Βλάβη επαναγγειώσεως (reperfusion injury) και απόπληκτο (stunning) μυοκάρδιο

ΘΩΜΑΣ ΠΑΠΑΔΟΠΟΥΛΟΣ,MD,PhD,FESC,FACC,FSCAIΕΠΕΜΒΑΤΙΚΟΣ ΚΑΡΔΙΟΛΟΓΟΣ, ΙΑΤΡΙΚΟ ΔΙΑΒΑΛΚΑΝΙΚΟ ΚΕΝΤΡΟ

ΕΠΙΣΤΗΜΟΝΙΚΟΣ ΣΥΝΕΡΓΑΤΗΣ, ΒΚΚ, ΙΠΠΟΚΡΑΤΕΙΟ ΓΠΝΘ

Time course of cell death

20 - 40 minutes to irreversible cell injury

~ 24 hours to coagulation necrosis

5 - 7 days to “yellow softening”

1 - 4 weeks: ventricular “remodeling”

6 - 8 weeks: fibrosis completed

IMPORTANT TARGETS OF CELL INJURYAerobic respiration – ATP depletion or decreased synthesis.

Cell membranes - plasma membranes, mitochondrial,

lysosomal and other organelle membranes.

Protein synthesis.

Cytoskeleton.

Genetic apparatus.

ATP DEPLETION - HYPOXIA/ISCHAEMIAMitochondria - reduced oxidative phosphorylation.

Cell membrane - reduced sodium pump.

Sodium and water enter the cell; potassium exits.

Endoplasmic reticulum dilates, the cell swells, blebs appear.

Anaerobic glycolysis occurs with loss of glycogen, accumulation of lactic acid, acid pH which interferes with enzymes.

Failure of the calcium pump leads to influx of Ca++ into the cell, activate various enzymes to the detriment of the cell.

RER, (κοκκώδες ενδοπλασματικό δίκτυο), loses ribosomes and protein synthesis falls -structural proteins (membranes,cytoskeleton) and enzymes.

THE IMPORTANCE OF CALCIUM•Influx of calcium to the cytosol comes from the extracellular fluid and stores in mitochondria and endoplasmic reticulum.

•Ca++ activates phospholipases (damages cell membranes),proteases (damages cell membranes and cytoskeleton) and endonucleases (damages DNA).

•This is one of the main mechanisms of cell death, either through severe damage to membranes of lysosomes and leakage of lysosomal enzymes or triggering apoptosis.

•Occurs particularly in hypoxia and ischaemia and with certain toxins. Preventing the rise in Ca++ or restoring to normal levels prevents cell death.

THE IMPORTANCE OF FREE RADICALS•Free radicals have a single unpaired electron in the outer orbit. They are highly reactive with adjacent molecules.

•Are usually derived from oxygen (OFR)to produce reactive oxygen species (ενεργές μορφές οξυγόνου) (ROS), superoxide, hydroxyl radicals,H2O2,etc.

•Are normally produced during cellular respiration. Protective molecules include superoxide dismutase, glutathione peroxidase, vitamin E, vitamin C, catalase.

•Produced in excess, they react with, and damage proteins, lipids, carbohydrates, nucleic acids.

•These damaged molecules may themselves be reactive species with a chain reaction being set up with widespread damage.

FREE RADICALSIn addition to oxygen-derived free radicals, nitric oxide (NO) can act as a free radical and be converted to an even more reactive anion.

Iron and copper catalyze free radical formation and are thus important in the generation of reactive oxygen species.

Binding to molecules such as transferrin, ferritin and ceruloplasmin is protective.

Free radicals cause lipid peroxidation in cell membranes, oxidation of amino acids and proteins resulting in fragmentation, and protein-protein cross linkages. Altered proteins are acted on by the proteosomes with further cell damage.

Morphology of Cell Injury

Reversible:

Cellular swelling and vacuole (κενοτόπια) formation (Hyodropic changes)

Changes at this stage are better appreciated by EM that may show blebbing(διόγκωση) of the plasma membrane, swelling of mitochondria and dilatation of ER

Fatty changes

Hydropic ChangeHydropic change is one of the early signs of cellular degeneration in response to injury.refers to the accumulation of water in the cell. This is clearly seen in this slide. The accumulation of water in the tubular cells is usually due to hypoxia of the tissue with a resultant decrease in aerobic respiration in the mitochondria and a decreased production ATP

Morphology of Cell InjuryIrreversible/Necrosis

The changes are produced by enzymatic digestion of dead cellular elements, denatunation (μετουσίουση) of proteins and autolysis (by lysosomal enzymes)

Cytoplasm - increased eosinophilia

Nucleus - nonspecific breakdown of DNA leading to pyknosis (shrinkage),

karyolysis (fading) and

karyorrhexis (fragmentation).

