Coronary Artery Occlusion Reperfusion Research Articles

Effect of live and inactivated probiotic strains of <i>Lactobacillus acidophilus</i> and <i>Bifidobacterium animalis</i> subsp. <i>lactis</i> on myocardial infarction size in rats with systemic inflammatory response syndrome

Within the concept of a heart-gut axis, new works are emerging to support the efficacy of probiotic strains to increase myocardial resistance to ischemia-reperfusion injury (IRI) in comorbidity. The question remains open whether the presence of live probiotic bacteria is a necessary condition for the realization of their cardioprotective effect. The aim of this work was to determine the manifestation of cardio-protective effect of living and pasteurized probiotic strains Lactobacillus acidophilus (LA-5) and Bifidobacterium animalis subsp. lactis (BB-12) in rats with systemic inflammatory response syndrome (SIRS). Myocardial resistance to IRI was assessed using an in vivo model of left coronary artery occlusion-reperfusion. Experiments were performed on male Wistar rats with improved conventional status with visceral obesity, chemically induced colitis and antibiotic-induced dysbiosis, which together provided the formation of (SIRS) against the background of oral administration of live and inactivated probiotic bacteria. Myocardial resistance to ischemia-reperfusion injury was assessed using the technique of left coronary artery occlusion in vivo. The infarct size in the group with simulated SIRS was significantly higher than in the control group 43% (39; 44) and 31% (28; 35), (p 0.05). In the SIRS group with the introduction of inactivated probiotic bacteria, the infarct size 45% (37; 48) did not differ from the SIRS group and was significantly higher than in the control (p 0.05). At the same time, the size of the infarction in the group with the introduction of live probiotics did not differ from that in the control group and amounted to 32% (28; 37). There are specific features of the action of live and inactivated probiotic microorganisms with preservation of cardioprotective effect when using live lacto- and bifidobacteria in animals with SIRS.

High Risk Non-ST Elevation Myocardial Infarction - A Case Report

Coronary artery disease (CAD) is the leading cause of cardiovascular mortality worldwide. Electrocardiogram (ECG) remains an important tool in the diagnosis of acute myocardial infarction (MI) and further risk stratification. ST segment elevation myocardial infarction (STEMI) is a medical emergency requiring early diagnosis and prompt reperfusion of occluded coronary artery to prevent morbidity and mortality. Recent studies have shown that a subset of patients with acute MI in the absence of ST segment elevation (non-ST elevation myocardial infarction [NSTEMI]) have an acute occlusion of the culprit artery on coronary angiography. The Aslanger’s pattern is a specific ECG finding in acute inferior myocardial infarction with multivessel disease. It allows identification of inferior wall myocardial infarction that does not show ST elevation in contiguous leads but needs rapid evaluation by coronary angiogram and revascularization. We presented a case of acute coronary syndrome whose ECG showed Aslanger’s pattern and was confirmed to have significant stenosis of the left main coronary artery and right coronary artery (RCA) by coronary angiogram. STEMI criteria of ST elevation involving two contiguous leads may not be sufficient in diagnosing critical coronary artery occlusions in clinical practice. Keywords: Acute Myocardial Infarction; Aslanger’s Pattern; ST-Elevation; NSTEMI

Conditional knock out of cytosolic thioredoxin (Trx) in cardiomyocytes impairs cardiac function and exacerbates ischemia-reperfusion injury

