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Aims Autophagy is activated in cardiomyocytes in ischaemic heart disease, but its dynamics and functional roles remain unclear after myocardial infarction. We observed the dynamics of cardiomyocyte autophagy and examined its role during postinfarction cardiac remodelling. Methods and results Myocardial infarction was induced in mice by ligating the left coronary artery. During both the subacute and chronic stages (1 and 3 weeks postinfarction, respectively), autophagy was found to be activated in surviving cardiomyocytes, as demonstrated by the up-regulated expression of microtubule-associated protein-1 light chain 3-II (LC3-II), p62 and cathepsin D, and by electron microscopic findings. Activation of autophagy, specifically the digestion step, was prominent in cardiomyocytes 1 week postinfarction, especially in those bordering the infarct area, while the formation of autophagosomes was prominent 3 weeks postinfarction. Bafilomycin A1 (an autophagy inhibitor) significantly aggravated postinfarction cardiac dysfunction and remodelling. Cardiac hypertrophy was exacerbated in this group and was accompanied by augmented ventricular expression of atrial natriuretic peptide. In these hearts, autophagic findings (i.e. expression of LC3-II and the presence of autophagosomes) were diminished, and activation of AMP-activated protein kinase was enhanced. Treatment with rapamycin (an autophagy enhancer) brought about opposite outcomes, including mitigation of cardiac dysfunction and adverse remodelling. A combined treatment with bafilomycin A1 and rapamycin offset each effect on cardiomyocyte autophagy and cardiac remodelling in the postinfarction heart. Conclusion These findings suggest that cardiomyocyte autophagy is an innate mechanism that protects against progression of postinfarction cardiac remodelling, implying that augmenting autophagy could be a therapeutic strategy.

Objectives Late treatment with erythropoietin (EPO), as well as the administration before the onset of or during the acute stage of myocardial infarction (MI), has recently been shown to mitigate post-MI heart failure. We investigated the mechanisms, including the downstream signaling pathways, for the beneficial effect of late treatment with EPO on chronic post-MI heart failure. Methods and results EPO (1500 U/kg, twice a week) was administered to mice beginning 6 weeks after induction of large MI. The EPO treatment for 4 weeks diminished left ventricular dilatation and improved function. It significantly reduced inflammatory cell infiltration and fibrosis, and increased vascular density in noninfarcted areas. The elevated levels of the inflammatory cytokines interleukin (IL)-1β, IL-6, tumor necrosis factor-α and transforming growth factor-β1 seen in the failing hearts were returned nearly to control levels by EPO treatment. Oxidative damage in surviving cardiomyocytes was also significantly attenuated by EPO. Expression of EPO receptor was upregulated in failing hearts, and EPO treatment led to myocardial activation of signal transducer and activator of transcription-3 (Stat3), Stat5, and Akt. These in vivo effects of EPO were confirmed in vitro in experiments that showed the anti-inflammatory and anti-oxidant effects of EPO to be mediated via Stat and Akt activation. Finally, the beneficial effects of EPO were found to persist for 4 weeks after discontinuing treatment. Conclusions It thus appears that Stat-mediated reduction of inflammation and cytokine production and Akt-mediated attenuation of oxidative stress accompany the beneficial effects of late treatment with EPO on chronic post-MI heart failure.

The most critical determinant of prognosis in patients with acute myocardial infarction (MI) is infarct magnitude, which can be established within several hours of an attack. The importance of the subsequent healing process is not negligible, however. In fact, much experimental and clinical evidence suggests that late reperfusion of the infarct-related coronary artery--i.e. at times too late to salvage the myocardium within the area at risk-is beneficial for reducing left ventricular remodelling and decreasing mortality ('open artery hypothesis'). For instance, one recent study highlighted the beneficial effects of late reperfusion therapy on the infarct tissue cell dynamics following acute MI. Nonetheless, several recent large, randomized clinical trials have failed to provide evidence of such benefits, refuting the clinical efficacy of late reperfusion. In addition, they also underscore the need for revised clinical studies in which there is less heterogeneity in the timing of reperfusion and in the initial infarct size, as well as the need for sustained patency of the recanalized artery. This review focuses on the effects of late reperfusion on the pathophysiology of MI in the context of the infarct tissue dynamics and clinical outcomes. We also discuss the issues that need to be resolved to improve clinical application.

