Chapter 11
Ischemiareperfusion injury
Zhao Mingyao
BMC.ZZU
Brief history
Simple phenomenon
• 1955, Sewell ligated coronary artery of dog,
restore blood flow after deligation.
• What happened ?
Clinical：
•
•
•
•
•
Shock , DIC
Bypass surgery
Fibrinolytic therapy
Cardiopulmonary operation
Organ transplantation
Concept of Ischemia-Reperfusion
Injury
The restoration of blood flow after
transient ischemia may induce
further reversible or irreversible
cellular injury
Features of IRI：
1. reversible  irreversible
2. Massive in organs
3.participating factors
oxygen paradox
calcium paradox
pH paradox
Perfusion fluid
Perfusion fluid
effect
O2 paradox
Ca2+
paradox
pH paradox
Without O2
Without
Ca2+
Acidosis
Normal O2
supply
with
Ca2+
Correcting
acidosis
Deteriorate
injury
Section 1 Etiology of IRI
1. Duration of ischemia
2. Dependency on O2 supply
3. The condition of reperfusion:
reperfusion pressure, speed, T, Na+, Ca2+, K+,
Mg2+
Effect of Ischemic time on perfusion
arrhythmia of rat
100
90
80
70
60
incidence
rate
发生率（%）
50
40
30
20
10
0
RVA
RVT
RVF
5min
10min
30min
Ischemic
time
缺血时间（min)
Section 2 mechanism of IRI
Part 1. Injury of free radicals
Concept and Types of FR
Free radicals are atoms or molecules with
unpaired electrons in their outer orbital
1. Non-lipid free radicals
2. Lipid free radicals
Classification
(1) Oxygen free radical（OFR) ---Induced by O2
O·-2
Types
OH·
1O
Rective
Oxygen
Species
(ROS)
2
OFR
H 2O 2
peroxynitrite
(2) Lipid radicals
types： L·
LO· Alkoxyl
LOO·
(3) Cl·、CH3 · (Methane )、
NO ·
1. Generation of free radical
1) Initiation
2) Propagation
3) Degradation
(1)Production and scavenging of OFR
1) Origin of O·-2 ：
①Mt
②Natural oxidation of some substances
③Enzyme catalysis
④Toxin acting on cell
2）Production process of OFR
O2
O2 + e
O2+ 2e +
Cytaa3
2H+
O2 + 3 e + 3H+
O2 + 4 e + 4H+
H2O2
SOD
HO + H2O
2 H2O
H2O2 nse
Single
electron
reduction
Single electron reduction of O2
Haber-Weiss reaction (without Fe2 )
O 2  + H 2O 2
－
O2 + OH +OH
SLOW
Fenton type of Haber-Weiss reaction
( with Fe 3 )
－
O 2  + H 2O 2
Fe
2
O2 + OH +OH
Fast
What significance ？？？
3）Scavenging of OFR
① Low molecule scavenger
② Enzymatic scavenger
Water-soluble
Lipid-soluble
①low molecule scavenger
*hydrofacies of intra- or extracell:
Cysteine、Vit C、
Glutathione
*Cellular lipid：
Vit E、 Vit A
Cytosol ：NADPH
②Enzymatic scavenger
Superoxide dismutase
(SOD)
Catalase (CAT)
Glutathione peroxidase
(GSH-Px)
Dismutation reaction
Single electron reduction of O2
2O2 + 2H+
SOD
H2O2 + O2
H2O2 nse
?
GSH-Px : containing selenium
scavenging large biological molecule peroxide
LOOH + 2GSH
GSSG + LOH + H2O
GSH-Px
GSH reductase
2GSH + NADP+
GSSG + NADPH + H+
(2) Mechanism of OFR ↑during IRI
1) Mitochondria pathway
Ca2+ enter Mt
Single electron
reduction of O2 ↑
hypoxia  MnSOD 
O-2· ↑
2) Xanthine oxidase(XO) pathway↑
Xanthine oxidase (XO )10%
Ca 2 + sensitive enzyme
xanthine dehydrogenase(XD) 90%
Ischemia:
Hypoxathine↑↑
ATP degradation
Reperfusion:
(1)Ca2+→protease
XD
XO
（2）restore O2
O2
xanthine + O·-2+ H2O2
O2
O·-2+ H2O2 + uric acid
XO role in formation of OFR
OH ·
3)Neutrophil pathway
C3,LTB4
Activates NP
hexose bypass
activation
Respiratory
burst
NADH(I)
NADPH(II) + O2
NADH oxidase
NADPH oxidase
H+ + O-2·+H2O2
4) Catecholamine autooxidation pathway
Methyl transferase Vanillylmandelic
Adr
monoamine oxidase
acid (VMA)
80% during stress
O2 - · 
adrenochrome
Renal
excretion
(3) The detrimental effects of
OFR to tissue
1）Lipid membrane
2）Protein: channel, pump,
3）Enzyme
4）Nuclear acid : DNA
Membrane lipid peroxidation
Biomacromolecle crosslinkage
Protein ~
Two sulfur ~
Lipid –pro ~