Abstract Introduction Coronary heart disease with myocardial infarction (MI) is a leading cause of mortality in the world despite timely reperfusion of occluded coronary artery. Myocardial damage due to restoration of blood flow, known as reperfusion injury account for about 50% of final MI size. The role of Trx in protection against myocardial ischemia reperfusion has been reported; however, these studies were mostly performed using ex vivo isolated mouse/rat heart with retrograde perfusion or with injected rhTrx. However, the role of loss of Trx specifically in the myocytes using a conditional deletion has never been reported. Here, we determined whether loss of Trx in myocytes would promote ischemia-reperfusion injury, even if the endocardial endothelial cells express normal levels of Trx. Purpose We investigated the effect of specific deletion of Trx in cardiomyocytes on base-line cardiac function and cardiac function in ischemia-reperfusion of heart using conditional knockout of Trx (aMHC-Trx-KO) in the cardiomyocytes with normal levels of Trx in the endothelial cells to determine specifc contribution of Trx in cardiac function in I/R. Methods A Trx floxed mouse line was created with introduction of loxP sites flanking the mouse Trx gene. Further, the conditional deletion of Trx in cardiomyocytes was produced by breeding homozygous Trx-floxed (Trxfl/fl) mice with aMHC-Cre mice strain. The resulting aMHC-Trx-KO mice was identified by genotyping and conditional deletion of Trx in myocytes was achieved by injecting Tomoxifen (75mg/Kg in oil). The aMHC-Trx-KO mice were subjected to 30 minutes of ischemia by ligation of left descending coronary artery(LAD) and reperfusion was performed by release of slipknot and allowing blood flow of 60 minutes before sacrificing animals. The animal protocol was approved by the IACUC of the Texas Tech University Health Sciences Center, Lubbock. Echocardiography on animals was performed using Vevo 3100 (Visual Sonic). Statistical analysis was performed by Prism 8.0 (GraphPad). Results Deletion of Trx caused significant cardiac dysfunction in aMHC-Trx-KO mice compared to Trxfl/fl mice without treatment with tomoxifen. The ejection fraction (EF%, 52.82 vs. 73.83) and fractional shortening (FS%, 41.42 vs.25.89) were significantly reduced. Further, these mice subjected to I/R showed exacerbated cardiac dysfunction with significant decrease in heart rate and did not survive the reperfusion. We also found significant mitochondrial structural abnormalities and mitochondrial dysfunction in aMHC-Trx-KO mice compared to non-transgenic or Trxfl/fl mice without tomoxifen treatment. Conclusion Deletion of Trx in cardiomyocyte causes significant myocardial dysfunction. Further, Trx is required to protect against myocardial dysfunction in ischemia-reperfusion injury. Our data also suggest that cardiac mitochondria is specifically impacted by loss of Trx deletion.Figure-1

Parathyroid Hormone-Related Peptide and Its Analog, Abaloparatide, Attenuate Lethal Myocardial Ischemia-Reperfusion Injury.

Parathyroid hormone-related peptide (PTHrP) is well-known to play a role in bone formation, and abaloparatide, an analog of PTHrP(1-34), is approved for the treatment of osteoporosis in post-menopausal women. PTHrP has also been reported to have cardiovascular effects, with recent data demonstrating that exogenously administered PTHrP can limit the death of isolated cardiomyocytes subjected to oxidative stress via upregulation of classic ‘survival kinase’ signaling. Our aim in the current study was to extend this concept and, employing both in vitro and in vivo models, establish whether PTHrP(1-36) and abaloparatide are cardioprotective in the setting of lethal myocardial ischemia-reperfusion injury. We report that preischemic administration of PTHrP(1-36) and abaloparatide attenuated cell death in HL-1 cardiomyocytes subjected to simulated ischemia-reperfusion, an effect that was accompanied by the augmented expression of phospho-ERK and improved preservation of phospho-Akt, and blocked by co-administration of the MEK-ERK inhibitor PD98059. Moreover, using the translationally relevant swine model of acute coronary artery occlusion-reperfusion, we make the novel observation that myocardial infarct size was significantly reduced in pigs pretreated with PTHrP(1-36) when compared with placebo-controls (13.1 ± 3.3% versus 42.0 ± 6.6% of the area of at-risk myocardium, respectively; p < 0.01). Taken together, these data provide the first evidence in support of the concept that pretreatment with PTHrP(1-36) and abaloparatide renders cardiomyocytes resistant to lethal myocardial ischemia-reperfusion injury.

Comparison of Non-human Primate versus Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes for Treatment of Myocardial Infarction.

SummaryNon-human primates (NHPs) can serve as a human-like model to study cell therapy using induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs). However, whether the efficacy of NHP and human iPSC-CMs is mechanistically similar remains unknown. To examine this, RNU rats received intramyocardial injection of 1 × 107 NHP or human iPSC-CMs or the same number of respective fibroblasts or PBS control (n = 9–14/group) at 4 days after 60-min coronary artery occlusion-reperfusion. Cardiac function and left ventricular remodeling were similarly improved in both iPSC-CM-treated groups. To mimic the ischemic environment in the infarcted heart, both cultured NHP and human iPSC-CMs underwent 24-hr hypoxia in vitro. Both cells and media were collected, and similarities in transcriptomic as well as metabolomic profiles were noted between both groups. In conclusion, both NHP and human iPSC-CMs confer similar cardioprotection in a rodent myocardial infarction model through relatively similar mechanisms via promotion of cell survival, angiogenesis, and inhibition of hypertrophy and fibrosis.

