Conditioned blood reperfusion during angioplasty (CoBRA) treatment of acute myocardial infarction

Reperfusion injury as a target for diminishing infarct size

Therapies for preventing reperfusion injury (RI) have been widely studied. However, the attempts to transfer cardioprotective therapies for reducing RI from experiments into clinical practice have been so far unsuccessful. Pathophysiological mechanisms of RI are complicated and compose of many pathways e.g. hypercontracture-mediated sarcolemma rupture, mitochondrial permeability transition pore persistent opening, reactive oxygen species formation, inflammation and no-reflow phenomenon. Based on research, it cannot be determined which mechanism dominates, probably they cooperate with a domination of one or another in different clinical circumstances. Our hypothesis is, that only intervention that at the same time interferes with different (all?) pathways of RI may turn out to be effective in decreasing the final area of infarction.

Cardioprotective Properties of Human Platelets Are Lost in Uncontrolled Diabetes Mellitus: A Study in Isolated Rat Hearts

Platelets affect myocardial damage from ischemia/reperfusion. Redox-dependent sphingosine-1-phosphate production and release are altered in diabetic platelets. Sphingosine-1-phosphate is a double-edged sword for ischemia/reperfusion injury. Therefore, we aimed to verify whether: (1) human healthy- or diabetic-platelets are cardioprotective, (2) sphingosine-1-phosphate receptors and downstream kinases play a role in platelet-induced cardioprotection, and (3) a correlation between platelet redox status and myocardial ischemia/reperfusion injury exists. Isolated rat hearts were subjected to 30-min ischemia and 1-h reperfusion. Infarct size was studied in hearts pretreated with healthy- or diabetic-platelets. Healthy-platelets were co-infused with sphingosine-1-phosphate receptor blocker, ERK-1/2 inhibitor, PI3K antagonist or PKC inhibitor to ascertain the cardioprotective mechanisms. In platelets we assessed (i) aggregation response to ADP, collagen, and arachidonic-acid, (ii) cyclooxygenase-1 levels, and (iii) AKT and ERK-phosphorylation. Platelet sphingosine-1-phosphate production and platelet levels of reactive oxygen species (ROS) were quantified and correlated to infarct size. Infarct size was reduced by about 22% in healthy-platelets pretreated hearts only. This cardioprotective effect was abrogated by either sphingosine-1-phosphate receptors or ERK/PI3K/PKC pathway blockade. Cyclooxygenase-1 levels and aggregation indices were higher in diabetic-platelets than healthy-platelets. Diabetic-platelets released less sphingosine-1-phosphate than healthy-platelets when mechanical or chemically stimulated in vitro. Yet, ROS levels were higher in diabetic-platelets and correlated with infarct size. Cardioprotective effects of healthy-platelet depend on the platelet’s capacity to activate cardiac sphingosine-1-phosphate receptors and ERK/PI3K/PKC pathways. However, diabetic-platelets release less S1P and lose cardioprotective effects. Platelet ROS levels correlate with infarct size. Whether these redox alterations are responsible for sphingosine-1-phosphate dysfunction in diabetic-platelets remains to be ascertained.

Ticagrelor attenuates myocardial ischaemia-reperfusion injury possibly through downregulating galectin-3 expression in the infarct area of rats

AIMS

The full benefits of myocardial revascularization strategies applied to acute myocardial infarction patients might be reduced by myocardial ischaemia and reperfusion (I/R) injury. It is known that inflammation plays an important role in the pathogenesis of I/R injury and galectin-3, a known inflammatory factor, is actively involved in ischaemia-induced inflammation and fibrosis of various organs. Previous studies demonstrated that anti-platelets therapy with ticagrelor, a new P2Y12 receptor antagonist, could effectively attenuate myocardial I/R injury and I/R injury-related inflammatory responses. It remains unknown whether the cardioprotective effects of ticagrelor are also mediated by modulating myocardial galectin-3 expression.

METHODS

We determined the ratio of infarct area (IA)/area at risk (AAR), expression of galectin-3, TNF-α and IL-6 in infarct area of rats treated with placebo (equal volume saline per gastric gavage immediately after LAD ligation, then once daily till study end) or ticagrelor (150 mg kg^-1 dissolved in saline per gastric gavage immediately after LAD ligation, then once daily till study end) at 24 h, 3 and 7 days post I (45 min)/R injury. Sham-operated rats served as control.

