Βλάβη xπανα v v xιώσ xως (reperfusion injury) και απόπληκ ... · Morphology...
Transcript of Βλάβη xπανα v v xιώσ xως (reperfusion injury) και απόπληκ ... · Morphology...
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