Development of the novel antiplatelet agent ADTM, originating from traditional Chinese medicine: a chemical proteomic analysis and in-vivo assessment of efficacy in an animal model

BackgroundAn ageing population and lifestyle changes have led to increased cardiovascular disease-related morbidity and mortality in China, where an estimated 230 million people have cardiovascular disease. Long-term antiplatelet therapy with aspirin and clopidogrel are used for treatment and post-stenting primary prevention of acute coronary syndrome, but the risk of bleeding complications is high. This study aimed to identify the target of the newly developed antiplatelet agent ADTM, originating from traditional Chinese herbs. We also investigated the antiplatelet and cardioprotective effects of ADTM. MethodsWe developed ADTM by conjugating danshensu and tetramethylpyrazine, which are active compounds in the herbs danshen (Salvia miltiorrhizae) and chuanxiong (Ligustium wallichii Franch), respectively. To identify the target of ADTM, we incubated its biotinylated analogue with rat blood platelet lysates, then used chemical proteomics to precipitate protein complexes. We compared the antiplatelet effect of ADTM with clopidogrel in a rat model in vivo by administrating ADTM (5–20 mg/kg) and clopidogrel (18 mg/kg) intravenously daily for 5 days, and inducing platelet aggregation by adenosine diphosphate. We also assessed the inhibitory effects of ADTM and clopidogrel on ferric chloride (FeCl3)-induced venous thrombus formation. We further assessed the cardioprotective effects of ADTM in a canine coronary artery occlusion-reperfusion model. The left anterior descending coronary artery was occluded for 20 min followed by reperfusion in five beagles (weighing about 12 kg). 15 min after occlusion, ADTM (6mg/kg) or nitroglycerin (45 μg) was administered for 3 min continuously. FindingsResults of chemical proteomics showed that ADTM targets ERp57. The inhibitory effects of ADTM on platelet aggregation were similar to clopidogrel in the rat model (mean 40% [SD 11] for ADTM [p=0·018 vs control] and 38% [9] for clopidogrel [p=0·0073 vs control; p=0·78 vs ADTM). Similarly, the inhibitory effects on FeCl3-induced venous thrombus formation were 50% (SD 10) for ADTM (p=0·0087 vs vehicle control) and 42% (6) for clopidogrel (p=0·0093 vs vehicle control; p=0·85 vs ADTM). ADTM increased mean coronary blood flow by 36% (SD 15; p=0·0165 for before vs after ADTM administration) and decreased mean arterial pressure (MAP) from 102 mm Hg (2·7) to 96 mm Hg (1·3; p=0·0031). Coronary blood flow did not differ between before and after nitroglycerin administration (p=0·49), but nitroglycerin did decrease mean arterial pressure from 102 mm Hg (1·6) to 92 mm Hg (1·5; p=0·0076). ADTM and nitroglycerin reduced the infarct size of cardiac tissue by a mean of 10% (SD 3; p=0·0217) and 8% (2; p=0·0072), respectively. InterpretationADTM is a ligand that targets ERp57 and displays antiplatelet and cardioprotective effects in animal models. ADTM represents a potential lead compound for further investigation and development of new antiplatelet drugs with reduced bleeding risk. FundingThe National Natural Science Foundation of China (NSFC-81403139) and University of Macau (MYRG2015-00161-ICMS-QRCM).

Efficacy of cardiac resynchronization in acutely infarcted canine hearts with electromechanical dyssynchrony.

