Ischemia-reperfusion injury (IRI) Chapter 10 Department of Pathophysiology, Anhui Medical University Yuxia Zhang

 Concepts: IRI, oxygen/calcium/pH paradox  Causes and conditions of IRI  Mechanisms of IRI injury  Metabolic and functional alterations  Prevention and treatment principle Contents

Introduction at 1960 ， Jenning:MI/R I 1968, brain ； 1972, kindey ； 1978, lung ； 1981, intestinal ； and so on Clinical phenomenon: bypass surgery,shock treatment,organ transplantation, thrombolysis, recovery of hearts after ischemic arrest ， Percutanueous Transluminal Coronary Angioplasty (PTCA) I/R I is a common phenomenon paradoxical phenomenon

1.Concept IRI the reestablishment of blood flow after prolonged ischemia aggravates the tissue damage.

pH paradox ischemia acidosis, disorder of function and metbolism on cell severe IRI pH paradox calcium paradox pre-perfuse rat heart with no calcium perfusion for 2min perfuse calcium perfusion, cell release enzyme myofibril over-constract, electron signals abnormal ， calcium paradox

Oxygen paradox Hypoxia liquid perfuse organ or culture without oxygen injury restore perfusion severe injury

2. Cause of ischemia-reperfusion injury and affecting factor Recover from cardiac arrest Organ transplantation Lysing thrombi （ 1 ） cause

（ 2 ） Affecting factor Duration of ischemia small animals 5-10min: arrhythmia 20-30min: ventricular tremor big animals 20-40min: reversible injury 40-60min:irreversible injury diversity between small and big animal

Branch circulation ： chronic O 2 consumption rate [K + ], [Mg 2+ ] condition of reperfusion T, pressure,pH,Na +,Ca 2+ protection T, pressure,Na +,Ca 2+ damage

3. Mechanisms of IRI role of oxygen free radical calcium overload role of leukocyte

(1)Role of oxygen free radical  concept and classification of free radical Free radical: Any atom or molecule possessing unpaired electrons Nitric oxide (NO. )Peroxynitrite （ ONOO - ) Cl 、 CH 3 、 NO Free radicals Oxygen free radicals(OFR) Superoxide anion (O 2.- ), Hydroxyl radical (OH. ) : Lipid peroxide radical ˉ : L LO LOO L LO LOO Others : Reactive oxygen species (ROS) : O 2 OH 1 O 2 H 2 O 2

formation of oxygen free radical nature oxidation of Hb, Cyt C O 2 O ‾∙ 2 H 2 O 2 OH ∙ H 2 O H 2 O oxidation of enzyme :XO Mitochondria: normal : O 2 +4e+4H + → H 2 O+ATP abnormal :O 2 +e → O · - 2 +e +2H + → H e+H + → OH · +e+H + → H 2 0 O ‾∙ 2

SOD O · O · H + H 2 O 2 +O 2 O · - 2 +H 2 O 2 OH · + OH · +O 2 Fenton Haber-Weiss ： SOD Fe 2+ Fe 3+ O · - 2 H 2 O 2 OH · + OH - Production of OH·

 Mechanism of increased OFR generation Xanthine oxidase pathway ： XO↑ Xanthine oxidase pathway ： XO↑ normal ： Endothelial cell ， XO 10% ， XD 90% OH OH xanthine + O 2 +H 2 O 2 – hypoxanthine ischemia – reperfusion Uric acid+O 2 +H 2 O 2 ATP ADP AMP XD Ca 2+ XO O2O2 O2O2

The effects of leucocyte ： respiratory burst The effects of leucocyte ： respiratory burst NADPH oxidase NADPH +2O 2 2O· - 2 +NADP + +H + NADH+O 2 H 2 O 2 +NAD + + 2H + NADH oxidase reperfusion ： oxygen consumption of infiltrated WBC:↑70-90% O2

Disfunction of mitochondria normal: O 2 +4e+4H + →H 2 O+ATP abnormal :O 2 +e→ O· - 2 +e +2H + →H e+H + →OH· +e+H + →H 2 0 catecholamine autooxidation AD adsenale + O· - 2 MAO

