reperfusion and
immediately centrifuged to isolate serum. At the end of the
reperfusion period, tissue samples of the liver, ischemic lobes
(le), of the kidney (cortex and medulla), of the heart (le
ventricle),andofthelungweresnapfrozeninliquidnitrogen.
2.4. Biochemical Assays. Liver and kidney injury was assessed
by serum release of alanine transaminase (ALT), aspartate
transaminase (AST), lactate dehydrogenase (LDH), crea-
tinine, and urea by an automated Hitachi  analyser
(Roche/Hitachi, Indianapolis, IN, USA).
Heart injury was assessed by serum evaluation of highly
specic marker of myocardial cell damage such as Troponin I
(cTN) by an automated Hitachi  analyser (Roche/Hitachi,
Indianapolis, IN, USA).
e amounts of released TNF-alpha in serum were quan-
tied by commercial rat TNF-alpha ELISA kit from R&D
Systems (Minneapolis, USA) according to the manufacture
instructions.
e amounts of malondialdehyde (MDA) formation
were quantied by HPLC method using the Chromsystems
assay kit (Chromsystems GmbH, M¨
unchen). e assay was
performed according to the manufacturer instructions with
some modications: briey, the derivatized samples were
incubated for  minutes at ∘C and nally used aer cen-
trifugation [].
Myeloperoxidase (MPO) activity was measured with
a uorimetric detection kit (Cayman Chemical) aer an
adequate tissue preparation. Briey liver, lung, kidney, and
heart tissues were homogenized (IKA-Ultraturrax T) in a
cooled . M potassium phosphate buer (pH .). Aer
addition of another equal volume of cooled . M potassium
phosphate buer, the homogenate was centrifuged at ∘C
for  min at . rpm in order to pellet insoluble cellular
debris []. Pellets were resuspended in a cooled . M
potassium phosphate buer (pH ) containing .% hexa-,-
bis-decyltrimethylammonium bromide (HTAB) and homog-
enized. Samples were sonicated for  sec and submitted to
two cycles of freeze/thaw. Finally samples were centrifuged at
∘C for  min at . rpm and supernatants were imme-
diately frozen at −∘Cforlateruser.OneunitofMPO
activity was dened as the amount of enzyme that caused the
formation of  nmol of uorophore per minute at ∘C.
2.5. Tissue Sources for MMPs Analysis. Aer sacrice liver,
kidney, heart, and lung were quickly excised and placed in
cold (∘C) buer ( mM Histidine,  mM sucrose, and
 mM EDTA, pH .) to remove blood. Liver and lung were
weighed and subsequently cut, frozen in liquid nitrogen and
stored at −∘C, until use. Kidney was cleaned of external
tissue; the renal cortex and medulla were separated and

e Scientic World Journal 
subsequently frozen in liquid nitrogen and stored at −∘C,
until use. Heart was separated in atria, right and le ventricle.
e le ventricle tissue samples were then frozen in liquid
nitrogenandstoredat−∘C, until use.
2.5.1. Hepatic Protein Isolation. Hepatic MMPs were extrac-
ted by homogenisation (IKA-Ultraturrax T) of frozen liver
tissue, in an ice-cold extraction buer ( :  wt/vol) con-
taining % Triton X-,  mmol/L Tris-HCl,  mmol/L
NaCl, and  mmol/L CaCl2,pH.[]. e homogenate
was then centrifuged ( min at . rpm at ∘C) and the
protein concentration of the supernatant was measured with
the colorimetric Lowry method []. Samples were stored at
−∘Cbeforeuse.
2.5.2. Renal Protein Isolation. Fiy milligrams of cortex and
medulla were used to homogenize in a dissociation buer
containing  mmol/L cacodylic acid, . mmol/L NaCl,
mmol/L ZnCl
2,  mmol/L CaCl2,.mmol/LNaN
3,and
.% Triton X-, pH . []. e homogenate was then
shaken at ∘Cforhandtheproteinconcentrationof
the supernatant was measured with the colorimetric Lowry
method []. Samples were stored at −∘Cbeforeuse.