Patients with acute myocardial infarction (MI), left bundle branch block (LBBB), and marked left ventricular (LV) decompensation suffer from nearly 50% early mortality. Whether cardiac resynchronization therapy (CRT) improves hemodynamic status in this condition is unknown. We tested CRT in this setting by using a canine model of delayed lateral wall (LW) activation combined with 2 hours of coronary artery occlusion-reperfusion. This study aimed to evaluate the acute hemodynamic effects of CRT during and immediately after MI. Adult dogs (n = 8) underwent open-chest 2-hour mid-left anterior descending artery occlusion followed by 1-hour reperfusion. Four pacing modes were compared: right atrial pacing, pseudo-left bundle block (right ventricular pacing), and CRT with the LV lead positioned at either the LW (LW-CRT) or the peri-infarct zone (peri-infarct zone-CRT). Continuous LV pressure-volume data, regional segment length, and proximal left anterior descending flow rates were recorded. At baseline, both right ventricular pacing and peri-infarct zone CRT reduced anterior wall regional work by ~50% (vs right atrial pacing). During coronary occlusion, this territory became dyskinetic, and dyskinesis rose further with both CRT modes as compared to pseudo-LBBB. Global cardiac output, stroke work, and ejection fraction all still improved by 11%-23%. After reperfusion, both CRT modes elevated infarct zone regional work and blood flow by ~10% as compared to pseudo-LBBB, as well as improved global function. CRT improves global chamber systolic function in left ventricles with delayed LW activation during and after sustained coronary occlusion. It does so while modestly augmenting infarct zone dyskinesis during occlusion and improving regional function and blood flow after reperfusion. These findings support CRT in the setting of early post-MI dyssynchronous heart failure.

Novel therapeutic strategies for cardioprotection.

The morbidity and mortality from ischemic heart disease (IHD) remain significant worldwide. The treatment for acute myocardial infarction has improved over the past decades, including early reperfusion of occluded coronary arteries. Although it is essential to re-open the artery as soon as possible, paradoxically this leads to additional myocardial injury, called acute ischemia-reperfusion injury (IRI), for which currently no effective therapy is available. Therefore, novel therapeutic strategies are required to protect the heart from acute IRI in order to reduce myocardial infarction size, preserve cardiac function and improve clinical outcomes in patients with IHD. In this review article, we will first outline the pathophysiology of acute IRI and review promising therapeutic strategies for cardioprotection. These include novel aspects of mitochondrial function, epigenetics, circadian clocks, the immune system, microvesicles, growth factors, stem cell therapy and gene therapy. We discuss the therapeutic potential of these novel cardioprotective strategies in terms of pharmacological targeting and clinical application.

Normobaric, intermittent hypoxia conditioning is cardio- and vasoprotective in rats

Favorable versus detrimental cardiovascular responses to intermittent hypoxia conditioning (IHC) are heavily dependent on experimental or pathological conditions, including the duration, frequency and intensity of the hypoxia exposures. Recently, we demonstrated that a program of moderate, normobaric IHC (FIO2 9.5-10% for 5-10 min/cycle, with intervening 4 min normoxia, 5-8 cycles/day for 20 days) in dogs afforded robust cardioprotection against infarction and arrhythmias induced by coronary artery occlusion-reperfusion, but this protection has not been verified in other species. Accordingly, in this investigation cardio- as well as vasoprotection were examined in male Wistar rats completing the normobaric IHC program or a sham program in which the rats continuously breathed atmospheric air. Myocardial ischemia and reperfusion (IR) was imposed by occlusion and reperfusion of the left anterior descending coronary artery in in situ experiments and by subjecting isolated, perfused hearts to global ischemia-reperfusion. Cardiac arrhythmias and myocardial infarct size were quantified in in situ experiments. Endothelial function was evaluated from the relaxation to acetylcholine of norepinephrine-precontracted aortic rings taken from in situ IR experiments, and from the increase in coronary flow produced by acetylcholine in isolated hearts. IHC sharply reduced cardiac arrhythmias during ischemia and decreased infarct size by 43% following IR. Endothelial dysfunction in aorta was marked after IR in sham rats, but not significant in IHC rats. Similar findings were found for the coronary circulations of isolated hearts. These findings support the hypothesis that moderate, normobaric IHC is cardio- and vasoprotective in a rat model of IR.

‘Going out on a limb’: SDF-1α/CXCR4 signaling as a mechanism of remote ischemic preconditioning?