Cell Death

Death of cells occurs in two ways:Necrosis--(irreversible injury) changes produced by enzymatic digestion of dead cellular elements

Apoptosis--vital process that helps eliminate unwanted cells--an internally programmed series of events effected by dedicated gene products

Apoptosis

Necrosis

Autophagy

When cells are faced with an inadequate supply of nutrients in their extracellular fluid (ECF), they may begin to cannibalize some of their internal organelles (e.g. mitochondria) for re-use of their components.

Mechanisms of Cell DeathMechanisms of cell death caused by different agents may vary. However, certain biochemical events are seen in the process of cell necrosis:

ATP depletion

Loss of calcium homeostasis and free cytosolic calcium

Free radicals: superoxide anions, Hydroxyl radicals, hydrogen peroxide

Defective membrane permeability

Mitochondrial damage

Cytoskeletal damage

ΘΕΡΑΠΕΥΤΙΚΗ ΑΝΤΙΜΕΤΩΠΙΣΗ ΤΗΣ ΙΣΧΑΙΜΙΑΣΕΠΑΝΑΓΓΕΙΩΣΗ

Φαρμακευτική επαναγγείωση

Θρομβολυτικά φάρμακα

Μηχανική επαναγγείωση

1. Διαδερμική Στεφανιαία Αγγειοπλαστική

2. Αορτοστεφανιαία παράκαμψη

ISCHAEMIA/REPERFUSION INJURYIf cells are reversibly injured due to ischaemia, complete recovery occurs following restoration of blood flow.

However, reperfusion can result in more damage including cell death.

This is due to incompletely metabolised products, producing reactive oxygen species, on re-introduction of oxygen

especially damaging to mitochondria

loss of anti-oxidants during ischemia

inflow of calcium with the renewed blood flow

recruitment of leukocytes to the injured area.

Reperfusion injury is especially important in ischemic damage to the heart and brain and in organ transplantation.

Various therapies and preventive measures are in use.

Clinical significance

It has been demonstrated that ischemia-reperfusion

injury may occur in many organs for example the heart,

brain, liver, kidney, lung, intestine, skeletal muscle and

skin etc..

It has very important practical significance to reduce

or prevent the ischemia-reperfusion injury, for such

as organ transplantation, microcirculation reperfusion in

shock, cardiac bypass surgery, thrombolysis, etc..

Experimental research found the calcium paradox,

oxygen paradox and pH paradox.

Mechanisms of

ischemia-reperfusion injury

1 Effect of free radicals

2 Calcium overload

3 Restoration of PH

4 Effect of white cells

Mechanism of IRI (ischemic reperfusion injury)

caused by FR

(1 ). Enhanced lipid peroxidation of

membrane

① Distroying structure of membrane

lipid peroxidation ↓unsaturated fatty acid

↓fluidity

↑permeability↑Internal flow

of Ca2+

2,2. Mechanism of IRI caused by Ca2+

overload

(1) Promoting sythesis of FR

(2) Aggravating acidosis

(3) Destroying cell membrane

↑Ca2+in cells→↑Ca2+-dependent proteases→↑XO→↑FR

↑Ca2+in cells→↑ATPases→ hydrolysis of ATP →↑H+

↑Ca2+in cells→activating phospholipase

Ischemia-reperfusion injury of myocardium induced by Ca2+ overload.

Ca2+ overload

Activation of Ca2+ dependent pathways

Ca2+accumulation

of mitochondrion

Activation of

myocardial excitation-

contraction coupling

Activation of

protease

Activation of

phospholipase A2

Dysfunction of

mitochondrion

Continual contraction

of myocardium OFR

Degradation of

membrane

phospholipid

Myocardium

necrosis

thromboxane

Thrombosis

Energy creation↓ Energy exhaustion↑ Injury of

membrane

arachidonic

acid

Mitochondrial permeability transition pore-MPTPand

Inducible nitric oxide synthase-iNOS

Effect of white cells

It has been manifested that the microvessel

and cell damage which mediated by leukocytes

play an important role in IRI.

