Chapt Er 11

Chapt er 11

Ischemia-reperfusion injury

Brief history

Simple phenomenon

• 1 ９５５年， Sewell ligated coronary artery of dog, restore blood flow after deligation. • What happened for this heart?

suggest the •１９６０年， Jennings concept of myocardial reperfusion injury firstly.

Clinic ： •

• • • •

Shock , DIC Bypass surgery Fibrinolytic therapy Cardiopulmonary operation Organ transplantation

PTCA (percutanerous transluminal coronary angioplasty/stent),

Cardiopulmonary resuscitation

Features of IRI ： 1. reversible → irreversible 2. Massive in organs 3.participating factors oxygen paradox calcium paradox pH paradox

perfusion

oxygen paradox

Without O2

calcium

without Ca2+

paradox pH parado x

acidosis

perfusion

Normal O2 supply

with Ca2+ Correcting acidosis

Deteriorate injury

Concept of IschemiaReperfusion Injury

The restoration of blood flow after transient ischemia may induce further reversible or irreversible cellular 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 发生率（%） 50 incidence rate40 30 20 10 0

RVA RVT RVF

5mi n

10mi n

30mi n

缺血时间（mi n)

Ischemic time

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

The Nobel Prize in Chemistry • 1971： Gerhard Herzberg • for his contributions to electronic structure and the geometry of molecules, particularly free radicals

CELLS

Classification (1) Oxygen free radical （ OFR) • Induced by O2 O·-2 types

OH· O2 OFR H2O2 ONOO1

Active oxygen

In a nutshell, this is how you could summarize his theory:

(2) Lipid radicals types ： L· LO· LOO· (3) Cl· 、 CH3 · 、 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 毒物作用于细胞

2 ） production process of OFR O2 + e Cytaa3

O2 •

O2+ 2e + 2H+

H2O2

O2 + 3 e + 3H+

HO• + H2O

O2 + 4 e + 4H+

2 H2O

SOD H2O2 nse

Single electron reductio Single electron reduction of

Dismutation reaction Single electron reduction of O2

2O2 • + 2H+

SOD

H2O2 + O2 H2O2 nse

Haber-Weiss reaction (without － • O2 + H 2O 2

SLOW

Fe

+2

)

O 2 + OH +OH•

Fenton type of HaberWeissreaction( with ) Fe

Fe

O 2 • + H 2O 2 －

+3

+2

Fast

O 2 + OH +OH•

What significance ？？？

.

OH 化学效应

3 ） Scavenging of OFR *low molecule ~

hydrofacies of intra- or extracell: Cysteine 、 Vit C 、 Glutathione

Cellular lipid ： Vit E 、 Vit A

Cytosol ： NADPH

*enzymatic ~ Glutathione peroxidase (GSH-Px)

Catalase (CAT)

Superoxide dismutase SOD

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: ATP degradation Hypoxathine↑↑

(1)Ca2+→protease reperfusi

O2

on: XD

XO

（ 2 ） restore O2

XO role in formation of OFR

xanthine + O·-2+ H2O2

O2 O·-2+ H2O2 +uric acid

OH ·

3)Neutrophil pathway C3,LTB4

Activates NP hexose

bypass activation

Respiratory burst NADH oxidase

NADH(I) + H + O 2·+H2O2 NADPH(II)+ O2 NADPH oxidase

4) Catecholamine autooxidation pathway

Vanillylmandelic Methyl transferase Adr monoamine oxidaseacid (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 linkage

Protein ~ Protein break

Lipid – pro ~

Two sulfur ~ -S-S-

OH HO

OH HO

CH3-SO Amino acid oxidation

fatty acid oxidation

Lipid-lipid ~ MDA released by oxidated fatty acid Malondialdehyde(MDA)

DNA disruption and chromosome aberration

induced by OH• about 80% damage

Part 2 Calcium overload

1. Calcium transportation and distribution Ca 2+ Ca 2+

Ca2+ binding Pr

Ca2+ pump SR

Ca 2+ Channel

Mt

Na + -Ca 2+ cotransporto r

2. Mechanism of ~ ① Na+ - Ca2+ exchange↑ ②ATP ↓: mitochondria, precursor ↓ ③Membrane permeability ↑ ④catecholamine ↑

NE

α1

H+

Gq

PLC

Ca2+

P1

Na+ IP3

Ca2+ SR

DG 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:

3.NO and ONOO production -

（ 1 ） NO • NO in VEC, little, physiological • NO in inflammatory cell, rich, cytotoxic (Mt respiration, aconitase activity, DNA synthesis) and OONO-

2. 抑制蛋白质功能： 脂质 - 蛋白质 - 胶原交 联 蛋白质 蛋白质交 联

蛋白 质断 裂

二硫交联 -S-S-

CH3-SO

氨基 酸 氧 化

脂质 - 蛋 白 质交 联

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 and lysophospholipids released reduced conduction velocity

Heart’s Electrical System

Bundle of His Sinus (SA) node AV node RA Tricuspid Valve RV

LA Mitral Valve Purkinje fibers LV

AP shortening + conduction slowing = re-entrant arrhythmia OFR, AP duration NE, Ca2+, phosphoinositide, channel Na+, K+

KATP

（ 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 + sensitivity for Ca2+

（ 3 ） myocardial metabolism ATP depletion ATP substrate catabolized, rushed out

Processes Involving Energy Production and Utilization by the Myocardium Ca++ Ca++ Ca++

O2 Fatty Acids Lactate Pyruvate

TCA cycle (Aerobic)

ATPase

ATP ATP

Glycolysis (Anaerobic)

Glucose

ATP

PC

Ca

++

ADP

CA++ T

T

C CPK

Myokinase

ATPm + A MA + ADP

Glucose-1-PO4 Glycogen

Energy Sources tricarboxylic acid cycle

Energy Pool phosphocreatin

Energy Use

C O N T R A C T I O N

（ 4 ） myocardial ultrastructure

2. Cerebral ischemia-reperfusion

injury

3.Hepatic Ischemia-Reperfusion Injury

(4) Renal ischemia-reperfusion injury

Section 4 principle of prevent and treatment 1. Controlling reperfusion condition 2. Antioxidant and OFR scavenging agents 3. Inhibition of neutrophil activation 4. Ca2+ antagonists or Ca2+ channel blocker

How prevent and treat IRI (1) Restore normal perfusion of tissue in time (2) Pharmacologic agents Ca2+ antagonist, Ca2+ channel blocker OFR scavenging agents glutathione peroxidase(GP) GSH + H2O2

GSSG + H2O

GP

Acute preconditioning: (classical preconditioning) • •

within ~2 h protein synthesis-independent

Delayed preconditioning: (ischemic tolerance) • •

24 h - 72 h after the initial insult altered gene expression→synthesis of proteins (antioxidant enzymes, NO synthase, etc.).