2.5.3. Cardiac and Pulmonary Protein Isolation. Le ventricle
myocardial and lung samples were homogenized in an ice-
cold extraction buer [] ( :  wt/vol) containing cacodylic
acid ( mmol/L), NaCl ( mmol/L), ZnCl2( mmol/L),
CaCl2( mmol/L), NaN3(. mmol/L), and Triton X-
.% vol/vol (pH ). e homogenate was then centrifuged
( min at . rpm) and the supernatant protein concentra-
tion was measured with the colorimetric Lowry method [].
Samples were stored at −∘Cbeforeuse.
2.6. MMPs Zymography. In order to detect MMPs activity
present in the samples, the homogenate protein content was
normalized by a nal concentration of  𝜇g/mL in sample
loading buer (. M Tris-HCl, % sucrose w/v, % SDS
w/v, and .% bromphenol blue w/v, pH .). Aer dilution
the samples were loaded onto electrophoretic gels (SDS-
PAGE) containing  mg/mL of gelatin under nonreducing
conditions [,], followed by zymography as described
previously [].
e zymograms were analyzed by densitometer (GS 
Densitometer BIORAD, Hercules, CA, USA) and data were
expressed as optical density (OD), reported to mg/mL
protein content.
2.7. Tissue Morphology. Liver and lung tissues were xed in
% paraformaldehyde in . M phosphate buer at pH .
for  hours, processed routinely and embedded in Paraplast
wax. Sections ( 𝜇m thick) were stained with hematoxylin
and eosin (H&E). To appraise the severity of hepatic injury,
H&E-stained sections were evaluated as follows: Grade ,
minimal or no evidence of injury; Grade , mild injury
consisting of cytoplasmic vacuolation and focal nuclear
pyknosis; Grade , moderate-to-severe injury with extensive
nuclear pyknosis, cytoplasmic hypereosinophilia, and loss of
intercellular borders; Grade , severe necrosis with disinte-
gration of hepatic cords, hemorrhage, occasional granulomas,
cytoplasmic pallor, and cellular swelling [].
To appraise the severity of lung injury, the number of
granulocytes was evaluated in H&E-stained sections and
calculated per microscopic eld []: the prepared sections
were coded and examined by an independent histologist in a
single-blind scoring procedure.
Kidney tissue was frozen in liquid nitrogen and stored
at −∘C. Sections ( 𝜇m thick) were stained with H&E.
Microscopic criteria for tubular damage are tubular brush
border loss, cytoplasmic swelling, and cellular debris.
2.8. Statistical Analysis. Results are expressed as mean ±
error standard as specied. Comparisons between groups
were performed by unpaired 𝑡-test. When data distribution
was not normal, according to the Kolmogorov-Smirnov test,
Mann-Whitney test was used. All statistical procedures were
performed using the MedCalc statistical soware package
(... version). Value of 𝑃 < 0.05 was considered
signicant.
3. Results
3.1. Liver I/R Injury. Asexpected,serumlevelsofAST,ALT,
and LDH increased signicantly in animals submitted to
ischemia ( min) and reperfusion ( min) as compared
with sham-operated group (Tab l e  ).
3.2. Kidney Function. Serum creatinine and urea did not
signicantly dier between sham and I/R groups (Table ).
3.3. Heart Biomarkers. Serum Troponin I (cTN), did not
show any dierence between groups (I/R versus sham-
operated) (Ta b l e  ).
3.4. Biochemical Parameters (TNF-Alpha, MDA, and MPO).
e serum concentrations of TNF-alpha, an index of Kupf-
fer cell activation, increased aer ischemia/reperfusion as
reported in Figure . No dierence in MDA formation, as
products of lipid peroxidation, was observed in liver and
lung (Table ). e same trend was found in kidney medulla
and heart samples as compared with sham group (Heart:
0.113 ± 0.005 versus 0.122 ± 0.009,resp.;Kidneymedulla
0.492 ± 0.098 versus 0.528 ± 0.129, resp.). e MDA levels
were signicantly higher in ischemic group compared with
sham animals only in kidney cortex (0.205 ± 0.011 versus
0.142 ± 0.022 nmoli/mg/prot, 𝑃 < 0.05).
Tissue MPO activity, an indirect evidence of neutrophil
inltration,wasmeasuredinliverandlung;meanMPO
activity was increased in liver and lung comparing the
ischemic group with sham animals (Tab l e  ). No changes in
the MPO levels were found in kidney and heart tissue during
hepatic I/R injury, as compared with sham group (data not
shown).