 Damage of oxygen-derived free radicals membrane lipid peroxidation cellular membrane lipid peroxidation permeability ↑ fluidity ↓ [Ca 2+ ] i calciumoverload [Na + ] i, [Ca 2+ ] i lipid cross-linked inhibition of Na + -pump and Ca 2+ -pump

membrane lipid peroxidation phospholipase C phospholipase D PGs, LTs TXA2 damage of mitochondria membrane ATP

enzymes ： channels: inhibition of protein function destruction of nuclear acid base hydroxylation 、 breakdown of DNA

HEALTHY CELL (left) | FREE RADICAL DAMAGE (right)

The abnormal increase of intracellular calcium which causes cell injury (2) Calcium overload Concept Metabolic pathway of [Ca 2+ ]i Ca 2+ pump in the cell membrane; Na + -Ca 2+ exchange pump in the cell membrane ; Ca 2+ pump in the mito. membrane ; Ca 2+ pump in endoplasmic reticulum

K+K+ Na + 3Na + Ca 2+ ATP↓ Na + ↑ Ca 2+ ↑ Ischemia  mechanism of calcium overload Reperfusion Abnormal Na + -Ca 2+ exchange direct activation ： intracellular sodium↑

indirect activation （ 1 ）： intracellular 【 H + 】 ↑ 3Na + Ca 2+ Na + K+K+ H+H+ Reperfusion H + ↓ H+↑H+↑ Na + ↑ Ca 2+ ↑ Ischemia H + ↑

indirect activation （ 2 ）： activation of PKC ischemia NE α 1 – receptor NE SR myofilament

catecholamine β – receptor [Ca 2+ ] i β Cellular membrane Ca 2+ ↑ L Ca 2+ - channel

Damage of mitochondria damage of cellular membrane: injury of biomembrane [Ca 2+ ] ↑ ATP Ca 2+ - ATPase calcium overload Damage of mitochondria and sarcoplasmic Damage of Sarcopasmic

 Pathogenesis of calcium overload Damage mitochondria ： ATP ↓ promote OFR formation ： damege aggravation Stimulating the phospholipase ： injury of membrane cell and cell organ mitochondrial dysfunction

(3) role of leukocyte activation,margination and aggregation of PMNs after reperfusion adhesion molecule ; chemotatic factor; mediators of inflammation

Neutrophil activation ROSInflammatory mediators Injury of Micro-vessels No-reflow phenomenon Cell injury Role of Neutrophil Reperfusion

Ischemia-reperfusion injury of heart 3. Changes of function and metabolism Changes in cardiac function Decrease of myocardial contractility ： myocardial stunning Eperfusion arrhythmia Changes in myocardial metabolism: ATP↓, ADP↑, AMP↑ Changes in myocardial structure: cell edma ， contraction band ， apoptosis

Heart Injury Ischemia-reperfusion injury Calcium overload Free radical Destroy of contractile protein Myocardial stunning Ca++ K+ Na+ ArrhythmiaCell death

Ischemia-reperfusion injury of brain ATP Na + -pump cellular edema Hypoxia of cells cellular acidosis Excitability transmitter inhibitive transmitter cAMP↑ cGMP↓ activate free fatty acid ↑ lipid peroxidation ↑ Hisconstructure:Edema, necrosis

4. Principles of prevention and treatment (1) restoring normal perfusion of tissue in time low temperature; low pressure; low flow; low natrium(sodium); low pH; low calcium

(2) improve the metabolism of the tissues ATP; cytochrome C; (3) sweep away free radical: VitE: lose e FR FR (lipid) VitC: clear OH ∙ (water) β-cartenoids: clear 1 O 2 GSH

enzyme scavenger ： 2 O ‾∙ 2 +2H + H 2 O + O 2 H 2 O 2 H 2 O+ O 2 (4) relieve of calcium overload Ca 2+ ion blok agent SOD CAT

5. CoQ Inhibit L (lipid free radical) 2L+ CoQ 2LH+ CoQ protein enzyme inhibitor: ulinastatin