Protein break
-S-S-
OH
HO
OH
HO
CH3-SLipid-lipid ~
O
Amino acid
oxidation
fatty acid
oxidation
MDA released by oxidated
fatty acid
Malondialdehyde (MDA)
DNA disruption and
chromosome aberration
induced by OH
about 80% damage
OH +2300
(hydroxyl)
Part 2 Calcium overload
1. Ca 2+ transportation and distribution
Ca 2+
Ca 2+
Ca2+
binding Pr
Ca 2+ Channel
Ca2+pump
SR
Mt
Na + - Ca 2+
cotransportor
2. Mechanism of ~
① Na+ - Ca2+ exchange↑:
H+-Na+ ↑; Na+ - Ca2+ ↑(forward mode
reverse mode); PKC triggers
②ATP ↓: mitochondria damage,
energy precursor ↓
③Membrane permeability ↑
④catecholamine ↑
NE
α1
H+
Ca2+
P1
Gq
PLC
Na+
DG
IP3
Ca2+
SR
PKC
Ca2+
filament
PKC activating Na+/Ca2+ exchanger indirectly
3. The detrimental effects of Ca2+
overload to tissue
(1) Activating Ca2+-activated protease
(2) Defects in membrane permeability
activating phospholipase A2
OFR
(3) Hypercontracture and reperfusion arrhythmia
cellular electrical action
(4)Mitochondria damage
Part 3. The endothelial injury
and neutrophil activation
1.The role of neutrophil activated
①Swelling
②Adhesion
③Infiltration
④Release: arachidonic acid, PAF, lysosomal
enzyme
⑤Respiratory burst
⑥Cell adhesion molecules(CAM):
selectins, integrins, immunoglobulin
superfamily
2. Mechanism of no-reflow
phenomenon
• Vaso-endothelial damage
• Vaso-endothelial edema
• Occlusion of microvascular luman
Rulo:
肉膜
3.NO and ONOO- production
• NO in VEC(eNOS), little, physiological
• NO in inflammatory cell(iNOS), rich,
cytotoxic (Mt respiration, aconitase activity,
DNA synthesis) and OONO-
peroxynitrite
Free radicals with a nitrogen center
① Nitric oxide(NO)
O2
NOS
L-arginine
NADPH
L-citrulline + NO
NADP+
② Peroxynitrite, ONOONO+O2.ONOO-
acidic
H2O
Killing bacterial & tumor
NO2. + OH. + H+
Inhibit function of protein: lipid-proteincollagen linkage
Pro-pro
linkage
disulfide
linkage
Protein
rupture
-S-S-
CH3-SO
Oxidation
of AA
Lipid-pro
linkage
Brief summary
Ca2+
Change of metabolism
& energy
？
OFR
VEC -NP
Ca2+ overload results in cellular death
Section 3
Body change during IRI
1. Heart
（1）Reperfusion arrhythmia
ATP-sensitive K+ channel open: hyperpolarization
long chain acylcarnitines & lysophospholipids released
reduced conduction velocity
AP shortening + conduction slowing
= re-entrant arrhythmia
Generation of ectopic beats
（2） Myocardial stunning
Myocardial contractile function is temporarily but
reversibly impaired for a period of hours to days
5 min ischemia, reperfusion, 40min later restoring
1 hr ischemia, reperfusion, a month later restoring
Mechanism of myocardial stunning
• OFR
• Ca2+ overload
• No-reflow
• ATP↓ + contractile protein sensitivity ↓ for
Ca2+
（3）Myocardial metabolism
ATP depletion
ATP substrate catabolized, rushed out
Processes Involving Energy Production and Utilization by the
Myocardium
Ca++
Ca++
O2
Fatty Acids
Lactate
Pyruvate
Ca++
TCA cycle
(Aerobic)
ATPase
ATP
+
ATP
Glycolysis
(Anaerobic)
Glucose
Ca+
ATP
PC
ADP
CA++T
T
C
CPK
Myokinase
ATP-M + A MA + ADP
Glucose-1-PO4
Glycogen
Energy Sources
Energy Pool
tricarboxylic acid cycle
phosphocreatine
Energy Use
C
O
N
T
R
A
C
T
I
O
N
（4） Myocardial ultrastructure
Contraction band necrosis
Interstitial haemorrhage
Neutrophilic plugging
Distal platelets–fibrin microembolisation
Histopathologic features in the myocardium following reperfusion.
2. Cerebral, Hepatic, Pulmonary, Renal
ischemia-reperfusion injury
Structure
Metabolism
function
change
Section 4
Principle of prevent & treatment
1. Controlling reperfusion condition
2. Antioxidant and OFR scavenging agents
3. Inhibition of neutrophil activation
4. Ca2+ antagonists or Ca2+ channel blocker
Zhao Mingyao