Ineffectiveness of methylprednisolone to reduce infarct size in experimental coronary occlusion

Anti-inflammatory therapies in myocardial infarction: failures, hopes and challenges

In the infarcted heart, the damage-associated molecular pattern proteins released by necrotic cells trigger both myocardial and systemic inflammatory responses. Induction of chemokines and cytokines and up-regulation of endothelial adhesion molecules mediate leukocyte recruitment in the infarcted myocardium. Inflammatory cells clear the infarct of dead cells and matrix debris and activate repair by myofibroblasts and vascular cells, but may also contribute to adverse fibrotic remodelling of viable segments, accentuate cardiomyocyte apoptosis and exert arrhythmogenic actions. Excessive, prolonged and dysregulated inflammation has been implicated in the pathogenesis of complications and may be involved in the development of heart failure following infarction. Studies in animal models of myocardial infarction (MI) have suggested the effectiveness of pharmacological interventions targeting the inflammatory response. This article provides a brief overview of the cell biology of the post-infarction inflammatory response and discusses the use of pharmacological interventions targeting inflammation following infarction. Therapy with broad anti-inflammatory and immunomodulatory agents may also inhibit important repair pathways, thus exerting detrimental actions in patients with MI. Extensive experimental evidence suggests that targeting specific inflammatory signals, such as the complement cascade, chemokines, cytokines, proteases, selectins and leukocyte integrins, may hold promise. However, clinical translation has proved challenging. Targeting IL-1 may benefit patients with exaggerated post-MI inflammatory responses following infarction, not only by attenuating adverse remodelling but also by stabilizing the atherosclerotic plaque and by inhibiting arrhythmia generation. Identification of the therapeutic window for specific interventions and pathophysiological stratification of MI patients using inflammatory biomarkers and imaging strategies are critical for optimal therapeutic design.

Modification of myocardial ischemic injury: a concentration response study of glucocorticoid supplementation during reperfusion

Reperfusion of the ischemic myocardium is routinely done during cardiac surgery and in the catheterization laboratory after acute regional ischemia. While reperfusion of the ischemic myocardium is necessary in order to regain full functional and biochemical recovery, the reperfusion by itself may aggravate the ischemic damage. Glucocorticoids have been shown to modify the outcome from ischemic injury in various experimental and clinical situations, but the results are conflicting. This protocol was performed using normothermic ischemic (30 minutes) isolated rat hearts, and postischemic reperfusion (30 minutes) with methylprednisolone sodium succinate (MPSS; 100-500-1,000 mg/L) was studied. All indices of myocardial function and all metabolic variables were significantly reduced after ischemia. MPSS (100 mg/L) improved dP/dTmax (recovery 68 +/- 3% v control 48 +/- 7%) and some of the other indices of left ventricular performance studied. MPSS (100 mg/L) also improved the tissue concentration of adenosine triphosphate (ATP) (13.8 +/- 0.5 mumol/g dry weight v control 11.3 +/- 0.8) and the total adenosine pool (16.8 +/- 0.7 mumol/g weight v control 13.9 +/- 0.8 mumol/g dry weight). MPSS (1,000 mg/L) impaired recovery of myocardial function (dP/dTmax, dP/dtmin, rate-pressure product [RPP]), increased tissue lactate (7.2 +/- 2.0 mumol/g dry weight v control 3.6 +/- 0.8), reduced glycogen (30.6 +/- 2.5 mumol/g dry weight v control 49.8 +/- 3.3), and energy charge (0.848 +/- 0.018 v control 0.890 +/- 0.010). It is concluded from the present experiments that modification of an ischemic injury by glucocorticoids given at the onset of reperfusion is possible, and that an optimal concentration of 100 mg/L exists for MPSS supplementation. MPSS in a concentration of 1,000 mg/L aggravated the reperfusion injury, probably by interference with cellular respiration.

Reduction of enzyme release from reperfused ischemic hearts by steroidal and non-steroidal prostaglandin synthesis inhibitors

Exacerbation of heart tissue damage by reperfusion of the ischemic myocardium is a well documented phenomenon. The present study was undertaken to evaluate prostaglandin (PG) involvement in reperfusion-induced damage of isolated globally ischemic rat hearts. Reperfusion produced significant increases in creatinephosphokinase (CPK) and lactic dehydrogenase (LDH) efflux which was accompanied by enhanced PG release. Three non-steroidal antiinflammatory drugs; indomethacin, mefenamic acid and ASA, and the steroidal agents; dexamethasone, hydrocortisone and methylprednisolone significantly reduced both the release of CPK and PGs upon reperfusion whereas only indomethacin and mefenamic acid decreased LDH release. There was a significant correlation between the inhibition of PG synthesis and the attenuation of CPK leakage by both non-steroidal (P less than 0.001) and steroidal (P = 0.02) antiinflammatory agents. In spite of beneficial effects on enzyme release, drug treatment did not enhance recovery of mechanical function after reperfusion. The results suggest that inhibition of PG biosynthesis may be beneficial in preserving membrane, particularly mitochondrial integrity of the reperfused myocardium.