Remote ischemic preconditioning (RIPC) is the intriguing phenomenon whereby brief, non-lethal episodes of ischemia in one organ or vascular bed render remote tissue resistant to a subsequent, sustained period of ischemia [23, 32]. While initially regarded as a laboratory curiosity [24], interest in RIPC was piqued by the observation that limb ischemia, achieved noninvasively by simple inflation of a blood pressure cuff, significantly reduced myocardial infarct size in the acute swine model of coronary artery occlusion-reperfusion [17]. In the ensuing years, since these first reports, progress has been made in defining the characteristics of RIPC-induced cardioprotection (including as-yet limited insights into cellular mechanisms), expansion of the concept beyond heart to encompass protection of other organs (including brain, kidney, liver and mesentery), and the investigation of RIPC in Phase II and III trials seeking to establish clinical efficacy in patients undergoing cardiac surgery or percutaneous intervention [2, 3, 6, 10, 14, 19, 20, 22, 24, 25, 31]. However, resolution of the distinguishing feature of RIPC has remained elusive [22, 24, 25]: how is the protective stimulus transferred or communicated from the site of the RIPC stimulus to the heart? Among the theories that have been proposed, considerable attention has focused on the concept that: (i) brief ischemia–reperfusion at the remote site triggers the release of one or more protective humoral factors, either directly or as a secondary consequence of neuronal stimulation; and (ii) the humoral factor(s) are then conveyed via the circulation to the myocardium [8, 22–25, 32]. Despite the emerging consensus that the factor(s) of interest are small (*3.5–15 kDa), presumably peptide(s), and hydrophobic [7, 28, 29], precise identification of the endogenous peptides transferred to the heart and capable of conferring cardioprotection has been problematic.

Coronary Microemboli Effects in Preexisting Acute Infarcts in a Swine Model: Cardiac MR Imaging Indices, Injury Biomarkers, and Histopathologic Assessment

To use cardiac magnetic resonance (MR) imaging indices, injury biomarkers, and microscopy for quantifying the effects of defined microemboli volume and sizes on viability, left ventricular (LV) function, and perfusion in preexisting acute myocardial infarcts in a swine model. Institutional approval was obtained to perform x-ray fluoroscopy and 90-minute left anterior descending coronary artery occlusion-reperfusion (single ischemic insult) in 16 pigs and coronary embolization in eight of the 16 pigs (32 mm(3), 40-120 μm microemboli) (double ischemic insults). Another eight pigs served as controls. Cardiac MR imaging results (viability, function, and perfusion), injury biomarkers (creatine-kinase-MB and troponin I), and histopathologic evaluations were quantified. Analysis of variance was performed, and a P value less than .02 was considered to indicate a significant difference. Delayed contrast material-enhanced MR imaging allowed simultaneous visualization of hyperenhanced large infarcts, hypoenhanced microvascular obstruction (MVO) zones, and moderately enhanced patchy microinfarcts in border zones, which represent different degrees of contraction and perfusion in the respective regions, in pigs subjected to double ischemic insults. The increase in myocardial damage was smaller in pigs with double insults (15.7% ± 1.1% of total LV mass) than in those with a single insult (12.4% ± 1.2%, P < .02), but the reduction in LV ejection fraction was disproportional (32% ± 0.6% and 38% ± 1%, P < .02, respectively). Delayed contrast-enhanced imaging can allow quantification of the MVO zone but can result in underestimation of the extent of myocardial damage compared with microscopy in animals subjected to double insults (18.2 ± 1.6, P < .02). A significant increase in cardiac injury biomarkers was observed at 18-24 hours in both cohorts. The additional effect of microemboli on troponin I was demonstrated at 68-72 hours (3.2 ng/mL ± 0.85 [3.20 μg/L ± 0.85] vs 1.34 ng/mL ± 0.43 [1.34 μg/L ± 0.43], P < .02). MR imaging has the potential to allow visualization of acute myocardial infarcts, MVO zones, and patchy microinfarcts simultaneously. The accentuated LV dysfunction caused by double ischemic insults was linked to expansion of the MVO zone, perfusion deficits, and myocardial damage.

Myocardial infarction and intramyocardial injection models in swine

Sustainable and reproducible large animal models that closely replicate the clinical sequelae of myocardial infarction (MI) are important for the translation of basic science research into bedside medicine. Swine are well accepted by the scientific community for cardiovascular research, and they represent an established animal model for preclinical trials for US Food and Drug Administration (FDA) approval of novel therapies. Here we present a protocol for using porcine models of MI created with a closed-chest coronary artery occlusion-reperfusion technique. This creates a model of MI encompassing the anteroapical, lateral and septal walls of the left ventricle. This model infarction can be easily adapted to suit individual study design and enables the investigation of a variety of possible interventions. This model is therefore a useful tool for translational research into the pathophysiology of ventricular remodeling and is an ideal testing platform for novel biological approaches targeting regenerative medicine. This model can be created in approximately 8-10 h.