3.5. Gelatinolytic Activity. e activity of gelatinase-A
(MMP-) and gelatinase-B (MMP-) was evaluated to inves-
tigate the extent of hepatic, renal, lung, and heart MMPs

e Scientic World Journal
T : Serum levels of AST, ALT, LDH, creatinine, urea, and Troponin I in animals submitted to ischemia/reperfusion (I/R). Sham-operated
group (control) has been compared with I/R group: ∗𝑃 < 0.05. ese are the mean results of  dierent experiments ±S.E.M.
SHAM (𝑛=15)I/R(𝑛=17)
AST mU/mL 118.92 ± 9.31 670.83 ± 180.33∗
ALT mU/mL 41.83 ± 3.48 609.17 ± 191.16∗
LDH mU/mL 2169.4 ± 486.2 8022.7 ± 2197.8∗
Creatinine mg/dL 0.67 ± 0.05 0.74 ± 0.04
Urea mg/dL 48.33 ± 1.94 48.17 ± 1.7
Troponin I ng/mL 0.02 ± 0.01 0.02 ± 0.01
T : Liver and lung levels of MDA and MPO in animals submitted to ischemia/reperfusion (I/R). Sham-operated group (control) has
been compared with I/R group: ∗𝑃 < 0.05. ese are the mean results of  dierent experiments ±S.E.M.
SHAM (𝑛=15)I/R(𝑛=17)
MDA
Liver nmoli/mg/prot 0.292 ± 0.072 0.293 ± 0.062
Lung nmoli/mg/prot 0.206 ± 0.022 0.210 ± 0.044
MPO
Liver nmoli/min/mL 1.7 ± 0.07 2.0 ± 0.06∗
Lung nmoli/min/mL 1.1 ± 0.01 1.2 ± 0.01∗
0
2
4
6
8
10
12
14
16
(pg/mL)
SHAM
I/R
∗
TNF-𝛼
F : Serum levels of TNF-𝛼in animals submitted to
ischemia/reperfusion (I/R). Sham operated group (control, 𝑛=15)
hasbeencomparedwithI/Rgroup(𝑛=17): ∗𝑃 < 0.05.eseare
the mean results of  dierent experiments ±S.E.M.
activity, potentially inducing interstitial degradation (Figure
). Both I/R and sham-operated groups showed detectable
MMP- and MMP- activities with the exception of the heart
where MMP- was not detectable.
In the liver, I/R was associated with a signicant increase
of gelatinase activity in the ischemic lobe (Figure ). Inter-
estingly, acute hepatic I/R was associated with lung MMP-
activation, while in kidney (cortex and the medulla) and in
heart no signicant dierence was observed between groups
(I/R versus sham). Only a no signicant increase in MMP-
was observed in kidney medulla (Figure ).
3.6. Liver Histology. A semiquantitative evaluation of liver
lesions showed a statistically signicant dierence in the
extent of liver damage when comparing sham-operated rats
and animals subjected to I/R (Score –: 0.6± 0.1 versus 2.4±
0.2,resp.).Intheischemiclobeoftheanimalssubmittedto
I/R several lobules showed a detectable damage. In particular,
hepatocyte necrosis and sinusoidal disarrangement (Figures
(b)-(c), Grade ) when compared with sham-operated
animals (Figure (a)).
3.7. Kidney Histology. When compared with the cortex of
sham-operated animals (Figure (a) andinset),thecortexof
animals submitted to hepatic I/R showed dilated interstitium.
Rats submitted to I/R showed damage to tubules with loss of
brushborderandpresenceofcellulardebris(Figure (b) and
inset). No signicant damageto glomeruli was detected. With
respect to the outer medulla of sham animals (Figure (c)),
the outer medulla of rats submitted to hepatic I/R showed
wider areas of interstitial uid accumulation in the inter-
stitium and disarrangement of thick limbs of Henle’s loop
(Figure (d)). In the inner medulla of animals submitted to
I/R, a few thin limbs of Henle’s loop appear dilated and with
increased cellularity in the stromal (Figure (f))withrespect
to sham animals (Figure (e)).
