Myocardial release of FKBP12 and increased production of FKBP12.6 in ischemia and reperfusion experimental models.

BACKGROUND: Coronary artery occlusion and reperfusion may trigger reversible and irreversible ischemic and reperfusion injury. The primary aim of this study was to evaluate protein release into the myocardium in a porcine model during ischemia and reperfusion to search for clarifying models for reperfusion injury and secondarily to investigate release and production of the immunophilins FKBP12/12.6 in this model and in cell cultures. METHODS: In a porcine model local myocardial ischemia was induced during 45min followed by 120min of reperfusion. Microdialysis samples from ischemic and non-ischemic areas were analyzed with surface-enhanced laser desorption ionization (SELDI) mass spectrometry (MS) and Western blotting (WB). Myocardial biopsies from areas at risk and control areas were analyzed with reverse transcription polymerase chain reaction (RT-PCR). Myocardial cell cultures from mice (HL-1 cells) were exposed to hypoxia and then analyzed with WB and RT-PCR. RESULTS: FK binding protein12 (FKBP12), ubiquitin and myoglobin were identified as being released during ischemia and reperfusion in microdialysates. RT-PCR analysis on the biopsies after ischemia revealed a non-significant increase in mRNA expression of FKBP12 and a significant increase in mRNA expression of FKBP12.6. Lysates from HL-1 cells exposed to hypoxia demonstrated increase of FKBP12 and a significant increase in mRNA expression of FKBP12.6. CONCLUSION: In a myocardial ischemic-reperfusion porcine model as well as in hypoxic HL-1 cells, release of FKBP12 and increased production of FKBP12.6 was demonstrated. The findings indicate important mechanisms related to these immunophilins in the reaction to ischemia/hypoxia and reperfusion in the heart.

Endocardial electromechanical mapping in a porcine acute infarct and reperfusion model evaluating the extent of myocardial ischemia.

OBJECTIVE: Catheter-based, left ventricular, electromechanical mapping (EMM) has evolved as a diagnostic tool to characterize ischemic and injured myocardium. In the acute setting, diagnostic criteria for ischemic or infarcted myocardium are not well defined. In the present study, the capacity of separating myocardium with evolving necrosis from viable myocardium was investigated. METHODS AND RESULTS: Pigs were subjected to balloon occlusion of the left anterior descending coronary artery for 45 minutes. Using the NOGATM cardiac mapping system, EMM was performed at the baseline and after two hours of reperfusion. EMMs were evaluated regarding unipolar voltage (UPV), bipolar voltage (BPV) and local linear shortening (LLS). The pigs were sacrificed four hours after reperfusion and morphological estimation of infarct size and localization was performed. Baseline UPV activity was significantly lower in the anterior, lateral and posterior basal segments as compared to the septal and posterior midventricular segments. After reperfusion, UPV, but not BPV, was significantly decreased in the apical, midventricular septal and basal segments. LLS demonstrated significant impairment of mobility in the septal midventricular segment. The thresholds for separating electromechanical activity at baseline from after infarction differed between the myocardial regions. The ability of EMM to correctly detect infarcted myocardium showed a sensitivity and specificity in the order of 50 85%, as compared to the morphological standard. CONCLUSION: In a porcine acute infarct and reperfusion model, electromechanical activity thresholds, for infarct detection, could be established, but there was significant intersegmental threshold variability at baseline and after infarction. Accordingly, applying general thresholds demonstrated a poor correlation between infarct extension evaluated by EMM and morphology.

Cyclosporine does not reduce myocardial infarct size in a porcine ischemia-reperfusion model.

Cyclosporine A (CsA) has been shown to protect against myocardial ischemia and reperfusion (I/R) injury in small animal models. The aim of the current study was to evaluate the effects of CsA on myocardial I/R injury in a porcine model. Pigs were randomized between CsA (10mg/kg; n = 12) or placebo (n = 15) and anesthetized with either isoflurane (phase I) or pentobarbital (phase II). By catheterization, the left descending coronary artery was occluded for 45 minutes, followed by reperfusion for 2 hours. Hearts were stained to quantify area at risk (AAR) and infarct size (IS). Myocardial biopsies were obtained for terminal dUTP nick end labeling and immunoblot analysis of proapoptotic proteins (apoptosis-inducing factor [AIF], BCL2/adenovirus E1B 19-kd interacting protein 3 [BNIP-3], and active caspase-3). Cyclosporine A did not reduce IS/AAR compared with placebo (49% vs 41%, respectively; P = .21). Pigs anesthetized with isoflurane had lower IS/AAR than pigs anesthetized with pentobarbital (39% vs 51%, respectively; P = .03). This reduction in IS/AAR seemed to be attenuated by CsA. Apoptosis-inducing factor protein expression was higher after CsA administration than after placebo (P = .02). Thus, CsA did not protect against I/R injury in this porcine model. The data suggest a possible deleterious interaction of CsA and isoflurane.

Failure to demonstrate myocardial protective effects of the ultra short-acting calcium antagonist clevidipine in a closed-chest reperfusion porcine model.

Restoration of myocardial perfusion is essential in acute myocardial infarction for the salvaging of myocardial tissue. However, reperfusion per se can provoke myocardial necrosis within the jeopardized tissue. Yet, no intervention has been successfully applied to the clinical situation in this matter. Clevidipine, an ultra-short acting calcium antagonist, has, in open-chest animal models, shown to reduce the extent of reperfusion injury. In the present study we intended to reproduce those findings in a closed-chest porcine model with a clinically applicable set up. Pigs were subjected to balloon occlusion of the left anterior descending coronary artery (LAD) for 45 minutes. During 25 minutes, starting 1 minute prior to reperfusion, clevidipine, Intralipid, or saline was infused antegradely into the endangered myocardium. As no significant effects on infarct size were achieved, the model was modified. In a second phase, different anesthesias were evaluated addressing the same issue. Nonetheless no significant effects on infarct size were observed. Different techniques of occluding LAD, in an open-chest model, were investigated in a third phase, and revealed no significant differences between the techniques. However, when comparing all the closed- versus open-chest models, significant reduction in infarct size by the use of clevidipine was only obtained in the open-chest models. We could not demonstrate any significant myocardial protective effect with clevidipine in our porcine, closed-chest, acute infarct, and reperfusion model. However, in a modified open-chest model we obtained significant reduction in infarct size. Further studies are required to explain the discrepancies.