Aims We investigated the effect of an erythropoietin (EPO)–gelatin hydrogel drug delivery system (DDS) applied to the heart on myocardial infarct (MI) size, left ventricular (LV) remodelling and function. Methods and results Experiments were performed in a rabbit model of MI. The infarct size was reduced, and LV remodelling and function were improved 14 days and 2 months after MI but not at 2 days after MI in the EPO-DDS group. The number of cluster of differentiation 31(CD31)-positive microvessels and the expression of erythropoietin receptor (EPO-R), phosphorylated-Akt (p-Akt), phosphorylated glycogen synthase kinase 3β (p-GSK-3β), phosphorylated extracellular signal-regulated protein kinase (p-ERK), phosphorylated signal transducer and activator of transcription 3 (p-Stat3), vascular endothelial growth factor (VEGF), and matrix metalloproteinase-1 (MMP-1) were significantly increased in the myocardium of the EPO-DDS group. Conclusion Post-MI treatment with an EPO-DDS improves LV remodelling and function by activating prosurvival signalling, antifibrosis, and angiogenesis without causing any side effect.

Objective: Granulocyte-colony stimulating factor (G-CSF) accelerates repair following myocardial infarction (MI). Recently, the beneficial effects of post-MI administration of G-CSF were reported to be mediated by direct activation of the Jak–Stat pathway in cardiomyocytes. Our aim was to test the hypothesis that bone marrow-derived cells recruited into the infarcted myocardium are the primary mediators of the beneficial effects by G-CSF. Methods and results MI was induced using a 30-min ischemia–reperfusion protocol (day 0) in 40 rabbits treated with G-CSF (10 μg/kg/day from days 3 to 7) or saline. Another 40 rabbits received the same G-CSF or saline protocol but also received AMD3100 (200 μg/kg/day), a specific inhibitor of CXCR4. On day 28 post-MI, left ventricular ejection fractions and end-diastolic dimensions were significantly better in the G-CSF group than in the control saline group, and the scar area/left ventricular wall area ratio was significantly smaller in the G-CSF group. G-CSF administration also led to increased mobilization of CXCR4+ bone marrow cells, including RAM11+ macrophages, into infarcted areas. And within those areas there was significant upregulation of expression of stromal cell-derived factor (SDF)-1, a chemoattractant of circulating CXCR4+ cells, as well as of the collagenase matrix metalloproteinase-1. AMD3100 significantly inhibited all of these beneficial effects of G-CSF, but did not affect the upregulation of SDF-1 or phospho-Stat3. Conclusion Recruitment of CXCR4+ cells into infarcted myocardial tissues via stimulation of the CXCR4/SDF-1 axis plays a critical role in the beneficial effects of G-CSF.

Objective: Whether bone marrow cells injected following acute myocardial infarction (MI) transdifferentiate into cardiomyocytes remains controversial, and how these cells affect repair-related cytokines is not known. Methods: Autologous bone marrow-derived mononuclear cells (BM-MNCs) labeled with DiI, 1,1′-dioctadecyl-1 to 3,3,3′,3′-tetramethylindocarbocyanine perchlorate, or saline were intravenously injected into rabbits 5 h following a 30-min ischemia and reperfusion protocol, and cardiac function and the general pathology of the infarcted heart were followed up 1 and 3 months post-MI. To search for regenerated myocardium, electron microscopy as well as confocal microscopy were performed in the infarcted myocardium 7 days post-MI. Expression levels of repair-related cytokines were evaluated by immunohistochemistry and Western blotting. Results: Improvements in cardiac function and reductions in infarct size were observed in the BM-MNC group 1 month and 3 months post-MI. Using electron microscopy 7 days after infarction, clusters of very immature (fetal) and relatively mature cardiomyocytes undergoing differentiation were identified in the infarcted anterior LV wall in the BM-MNC group, though their numbers were small. These cells contained many small and dense DiI particles (a BM-MNC marker), indicating that cardiomyocytes had regenerated from the injected BM-MNCs. The expression of both transforming growth factor-β, which stimulates collagen synthesis and matrix metalloproteinase-1, a collagenase, were both down-regulated 7 days and 1 month post-MI in the BM-MNC group. Stromal cell-derived factor-1, which is known to recruit BM-MNCs into target tissues, was overexpressed in the infarcted areas of BM-MNC hearts 7 days post-MI. Conclusions: Intravenous transplantation of BM-MNCs leads to the development of BM-MNC-derived myocyte-like cells and regulates the expression of repair-related cytokines that facilitate repair following myocardial infarction.