3.8. Lung Histology. A signicantly higher number of gran-
ulocyteswerefoundinthewallandlumenofalveoliofrats
submitted to I/R as compared with sham rats (Figure ). In
contrast with the lungs of sham-operated animals (Figures
(a),(b),and(c)), in the lungs of animals submitted to
hepatic I/R alveoli appear to be dilated (Figures (d) and
(e)), rare erythrocytes in alveolar capillaries (Figure (e)),
dilated lymphatics (Figure (d)), and abundant granulocytes

e Scientic World Journal 
0
0.1
0.2
0.3
0.4
0.5
MMP-2 MMP-9
Liver
∗
∗
SHAM
I/R
(OD ∗mm2/mg/mL protein)
(a)
MMP-2 MMP-9
0
0.25
0.5
0.75
1
1.25
1.5 Lung
∗
SHAM
I/R
(OD ∗mm2/mg/mL protein)
(b)
0
0.25
0.5
0.75
1
MMP-2
Heart
SHAM
I/R
(OD ∗mm2/mg/mL protein)
(c)
MMP-2 MMP-9
0
0.25
0.5
0.75
1Kidney medulla
SHAM
I/R
(OD ∗mm2/mg/mL protein)
(d)
MMP-2 MMP-9
0
0.25
0.5
0.75
1Kidney cortex
SHAM
I/R
(OD ∗mm2/mg/mL protein)
(e)
F : Bar graphs of MMP- and MMP- activity in ischemic liver lobe (a), lung (b), heart (c), kidney cortex (d), and medulla (e). Sham-
operated group (control, 𝑛=15) has been compared with I/R group (𝑛=17): ∗𝑃 < 0.05.Dataareshownasmeanvalues±SEM.

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CL
CL
P
P
P
(a)
CL
P
P
(b)
P
P
∗
∗
∗
(c)
F : Representative light micrographs of the le liver lobe of sham-operated rats (a) and of the le lobe of rats submitted to
ischemia/reperfusion (I/R) (b and c). Hematoxylin and eosin staining. e sham animal shows normal hepatocyte and sinusoid morphology
(a). In animals submitted to I/R the lower magnication picture (b) shows decreased eosinophilia of hepatocytes, hepatocyte vacuolation,
disarrangement of hepatocyte cords, and altered sinusoidal dilatation (b). An area of extensive hepatocyte necrosis and plate disintegration
(black stars) is shown under higher magnication in (c), example of grade . P: portal vein; CL: centrolobular vein.
DCT
DCT
G
50 𝜇m
010𝜇m
(a)
DCT
50 𝜇m
010𝜇m
(b)
THL
THL
50 𝜇m
(c)
THL
THL
∗
∗
50 𝜇m
(d)
tHL
tHL
50 𝜇m
(e)
tHL
tHL 50 𝜇m
(f)
F : Representative light micrographs of kidney samples obtained from sham-operated rats (a, b, and c) and from rats submitted to
hepatic ischemia/reperfusion (I/R) (d, e, and f). Cortex (a, b), outer medulla (c, d), and inner medulla (e; f) are illustrated. Hematoxylin and
eosin staining. With respect to the normal morphology of the cortex of sham animals (a), the cortex of animals submitted to hepatic I/R (b)
shows dilated interstitium and injury to a few tubules. e insets in (a) show a normal distal convolute tubule (DCT) and in (b) patchy areas
of dilatation. With respect to the normal morphology of the outer medulla of sham animals (c), the outer medulla of animals submitted to
hepatic I/R shows extended areas of interstitial uid (asterisk) apparently displacing thick limbs of Henle’s loop (THL). Respect to the inner
medulla of sham animals (e), the inner medulla of animals submitted to I/R (f), shows slightly dilated thin limbs of Henle’s loop (tHL) and
increased cellularity in the stromal.

e Scientic World Journal 
0
2
4
6
8
10
Cells/fields
Granulocytes
SHAM
I/R
∗
F : Changes of lung granulocytes in response to hepatic I/R
injury. Lung samples were obtained from sham-operated rats, not
submittedtohepaticI/R,andfromratswhosehepaticlobeswere
submitted to  min of ischemia and hence reperfused for  min.
e number of granulocytes was calculated per microscopic eld.
∗𝑃 < 0.05. Data are shown as mean values ±SEM.
and mononuclear cells in the lumen and stroma of arteries
(Figures (e) and (f)) and in the lumen of bronchi (not
shown).