(1) Increased production of adhesion molecules

Mechanism of neutrophils increase

during IRI

Selectin ---- P- selectin, L- selectin

Integrin ---- CD11/CD18

Immunoglobulin superfamily ---- ICAM-1, VCAM-1

(2) Increased production of chemokines

leukotriene、prostaglandin、PAF、kinin

neutrophils

Injury of tissue

(1) Injury of microvessel

3,2. Mechanism of IRI mediated by

neutrophils

(2) Injury of cells

① Alteration of hemorheology in microvessel

② Alteration of microvessel calibre

③ Increase of microvessel permeability

no

-flow

ph

en

om

en

on

ΑΠΟΠΛΗΚΤΟ ΜΥΟΚΑΡΔΙΟMYOCARDIAL STUNNING

Απόπληκτο μυοκάρδιο-StunningΠαρατεταμένη και πλήρως αναστρέψιμη δυσλειτουργία του ισχαιμικού

μυοκαρδίου, η οποία επιμένει παρά την φυσιολογική αιματική κυκλοφορία

Prolonged and fully reversible dysfunction of the ischemic heart that persists despite the normalization of blood flow.

1st described by Heyndrickx et al in 1975 in conscious dogs undergoing brief coronary occlusions.

In that study regional contractile dysfunction lasted for 6 hrs following 5 min and > 24 hrs following 15 min of ischemia.

Features of stunningNormal perfusion.

Depressed myocardial function.

Dissociation of usual relationship between subendocardial flow and function.

Reversible .

Function improves with inotropic agents.

Anatomical and biological determinants of the cardiomyocyte’sresponse to ischemic insult.

Stunning occurs in a wide variety of settings that differ from one another in several aspects

At experimental level it can occur during

1. Single , completely reversible episode of

regional ischemia (< 20 min )

2. Multiple, completely reversible episodes of

regional ischemia

3. Partly reversible plus partly irreversible

ischemia in vivo ( > 20 min & < 3 hrs)

4 After global ischemia in vitro (isolated heart preparations)

5. After global ischemia in vivo (cardioplegic arrest)

6. After exercise-induced ischemia

Clinical Relevance

In the clinical setting stunning can occur

1. Brief period of total coronary occlusion:

pts with angina due to spasm

2. Global ischemia after cardiopulmonary bypass.

3. In combination : Subendocardium is infarcted and

overlying subepicardium reversibly injured in MI

4. Following exercise in presence of a flow limiting

stenosis

5. Ischemic bout that is induced by PCI

Mechanisms of Stunning

There is no unified view of pathogenesis of stunning

Most plausible hypotheses are

Oxyradical hypothesis : oxidant stress secondary

to the generation of ROS.

Calcium hypothesis : results from disturbance of

cellular calcium homeostasis.

Oxyradical Hypothesis

Role of ROS in pathogenesis of stunning is proven

Its role in all settings of stunning is unclear

ROS-mediated injury responsible for stunning occurs in initial moments of reperfusion

Antioxidant therapies alleviate stunning whether begun before ischemia or just prior to reperfusion

But ineffective when begun after reperfusion

None of the antioxidant therapies completely prevented myocardial stunning

Calcium hypothesisTransient Ca2+ overload activates Ca2+-dependent proteases which degrades and induces covalent (ομοιοπολικές) modifications of myofilaments.

It results in ↓ responsiveness to Ca2+, manifested by a decrease in maximal force of contraction.

Prevention and treatment of

Ischemic Reperfusion Injury

Elimination of ischemia causes and an

early recovery of blood flow

Controlling conditions of reperfusion

Improving metabolism of ischemia tissues

Lower temperature, pressure, pH, flow speed, Ca2+, Na+ and

higher K+

ATP, cytochrome C and hydroquinone

Previous problematic approaches to reduce lethal reperfusion injury in patients with AMI

• Antioxidants

• Reduction of intracellular Ca2+ overload and Na+–H+ exchange inhibitors

• Anti-inflammatory agents

• Adenosine

• Metabolic modulation (glucose, insulin, and potassium)

• Magnesium

• Nicorandil

• Therapeutic hypothermia

New cardioprotective strategies for reducing lethal reperfusion injury in patients with AMI• Ischemic postconditioning

• Remote ischemic postconditioning

• RISK Pathway activators

◦ Atrial natriuretic peptide

◦ Glucagon-like peptide 1

◦ Darbepoetin alfa (long-acting erythropoietin analogue)

◦ Atorvastatin

• Protein kinase c-delta inhibitor (KAI-9803)

• Mitochondrial PTP inhibition

◦ Cyclosporin

◦ Other

Circ J 2017; 81: 131 – 141 doi: 10.1253/circj.CJ-16-1124

Reperfusion Damage

― A Story of Success, Failure, and Hope ―

Roberto Ferrari, MD, PhD; Cristina Balla, MD; Michele Malagù, MD; Gabriele Guardigli, MD; Giampaolo Morciano, MD, PhD; Matteo Bertini, MD; Simone Biscaglia, MD; Gianluca Campo, MD

ΣΑΣ ΕΥΧΑΡΙΣΤΩ ΓΙΑ ΤΗΝ ΠΡΟΣΟΧΗ ΣΑΣ