RESULTS

Our results showed that ticagrelor treatment significantly reduced IA/AAR ratio at 3 and 7 days post I/R, downregulated mRNA and protein expression of galectin-3, as well as mRNA expression of TNF-α and IL-6 in infarct area at 24 h, 3 and 7 days post I/R.

CONCLUSIONS

Our results suggest that the cardioprotective effects of ticagrelor might partly be mediated by downregulating galectin-3 expression in infarct area in this rat model of myocardial I/R injury.

Platelets, diabetes and myocardial ischemia/reperfusion injury

Mechanisms underlying the pathogenesis of ischemia/reperfusion injury are particularly complex, multifactorial and highly interconnected. A complex and entangled interaction is also emerging between platelet function, antiplatelet drugs, coronary diseases and ischemia/reperfusion injury, especially in diabetic conditions. Here we briefly summarize features of antiplatelet therapy in type 2 diabetes (T2DM). We also treat the influence of T2DM on ischemia/reperfusion injury and how anti-platelet therapies affect post-ischemic myocardial damage through pleiotropic properties not related to their anti-aggregating effects. miRNA-based signature associated with T2DM and its cardiovascular disease complications are also briefly considered. Influence of anti-platelet therapies and different effects of healthy and diabetic platelets on ischemia/reperfusion injury need to be further clarified in order to enhance patient benefits from antiplatelet therapy and revascularization. Here we provide insight on the difficulty to reduce the cardiovascular risk in diabetic patients and report novel information on the cardioprotective role of widely used anti-aggregant drugs.

Reperfusion injury following cerebral ischemia: pathophysiology, MR imaging, and potential therapies

Introduction

Restoration of blood flow following ischemic stroke can be achieved by means of thrombolysis or mechanical recanalization. However, for some patients, reperfusion may exacerbate the injury initially caused by ischemia, producing a so-called “cerebral reperfusion injury”. Multiple pathological processes are involved in this injury, including leukocyte infiltration, platelet and complement activation, postischemic hyperperfusion, and breakdown of the blood–brain barrier.

Methods/results and conclusions

Magnetic resonance imaging (MRI) can provide extensive information on this process of injury, and may have a role in the future in stratifying patients’ risk for reperfusion injury following recanalization. Moreover, different MRI modalities can be used to investigate the various mechanisms of reperfusion injury. Antileukocyte antibodies, brain cooling and conditioned blood reperfusion are potential therapeutic strategies for lessening or eliminating reperfusion injury, and interventionalists may play a role in the future in using some of these therapies in combination with thrombolysis or embolectomy. The present review summarizes the mechanisms of reperfusion injury and focuses on the way each of those mechanisms can be evaluated by different MRI modalities. The potential therapeutic strategies are also discussed.

Conditioned blood reperfusion markedly enhances neurologic recovery after prolonged cerebral ischemia

OBJECTIVES

To determine whether controlled reperfusion using conditioned leukodepleted blood can substantially limit cerebral reperfusion injury following prolonged ischemia.

METHODS

Eighteen pigs (25-35 kg) underwent 90 minutes of hypothermic circulatory arrest (19 degrees C) to produce brain ischemia. At the start of rewarming, 10 pigs received uncontrolled reperfusion with unmodified (normal) blood. The other 8 pigs underwent 10 minutes of controlled reperfusion by selectively perfusing both common carotid arteries with blood passed through a CoBRA filter. This filter conditions the blood by removing white blood cells, platelets, and attenuating complement. Two other pigs underwent cooling and rewarming only (controls) without ischemia. Neurologic assessment was done using neurologic deficit scoring (0 = normal, 500 = brain death), and jugular venous samples were obtained for biochemical analysis postreperfusion.

RESULTS

There were no statistical differences in hemodynamics between groups. At 6 hours postanesthesia, all animals receiving normal blood were substantially neurologically impaired. At 24 hours, they all had abnormal positioning and all but 1 were unable to sit or stand (neurologic score 124 +/- 19). In contrast, nonischemic controls and pigs receiving conditioned blood reperfusion showed only minor neurologic deficits at 6 hours, and at 24 hours all were considered normal (neurologic scores 0 and 6 +/- 5; P <.005 vs uncontrolled reperfusion). Compared with pigs receiving normal blood reperfusion, oxygen free radical formation (conjugated dienes 1.70 +/- 0.03 vs 1.60 +/- 0.02 Abs 240 nm; P <.05 vs uncontrolled reperfusion), and endothelin-1 release (2.12 +/- 0.09 vs 1.84 +/- 0.06 pg/mL; P <.05 vs uncontrolled reperfusion) were also significantly lower in animals receiving conditioned blood.