4. Discussion
isstudyshowsthatmoderateacutehepaticischemia/
reperfusion (I/R) injury increases MMPs activity not only in
theischemicliverregionbutalsointhelung,associatedwith
histological damage in liver, lung, and kidney. e concomi-
tant increase in serum TNF-alpha suggests a potential role for
this cytokine in the development of multiorgan dysfunction
arising from isolated hepatic I/R injury. A moderate hepatic
I/R injury is able to increase MMPs activity not only in the
ischemic region, as previously reported [,], but also
in the nonischemic lobe associated with several histological
signs of interstitial and cellular damage []. is event is
probably TNF-alpha-mediated, fully supporting the hypoth-
esis that a direct connection exists between the events taking
placeinboththedamagedlobeandthenonischemicliver.
4.1. e Involvement of Lung in the Hepatic I/R Injury. e
results of the present work suggest that a sizeable release of
hepatic enzymes in the blood stream following acute liver
I/R injury is associated with increased MMP activity, in
particular MMP- also in distant organs, such as the lung.
Multiorgan failure (MOF) is the simultaneous dysfunction of
several organs, and it represents one of the most intriguing
clinical problems arising in patients admitted to the Inten-
sive Care Unit []. A central mechanism leading to MOF
seems to be I/R injury []. Oxygen-derived free radicals,
cytokines, and activated neutrophils have been found to
be involved in the I/R liver damage []triggeringthe
systemic inammatory response that contributes to distant
organ injury []. Although the involved mechanism is still
unclear, the observed increase in MMP- activity appears
to be connected with the high serum levels of TNF-alpha
representing the connection between the hepatic I/R damage
and “at-a-distance” lung alterations.
MMPs are not expressed during normal conditions but
their expression and activity increase during inammation
[]. MMP- is one of the families of MMPs, which degrades
ECM, and it is induced by many inammatory factors,
including IL-beta, IL-, and TNF-alpha. MMP- is stored in
the tertiary granules of polymorphonuclear leukocytes which
are key eectors in acute inammatory diseases. In addition
MMP- can actively assist MPO activation, an index of
neutrophil inltration []. Once an inammatory response
is initiated, neutrophils are the rst cells to be recruited to the
sites of injury or []infection[]. Aer hepatic I/R injury
liver MPO activity increased in the ischemic tissue and a
few neutrophils were occasionally seen in edematous portal
spaces, and/or forming small granulomas around necrotic
cells in ischemic lobes. Interestingly, a similar increase of
MPO levels was also observed in the lung tissue, associated
with a high number of granulocytes as compared with the
control group.
Previous data also show increased neutrophil inltration
in the liver and in other organs such as the lung aer hepatic
I/R, suggesting that neutrophils contribute to MOF induced
by hepatic I/R []. In the present study, I/R injury was not
associated with an oxidative damage in the liver and in the
lung despite early signs of tissue damage. No signicant
dierencewasobservedinMDAlevels,alipidperoxidation
product, conrming our previous work in which liver MMP
activation was shown to be an MDA-independent event [].
A more prolonged reperfusion time is required to obtain a
signicant increase in MDA levels aer hepatic I/R damage
[].
4.2. Kidney Involvement in the Hepatic I/R Injury. No increase
in MMPs and MPO was observed in the kidney. Previ-
ously, Miranda et al. [] demonstrated that  min hepatic
ischemia associated with  or  hours reperfusion induced
an increase in MPO and MDA in distant organ such as
the lung and the kidney. In the present work we conrm
the increase in pulmonary MPO and the absence of these
alterations in other organs such as the kidney. A possible
explanation is strictly connected with the short duration of
both ischemia ( min) and reperfusion ( min) period in
our experimental model, as well as with the much lower
transaminase levels, -times lower than those observed by
Miranda et al. []. No changes in MDA formation was
found in distant organs such as the kidney, thus conrming
the limited damage induced in our experimental setting, as
supported by previous reports showing that the hepatic MDA
levels aer  min ischemia followed by min reperfusion
were comparable to those observed in sham animals [].
We did only nd increased MDA levels in the kidney
cortex. Further studies will be performed to explain this
nding. e histological analysis reveals some alterations
such as focal patchy areas of dilatation and much higher uid
accumulation in rats submitted to I/R versus control group.