Objective: In cultured cardiomyocytes, apoptosis is induced not by Fas stimulation, a popular inducer of apoptosis, but by an additional treatment with actinomycin D (AD), a transcription inhibitor, although the mechanism is unknown. Our hypothesis is that Fas stimulation not only activates pro-apoptotic signals but also may inhibit some of them, and this inhibition is blocked by AD. Methods: Cultured neonatal mouse cardiomyocytes were treated with agonistic anti-Fas antibody (FA), AD, or both (FA+AD). In this system, apoptotic signals related to Fas-induced apoptotic pathways were examined by RT-PCR and immunoblotting. In addition, antisense oligonucleotide (AS) studies were carried out. Results: The treatment with FA+AD induced up-regulation of Fas, activation of c-Jun N-terminal kinase (JNK), which is one of the key molecules of the alternate pathway of Fas-induced apoptosis, up-regulation of Bax, up-regulation and activation of caspase-3, activation of caspase-3-dependent DNase (CAD), and final DNA fragmentation and apoptotic morphologies in cardiomyocytes. FA alone or AD alone did not affect any part of the above pathway. However, mRNA of mitogen-activated protein kinase phosphatase-1 (MKP-1), an inactivator of JNK, was up-regulated by FA alone, but not by FA+AD or AD alone. Pretreatment with AS against MKP-1 induced apoptosis in FA alone-treated cardiomyocytes, whereas AS against JNK1 prevented apoptosis induced by FA+AD. On the other hand, FA+AD did not result in the activation of either caspase-8, one of the key molecules of the classic pathway in Fas-induced apoptosis, p38 MAPK, or extracellular signal-regulated kinase (ERK). Conclusions: Cardiomyocyte apoptosis by FA+AD depends on the alternate pathway through the JNK, Bax and caspase-3, and CAD-dependent pathways including a positive feedback mechanism of Fas up-regulation. The molecular mechanism that prevents Fas stimulation alone from inducing apoptosis involves up-regulation of MKP-1, an inhibitor of JNK; this up-regulation is inhibited by AD.

Objective: Caspase family proteases are recognized as key mediators of apoptosis. However, the role of caspases in the ischemia–reperfused heart remains uncertain. We evaluated the effect of caspase inhibitors on myocardial infarct size and the myocyte DNA fragmentation in the ischemia–reperfused rat hearts. Methods: Three groups of Sprague–Dawley rats ( n =7, each) were subjected to 30 min of ischemia followed by 6 h of reperfusion. One of the following drugs: (1) YVAD-aldehyde, a caspase-1-like protease inhibitor (3.5 mg/kg; YVAD), (2) DEVD-aldehyde, a caspase-3-like protease inhibitor (3.5 mg/kg, DEVD), (3) vehicle (140 μl/kg) was administered intravenously 5 min prior to the ischemia in each group. Myocardial infarct size was defined by triphenyltetrazolium chloride (TTC) staining. Immunohistochemical staining by in situ nick end labeling (TUNEL) of cardiomyocytes and DNA electrophoresis were used for detecting DNA fragmentation. Ultrastructural analysis was done by electron microscopy. The caspase activity was measured in the myocardium of both groups. Results: The percentage of TUNEL-positive myocyte nuclei (%AP) was quantified by microscopy. A ladder pattern was detected by electrophoresis of DNA from the risk area and TUNEL-positive myocytes were seen in the risk area. The %AP was significantly reduced from 20±1% to 12±3% by YVAD and to 10±3% by DEVD (both P