Myocardial strain in sub-acute peri-infarct myocardium

In the absence of additional ischemic insults, the peri-infarct region surrounding the infarct myocardium can recover function. T2 weighted MRI signal is sensitive to edema and used to detect peri-infarct, salvageable myocardium. The main purpose of this study was to investigate the alterations in myocardial strain in the peri-infarct myocardium as compared to normal and infarct myocardium. Comprehensive MRI of the myocardium was performed in five pigs 6-7 days following coronary artery occlusion-reperfusion myocardial injury. MRI included tagged cine images for myocardial strain, T2weighted (T2w)-images and late gadolinium enhancement (LGE) for assessing myocardial viability. Automated signal intensity thresholds were used to define tissue edema and myocardial infarct. Maximum-shortening strains were analyzed in the infarct, peri-infarct and normal myocardial sectors. The results were correlated with triphenyltetrazolium-chloride (TTC) and hemotoxylin-eosin stained tissue images. We found an excellent correlation of LGE with TTC (r = 0.94, P < 0.05). T2w-images markedly overestimated the infarct size (25 +/- 3%). Both the healthy and peri-infarct myocardial sectors had higher myocardial strain than infarct myocardial sectors (P < 0.05). Clear demarcation between infarct and non-infarct myocardium was noted on histology. Peri-infarct myocardium continues to demonstrate T2 signal enhancement to at least 7 days, but this region has preserved mechanical function. T2-weighted imaging and myocardial strain measurements provide complementary information and both may be useful for characterization of the peri-infarct myocardium.

Hypoxic conditioning suppresses nitric oxide production upon myocardial reperfusion.

Physiologically modulated concentrations of nitric oxide (NO) are generally beneficial, but excessive NO can injure myocardium by producing cytotoxic peroxynitrite. Recently we reported that intermittent, normobaric hypoxia conditioning (IHC) produced robust cardioprotection against infarction and lethal arrhythmias in a canine model of coronary occlusion-reperfusion. This study tested the hypothesis that IHC suppresses myocardial nitric oxide synthase (NOS) activity and thereby dampens explosive, excessive NO formation upon reperfusion of occluded coronary arteries. Mongrel dogs were conditioned by a 20 d program of IHC (FIO(2) 9.5-10%; 5-10 min hypoxia/cycle, 5-8 cycles/d with intervening 4 min normoxia). One day later, ventricular myocardium was sampled for NOS activity assays, and immunoblot detection of the endothelial NOS isoform (eNOS). In separate experiments, myocardial nitrite (NO(2)(-)) release, an index of NO formation, was measured at baseline and during reperfusion following 1 h occlusion of the left anterior descending coronary artery (LAD). Values in IHC dogs were compared with respective values in non-conditioned, control dogs. IHC lowered left and right ventricular NOS activities by 60%, from 100-115 to 40-45 mU/g protein (P < 0.01), and decreased eNOS content by 30% (P < 0.05). IHC dampened cumulative NO(2)(-) release during the first 5 min reperfusion from 32 +/- 7 to 14 +/- 2 mumol/g (P < 0.05), but did not alter hyperemic LAD flow (15 +/- 2 vs. 13 +/- 2 ml/g). Thus, IHC suppressed myocardial NOS activity, eNOS content, and excessive NO formation upon reperfusion without compromising reactive hyperemia. Attenuation of the NOS/NO system may contribute to IHC-induced protection of myocardium from ischemia-reperfusion injury.