e Scientic World Journal
alv
50 𝜇m
(a)
25 𝜇m
alv
(b)
25 𝜇m
(c)
alv
B
AL
50 𝜇m
(d)
25 𝜇m
alv
A
(e)
alv
B
A25 𝜇m
(f)
F : Representative sections of lung tissue from sham-operated animals (a, b, and c) and from animals submitted to hepatic
ischemia/reperfusion (I/R) (d, e, and f). Hematoxylin and eosin staining. e sections from sham animals show the typical morphology
of bronchi (B), blood vessels, and alveoli (alv) with associated capillaries; alveolar capillaries are recognizable in high magnication (c), by
erythrocytes in the lumen. In the lung tissues of animals submitted to hepatic I/R alveoli appear to be dilated. (d, e) Dilated lymph vessels (L)
surrounding arteries (A) and an abundant number of inammatory cells (arrowheads) in the lumen and stroma of blood vessels (f).
4.3. Heart Involvement in the Hepatic I/R Injury. No changes
in heart MMPs, MDA, and MPO were observed, probably
because cardiac dysfunction has been reported to follow only
major liver surgical procedures when the liver is subjected to
an important decrease in blood ow or aer transplantation
[]. Meyer et al. [] demonstrated that hepatic I/R induced
the upregulation of ICAM, one of the adhesion molecules,
mediated by TNF-alpha in distant organs such as the heart
and the kidney. ey evaluated the damage aer -hour
reperfusion and probably this is the reason why we did
not nd any cardiac alteration aer -hour reperfusion; our
hypothesis is supported by the strict correlation that exists
between lipid peroxidation formation and ischemia time in
the rat liver: only aer  hours of reperfusion a marked MDA
was shown [].
4.4. Hepatic I/R Injury and MOF. Multiple organ dysfunc-
tion syndrome/failure is an important cause of death in
the surgical intensive care unit. As a syndrome, MODS is
dened as altered organ function in the setting of sepsis,
septic shock, or systemic inammatory response syndrome.
Our data show that also aer hepatic I/R, biochemical and
histological changes do occur in distant organs and these
events are traceable very early during reperfusion aer a brief
transient ischemia. A histopathology examination showed
that hepatic, pulmonary, and renal tissue were more injured,
albeit slightly, in the I/R rats than in sham animal. In
particular increased MMP- activity was associated with
early lung injury. Recently, some studies have shown that
signicant increases in active MMP- are associated with a
multiple organ dysfunction in an infection model []. Our
results suggest that aer hepatic I/R an increased MMP-
activation in distant organ can occur representing (a) a step
forward the comprehension of the mechanisms involved in
MOFand(b)aninnovativetargetforlimitingtheMOF
progression.

e Scientic World Journal 
Interestingly, Rahman et al. recently demonstrated a
novel role of MMPs in regulating inltration of neutrophils
by controlling platelets secretion of CDL, a factor involved
in the septic lung injury. eir results suggested that targeting
MMPs may be a useful strategy for limiting lung injury [].
Experiments are in progress in our laboratory for increasing
both ischemia and reperfusion period.
Interestingly, the present work highlights that already
aer a relatively short I/R period an acute distant organ
damage occurs and that the lung is the rst organ involved,
suggesting that the increase in lung MMP- activity may
represent a key and early event involved in the pathogenesis
of hepatopulmonary syndrome, whereas kidney injury may
occur later and cardiac alterations may be observed only aer
a period of reperfusion longer than  hour [].
e likelihood that an ischemic and reperfused organ
can directly induce a remote organ failure is of a signicant
clinical importance: these eects must be taken into account
when treating patients aer liver transplantation and these
ndings may have important practical applications in the
clinical management of liver transplantation, as well as in the
procedures involving no ow-reow conditions.
Abbreviations
MMP: Matrix metalloproteinases
I/R: Ischemia-reperfusion
MDA: Malondialdehyde
MPO: Myeloperoxidase.
Conflict of Interests
e authors state that no conict of interest or nancial dis-
closure exists.
Authors’ Contribution
Giuseppina Palladini and Andrea Ferrigno contributed
equally in this paper.
Acknowledgments
e authors thank Mr. Gaetano Viani and Massimo Costa
for the skillful technical assistance, Dr. Enrico Scoglio for the
technicalsupportduringtheHPLCassay,andMrs.Nicoletta
Breda for the editing assistance. is work was funded by
F.A.R. –—University of Pavia.
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