Objective: Ischaemic preconditioning may be mediated by oxygen free radicals generated during preconditioning. Conflicting results have been reported regarding the effect of superoxide dismutase (SOD) in attenuating the cardioprotective effect of preconditioning. The aim of the study was to reconcile this conflict by examining the effect of three different oxyradical scavengers on the infarct size limiting effect of preconditioning, Methods: Anaesthetised open chest rabbits were subjected to 30 min coronary occlusion and 48 h reperfusion. In the preconditioning groups, rabbits were subjected to a single 5 min occlusion and 5 min reperfusion before 30 min sustained ischaemia. In these groups, the oxyradical scavengers SOD (15 000 U·kg−1), N-2-mercaptopropionyl glycine (MPG, 20 mg·kg−1), and dimethylthiourea (DMTU, 500 mg·kg−1), or placebo saline, were infused before and during preconditioning, in the non-preconditioning groups, these agents were given in the same time frame before 30 min of ischaemia. After 2 d reperfusion, infarct size was measured microscopically. Results: In the saline treated controls, preconditioning markedly limited microscopical infarct size (percent of area at risk): 13(SEM 3)% (n = 9) v 49(9)% (n = 8), p < 0.05. Treatment of the preconditioning groups with SOD or MPG attenuated this cardioprotection [infarct size 31(5)% (n = 11) and 42(8)% (n = 11), respectively, p < 0.05 v the saline treated preconditioning group], but treatment with DMTU did not [infarct size 23(6)% (n = 11), p = NS v the saline treated preconditioning group]. In the non-preconditioning groups, none of the treatments modified infarct size: 50(9)% (n = 7), 56(5)% (n = 8), and 61(6)%, (n = 8), respectively, p = NS v saline treated control. Conclusions: Cardioprotection by preconditioning is mediated, at least in part, by oxyradicals which are scavenged by SOD or MPG in rabbits. Cardiovascular Research 1994; 28: 980-986

Objective: (NZW × BXSB)F1 male mice were used as a model to study the effects of chronic administration of nifedipine and diltiazem on small coronary artery disease and mortality. Methods: 16 week old (NZW × BXSB)F1 male mice were given either nifedipine (n=29) at 20 mg·kg−1·d−1 orally or diltiazem (n=28) at 100 mg·kg−1·d−1 orally in two divided doses until they were 24 weeks old (ie, for 60 d). Age matched control mice were given an equivalent volume of vehicle (n=30). Mice that died received immediate necropsy. After 60 d, all surviving mice were killed and hearts and kidneys were examined histologically. Results: The survival rate at 24 weeks was significantly higher in mice given nifedipine than in the controls (71% and 47%, respectively, p

Study objective – Protective effects of nipradilol, a newly synthesised vasodilating β adrenoceptor antagonist, isosorbide dinitrate, and bunazosin on coronary artery constriction induced by intracoronary injection of acetylcholine were determined by coronary arteriography and compared in vivo in pigs. Design – Acetylcholine (12.5,25,50, 100 and 200 μg) was given into the right coronary artery under left ventricular pacing to maintain constant systemic haemodynamics. Percentage narrowing of the major epicardial coronary artery was used as an indicator of constriction of the large coronary arteries, and the time required for the contrast medium to reach the posterior descending coronary artery from the ostium of the right coronary artery (blood flow delay) was used as an indicator of constriction of the small coronary arteries. Subjects – 15 farm pigs weighing 80 to 90 kg were used. Measurements and main results – A marked blood flow delay of over 7.0 s (control: ≤1.8 s) with less than 34% narrowing of the epicardial major coronary artery was observed in 13 of 15 pigs with 12.5-50 μg of acetylcholine, and in the other two pigs with 100 μg of acetylcholine. When marked blood flow delay occurred, the perfused right ventricular myocardium became macroscopically anaemic (ischaemic). Over 75% narrowing of the major epicardial coronary artery was induced in six of the 15 pigs, and over 50% narrowing in 12, with marked blood flow delay with 100 to 200 μg of acetylcholine. However, after intracoronary infusion of 10 μg of nipradilol, acetylcholine induced narrowing in the epicardial major coronary artery was significantly reduced from 44- 79% in control to 19-37% despite 200 μg of acetylcholine, though the time delay in coronary blood flow did not change significantly. By pretreatment with intracoronary isosorbide dinitrate (2.5 mg), the percent narrowing of the large coronary artery and the time delay in coronary blood flow were signifcantly reduced (narrowing from 32-84% to 10.27%; time delay from 7.6-41.6 s to 2.7-22.7 s). Pretreatment with intracoronary bunazosin, an α 1 adrenoceptor antagonist (100 μg), showed no protective effect on narrowing of the epicardial major coronary artery or blood flow delay. Conclusions – Isosorbide dinitrate prevents coronary artery constriction induced by acetylcholine in swine. Nipradilol prevents large, but not small, coronary artery constriction, probably through a direct nitrate like vasodilating action.