CONCLUSIONS

Following prolonged cerebral ischemia, reperfusion injury is avoided by delivering conditioned blood, which is devoid of white cells, platelets, and membrane attack complex. These results suggest that this modality is clinically useful in situations where the brain is subjected to prolonged ischemia.

Deep hypothermic circulatory arrest and global reperfusion injury: avoidance by making a pump prime reperfusate--a new concept

OBJECTIVE

We sought to determine whether damage after deep hypothermic circulatory arrest can be diminished by changing pump prime components when reinstituting cardiopulmonary bypass.

METHODS

Fifteen piglets (2-3 months old) were cooled to 19 degrees C by using the alpha-stat pH strategy. Five were cooled and rewarmed without ischemia (control animals), and the other 10 piglets underwent 90 minutes of deep hypothermic circulatory arrest. Of these, 5 were rewarmed and reperfused without altering the cardiopulmonary bypass circuit blood prime. In the other 5 animals, the bypass blood prime was modified (leukocyte depleted, hypocalcemic, hypermagnesemic, pH-stat, normoxic, mannitol, and an Na(+)/H(+) exchange inhibitor) during circulatory arrest before starting warm reperfusion. Oxidant injury was assessed on the basis of conjugated dienes, vascular changes on the basis of endothelin levels, myocardial function on the basis of cardiac output and dopamine need, lung injury on the basis of pulmonary vascular resistance and oxygenation, and cellular damage on the basis of release of creatine kinase and aspartate aminotransferase. Neurologic assessment (score 0, normal; score 500, brain death) was done 6 hours after discontinuing cardiopulmonary bypass.

RESULTS

Compared with animals undergoing cardiopulmonary bypass without ischemia (control animals), deep hypothermic circulatory arrest without modification of the reperfusate produced an oxidant injury (conjugated dienes increased 0.78 vs 1.71 absorbance (Abs) 240 nmol/L per 0.5 mL, P <.001 vs control animals), depressed cardiac output (6.0 vs 4.0 L/min, P <.05 vs control subjects), prolonged dopamine need (P <.001 vs control subjects), elevated pulmonary vascular resistance (74% vs 197%, P <.05 vs control subjects), reduced oxygenation (P <.01 vs control subjects), increased neurologic injury (56 vs 244, P <.001 vs control subjects), and increased release of creatine kinase (2695 vs 6974 U/L, P <.05 vs control subjects), aspartate aminotransferase (144 vs 229 U/L), and endothelin (1.02 vs 2.56 pg/mL, P <.001 vs control subjects). Conversely, the oxidant injury was markedly limited (conjugated dienes of 0.85 +/- 0.09 Abs 240 nmol/L per 0.5 mL, P <.001 vs unmodified pump prime) with modification of cardiopulmonary bypass prime, resulting in increased cardiac output (5.1 +/- 0.8 L/min), minimal dopamine need (P <.001 vs unmodified pump prime), no increase in pulmonary vascular resistance (44% +/- 31%, P <.01 vs unmodified pump prime) or endothelin levels (0.64 +/- 0.15 pg/mL, P <.001 vs unmodified pump prime), complete recovery of oxygenation (P <.01 vs unmodified pump prime), reduced neurologic damage (144 +/- 33, P <.05 vs unmodified pump prime), and lower release of aspartate aminotransferase (124 +/- 23 U/L, P <.05 vs unmodified pump prime) and creatine kinase (3366 +/- 918, P <.05 vs unmodified pump prime).

CONCLUSIONS

A global reperfusion injury after deep hypothermic circulatory arrest was identified and changed. The injury is mediated by oxygen-derived free radicals, resulting in organ and endothelial dysfunction. Modification of global organ and endothelial damage is achieved by modifying the blood prime in the cardiopulmonary bypass circuit to deliver a controlled global reperfusate when reinstituting bypass.