Intermittent, normobaric hypoxia evokes adaptive modifications of nitric oxide synthase in canine myocardium

Background: Physiologically modulated concentrations of nitric oxide (NO) are generally beneficial, but excessive NO can injure myocardium by producing cytotoxic peroxynitrite. Recently we reported that intermittent, normobaric hypoxia conditioning (IHC) produced robust cardioprotection against infarction and lethal arrhythmias in a canine model of coronary occlusion‐reperfusion, and that IHC dampens explosive, cytotoxic NO formation upon reperfusion of occluded coronary arteries. Hypothesis: IHC suppresses myocardial nitric oxide synthase (NOS) activity and contents of NOS isoforms. Methods: Mongrel dogs were conditioned by a 20 d IHC program (FIO2 9.5–10%; 5–10 min hypoxia/cycle, 5–8 cycles/d with intervening 4 min normoxia). One day later, ventricular myocardium was sampled for NOS activity assays, and immunoblot detection of endothelial and inducible NOS isoforms (eNOS, iNOS) and phosphorylated eNOS. Values in IHC dogs were compared with respective values in non‐conditioned, control dogs. Results: IHC lowered left and right ventricular NOS activities by 60%, from 100–115 to 40–45 mU/g protein (P &lt; 0.01), and decreased eNOS and iNOS contents by 30 and 50%, respectively (P&lt;0.05). IHC increased fractional phosphorylation of eNOS S1177 by &lt; 2.5‐fold without altering T495 phosphorylation, a pattern that activates eNOS. Conclusions: IHC suppressed myocardial NOS activity, and eNOS and iNOS contents, but enhanced S1177 phosphorylation of the remaining eNOS. Thus, potentially cardioprotective attenuation of NOS activity may be due primarily to IHC suppression of iNOS. Support: NIH AT‐003598

Macrophage Colony-Stimulating Factor Improves Cardiac Function after Ischemic Injury by Inducing Vascular Endothelial Growth Factor Production and Survival of Cardiomyocytes

Macrophage colony-stimulating factor (M-CSF), known as a hematopoietic growth factor, induces vascular endothelial growth factor (VEGF) production from skeletal muscles. However, the effects of M-CSF on cardiomyocytes have not been reported. Here, we show M-CSF increases VEGF production from cardiomyocytes, protects cardiomyocytes and myotubes from cell death, and improves cardiac function after ischemic injury. In mice, M-CSF increased VEGF production in hearts and in freshly isolated cardiomyocytes, which showed M-CSF receptor expression. In rat cell line H9c2 cardiomyocytes and myotubes, M-CSF induced VEGF production via the Akt signaling pathway, and M-CSF pretreatment protected these cells from H(2)O(2)-induced cell death. M-CSF activated Akt and extracellular signal-regulated kinase signaling pathways and up-regulated downstream anti-apoptotic Bcl-xL expression in these cells. Using goats as a large animal model of myocardial infarction, we found that M-CSF treatment after the onset of myocardial infarction by permanent coronary artery ligation promoted angiogenesis in ischemic hearts but did not reduce the infarct area. M-CSF pretreatment of the goat myocardial infarction model by coronary artery occlusion-reperfusion improved cardiac function, as assessed by hemodynamic parameters and echocardiography. These results suggest M-CSF might be a novel therapeutic agent for ischemic heart disease.

Reducing the Door-to-Balloon Time for Myocardial Infarction with ST-Segment Elevation

It has been 27 years since the initial report of successful reperfusion of occluded coronary arteries with thrombolytic therapy in patients with acute myocardial infarction,1 and 20 years since the initial report of the feasibility and safety of primary percutaneous coronary intervention (PCI) in the same setting.2 During the past decade, primary PCI has gradually emerged as the preferred treatment strategy for acute myocardial infarction with ST-segment elevation.3,4 However, for both primary PCI and thrombolytic therapy, analyses have consistently shown that timely reperfusion remains a key component in improving the survival of patients.5–7 For primary PCI, the standard . . .

Bone-marrow-derived progenitor cell therapy in need of proof of concept: design of the REPAIR-AMI trial

Early reperfusion of occluded coronary arteries has significantly reduced early mortality and improved the long-term prognosis of patients with an acute myocardial infarction. However, the development of postinfarction heart failure remains a major challenge. Initial experimental studies indicated that mononuclear progenitor cells derived from the bone marrow may contribute to the functional regeneration of freshly infarcted myocardium and increase neovascularization of ischemic areas. A number of clinical pilot trials have now transferred the experimental approach into the clinical arena, aiming at regenerating myocardial function with infusion of bone-marrow-derived progenitor cells in patients after an acute myocardial infarction. While these initial trials using intracoronary infusion of bone-marrow-derived progenitor cells indeed suggested that such a strategy appears to be feasible and safe in patients with an acute myocardial infarction, there is definitely a pressing need for a proof-of-concept study documenting a potentially beneficial effect of progenitor cell therapy on cardiac function.

Vitamin E reduces myocardial infarct size in type 2 diabetes

The interrelationship of type 2 diabetes (T2D), inflammation and ischemic heart disease (IHD) is not clear. We suspect that a low-level, chronic inflammatory response aggravates leukocyte-mediated ischemia-reperfusion (I/R) injury in the T2D heart. The purposes of this study were to: 1.) determine if myocardial injury due to I/R was increased in the Zucker Diabetic Fatty (ZDF) model of T2D, 2.) determine if treatment with vitamin E would attenuate ischemic injury. Zucker Lean Controls (ZLC) and ZDF rats were subjected to a left anterior descending coronary artery occlusion-reperfusion protocol. The recovery of left ventricular function and myocardial infarct size were determined. Neutrophil reactive oxygen species (PMN ROS) was measured in whole blood prior to ischemia. Four groups were studied. Group 1: ZLC-Placebo, Group 2: ZLC-Vit E, Group 3: ZDF-P and Group 4: ZDF-E. We found that the recovery of ventricular function (+dP/dt) was somewhat depressed in the diabetic group (ZLC-P = 87.4% ± 11.7 SEM, ZDF-P = 68.1% ± 5.5, P=NS), however, the recovery of the ZDF-E group was improved significantly (ZDF-E = 97.4% ± 10.3). The myocardial infarct size was significantly increased in the ZDF-P group but was reduced with vitamin E treatment (ZLC-P = 43.0% ± 1.9, ZDF-P = 57.0% ± 3.9, ZDF-E = 33.9% ± 5.1, P≤0.05). In addition, vitamin E treatment significantly reduced the chronic increase in PMN ROS observed in the ZDF-P group (P≤0.05). These findings indicate that ischemic injury is significantly increased in the ZDF heart and is associated with increased PMN ROS. Treatment with vitamin E reduced both PMN ROS and the severity of IHD in T2D. Supported by NIH HLB 58859.

Thaliporphine protects ischemic and ischemic‐reperfused rat hearts via an NO‐dependent mechanism

AbstractIn ischemia or ischemia‐reperfusion (I/R), nitric oxide (NO) can potentially exert several beneficial effects. Thaliporphine, a natural alkaloid with Ca2+ channel‐activating and Na+/K+ channel‐blocking activities, increased NO levels and exerted cardioprotective action in ischemic or I/R rats. The role of NO in the cardioprotective actions of thaliporphine was assessed. The severity of rhythm disturbances and mortality in anesthetized rats with either coronary artery occlusion for 30 min, or 5 min followed by 30‐min reperfusion, were monitored and compared in thaliporphine‐ vs. placebo‐treated groups. Thaliporphine treatment significantly increased NO and decreased lactate dehydrogenase (LDH) levels in the blood during the end period of ischemia or I/R. These changes in NO and LDH levels by thaliporphine were associated with a reduction in the incidence and duration of ventricular tachycardia (VT) and ventricular fibrillation (VF) during ischemic or I/R period. The mortality of animals was also completely prevented by 1 × 10–8 moles/kg of thaliporphine. In animals subjected to 4 h of left coronary artery occlusion, 1 × 10–7 moles/kg of thaliporphine dramatic reduced cardiac infarct zone from 46 ± 6% to 7.1 ± 1.9%. Inhibition of NO synthesis with 3.7 × 10–6 moles/kg of Nω ‐nitro‐L‐arginine methyl ester (L‐NAME) abolished the beneficial effects of thaliporphine during 30 min or 4 h myocardial ischemia. However, the antiarrhythmic activity and mortality reduction efficacy of thaliporphine during reperfusion after 5 min of ischemia was only partially antagonized by L‐NAME. These results showed that thaliporphine efficiently exerted the cardioprotections either in acute or prolonged coronary artery occlusion or occlusion‐reperfusion situations. The fact that thaliporphine induced cardioprotective effects were abrogated by L‐NAME indicates that NO is an important mediator for the cardioprotective effects of thaliporphine in acute or prolonged ischemia, whereas antioxidant activities may contribute to the protection of I/R injury. Drug Dev. Res. 52:446–453, 2001. © 2001 Wiley‐Liss, Inc.